WorldWideScience

Sample records for random media model

  1. Geometric Models for Isotropic Random Porous Media: A Review

    Directory of Open Access Journals (Sweden)

    Helmut Hermann

    2014-01-01

    Full Text Available Models for random porous media are considered. The models are isotropic both from the local and the macroscopic point of view; that is, the pores have spherical shape or their surface shows piecewise spherical curvature, and there is no macroscopic gradient of any geometrical feature. Both closed-pore and open-pore systems are discussed. The Poisson grain model, the model of hard spheres packing, and the penetrable sphere model are used; variable size distribution of the pores is included. A parameter is introduced which controls the degree of open-porosity. Besides systems built up by a single solid phase, models for porous media with the internal surface coated by a second phase are treated. Volume fraction, surface area, and correlation functions are given explicitly where applicable; otherwise numerical methods for determination are described. Effective medium theory is applied to calculate physical properties for the models such as isotropic elastic moduli, thermal and electrical conductivity, and static dielectric constant. The methods presented are exemplified by applications: small-angle scattering of systems showing fractal-like behavior in limited ranges of linear dimension, optimization of nanoporous insulating materials, and improvement of properties of open-pore systems by atomic layer deposition of a second phase on the internal surface.

  2. Method of model reduction and multifidelity models for solute transport in random layered porous media

    Science.gov (United States)

    Xu, Zhijie; Tartakovsky, Alexandre M.

    2017-09-01

    This work presents a method of model reduction that leads to models with three solutions of increasing fidelity (multifidelity models) for solute transport in a bounded layered porous media with random permeability. The model generalizes the Taylor-Aris dispersion theory to stochastic transport in random layered porous media with a known velocity covariance function. In the reduced model, we represent (random) concentration in terms of its cross-sectional average and a variation function. We derive a one-dimensional stochastic advection-dispersion-type equation for the average concentration and a stochastic Poisson equation for the variation function, as well as expressions for the effective velocity and dispersion coefficient. In contrast to the linear scaling with the correlation length and the mean velocity from macrodispersion theory, our model predicts a nonlinear and a quadratic dependence of the effective dispersion on the correlation length and the mean velocity, respectively. We observe that velocity fluctuations enhance dispersion in a nonmonotonic fashion (a stochastic spike phenomenon): The dispersion initially increases with correlation length λ, reaches a maximum, and decreases to zero at infinity (correlation). Maximum enhancement in dispersion can be obtained at a correlation length about 0.25 the size of the porous media perpendicular to flow. This information can be useful for engineering such random layered porous media. Numerical simulations are implemented to compare solutions with varying fidelity.

  3. Reduced-Order Monte Carlo Modeling of Radiation Transport in Random Media

    Science.gov (United States)

    Olson, Aaron

    The ability to perform radiation transport computations in stochastic media is essential for predictive capabilities in applications such as weather modeling, radiation shielding involving non-homogeneous materials, atmospheric radiation transport computations, and transport in plasma-air structures. Due to the random nature of such media, it is often not clear how to model or otherwise compute on many forms of stochastic media. Several approaches to evaluation of transport quantities for some stochastic media exist, though such approaches often either yield considerable error or are quite computationally expensive. We model stochastic media using the Karhunen-Loeve (KL) expansion, seek to improve efficiency through use of stochastic collocation (SC), and provide higher-order information of output values using the polynomial chaos expansion (PCE). We study and demonstrate method convergence and apply the new methods to both spatially continuous and spatially discontinuous stochastic media. New methods are shown to produce accurate solutions for reasonable computational cost for several problem when compared with existing solution methods. Spatially random media are modeled using transformations of the Gaussian-distributed KL expansion-continuous random media with a lognormal transformation and discontinuous random media with a Nataf transformation. Each transformation preserves second-order statistics for the quantity-atom density or material index, respectively-being modeled. The Nystrom method facilitates numerical solution of the KL eigenvalues and eigenvectors, and a variety of methods are investigated for sampling KL eigenfunctions as a function of solved eigenvectors. The infinite KL expansion is truncated to a finite number of terms each containing a random variable, and material realizations are created by either randomly or deterministically sampling from the random variables. Deterministic sampling is performed with either isotropic or anisotropic

  4. First-principles modeling of electromagnetic scattering by discrete and discretely heterogeneous random media

    Energy Technology Data Exchange (ETDEWEB)

    Mishchenko, Michael I., E-mail: michael.i.mishchenko@nasa.gov [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Dlugach, Janna M. [Main Astronomical Observatory of the National Academy of Sciences of Ukraine, 27 Zabolotny Str., 03680, Kyiv (Ukraine); Yurkin, Maxim A. [Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Institutskaya str. 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova 2, 630090 Novosibirsk (Russian Federation); Bi, Lei [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Cairns, Brian [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Liu, Li [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Columbia University, 2880 Broadway, New York, NY 10025 (United States); Panetta, R. Lee [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Travis, Larry D. [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Yang, Ping [Department of Atmospheric Sciences, Texas A& M University, College Station, TX 77843 (United States); Zakharova, Nadezhda T. [Trinnovim LLC, 2880 Broadway, New York, NY 10025 (United States)

    2016-05-16

    A discrete random medium is an object in the form of a finite volume of a vacuum or a homogeneous material medium filled with quasi-randomly and quasi-uniformly distributed discrete macroscopic impurities called small particles. Such objects are ubiquitous in natural and artificial environments. They are often characterized by analyzing theoretically the results of laboratory, in situ, or remote-sensing measurements of the scattering of light and other electromagnetic radiation. Electromagnetic scattering and absorption by particles can also affect the energy budget of a discrete random medium and hence various ambient physical and chemical processes. In either case electromagnetic scattering must be modeled in terms of appropriate optical observables, i.e., quadratic or bilinear forms in the field that quantify the reading of a relevant optical instrument or the electromagnetic energy budget. It is generally believed that time-harmonic Maxwell’s equations can accurately describe elastic electromagnetic scattering by macroscopic particulate media that change in time much more slowly than the incident electromagnetic field. However, direct solutions of these equations for discrete random media had been impracticable until quite recently. This has led to a widespread use of various phenomenological approaches in situations when their very applicability can be questioned. Recently, however, a new branch of physical optics has emerged wherein electromagnetic scattering by discrete and discretely heterogeneous random media is modeled directly by using analytical or numerically exact computer solutions of the Maxwell equations. Therefore, the main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell–Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell–Lorentz equations, we trace the development

  5. A continuous time random walk model for Darcy-scale anomalous transport in heterogeneous porous media.

    Science.gov (United States)

    Comolli, Alessandro; Hakoun, Vivien; Dentz, Marco

    2017-04-01

    Achieving the understanding of the process of solute transport in heterogeneous porous media is of crucial importance for several environmental and social purposes, ranging from aquifers contamination and remediation, to risk assessment in nuclear waste repositories. The complexity of this aim is mainly ascribable to the heterogeneity of natural media, which can be observed at all the scales of interest, from pore scale to catchment scale. In fact, the intrinsic heterogeneity of porous media is responsible for the arising of the well-known non-Fickian footprints of transport, including heavy-tailed breakthrough curves, non-Gaussian spatial density profiles and the non-linear growth of the mean squared displacement. Several studies investigated the processes through which heterogeneity impacts the transport properties, which include local modifications to the advective-dispersive motion of solutes, mass exchanges between some mobile and immobile phases (e.g. sorption/desorption reactions or diffusion into solid matrix) and spatial correlation of the flow field. In the last decades, the continuous time random walk (CTRW) model has often been used to describe solute transport in heterogenous conditions and to quantify the impact of point heterogeneity, spatial correlation and mass transfer on the average transport properties [1]. Open issues regarding this approach are the possibility to relate measurable properties of the medium to the parameters of the model, as well as its capability to provide predictive information. In a recent work [2] the authors have shed new light on understanding the relationship between Lagrangian and Eulerian dynamics as well as on their evolution from arbitrary initial conditions. On the basis of these results, we derive a CTRW model for the description of Darcy-scale transport in d-dimensional media characterized by spatially random permeability fields. The CTRW approach models particle velocities as a spatial Markov process, which is

  6. Electromagnetic scattering from random media

    CERN Document Server

    Field, Timothy R

    2009-01-01

    - ;The book develops the dynamical theory of scattering from random media from first principles. Its key findings are to characterize the time evolution of the scattered field in terms of stochastic differential equations, and to illustrate this framework

  7. Continuous-time random-walk model for anomalous diffusion in expanding media

    Science.gov (United States)

    Le Vot, F.; Abad, E.; Yuste, S. B.

    2017-09-01

    Expanding media are typical in many different fields, e.g., in biology and cosmology. In general, a medium expansion (contraction) brings about dramatic changes in the behavior of diffusive transport properties such as the set of positional moments and the Green's function. Here, we focus on the characterization of such effects when the diffusion process is described by the continuous-time random-walk (CTRW) model. As is well known, when the medium is static this model yields anomalous diffusion for a proper choice of the probability density function (pdf) for the jump length and the waiting time, but the behavior may change drastically if a medium expansion is superimposed on the intrinsic random motion of the diffusing particle. For the case where the jump length and the waiting time pdfs are long-tailed, we derive a general bifractional diffusion equation which reduces to a normal diffusion equation in the appropriate limit. We then study some particular cases of interest, including Lévy flights and subdiffusive CTRWs. In the former case, we find an analytical exact solution for the Green's function (propagator). When the expansion is sufficiently fast, the contribution of the diffusive transport becomes irrelevant at long times and the propagator tends to a stationary profile in the comoving reference frame. In contrast, for a contracting medium a competition between the spreading effect of diffusion and the concentrating effect of contraction arises. In the specific case of a subdiffusive CTRW in an exponentially contracting medium, the latter effect prevails for sufficiently long times, and all the particles are eventually localized at a single point in physical space. This "big crunch" effect, totally absent in the case of normal diffusion, stems from inefficient particle spreading due to subdiffusion. We also derive a hierarchy of differential equations for the moments of the transport process described by the subdiffusive CTRW model in an expanding medium

  8. Continuous-time random-walk model of transport in variably saturated heterogeneous porous media.

    Science.gov (United States)

    Zoia, Andrea; Néel, Marie-Christine; Cortis, Andrea

    2010-03-01

    We propose a unified physical framework for transport in variably saturated porous media. This approach allows fluid flow and solute migration to be treated as ensemble averages of fluid and solute particles, respectively. We consider the cases of homogeneous and heterogeneous porous materials. Within a fractal mobile-immobile continuous time random-walk framework, the heterogeneity will be characterized by algebraically decaying particle retention times. We derive the corresponding (nonlinear) continuum-limit partial differential equations and we compare their solutions to Monte Carlo simulation results. The proposed methodology is fairly general and can be used to track fluid and solutes particles trajectories for a variety of initial and boundary conditions.

  9. On the effect of random inhomogeneities in Kerr media modelled by a nonlinear Schroedinger equation

    Energy Technology Data Exchange (ETDEWEB)

    Villarroel, Javier [Facultad de Ciencias, Universidad de Salamanca, Plaza Merced s/n, E-37008 Salamanca (Spain); Montero, Miquel, E-mail: javier@usal.e, E-mail: miquel.montero@ub.ed [Departament de FIsica Fonamental, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain)

    2010-07-14

    We consider the propagation of optical beams under the interplay of dispersion and Kerr nonlinearity in optical fibres with impurities distributed at random uniformly on the fibre. By using a model based on the nonlinear Schroedinger equation we clarify how such inhomogeneities affect different aspects such as the number of solitons present and the intensity of the signal. We also obtain the mean distance for the signal to dissipate to a given level.

  10. Wave propagation and scattering in random media

    CERN Document Server

    Ishimaru, Akira

    1978-01-01

    Wave Propagation and Scattering in Random Media, Volume 2, presents the fundamental formulations of wave propagation and scattering in random media in a unified and systematic manner. The topics covered in this book may be grouped into three categories: waves in random scatterers, waves in random continua, and rough surface scattering. Random scatterers are random distributions of many particles. Examples are rain, fog, smog, hail, ocean particles, red blood cells, polymers, and other particles in a state of Brownian motion. Random continua are the media whose characteristics vary randomly an

  11. Modeling of Electromagnetic Scattering by Discrete and Discretely Heterogeneous Random Media by Using Numerically Exact Solutions of the Maxwell Equations

    Science.gov (United States)

    Dlugach, Janna M.; Mishchenko, Michael I.

    2017-01-01

    In this paper, we discuss some aspects of numerical modeling of electromagnetic scattering by discrete random medium by using numerically exact solutions of the macroscopic Maxwell equations. Typical examples of such media are clouds of interstellar dust, clouds of interplanetary dust in the Solar system, dusty atmospheres of comets, particulate planetary rings, clouds in planetary atmospheres, aerosol particles with numerous inclusions and so on. Our study is based on the results of extensive computations of different characteristics of electromagnetic scattering obtained by using the superposition T-matrix method which represents a direct computer solver of the macroscopic Maxwell equations for an arbitrary multisphere configuration. As a result, in particular, we clarify the range of applicability of the low-density theories of radiative transfer and coherent backscattering as well as of widely used effective-medium approximations.

  12. MODERN MEDIA EDUCATION MODELS

    Directory of Open Access Journals (Sweden)

    Alexander Fedorov

    2011-03-01

    Full Text Available The author supposed that media education models can be divided into the following groups:- educational-information models (the study of the theory, history, language of media culture, etc., based on the cultural, aesthetic, semiotic, socio-cultural theories of media education;- educational-ethical models (the study of moral, religions, philosophical problems relying on the ethic, religious, ideological, ecological, protectionist theories of media education;- pragmatic models (practical media technology training, based on the uses and gratifications and ‘practical’ theories of media education;- aesthetical models (aimed above all at the development of the artistic taste and enriching the skills of analysis of the best media culture examples. Relies on the aesthetical (art and cultural studies theory; - socio-cultural models (socio-cultural development of a creative personality as to the perception, imagination, visual memory, interpretation analysis, autonomic critical thinking, relying on the cultural studies, semiotic, ethic models of media education.

  13. Modern Media Education Models

    Science.gov (United States)

    Fedorov, Alexander

    2011-01-01

    The author supposed that media education models can be divided into the following groups: (1) educational-information models (the study of the theory, history, language of media culture, etc.), based on the cultural, aesthetic, semiotic, socio-cultural theories of media education; (2) educational-ethical models (the study of moral, religions,…

  14. Wave Propagation inside Random Media

    Science.gov (United States)

    Cheng, Xiaojun

    This thesis presents results of studies of wave scattering within and transmission through random and periodic systems. The main focus is on energy profiles inside quasi-1D and 1D random media. The connection between transport and the states of the medium is manifested in the equivalence of the dimensionless conductance, g, and the Thouless number which is the ratio of the average linewidth and spacing of energy levels. This equivalence and theories regarding the energy profiles inside random media are based on the assumption that LDOS is uniform throughout the samples. We have conducted microwave measurements of the longitudinal energy profiles within disordered samples contained in a copper tube supporting multiple waveguide channels with an antenna moving along a slit on the tube. These measurements allow us to determine the local density of states (LDOS) at a location which is the sum of energy from all incoming channels on both sides. For diffusive samples, the LDOS is uniform and the energy profile decays linearly as expected. However, for localized samples, we find that the LDOS drops sharply towards the middle of the sample and the energy profile does not follow the result of the local diffusion theory where the LDOS is assumed to be uniform. We analyze the field spectra into quasi-normal modes and found that the mode linewidth and the number of modes saturates as the sample length increases. Thus the Thouless number saturates while the dimensionless conductance g continues to fall with increasing length, indicating that the modes are localized near the boundaries. This is in contrast to the general believing that g and Thouless number follow the same scaling behavior. Previous measurements show that single parameter scaling (SPS) still holds in the same sample where the LDOS is suppressed te{shi2014microwave}. We explore the extension of SPS to the interior of the sample by analyzing statistics of the logrithm of the energy density ln W(x) and found that

  15. Non-diffractive beam in random media

    Science.gov (United States)

    Shiina, Tatsuo

    2017-09-01

    Beam propagation has been given important attention in a variety of applications in medicine, remote sensing and information science. Especially, the beam propagation in highly scattering media, which is called random media, is important. In general, the multiple scattering gets rid of beam characteristics, e.g., intensity distribution, phase front, and polarization. In this study, self-converging effect of annular beam was applied in random media. Diluted milk was used as random media, and the transmitted light was detected with a narrow view angle of 5.5mrad. The collimated annular beam of a few tens millimeters takes a few hundred meters to transform its beam shape into the non-diffractive beam in free space, while this transformation was shorten only to 20 cm in random media, that is, the collimated annular beam caused its transformation at only 20 cm in random media. The transformed beam kept its optical characteristics of ;non-diffractive beam;. Such transformation of the annular beam needs the appropriate condition of random media. Media concentration and propagation distance control the generation of the center peak intensity of the transformed beam. This study indicates the generation of the non-diffractive beam in random media and reveals its appropriate condition.

  16. Entanglement dynamics in random media

    Science.gov (United States)

    Menezes, G.; Svaiter, N. F.; Zarro, C. A. D.

    2017-12-01

    We study how the entanglement dynamics between two-level atoms is impacted by random fluctuations of the light cone. In our model the two-atom system is envisaged as an open system coupled with an electromagnetic field in the vacuum state. We employ the quantum master equation in the Born-Markov approximation in order to describe the completely positive time evolution of the atomic system. We restrict our investigations to the situation in which the atoms are coupled individually to two spatially separated cavities, one of which displays the emergence of light-cone fluctuations. In such a disordered cavity, we assume that the coefficients of the Klein-Gordon equation are random functions of the spatial coordinates. The disordered medium is modeled by a centered, stationary, and Gaussian process. We demonstrate that disorder has the effect of slowing down the entanglement decay. We conjecture that in a strong-disorder environment the mean life of entangled states can be enhanced in such a way as to almost completely suppress quantum nonlocal decoherence.

  17. Neutron transport in random media

    Energy Technology Data Exchange (ETDEWEB)

    Makai, M. [KFKI Atomic Energy Research Institute, Budapest (Hungary)

    1996-08-01

    The survey reviews the methods available in the literature which allow a discussion of corium recriticality after a severe accident and a characterization of the corium. It appears that to date no one has considered the eigenvalue problem, though for the source problem several approaches have been proposed. The mathematical formulation of a random medium may be approached in different ways. Based on the review of the literature, we can draw three basic conclusions. The problem of static, random perturbations has been solved. The static case is tractable by the Monte Carlo method. There is a specific time dependent case for which the average flux is given as a series expansion.

  18. Cherenkov radiation threshold in random inhomogeneous media

    CERN Document Server

    Grichine, V M

    2009-01-01

    Cherenkov radiation in media with random inhomogeneities like aerogel or Earth atmosphere is discussed. The spectral-angular distribution of Cherenkov photons emitted by relativistic charged particle and averaged over the dielectric permittivity fluctuations shows angular broadening similarly to the case of media with the photon absorption. The broadening results in the smoothing of Cherenkov threshold, and therefore media with strong photon scattering have more extended dependence of Cherenkov light output on the particle speed. It can be potentially used for the particle identification

  19. Quantum optics in multiple scattering random media

    DEFF Research Database (Denmark)

    Lodahl, Peter

    Quantum Optics in Multiple Scattering Random Media Peter Lodahl Research Center COM, Technical University of Denmark, Dk-2800 Lyngby, Denmark. Coherent transport of light in a disordered random medium has attracted enormous attention both from a fundamental and application point of view. Coherent...... quantum optics in multiple scattering media and novel fundamental phenomena have been predicted when examining quantum fluctuations instead of merely the intensity of the light [1]. Here I will present the first experimental study of the propagation of quantum noise through an elastic, multiple scattering...

  20. Mathematical Problems in Imaging in Random Media

    Science.gov (United States)

    2015-01-15

    random media but flat boundaries. 2 distribution to a random Markov diffusion P whose generator can be computed explicitly in terms of the...Note how the numerically computed weights (blue line) match those computed analytically (red). Note also that the algorithm estimates that only the first...source electromagnetic inversion. We analyzed theoretically the algorithm and assesed its performance using numerical simulations. • The solicited article

  1. Modelling Digital Media Objects

    DEFF Research Database (Denmark)

    Troelsgaard, Rasmus

    The goal of this thesis is to investigate two relevant issues regarding computational representation and classification of digital multi-media objects. With a special focus on music, a model for representation of objects comprising multiple heterogeneous data types is investigated. Necessary...

  2. A KDE-Based Random Walk Method for Modeling Reactive Transport With Complex Kinetics in Porous Media

    Science.gov (United States)

    Sole-Mari, Guillem; Fernà ndez-Garcia, Daniel; Rodríguez-Escales, Paula; Sanchez-Vila, Xavier

    2017-11-01

    In recent years, a large body of the literature has been devoted to study reactive transport of solutes in porous media based on pure Lagrangian formulations. Such approaches have also been extended to accommodate second-order bimolecular reactions, in which the reaction rate is proportional to the concentrations of the reactants. Rather, in some cases, chemical reactions involving two reactants follow more complicated rate laws. Some examples are (1) reaction rate laws written in terms of powers of concentrations, (2) redox reactions incorporating a limiting term (e.g., Michaelis-Menten), or (3) any reaction where the activity coefficients vary with the concentration of the reactants, just to name a few. We provide a methodology to account for complex kinetic bimolecular reactions in a fully Lagrangian framework where each particle represents a fraction of the total mass of a specific solute. The method, built as an extension to the second-order case, is based on the concept of optimal Kernel Density Estimator, which allows the concentrations to be written in terms of particle locations, hence transferring the concept of reaction rate to that of particle location distribution. By doing so, we can update the probability of particles reacting without the need to fully reconstruct the concentration maps. The performance and convergence of the method is tested for several illustrative examples that simulate the Advection-Dispersion-Reaction Equation in a 1-D homogeneous column. Finally, a 2-D application example is presented evaluating the need of fully describing non-bilinear chemical kinetics in a randomly heterogeneous porous medium.

  3. Optical wireless communication through random media

    Science.gov (United States)

    Arnon, Shlomi

    2011-03-01

    The growing need for high data-rate communication both through the atmosphere and the ocean (sub-sea) has stimulated considerable interest in optical wireless communication (OWC) technologies. The main advantages of OWC as compared with RF communication in the atmosphere and with acoustic communication in sub-sea applications are a) high achievable data-rate, b) small size of equipment and c) low power-consumption. On the other hand the characteristics of the communication channel in both scenarios are stochastic with high values of variance, which severely degrades OWC communication system performance. In this paper we present a tutorial discussing the effects of random media on OWC and expand on two examples: Monte-Carlo simulation for sub-sea communication and mathematical synthesis using Meijer G-function for OWC through atmospheric turbulence. These two examples demonstrate that it is possible to gain significant insights on the effects of the random channel on system performance. The results of the different analysis methods could also indicate solutions for the improvement of performance using adaptive solutions or for extending the communication range by applying a multi-hop concept. We summarize the paper with a brief review of two emerging research fields that could, surprisingly, benefit from the characteristics of light propagation through random media and its effect on the communication system performance. The first research field is trans-cutaneous OWC and the second is an unguided optical communication bus for next-generation computers.

  4. Manifolds in random media: beyond the variational approximation

    Science.gov (United States)

    Goldschmidt, Yadin Y.

    1994-01-01

    In this paper we give a closed form expression for the 1/d corrections to the selfenergy characterizing the correlation function of a manifold in random media. This amounts to the first confection beyond the variational approximation. At this time we were able to evaluate these corrections in the high temperature "phase" of the notorious toy-model describing a classical particle subject to the influence of both a harmonic potential and a random potential. Although in this phase the correct solution is replica symmetric the calculation is non-trivial. The outcome is compared with previous analytical and numerical results. The corrections diverge at the "transition" temperature.

  5. Electromagnetic Wave Propagation in Random Media

    DEFF Research Database (Denmark)

    Pécseli, Hans

    1984-01-01

    The propagation of a narrow frequency band beam of electromagnetic waves in a medium with randomly varying index of refraction is considered. A novel formulation of the governing equation is proposed. An equation for the average Green function (or transition probability) can then be derived....... A Fokker-Planck type equation is contained as a limiting case. The results are readily generalized to include the features of the random coupling model and it is argued that the present problem is particularly suited for an analysis of this type....

  6. Laser beam propagation through random media

    CERN Document Server

    Andrews, Larry C

    2005-01-01

    Since publication of the first edition of this text in 1998, there have been several new, important developments in the theory of beam wave propagation through a random medium, which have been incorporated into this second edition. Also new to this edition are models for the scintillation index under moderate-to-strong irradiance fluctuations; models for aperture averaging based on ABCD ray matrices; beam wander and its effects on scintillation; theory of partial coherence of the source; models of rough targets for ladar applications; phase fluctuations; analysis of other beam shapes; plus exp

  7. Modeling Transport in Fractured Porous Media with the Random-Walk Particle Method: The Transient Activity Range and the Particle-Transfer Probability

    Energy Technology Data Exchange (ETDEWEB)

    Lehua Pan; G.S. Bodvarsson

    2001-10-22

    Multiscale features of transport processes in fractured porous media make numerical modeling a difficult task, both in conceptualization and computation. Modeling the mass transfer through the fracture-matrix interface is one of the critical issues in the simulation of transport in a fractured porous medium. Because conventional dual-continuum-based numerical methods are unable to capture the transient features of the diffusion depth into the matrix (unless they assume a passive matrix medium), such methods will overestimate the transport of tracers through the fractures, especially for the cases with large fracture spacing, resulting in artificial early breakthroughs. We have developed a new method for calculating the particle-transfer probability that can capture the transient features of diffusion depth into the matrix within the framework of the dual-continuum random-walk particle method (RWPM) by introducing a new concept of activity range of a particle within the matrix. Unlike the multiple-continuum approach, the new dual-continuum RWPM does not require using additional grid blocks to represent the matrix. It does not assume a passive matrix medium and can be applied to the cases where global water flow exists in both continua. The new method has been verified against analytical solutions for transport in the fracture-matrix systems with various fracture spacing. The calculations of the breakthrough curves of radionuclides from a potential repository to the water table in Yucca Mountain demonstrate the effectiveness of the new method for simulating 3-D, mountain-scale transport in a heterogeneous, fractured porous medium under variably saturated conditions.

  8. A randomized trial of social media from Circulation.

    Science.gov (United States)

    Fox, Caroline S; Bonaca, Marc A; Ryan, John J; Massaro, Joseph M; Barry, Karen; Loscalzo, Joseph

    2015-01-06

    Medical journals use social media to distribute the findings of published articles. Whether social media exposure to original articles improves article impact metrics is uncertain. Articles were randomized to receive targeted social media exposure from Circulation, including postings on the journal's Facebook and Twitter feeds. The primary end point was 30-day article page views. We conducted an intention-to-treat analysis comparing article page views by the Wilcoxon Rank sum test between articles randomized to social media as compared with those in the control group, which received no social media from Circulation. Prespecified subgroups included article type (population/clinical/basic), US versus non-US corresponding author, and whether the article received an editorial. Overall, 243 articles were randomized: 121 in the social media arm and 122 in the control arm. There was no difference in median 30-day page views (409 [social media] versus 392 [control], P=0.80). No differences were observed by article type (clinical, population, or basic science; P=0.19), whether an article had an editorial (P=0.87), or whether the corresponding author was from the United States (P=0.73). A social media strategy for a cardiovascular journal did not increase the number of times an article was viewed. Further research is necessary to understand and quantify the ways in which social media can increase the impact of published cardiovascular research. © 2014 American Heart Association, Inc.

  9. Infinite range correlations of intensity in random media

    Indian Academy of Sciences (India)

    Infinite range correlations of intensity in random media. A RETZKER and B SHAPIRO. Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel. Abstract. We study a new type of long-range correlations for waves propagating in a random medium. These correlations originate from scattering events ...

  10. Statistical methods for mechanical characterization of randomly reinforced media

    Science.gov (United States)

    Tashkinov, Mikhail

    2017-12-01

    Advanced materials with heterogeneous microstructure attract extensive interest of researchers and engineers due to combination of unique properties and ability to create materials that are most suitable for each specific application. One of the challenging tasks is development of models of mechanical behavior for such materials since precision of the obtained numerical results highly depends on level of consideration of features of their heterogeneous microstructure. In most cases, numerical modeling of composite structures is based on multiscale approaches that require special techniques for establishing connection between parameters at different scales. This work offers a review of instruments of the statistics and the probability theory that are used for mechanical characterization of heterogeneous media with random positions of reinforcements. Such statistical descriptors are involved in assessment of correlations between the microstructural components and are parts of mechanical theories which require formalization of the information about microstructural morphology. Particularly, the paper addresses application of the instruments of statistics for geometry description and media reconstruction as well as their utilization in homogenization methods and local stochastic stress and strain field analysis.

  11. Random regression models

    African Journals Online (AJOL)

    zlukovi

    modelled as a quadratic regression, nested within parity. The previous lactation length was ... This proportion was mainly covered by linear and quadratic coefficients. Results suggest that RRM could .... The multiple trait models in scalar notation are presented by equations (1, 2), while equation. (3) represents the random ...

  12. Discontinuous percolation transitions in epidemic processes, surface depinning in random media, and Hamiltonian random graphs

    Science.gov (United States)

    Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter

    2012-07-01

    Discontinuous percolation transitions and the associated tricritical points are manifest in a wide range of both equilibrium and nonequilibrium cooperative phenomena. To demonstrate this, we present and relate the continuous and first-order behaviors in two different classes of models: The first are generalized epidemic processes that describe in their spatially embedded version—either on or off a regular lattice—compact or fractal cluster growth in random media at zero temperature. A random graph version of these processes is mapped onto a model previously proposed for complex social contagion. We compute detailed phase diagrams and compare our numerical results at the tricritical point in d=3 with field theory predictions of Janssen [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.70.026114 70, 026114 (2004)]. The second class consists of exponential (“Hamiltonian,” i.e., formally equilibrium) random graph models and includes the Strauss and the two-star model, where “chemical potentials” control the densities of links, triangles, or two-stars. When the chemical potentials in either graph model are O(logN), the percolation transition can coincide with a first-order phase transition in the density of links, making the former also discontinuous. Hysteresis loops can then be of mixed order, with second-order behavior for decreasing link fugacity, and a jump (first order) when it increases.

  13. Exactly averaged equations for flow and transport in random media

    Energy Technology Data Exchange (ETDEWEB)

    Shvidler, Mark; Karasaki, Kenzi [Lawrence Berkeley National Lab., Earth Sciences Division, Berkeley, CA (United States)

    2001-07-01

    It is well known that exact averaging of the equations of flow and transport in random porous media can be realized only for a small number of special, occasionally exotic, fields. On the other hand, the properties of approximate averaging methods are not yet fully understood. For example, the convergence behavior and the accuracy of truncated perturbation series. Furthermore, the calculation of the high-order perturbations is very complicated. These problems for a long time have stimulated attempts to find the answer for the question: Are there in existence some exact general and sufficiently universal forms of averaged equations? If the answer is positive, there arises the problem of the construction of these equations and analyzing them. There exist many publications related to these problems and oriented on different applications: hydrodynamics, flow and transport in porous media, theory of elasticity, acoustic and electromagnetic waves in random fields, etc. We present a method of finding the general form of exactly averaged equations for flow and transport in random fields by using (1) an assumption of the existence of Green's functions for appropriate stochastic problems, (2) some general properties of the Green's functions, and (3) the some basic information about the random fields of the conductivity, porosity and flow velocity. We present a general form of the exactly averaged non-local equations for the following cases. 1. Steady-state flow with sources in porous media with random conductivity. 2. Transient flow with sources in compressible media with random conductivity and porosity. 3. Non-reactive solute transport in random porous media. We discuss the problem of uniqueness and the properties of the non-local averaged equations, for the cases with some types of symmetry (isotropic, transversal isotropic, orthotropic) and we analyze the hypothesis of the structure non-local equations in general case of stochastically homogeneous fields

  14. Social media modeling and computing

    CERN Document Server

    Hoi, Steven CH; Boll, Susanne; Xu, Dong; Jin, Rong; King, Irwin

    2011-01-01

    Presents contributions from an international selection of preeminent experts in the field Discusses topics on social-media content analysis, and examines social-media system design and analysis Describes emerging applications of social media

  15. Lensless imaging based on coherent backscattering in random media

    Directory of Open Access Journals (Sweden)

    Lei Xu

    2014-08-01

    Full Text Available We studied lensless imaging due to coherent backscattering in random media both theoretically and experimentally. The point spread function of the lensless imaging system was derived. Parameters such as the volume fraction of the scatterer in the random scattering medium, the diameter of the scatterer, the distance between the object to be imaged and the surface of the random scattering medium were optimized to improve the image contrast and resolution. Moreover, for complicated objects, high contrast and quality images were achieved through the high-order intensity correlation measurement on the image plane, which may propel this imaging technique to practical applications.

  16. Russian and Western Media Literacy Education Models

    Directory of Open Access Journals (Sweden)

    Alexander Fedorov

    2014-04-01

    Full Text Available In different countries there is a wide range of the prospective media literacy education models, which are used in the process of education and upbringing. With that the analysis of the central models demonstrates that the most typical synthetic models belong to three groups: Group A. Media education models, representing the synthesis of the aesthetical and sociocultural models. Group B. Media education models, representing the synthesis of the aesthetical, informative and ethical models. Group C. Media education models, representing the synthesis of the sociocultural, informative and practical-pragmatic models. Therewith the models of group C are most spread and supported today in the majority of countries. Modern media education models lean towards the maximum usage of the potential possibilities of media education depending on the aims and objectives; they are characterized by the variability, options of the entire or fragmental integration into the education process.

  17. The differential susceptibility to media effects model

    NARCIS (Netherlands)

    Valkenburg, P.M.; Peter, J.

    2013-01-01

    In this theoretical article, we introduce the Differential Susceptibility to Media Effects Model (DSMM), a new, integrative model to improve our understanding of media effects. The DSMM organizes, integrates, and extends the insights developed in earlier microlevel media-effects theories. It

  18. Normalizing Social Media Texts by Combining Word Embeddings and Edit Distances in a Random Forest Regressor

    NARCIS (Netherlands)

    van der Goot, Rob

    2016-01-01

    In this work, we adapt the traditional framework for spelling correction to the more novel task of normalization of social media content. To generate possible normalization candidates, we complement the traditional approach with a word embeddings model. To rank the candidates we will use a random

  19. Digital ultrasonically encoded (DUE) optical focusing into random media

    CERN Document Server

    Tay, Jian Wei; Suzuki, Yuta; Wang, Lihong V

    2013-01-01

    Focusing light into opaque random or scattering media such as biological tissue is a much sought-after goal for biomedical applications such as photodynamic therapy, optical manipulation, and photostimulation. However, focusing with conventional lenses is restricted to one transport mean free path in scattering media, limiting both optical penetration depth and resolution. Focusing deeper is possible by using optical phase conjugation or wavefront shaping to compensate for the scattering. For practical applications, wavefront shaping offers the advantage of a robust optical system that is less sensitive to optical misalignment. Here, the phase of the incident light is spatially tailored using a phase-shifting array to pre-compensate for scattering. The challenge, then, is to determine the phase pattern which allows light to be optimally delivered to the target region. Optimization algorithms are typically employed for this purpose, with visible particles used as targets to generate feedback. However, using th...

  20. Optimal coherence for beam propagation through random media

    Science.gov (United States)

    Schulz, Timothy J.; Liu, Baoyong

    2005-08-01

    In this paper we consider the optimal coherence for beam propagation through random media. First, we demonstrate that a beam that maximizes the average receiver intensity is fully coherent, and that the upper bounds on received intensity are nearly attained by a beam that is focused for clear air. Second, we demonstrate that a beam that maximizes the scintillation index (along with other criteria that trade-off the mean and standard deviation for the received intensity) is, in general, partially coherent. We conclude with an example in which modal intensities are optimized for a beam that is constructed from Hermite-Gaussian modes.

  1. Comparison of media literacy and usual education to prevent tobacco use: a cluster randomized trial

    Science.gov (United States)

    Douglas, Erika L.; Land, Stephanie R.; Miller, Elizabeth; Fine, Michael J.

    2014-01-01

    BACKGROUND Media literacy programs have shown potential for reduction of adolescent tobacco use. We aimed to determine if an anti-smoking media literacy curriculum improves students’ media literacy and affects factors related to adolescent smoking. METHODS We recruited 1170 9th grade students from 64 classrooms in 3 public urban high schools. Students were randomized by classroom to a media literacy curriculum versus a standard educational program. In an intent-to-treat analysis, we used multi-level modeling to determine if changes in study outcomes were associated with the curricular intervention, controlling for baseline student covariates and the clustering of students within classrooms. RESULTS Among participants, mean age was 14.5 years and 51% were male, with no significant differences in baseline characteristics between groups. Smoking media literacy changed more among intervention participants compared with control participants (0.24 vs. 0.08, p media literacy curriculum is more effective than a standard educational program in teaching media literacy and improving perceptions of the true prevalence of smoking among adolescents. PMID:25099425

  2. Comparison of media literacy and usual education to prevent tobacco use: a cluster-randomized trial.

    Science.gov (United States)

    Primack, Brian A; Douglas, Erika L; Land, Stephanie R; Miller, Elizabeth; Fine, Michael J

    2014-02-01

    Media literacy programs have shown potential for reduction of adolescent tobacco use. We aimed to determine if an anti-smoking media literacy curriculum improves students' media literacy and affects factors related to adolescent smoking. We recruited 1170 9th-grade students from 64 classrooms in 3 public urban high schools. Students were randomized by classroom to a media literacy curriculum versus a standard educational program. In an intent-to-treat analysis, we used multilevel modeling to determine if changes in study outcomes were associated with the curricular intervention, controlling for baseline student covariates and the clustering of students within classrooms. Among participants, mean age was 14.5 years and 51% were male, with no significant differences in baseline characteristics between groups. Smoking media literacy changed more among intervention participants compared with control participants (0.24 vs. 0.08, p media literacy curriculum is more effective than a standard educational program in teaching media literacy and improving perceptions of the true prevalence of smoking among adolescents. © 2014, American School Health Association.

  3. Mass transport in fracture media: impact of the random function model assumed for fractures conductivity; Transporte de masa en medio fracturado: impacto del modelo estocastico de conductividad en las fracturas

    Energy Technology Data Exchange (ETDEWEB)

    Capilla, J. E.; Rodrigo, J.; Gomez Hernandez, J. J.

    2003-07-01

    Characterizing the uncertainty of flow and mass transport models requires the definition of stochastic models to describe hydrodynamic parameters. Porosity and hydraulic conductivity (K) are two of these parameters that exhibit a high degree of spatial variability. K is usually the parameter whose variability influence to a more extended degree solutes movement. In fracture media, it is critical to properly characterize K in the most altered zones where flow and solutes migration tends to be concentrated. However, K measurements use to be scarce and sparse. This fact calls to consider stochastic models that allow quantifying the uncertainty of flow and mass transport predictions. This paper presents a convective transport problem solved in a 3D block of fractured crystalline rock. the case study is defined based on data from a real geological formation. As the scarcity of K data in fractures does not allow supporting classical multi Gaussian assumptions for K in fractures, the non multi Gaussian hypothesis has been explored, comparing mass transport results for alternative Gaussian and non-Gaussian assumptions. The latter hypothesis allows reproducing high spatial connectivity for extreme values of K. This feature is present in nature, might lead to reproduce faster solute pathways, and therefore should be modeled in order to obtain reasonably safe prediction of contaminants migration in a geological formation. The results obtained for the two alternative hypotheses show a remarkable impact of the K random function model in solutes movement. (Author) 9 refs.

  4. The Models and Politics of Mobile Media

    Directory of Open Access Journals (Sweden)

    Gerard Goggin

    2008-01-01

    Full Text Available In this paper I seek to critically evaluate the models at play in an important area of new media cultures -- mobile media. By 'mobile', I mean the new technologies, cultural practices, and arrangements of production, consumption, and exchange, emerging with hand-held, networked devices --especially those based on mobile cellular networks. These mobile phone technologies are now commonly being framed as media; and so we see the appearance of objects such as mobile television, mobile film, mobile games, and mobile Internet. This much-heralded move, with its large cultural and commercial claims, raises important theoretical and political questions. To zero in on what it at stake in the shift from mobile phone to mobile media, I consider three distinct though related models that for ease of reference I will term: phones; commons; publics. Firstly, I look at the model of the telephone (latterly, telecommunications that is still strongly influential in the shaping of mobiles as they now figure as media. This is something that is not widely recognised, however -- for instance, when mobiles as simply seen as an extension of new media cultures based on ideas formed through the experience of the Internet. Secondly, I consider the model of the commons and what light it throws on the politics of mobile media. Discussions of the commons -- for instance, the lucid work of Yochai Benkler in his 2006 The Wealth of Networks -- typically take the Internet as their paradigm example. But what how does the model of commons relate to mobiles, and what might it tell us about mobile media? Thirdly, while the telephone and mobile phone also have often been modelled through the concept of 'community', mobile media encourage us to think about the different and sometimes opposed model of publics. In drawing upon recent work on publics, what I am interested here is how new kinds of publics are emerging with mobile media.

  5. Directed polymer in random media, in two dimensions: numerical study of the aging dynamics

    OpenAIRE

    Barrat, A

    1997-01-01

    Following a recent work by Yoshino, we study the aging dynamics of a directed polymer in random media, in 1+1 dimensions. Through temperature quench, and temperature cycling numerical experiments similar to the experiments on real spin glasses, we show that the observed behaviour is comparable to the one of a well known mean field spin glass model. The observation of various quantities (correlation function, ``clonation'' overlap function) leads to an analysis of the phase space landscape.

  6. Transition Fronts in Time Heterogeneous and Random Media of Ignition Type

    OpenAIRE

    Shen, Wenxian; Shen, Zhongwei

    2014-01-01

    The current paper is devoted to the investigation of wave propagation phenomenon in reaction-diffusion equations with ignition type nonlinearity in time heterogeneous and random media. It is proven that such equations in time heterogeneous media admit transition fronts or generalized traveling wave solutions with time dependent profiles and that such equations in time random media admit generalized traveling wave solutions with random profiles. Important properties of generalized traveling wa...

  7. Effects of a brief school-based media literacy intervention on digital media use in adolescents: cluster randomized controlled trial.

    Science.gov (United States)

    Walther, Birte; Hanewinkel, Reiner; Morgenstern, Matthis

    2014-09-01

    The aim of this study was to evaluate the effects of a four-session school-based media literacy curriculum on adolescent computer gaming and Internet use behavior. The study comprised a cluster randomized controlled trial with three assessments (baseline, posttest, and 12-month follow-up). At baseline, a total of 2,303 sixth and seventh grade adolescents from 27 secondary schools were assessed. Of these, 1,843 (80%) could be reached at all three assessments (Mage=12.0 years; SD=0.83). Students of the intervention group received the media literacy program Vernetzte www.Welten ("Connected www.Worlds ") implemented by trained teachers during class time. The control group attended regular class. Main outcome measures were adolescents' computer gaming and Internet use: days per month, hours per day, and addictive use patterns. Parental media monitoring and rules at home were assessed as secondary outcomes. Results of multilevel growth-curve models revealed a significant intervention effect in terms of a lower increase in self-reported gaming frequency (β = -1.10 [95% CI -2.06, -0.13]), gaming time (β = -0.27 [95% CI -0.40, -0.14]), and proportion of excessive gamers (AOR=0.21 [95% CI 0.08, 0.57]) in the intervention group. There were also significant group-time interactions for the addictive gaming scale (β=-0.08 [95% CI -0.12, -0.04]), and the Internet Addiction Scale (β = -0.06 [95% CI -0.10, -0.01]). No effect was found for days and hours of Internet use or parental media behavior. The study shows that the program Vernetzte www.Welten can influence adolescents' media use behavior. Future research should address mediating and moderating variables of program effects.

  8. Variational Calculation of Effective Parameters in Random Porous Media

    Science.gov (United States)

    Hristopulos, Dionissios T.; Christakos, George

    1998-03-01

    Effective parameters are used in stochastic hydrology and petroleum engineering as estimates of the coarse-grained behavior of fluid flow and transport. Stochastic effective parameter estimation involves averaging over the local heterogeneity. Explicit evaluation methods are often based on low order perturbation expansions. We obtain more general estimates using a variational scheme that employs auxiliary probability measures. The average over the local fluctuations is evaluated by means of the logarithm transform and the replica trick. The equations satisfied by the effective parameters are obtained variationally from an effective free energy functional. We use this method for the evaluation of the effective permeability of random porous media with Gaussian local fluctuations. The resulting equations are solved explicitly in specific cases, and the results are compared with leading-order perturbation estimates and experimental data. Explicit finite-size expressions are obtained using momentum-space filters. The implications of the finite size behavior for the scaleup problem are discussed.

  9. Monte Carlo particle transport in random media: The effects of mixing statistics

    Science.gov (United States)

    Larmier, Coline; Zoia, Andrea; Malvagi, Fausto; Dumonteil, Eric; Mazzolo, Alain

    2017-07-01

    Particle transport in random media obeying a given mixing statistics is key in several applications in nuclear reactor physics and more generally in diffusion phenomena emerging in optics and life sciences. Exact solutions for the ensemble-averaged physical observables are hardly available, and several approximate models have been thus developed, providing a compromise between the accurate treatment of the disorder-induced spatial correlations and the computational time. In order to validate these models, it is mandatory to use reference solutions in benchmark configurations, typically obtained by explicitly generating by Monte Carlo methods several realizations of random media, simulating particle transport in each realization, and finally taking the ensemble averages for the quantities of interest. In this context, intense research efforts have been devoted to Poisson (Markov) mixing statistics, where benchmark solutions have been derived for transport in one-dimensional geometries. In a recent work, we have generalized these solutions to two and three-dimensional configurations, and shown how dimension affects the simulation results. In this paper we will examine the impact of mixing statistics: to this aim, we will compare the reflection and transmission probabilities, as well as the particle flux, for three-dimensional random media obtained by using Poisson, Voronoi and Box stochastic tessellations. For each tessellation, we will furthermore discuss the effects of varying the fragmentation of the stochastic geometry, the material compositions, and the cross sections of the background materials.

  10. Stochastic dynamics modeling solute transport in porous media modeling solute transport in porous media

    CERN Document Server

    Kulasiri, Don

    2002-01-01

    Most of the natural and biological phenomena such as solute transport in porous media exhibit variability which can not be modeled by using deterministic approaches. There is evidence in natural phenomena to suggest that some of the observations can not be explained by using the models which give deterministic solutions. Stochastic processes have a rich repository of objects which can be used to express the randomness inherent in the system and the evolution of the system over time. The attractiveness of the stochastic differential equations (SDE) and stochastic partial differential equations (SPDE) come from the fact that we can integrate the variability of the system along with the scientific knowledge pertaining to the system. One of the aims of this book is to explaim some useufl concepts in stochastic dynamics so that the scientists and engineers with a background in undergraduate differential calculus could appreciate the applicability and appropriateness of these developments in mathematics. The ideas ...

  11. A Theoretical Understanding of Circular Polarization Memory in Random Media

    Science.gov (United States)

    Dark, Julia

    Radiative transport theory describes the propagation of light in random media that absorb, scatter, and emit radiation. To describe the propagation of light, the full polarization state is quantified using the Stokes parameters. For the sake of mathematical convenience, the polarization state of light is often neglected leading to the scalar radiative transport equation for the intensity only. For scalar transport theory, there is a well-established body of literature on numerical and analytic approximations to the radiative transport equation. We extend the scalar theory to the vector radiative transport equation (vRTE). In particular, we are interested in the theoretical basis for a phenomena called circular polarization memory. Circular polarization memory is the physical phenomena whereby circular polarization retains its ellipticity and handedness when propagating in random media. This is in contrast to the propagation of linear polarization in random media, which depolarizes at a faster rate, and specular reflection of circular polarization, whereby the circular polarization handedness flips. We investigate two limits that are of known interest in the phenomena of circular polarization memory. The first limit we investigate is that of forward-peaked scattering, i.e. the limit where most scattering events occur in the forward or near-forward directions. The second limit we consider is that of strong scattering and weak absorption. In the forward-peaked scattering limit we approximate the vRTE by a system of partial differential equations motivated by the scalar Fokker-Planck approximation. We call the leading order approximation the vector Fokker-Planck approximation. The vector Fokker Planck approximation predicts that strongly forward-peaked media exhibit circular polarization memory where the strength of the effect can be calculated from the expansion of the scattering matrix in special functions. In addition, we find in this limit that total intensity

  12. Media Accountability Systems: Models, proposals and outlooks

    Directory of Open Access Journals (Sweden)

    Fernando O. Paulino

    2007-06-01

    Full Text Available This paper analyzes one of the basic actions of SOS-Imprensa, the mechanism to assure Media Accountability with the goal of proposing a synthesis of models for the Brazilian reality. The article aims to address the possibilities of creating and improving mechanisms to stimulate the democratic press process and to mark out and assure freedom of speech and personal rights with respect to the media. Based on the Press Social Responsibility Theory, the hypothesis is that the experiences analyzed (Communication Council, Press Council, Ombudsman and Readers Council are alternatives for accountability, mediation and arbitration, seeking visibility, trust and public support in favor of fairer media.

  13. Competency model and standards for media education

    Directory of Open Access Journals (Sweden)

    Gerhard TULODZIECKI

    2012-12-01

    Full Text Available In Germany, educational standards for key school subjects have been developed as a consequence of the results of international comparative studies like PISA. Subsequently, supporters of interdisciplinary fields such as media education have also started calling for goals in the form of competency models and standards. In this context a competency standard model for media education will be developed with regard to the discussion about media competence and media education. In doing so the development of a competency model and the formulation of standards is described consequently as a decision making process. In this process decisions have to be made on competence areas and competence aspects to structure the model, on criteria to differentiate certain levels of competence, on the number of competence levels, on the abstraction level of standard formulations and on the tasks to test the standards. It is shown that the discussion on media education as well as on competencies and standards provides different possibilities of structuring, emphasizing and designing a competence standard model. Against this background we describe and give reasons for our decisions and our competency standards model. At the same time our contribution is meant to initiate further developments, testing and discussion.

  14. A numerical study of rays in random media. [Monte Carlo method simulation

    Science.gov (United States)

    Youakim, M. Y.; Liu, C. H.; Yeh, K. C.

    1973-01-01

    Statistics of electromagnetic rays in a random medium are studied numerically by the Monte Carlo method. Two dimensional random surfaces with prescribed correlation functions are used to simulate the random media. Rays are then traced in these sample media. Statistics of the ray properties such as the ray positions and directions are computed. Histograms showing the distributions of the ray positions and directions at different points along the ray path as well as at given points in space are given. The numerical experiment is repeated for different cases corresponding to weakly and strongly random media with isotropic and anisotropic irregularities. Results are compared with those derived from theoretical investigations whenever possible.

  15. Applying East Asian Media Diplomacy Models to African Media: A ...

    African Journals Online (AJOL)

    The last two decades have seen the extensive expansion of South African and Nigerian media on the African continent. However, while the link between media and diplomacy, and the role of media in visualising the state for foreign audiences have received a lot of scholarly attention internationally, relatively little work has ...

  16. A functional renormalization method for wave propagation in random media

    Science.gov (United States)

    Lamagna, Federico; Calzetta, Esteban

    2017-08-01

    We develop the exact renormalization group approach as a way to evaluate the effective speed of the propagation of a scalar wave in a medium with random inhomogeneities. We use the Martin-Siggia-Rose formalism to translate the problem into a non equilibrium field theory one, and then consider a sequence of models with a progressively lower infrared cutoff; in the limit where the cutoff is removed we recover the problem of interest. As a test of the formalism, we compute the effective dielectric constant of an homogeneous medium interspersed with randomly located, interpenetrating bubbles. A simple approximation to the renormalization group equations turns out to be equivalent to a self-consistent two-loops evaluation of the effective dielectric constant.

  17. Directed polymer in random media in two dimensions: Numerical study of the aging dynamics

    Science.gov (United States)

    Barrat, A.

    1997-05-01

    Following a recent work by Yoshino [J. Phys. A 29, 1421 (1996)], we study the aging dynamics of a directed polymer in random media, in 1+1 dimensions. Through temperature quench and temperature cycling numerical experiments similar to the experiments on real spin glasses, we show that the observed behavior is comparable to that of a well-known mean-field spin glass model. The observation of various quantities (correlation function, ``clonation'' overlap function, etc.) leads to an analysis of the phase space landscape.

  18. Randomized Item Response Theory Models

    NARCIS (Netherlands)

    Fox, Gerardus J.A.

    2005-01-01

    The randomized response (RR) technique is often used to obtain answers on sensitive questions. A new method is developed to measure latent variables using the RR technique because direct questioning leads to biased results. Within the RR technique is the probability of the true response modeled by

  19. Modifying media content for preschool children: a randomized controlled trial.

    Science.gov (United States)

    Christakis, Dimitri A; Garrison, Michelle M; Herrenkohl, Todd; Haggerty, Kevin; Rivara, Frederick P; Zhou, Chuan; Liekweg, Kimberly

    2013-03-01

    Although previous studies have revealed that preschool-aged children imitate both aggression and prosocial behaviors on screen, there have been few population-based studies designed to reduce aggression in preschool-aged children by modifying what they watch. We devised a media diet intervention wherein parents were assisted in substituting high quality prosocial and educational programming for aggression-laden programming without trying to reduce total screen time. We conducted a randomized controlled trial of 565 parents of preschool-aged children ages 3 to 5 years recruited from community pediatric practices. Outcomes were derived from the Social Competence and Behavior Evaluation at 6 and 12 months. At 6 months, the overall mean Social Competence and Behavior Evaluation score was 2.11 points better (95% confidence interval [CI]: 0.78-3.44) in the intervention group as compared with the controls, and similar effects were observed for the externalizing subscale (0.68 [95% CI: 0.06-1.30]) and the social competence subscale (1.04 [95% CI: 0.34-1.74]). The effect for the internalizing subscale was in a positive direction but was not statistically significant (0.42 [95% CI: -0.14 to 0.99]). Although the effect sizes did not noticeably decay at 12 months, the effect on the externalizing subscale was no longer statistically significant (P = .05). In a stratified analysis of the effect on the overall scores, low-income boys appeared to derive the greatest benefit (6.48 [95% CI: 1.60-11.37]). An intervention to reduce exposure to screen violence and increase exposure to prosocial programming can positively impact child behavior.

  20. The weighted random graph model

    Science.gov (United States)

    Garlaschelli, Diego

    2009-07-01

    We introduce the weighted random graph (WRG) model, which represents the weighted counterpart of the Erdos-Renyi random graph and provides fundamental insights into more complicated weighted networks. We find analytically that the WRG is characterized by a geometric weight distribution, a binomial degree distribution and a negative binomial strength distribution. We also characterize exactly the percolation phase transitions associated with edge removal and with the appearance of weighted subgraphs of any order and intensity. We find that even this completely null model displays a percolation behaviour similar to what is observed in real weighted networks, implying that edge removal cannot be used to detect community structure empirically. By contrast, the analysis of clustering successfully reveals different patterns between the WRG and real networks.

  1. Can Babies Learn to Read? A Randomized Trial of Baby Media

    Science.gov (United States)

    Neuman, Susan B.; Kaefer, Tanya; Pinkham, Ashley; Strouse, Gabrielle

    2014-01-01

    Targeted to children as young as 3 months old, there is a growing number of baby media products that claim to teach babies to read. This randomized controlled trial was designed to examine this claim by investigating the effects of a best-selling baby media product on reading development. One hundred and seventeen infants, ages 9 to 18 months,…

  2. Remarks on the Radiative Transfer Approach to Scattering of Electromagnetic Waves in Layered Random Media

    Science.gov (United States)

    2010-03-01

    AFRL-RY-HS-TR-2010-0029 REMARKS ON THE RADIATIVE TRANSFER APPROACH TO SCATTERING OF ELECTROMAGNETIC WAVES IN LAYERED RANDOM MEDIA...TRANSFER APPROACH TO SCATTERING OF ELECTROMAGNETIC WAVES IN LAYERED RANDOM MEDIA 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT NUMBER 5c. PROGRAM...Beckmann and A. Spizzichino. The Scattering of Electromagnetic Waves from Rough Surfaces. Artech House, Norwood, Massachusetts, 1987. [3] G. S. Brown. A

  3. Dynamic randomization and a randomization model for clinical trials data.

    Science.gov (United States)

    Kaiser, Lee D

    2012-12-20

    Randomization models are useful in supporting the validity of linear model analyses applied to data from a clinical trial that employed randomization via permuted blocks. Here, a randomization model for clinical trials data with arbitrary randomization methodology is developed, with treatment effect estimators and standard error estimators valid from a randomization perspective. A central limit theorem for the treatment effect estimator is also derived. As with permuted-blocks randomization, a typical linear model analysis provides results similar to the randomization model results when, roughly, unit effects display no pattern over time. A key requirement for the randomization inference is that the unconditional probability that any patient receives active treatment is constant across patients; when this probability condition is violated, the treatment effect estimator is biased from a randomization perspective. Most randomization methods for balanced, 1 to 1, treatment allocation satisfy this condition. However, many dynamic randomization methods for planned unbalanced treatment allocation, like 2 to 1, do not satisfy this constant probability condition, and these methods should be avoided. Copyright © 2012 John Wiley & Sons, Ltd.

  4. The New Digital Media Value Network: Proposing an Interactive Model of Digital Media Value Activities

    Directory of Open Access Journals (Sweden)

    Sylvia Chan-Olmsted

    2016-07-01

    Full Text Available This study models the dynamic nature of today’s media markets using the framework of value-adding activities in the provision and consumption of media products. The proposed user-centric approach introduces the notion that the actions of external users, social media, and interfaces affect the internal value activities of media firms via a feedback loop, and therefore should themselves be considered value activities. The model also suggests a more comprehensive list of indicators for value assessment.

  5. A Social Information Processing Model of Media Use in Organizations.

    Science.gov (United States)

    Fulk, Janet; And Others

    1987-01-01

    Presents a model to examine how social influence processes affect individuals' attitudes toward communication media and media use behavior, integrating two research areas: media use patterns as the outcome of objectively rational choices and social information processing theory. Asserts (in a synthesis) that media characteristics and attitudes are…

  6. The media effect in Axelrod's model explained

    Science.gov (United States)

    Peres, L. R.; Fontanari, J. F.

    2011-11-01

    We revisit the problem of introducing an external global field —the mass media— in Axelrod's model of social dynamics, where in addition to their nearest neighbors, the agents can interact with a virtual neighbor whose cultural features are fixed from the outset. The finding that this apparently homogenizing field actually increases the cultural diversity has been considered a puzzle since the phenomenon was first reported more than a decade ago. Here we offer a simple explanation for it, which is based on the pedestrian observation that Axelrod's model exhibits more cultural diversity, i.e., more distinct cultural domains, when the agents are allowed to interact solely with the media field than when they can interact with their neighbors as well. In this perspective, it is the local homogenizing interactions that work towards making the absorbing configurations less fragmented as compared with the extreme situation in which the agents interact with the media only.

  7. Randomized Controlled Trial of Social Media: Effect of Increased Intensity of the Intervention.

    Science.gov (United States)

    Fox, Caroline S; Gurary, Ellen B; Ryan, John; Bonaca, Marc; Barry, Karen; Loscalzo, Joseph; Massaro, Joseph

    2016-04-27

    A prior randomized controlled trial of social media exposure at Circulation determined that social media did not increase 30-day page views. Whether insufficient social media intensity contributed to these results is uncertain. Original article manuscripts were randomized to social media exposure compared with no social media exposure (control) at Circulation beginning in January 2015. Social media exposure consisted of Facebook and Twitter posts on the journal's accounts. To increase social media intensity, a larger base of followers was built using advertising and organic growth, and posts were presented in triplicate and boosted on Facebook and retweeted on Twitter. The primary outcome was 30-day page views. Stopping rules were established at the point that 50% of the manuscripts were randomized and had 30-day follow-up to compare groups on 30-day page views. The trial was stopped for futility on September 26, 2015. Overall, 74 manuscripts were randomized to receive social media exposure, and 78 manuscripts were randomized to the control arm. The intervention and control arms were similar based on article type (P=0.85), geographic location of the corresponding author (P=0.33), and whether the manuscript had an editorial (P=0.80). Median number of 30-day page views was 499.5 in the social media arm and 450.5 in the control arm; there was no evidence of a treatment effect (P=0.38). There were no statistically significant interactions of treatment by manuscript type (P=0.86), by corresponding author (P=0.35), by trimester of publication date (P=0.34), or by editorial status (P=0.79). A more intensive social media strategy did not result in increased 30-day page views of original research. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  8. Modeling Trolling in Social Media Conversations

    OpenAIRE

    Mojica, Luis Gerardo

    2016-01-01

    Social media websites, electronic newspapers and Internet forums allow visitors to leave comments for others to read and interact. This exchange is not free from participants with malicious intentions, who troll others by positing messages that are intended to be provocative, offensive, or menacing. With the goal of facilitating the computational modeling of trolling, we propose a trolling categorization that is novel in the sense that it allows comment-based analysis from both the trolls' an...

  9. Condition for invariant spectrum of an electromagnetic wave scattered from an anisotropic random media.

    Science.gov (United States)

    Li, Jia; Wu, Pinghui; Chang, Liping

    2015-08-24

    Within the accuracy of the first-order Born approximation, sufficient conditions are derived for the invariance of spectrum of an electromagnetic wave, which is generated by the scattering of an electromagnetic plane wave from an anisotropic random media. We show that the following restrictions on properties of incident fields and the anisotropic media must be simultaneously satisfied: 1) the elements of the dielectric susceptibility matrix of the media must obey the scaling law; 2) the spectral components of the incident field are proportional to each other; 3) the second moments of the elements of the dielectric susceptibility matrix of the media are inversely proportional to the frequency.

  10. A simple homogeneous model for regular and irregular metallic wire media samples

    Science.gov (United States)

    Kosulnikov, S. Y.; Mirmoosa, M. S.; Simovski, C. R.

    2018-02-01

    To simplify the solution of electromagnetic problems with wire media samples, it is reasonable to treat them as the samples of a homogeneous material without spatial dispersion. The account of spatial dispersion implies additional boundary conditions and makes the solution of boundary problems difficult especially if the sample is not an infinitely extended layer. Moreover, for a novel type of wire media - arrays of randomly tilted wires - a spatially dispersive model has not been developed. Here, we introduce a simplistic heuristic model of wire media samples shaped as bricks. Our model covers WM of both regularly and irregularly stretched wires.

  11. A Mixed Effects Randomized Item Response Model

    Science.gov (United States)

    Fox, J.-P.; Wyrick, Cheryl

    2008-01-01

    The randomized response technique ensures that individual item responses, denoted as true item responses, are randomized before observing them and so-called randomized item responses are observed. A relationship is specified between randomized item response data and true item response data. True item response data are modeled with a (non)linear…

  12. Development of Animal Models of Otitis Media

    OpenAIRE

    Park, Moo Kyun; Lee, Byung Don

    2013-01-01

    Otitis media is defined as inflammation of the middle ear, including the auditory ossicles and the Eustachian tube. Otitis media is a major health problem in many societies. The causes of otitis media includes infection and anatomic/physiologic, host, and environmental factors. In general, otitis media is a childhood disease, and anatomic and physiologic changes have great effects on its development. Thus, in vitro or human experimental studies of otitis media are difficult. Several experimen...

  13. Electrical generation of stationary light in random scattering media

    Science.gov (United States)

    Redmond, S. M.; Armstrong, G. L.; Chan, H.-Y.; Mattson, E.; Mock, A.; Li, B.; Potts, J. R.; Cui, M.; Rand, S. C.; Oliveira, S. L.; Marchal, J.; Hinklin, T.; Laine, R. M.

    2004-01-01

    In recent years there has been great interest in controlling the speed of propagation of electromagnetic waves. In gases and crystals, coherent techniques have been applied to alter the speed of light without changing the physical or chemical structure of the medium. Also, light transmitted by highly disordered solids has exhibited signatures of Anderson localization, indicating the existence of a regime of ``stopped'' light that is mediated by random elastic scattering. However, to date, light has not been generated in a random medium as a pointlike excitation that is fixed in space from the outset. Here we report experimental evidence for the electrical generation and confinement of light within nanosized volumes of a random dielectric scattering medium in which a population inversion has been established, and discuss the properties of these novel light sources.

  14. Modeling for write synchronization in bit patterned media recording

    Science.gov (United States)

    Lin, Maria Yu; Chan, Kheong Sann; Chua, Melissa; Zhang, Songhua; Kui, Cai; Elidrissi, Moulay Rachid

    2012-04-01

    Bit patterned media recording (BPMR) is a contender for next generation technology after conventional granular magnetic recording (CGMR) can no longer sustain the continued areal density growth. BPMR has several technological hurdles that need to be overcome, among them is solving the problem of write synchronization. With CGMR, grains are randomly distributed and occur almost all over the media. In contrast, BPMR has grains patterned into a regular lattice on the media with an approximate 50% duty cycle. Hence only about a quarter of the area is filled with magnetic material. During writing, the clock must be synchronized to the islands or the written in error rate becomes unacceptably large and the system fails. Maintaining synchronization during writing is a challenge as the system is not able to read and write simultaneously. Hence reading must occur periodically between the writing frequently enough to re-synchronize the writing clock to the islands. In this work, we study the requirements on the lengths of the synchronization and data sectors in a BPMR system using an advanced model for BPMR, and taking into consideration different spindle motor speed variations, which is the main cause of the mis-synchronization.

  15. Model of Market Share Affected by Social Media Reputation

    Science.gov (United States)

    Ishii, Akira; Kawahata, Yasuko; Goto, Ujo

    Proposal of market theory to put the effect of social media into account is presented in this paper. The standard market share model in economics is employed as a market theory and the effect of social media is considered quantitatively using the mathematical model for hit phenomena. Using this model, we can estimate the effect of social media in market share as a simple market model simulation using our proposed method.

  16. Effects of aggregation on the permittivity of random media containing monodisperse spheres

    Science.gov (United States)

    Doyle, Timothy E.; Tew, Adam T.; Jain, Rahul; Robinson, David A.

    2009-12-01

    Numerical simulations were used to calculate the effective permittivities of three-dimensional random particle suspensions containing up to 2440 particles and exhibiting two types of particle aggregation. The particles were modeled as 200 μm spheres that were aggregated into either large spherical clusters or into foam-type microstructures with large spherical voids. Multiple scattering of 0.01-10.0 GHz electromagnetic fields was simulated using a first-principles iterative multipole approach with matrix and particle permittivities of 1.0 and 8.5, respectively. The computational results showed both significant and highly significant trends. Aggregation into spherical clusters decreased the effective permittivity by up to 3.2±0.2%, whereas aggregation into foam-type microstructures increased the effective permittivity by up to 3.0±1.6%. The effective permittivity trends exhibited little change with frequency. These results were compared to effective medium approximations that predicted higher permittivities than those from the simulations and showed opposite trends for cluster aggregation. Three theories are proposed to explain the simulation results. The first theory invokes a waveguidelike mechanism. The simulations indicate that the wave fields propagate more through the continuous paths of greater or lesser particle density created by aggregation, rather than through the isolated particle clusters or large voids. This quasicontinuous phase, or quasimatrix, therefore behaves like a random waveguide structure in the material. A second theory is proposed where the quasicontinuous phase governs the behavior of the system by a percolationlike process. In this theory, the multipole interactions are modeled as the percolation of virtual charges tunneling from one particle to another. A third mechanism for the permittivity changes is also proposed involving collective polarization effects associated with the particle clusters or large voids. The simulation results

  17. Infinite range correlations of intensity in random media

    Indian Academy of Sciences (India)

    We study a new type of long-range correlations for waves propagating in a random medium. These correlations originate from scattering events which take place close to a point source. The scattered waves propagate by diffusion to distant regions. In this way long range correlations, between any pair of distant points, are ...

  18. Upscaling solute transport in naturally fractured porous media with the continuous time random walk method

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, S.; Cortis, A.; Birkholzer, J.T.

    2010-04-01

    Solute transport in fractured porous media is typically 'non-Fickian'; that is, it is characterized by early breakthrough and long tailing and by nonlinear growth of the Green function-centered second moment. This behavior is due to the effects of (1) multirate diffusion occurring between the highly permeable fracture network and the low-permeability rock matrix, (2) a wide range of advection rates in the fractures and, possibly, the matrix as well, and (3) a range of path lengths. As a consequence, prediction of solute transport processes at the macroscale represents a formidable challenge. Classical dual-porosity (or mobile-immobile) approaches in conjunction with an advection-dispersion equation and macroscopic dispersivity commonly fail to predict breakthrough of fractured porous media accurately. It was recently demonstrated that the continuous time random walk (CTRW) method can be used as a generalized upscaling approach. Here we extend this work and use results from high-resolution finite element-finite volume-based simulations of solute transport in an outcrop analogue of a naturally fractured reservoir to calibrate the CTRW method by extracting a distribution of retention times. This procedure allows us to predict breakthrough at other model locations accurately and to gain significant insight into the nature of the fracture-matrix interaction in naturally fractured porous reservoirs with geologically realistic fracture geometries.

  19. Exactly averaged stochastic equations for flow and transport in random media

    Energy Technology Data Exchange (ETDEWEB)

    Shvidler, Mark; Karasaki, Kenzi

    2001-11-30

    It is well known that exact averaging of the equations of flow and transport in random porous media are at present realized only for a small number of special, occasionally exotic, fields. On the other hand, the properties of approximate averaging methods are not yet fully understood. For example, the convergence behavior and the accuracy of truncated perturbation series are not well known. Furthermore, the calculation of the high-order perturbations is very complicated. These problems for a long time have stimulated attempts to find the answer for the question: Are there in existence some exact general and sufficiently universal forms of averaged equations? If the answer is positive, there arises the problem of the construction of these equations and analyzing them. There exist many publications related to these problems and oriented on different applications: hydrodynamics, flow and transport in porous media, theory of elasticity, acoustic and electromagnetic waves in random fields, etc. We present a method of finding some general forms of exactly averaged equations for flow and transport in random fields by using (1) an assumption of the existence of Green's functions for appropriate stochastic problems, (2 ) some general properties of the Green's functions, and (3) the some basic information about the random fields of the conductivity, porosity and flow velocity. We present some general forms of the exactly averaged non-local equations for the following cases. 1. Steady-state flow with sources in porous media with random conductivity. 2. Transient flow with sources in compressible media with random conductivity and porosity. 3. Non-reactive solute transport in random porous media. We discuss the problem of uniqueness and the properties of the non-local averaged equations, for the cases with some types of symmetry (isotropic, transversal isotropic, orthotropic) and we analyze the hypothesis of the structure of non-local equations in a general case of

  20. The Journey of Business Model Innovation in Media Agencies

    DEFF Research Database (Denmark)

    Jensen, Henrik; Sund, Kristian J.

    New digital entrants in the media industry have changed the competitive landscape for advertisers and media alike. In particular, over the past decade media agencies have grown more rapidly than the media market as a whole, securing a larger share of the value generated in the advertising value...... chain. Based on secondary data and in-depth interviews with 11 Danish media agency CEOs, and using the nine building blocks suggested in the business model canvas framework of Osterwalder and Pigneur (2010), we develop a grounded process model describing how these agencies have altered their business...

  1. Modeling Endovascular Coils as Heterogeneous Porous Media

    Science.gov (United States)

    Yadollahi Farsani, H.; Herrmann, M.; Chong, B.; Frakes, D.

    2016-12-01

    Minimally invasive surgeries are the stat-of-the-art treatments for many pathologies. Treating brain aneurysms is no exception; invasive neurovascular clipping is no longer the only option and endovascular coiling has introduced itself as the most common treatment. Coiling isolates the aneurysm from blood circulation by promoting thrombosis within the aneurysm. One approach to studying intra-aneurysmal hemodynamics consists of virtually deploying finite element coil models and then performing computational fluid dynamics. However, this approach is often computationally expensive and requires extensive resources to perform. The porous medium approach has been considered as an alternative to the conventional coil modeling approach because it lessens the complexities of computational fluid dynamics simulations by reducing the number of mesh elements needed to discretize the domain. There have been a limited number of attempts at treating the endovascular coils as homogeneous porous media. However, the heterogeneity associated with coil configurations requires a more accurately defined porous medium in which the porosity and permeability change throughout the domain. We implemented this approach by introducing a lattice of sample volumes and utilizing techniques available in the field of interactive computer graphics. We observed that the introduction of the heterogeneity assumption was associated with significant changes in simulated aneurysmal flow velocities as compared to the homogeneous assumption case. Moreover, as the sample volume size was decreased, the flow velocities approached an asymptotical value, showing the importance of the sample volume size selection. These results demonstrate that the homogeneous assumption for porous media that are inherently heterogeneous can lead to considerable errors. Additionally, this modeling approach allowed us to simulate post-treatment flows without considering the explicit geometry of a deployed endovascular coil mass

  2. Reporting of Randomized Trials in Common Cancers in the Lay Media.

    Science.gov (United States)

    Ribnikar, Domen; Goldvaser, Hadar; Ocana, Alberto; Templeton, Arnoud J; Seruga, Bostjan; Amir, Eitan

    2018-01-01

    Limited data exist about the role of the lay media in the dissemination of results of randomized controlled trials (RCTs) in common cancers. Completed phase III RCTs evaluating new drugs in common cancers between January 2005 and October 2016 were identified from ClinicalTrials.gov. Lay media reporting was identified by searching LexisNexis Academic. Scientific reporting was defined as presentation at an academic conference or publication in full. Associations between reporting in the lay media before scientific reporting and study design and sponsorship were evaluated using logistic regression. Of 180 RCTs identified, 52% were reported in the lay media and in 27%, lay media reporting occurred before scientific reporting with an increasing trend over time (p = 0.009). Reporting in the lay media before scientific reporting was associated with positive results (OR: 2.10, p = 0.04), targeted therapy compared to chemotherapy (OR: 4.75, p = 0.006), immunotherapy compared to chemotherapy (OR: 7.60, p = 0.02), and prostate cancer compared to breast cancer (OR: 3.25, p = 0.02). Over a quarter of all RCTs in common cancers are reported in the lay media before they are reported scientifically with an increasing proportion over time. Positive trials, studies in prostate cancer, and trials of immunotherapy are associated with early reporting in the lay media. © 2017 S. Karger AG, Basel.

  3. Prestack exploding reflector modeling and migration in TI media

    KAUST Repository

    Wang, H.

    2014-01-01

    Prestack depth migration in anisotropic media, especially those that exhibit tilt, can be costly using reverse time migration (RTM). We present two-way spectral extrapolation of prestack exploding reflector modeling and migration (PERM) in acoustic transversely isotropic (TI) media. We construct systematic ways to evaluate phase angles and phase velocities in dip oriented TI (DTI), vertical TI (VTI) and tilted TI (TTI) media. Migration results from the Marmousi VTI model and the BP2007 TTI model show the feasibility of our approach.

  4. Multilevel and quasi-Monte Carlo methods for uncertainty quantification in particle travel times through random heterogeneous porous media.

    Science.gov (United States)

    Crevillén-García, D; Power, H

    2017-08-01

    In this study, we apply four Monte Carlo simulation methods, namely, Monte Carlo, quasi-Monte Carlo, multilevel Monte Carlo and multilevel quasi-Monte Carlo to the problem of uncertainty quantification in the estimation of the average travel time during the transport of particles through random heterogeneous porous media. We apply the four methodologies to a model problem where the only input parameter, the hydraulic conductivity, is modelled as a log-Gaussian random field by using direct Karhunen-Loéve decompositions. The random terms in such expansions represent the coefficients in the equations. Numerical calculations demonstrating the effectiveness of each of the methods are presented. A comparison of the computational cost incurred by each of the methods for three different tolerances is provided. The accuracy of the approaches is quantified via the mean square error.

  5. Polymer Dynamics in Random Media, Replica Theory, Ternary Systems: Mappings and Equivalences

    NARCIS (Netherlands)

    U. Ebert (Ute); L. Schäfer

    1994-01-01

    htmlabstractFor polymer dynamics in quenched random media a renormalizability proof is lacking and calculations are lengthy. We here propose and define the static and the ergodic limit of the dynamic theory, and show, that these limits are equivalent to well-known renormalizable static polymer

  6. Elliptic random-walk equation for suspension and tracer transport in porous media

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Bedrikovetsky, P. G.

    2008-01-01

    We propose a new approach to transport of the suspensions and tracers in porous media. The approach is based on a modified version of the continuous time random walk (CTRW) theory. In the framework of this theory we derive an elliptic transport equation. The new equation contains the time and the...

  7. Analysis of a non-diffractive beam generated from an annular beam in random media

    Science.gov (United States)

    Peng, Ziqi; Shiina, Tatsuo

    2017-11-01

    An annular beam has the ability to self-transform into a non-diffractive beam when it propagates in air at a long distance. In our previous study, we propagated an annular beam in random media and obtained a non-diffractive beam at a short propagation distance of a few tens centimeters by adjusting the concentration of random media and narrowing the view angle of the receiver. In this paper, we aim to analyze the components and characteristics of a non-diffractive beam and elucidate how the non-diffractive beam is generated in random media. The intensity variation of the scattered waveform is examined when the distance between the receiver and the back plane of a medium tank is changed. The waveform scattered in random media is constructed from forward scattering light at the center and multiple scattering light in the surrounding part. The forward scattering light at the center generates the non-diffractive beam. In numerical analysis based on diffusion theory, the calculation result of the non-diffractive beam shows agreement with the experimental result.

  8. Synthetic benchmark for modeling flow in 3D fractured media

    Science.gov (United States)

    de Dreuzy, Jean-Raynald; Pichot, Géraldine; Poirriez, Baptiste; Erhel, Jocelyne

    2013-01-01

    Intensity and localization of flows in fractured media have promoted the development of a large range of different modeling approaches including Discrete Fracture Networks, pipe networks and equivalent continuous media. While benchmarked usually within site studies, we propose an alternative numerical benchmark based on highly-resolved Discrete Fracture Networks (DFNs) and on a stochastic approach. Test cases are built on fractures of different lengths, orientations, aspect ratios and hydraulic apertures, issuing the broad ranges of topological structures and hydraulic properties classically observed. We present 18 DFN cases, with 10 random simulations by case. These 180 DFN structures are provided and fully documented. They display a representative variety of the configurations that challenge the numerical methods at the different stages of discretization, mesh generation and system solving. Using a previously assessed mixed hybrid finite element method (Erhel et al., 2009a), we systematically provide reference flow and head solutions. Because CPU and memory requirements stem mainly from system solving, we study direct and iterative sparse linear solvers. We show that the most cpu-time efficient method is a direct multifrontal method for small systems, while conjugate gradient preconditioned by algebraic multrigrid is more relevant at larger sizes. Available results can be used further as references for building up alternative numerical and physical models in both directions of improving accuracy and efficiency.

  9. The parabolic Anderson model random walk in random potential

    CERN Document Server

    König, Wolfgang

    2016-01-01

    This is a comprehensive survey on the research on the parabolic Anderson model – the heat equation with random potential or the random walk in random potential – of the years 1990 – 2015. The investigation of this model requires a combination of tools from probability (large deviations, extreme-value theory, e.g.) and analysis (spectral theory for the Laplace operator with potential, variational analysis, e.g.). We explain the background, the applications, the questions and the connections with other models and formulate the most relevant results on the long-time behavior of the solution, like quenched and annealed asymptotics for the total mass, intermittency, confinement and concentration properties and mass flow. Furthermore, we explain the most successful proof methods and give a list of open research problems. Proofs are not detailed, but concisely outlined and commented; the formulations of some theorems are slightly simplified for better comprehension.

  10. Modeling fluorescent light distributions in scattering media

    Science.gov (United States)

    Phillips, Kevin G.; Jacques, Steven L.

    2010-02-01

    It is hoped that the non-invasive optical characterization of physiological features of normal and diseased epithelia can be assessed through the fluorescent emission of such tissues. With a high percentage of cancers arising in the epithelium, the characterization of carcinogenesis in such tissues is imperative. Fluorescent emission from the epithelium, e.g. oral mucosa, has been shown to be sensitive to physiological features, such as cellular morphology, and the amount and types of biochemical agents present in the tissue. Efforts to distinguish the spectral signatures of diseased and healthy states of tissues from fluorescence have been confounded by the distortion of the intrinsic fluorescent signature as a result of wavelength dependent absorption and scattering within the tissue. Theoretical models of light propagation in biological media are required for understanding the distortion of the intrinsic fluorescence arising from compromised tissues. In this work we model the distortion of the intrinsic fluorescence emitted from a tissue with wavelength dependent optical properties, arising from varying blood and water content, using the radiative transport equation. As an example, we demonstrate the ability of blood and water content to distort the signal of a white light source as it is embedded deeper into a tissue.

  11. Overlap Synchronisation in Multipartite Random Energy Models

    Science.gov (United States)

    Genovese, Giuseppe; Tantari, Daniele

    2017-12-01

    In a multipartite random energy model, made of a number of coupled generalised random energy models (GREMs), we determine the joint law of the overlaps in terms of the ones of the single GREMs. This provides the simplest example of the so-called overlap synchronisation.

  12. Media Exposure: How Models Simplify Sampling

    DEFF Research Database (Denmark)

    Mortensen, Peter Stendahl

    1998-01-01

    In media planning, the distribution of exposures to more ad spots in more media (print, TV, radio) is crucial to the evaluation of the campaign. If such information should be sampled, it would only be possible in expensive panel-studies (eg TV-meter panels). Alternatively, the distribution...

  13. Numerically Exact Computer Simulations of Light Scattering by Densely Packed, Random Particulate Media

    Science.gov (United States)

    Dlugach, Janna M.; Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

    2011-01-01

    Direct computer simulations of electromagnetic scattering by discrete random media have become an active area of research. In this progress review, we summarize and analyze our main results obtained by means of numerically exact computer solutions of the macroscopic Maxwell equations. We consider finite scattering volumes with size parameters in the range, composed of varying numbers of randomly distributed particles with different refractive indices. The main objective of our analysis is to examine whether all backscattering effects predicted by the low-density theory of coherent backscattering (CB) also take place in the case of densely packed media. Based on our extensive numerical data we arrive at the following conclusions: (i) all backscattering effects predicted by the asymptotic theory of CB can also take place in the case of densely packed media; (ii) in the case of very large particle packing density, scattering characteristics of discrete random media can exhibit behavior not predicted by the low-density theories of CB and radiative transfer; (iii) increasing the absorptivity of the constituent particles can either enhance or suppress typical manifestations of CB depending on the particle packing density and the real part of the refractive index. Our numerical data strongly suggest that spectacular backscattering effects identified in laboratory experiments and observed for a class of high-albedo Solar System objects are caused by CB.

  14. Low-coherence interferometry as a method for assessing the transport parameters in randomly inhomogeneous media

    Science.gov (United States)

    Zimnyakov, D. A.; Sina, J. S.; Yuvchenko, S. A.; Isaeva, E. A.; Chekmasov, S. P.; Ushakova, O. V.

    2014-01-01

    The specific features of using low-coherence interferometric probing of layers in randomly inhomogeneous media for determination of the radiation propagation transport length both in diffuse regime and in the case of optically thin media are discussed. The transport length is determined by the rate of exponential decay of the interference signal with the increase in the path length difference between the light beams in the reference arm of the low-coherence interferometer and in the object arm, containing the probed layer as a diffuse reflector. The results are presented of experimental testing of the discussed approach with the use of layers of densely packed titanium dioxide nanoparticles and polytetrafluoroethylene.

  15. Eigenview on Jones matrix models of homogeneous anisotropic media

    Directory of Open Access Journals (Sweden)

    Savenkov S.

    2010-06-01

    Full Text Available The polarization of light when it passes through optical medium can change as a result of change in the amplitude (dichroism or phase shift (birefringence of the electric vector. The anisotropic properties of media can be determined from these two optical effects. Our main concern here is to revisit the factor of eigenpolarizations and eigenvalues in modeling of polarization properties of homogeneous media and elucidate certain new features in polarization behavior of birefringent and dichroic media.

  16. MODEL LITERASI MEDIA PADA ANAK DALAM MENCEGAH KONFLIK SOSIAL

    OpenAIRE

    Alip Kunandar

    2014-01-01

    This study is the first step to find a model of media literacy related to the prevention of social conflicts. Focus Group Discussion (FGD) used to find patterns of media consumption on children’s television, where to watch, and accompaniment patterns while watching television. FGD also used to find some examples of media content that has the potential to trigger social conflict. The results showed the existence of irregularities in terms of time children watch television, as well ...

  17. New specifications for exponential random graph models

    NARCIS (Netherlands)

    Snijders, Tom A. B.; Pattison, Philippa E.; Robins, Garry L.; Handcock, Mark S.; Stolzenberg, RM

    2006-01-01

    The most promising class of statistical models for expressing structural properties of social networks observed atone moment in time is the class of exponential random graph models (ERGMs), also known as p* models. The strong point of these models is that they can represent a variety of structural

  18. Comments on the random Thirring model

    Science.gov (United States)

    Berkooz, Micha; Narayan, Prithvi; Rozali, Moshe; Simón, Joan

    2017-09-01

    The Thirring model with random couplings is a translationally invariant generalisation of the SYK model to 1+1 dimensions, which is tractable in the large N limit. We compute its two point function, at large distances, for any strength of the random coupling. For a given realisation, the couplings contain both irrelevant and relevant marginal operators, but statistically, in the large N limit, the random couplings are overall always marginally irrelevant, in sharp distinction to the usual Thirring model. We show the leading term to the β function in conformal perturbation theory, which is quadratic in the couplings, vanishes, while its usually subleading cubic term matches our RG flow.

  19. Random matrix model for disordered conductors

    Indian Academy of Sciences (India)

    Keywords. Disordered conductors; random matrix theory; Dyson's Coulomb gas model. ... An interesting random walk problem associated with the joint probability distribution of the ensuing ensemble is discussed and its connection with level dynamics is brought out. It is further proved that Dyson's Coulomb gas analogy ...

  20. A New Appraoch to Modeling Immiscible Two-phase Flow in Porous Media

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander; Stenby, Erling Halfdan

    based on Rapoport-Leas Equation and Film Model, a systematic literature review of the LBM CFD methods including the particle-based LBM and porous-medium-based LBM for multiphase flow, and the sample calculation of particle-based LBM in a random porous medium. Finally we come to present a new approach......In this work we present a systematic literature review regarding the macroscopic approaches to modeling immiscible two-phase flow in porous media, the formulation process of the incorporate PDE based on Film Model(viscous coupling), the calculation of saturation profile around the transition zone...... to modeling immiscible two-phase flow in porous media. The suggested approach to immiscible two-phase flow in porous media describes the dispersed mesoscopic fluids’ interfaces which are highly influenced by the injected interfacial energy and the local interfacial energy capacity. It reveals a new...

  1. Adolescents' impressions of antismoking media literacy education: qualitative results from a randomized controlled trial.

    Science.gov (United States)

    Primack, Brian A; Fine, Danielle; Yang, Christopher K; Wickett, Dustin; Zickmund, Susan

    2009-08-01

    Although media literacy represents an innovative venue for school-based antismoking programming, studies have not systematically compared student impressions of these and traditional programs. This study utilized data from a randomized trial comparing these two types of programs. After each program, students responded to three open-ended questions related to their assigned curriculum. Two coders, blinded to student assignments, independently coded these data. Coders had strong inter-rater agreement (kappa = 0.77). Our primary measures were spontaneously noted overall assessment, enjoyment/interest and the likelihood of changing smoking behavior. Of the 531 participants, 255 (48.0%) were randomized to the intervention (media literacy) group. Intervention participants had more net positive responses [rate ratio (RR) = 1.27, 95% confidence interval (CI) = 1.05, 1.54], more responses rating the program as compelling (RR = 1.63, 95% CI = 1.16, 2.29) and fewer responses rating the program as non-compelling (RR = 0.62, 95% CI = 0.39, 0.97). However, the intervention group was not more likely to suggest that the curriculum was likely to change behavior positively (RR = 0.57, 95% CI = 0.30, 1.06). Findings suggest that although media literacy provides a compelling format for the delivery of anti-tobacco programming, integration of components of traditional programming may help media literacy programs achieve maximal efficacy.

  2. Supersymmetric SYK model and random matrix theory

    Science.gov (United States)

    Li, Tianlin; Liu, Junyu; Xin, Yuan; Zhou, Yehao

    2017-06-01

    In this paper, we investigate the effect of supersymmetry on the symmetry classification of random matrix theory ensembles. We mainly consider the random matrix behaviors in the N=1 supersymmetric generalization of Sachdev-Ye-Kitaev (SYK) model, a toy model for two-dimensional quantum black hole with supersymmetric constraint. Some analytical arguments and numerical results are given to show that the statistics of the supersymmetric SYK model could be interpreted as random matrix theory ensembles, with a different eight-fold classification from the original SYK model and some new features. The time-dependent evolution of the spectral form factor is also investigated, where predictions from random matrix theory are governing the late time behavior of the chaotic hamiltonian with supersymmetry.

  3. Entropy Characterization of Random Network Models

    Directory of Open Access Journals (Sweden)

    Pedro J. Zufiria

    2017-06-01

    Full Text Available This paper elaborates on the Random Network Model (RNM as a mathematical framework for modelling and analyzing the generation of complex networks. Such framework allows the analysis of the relationship between several network characterizing features (link density, clustering coefficient, degree distribution, connectivity, etc. and entropy-based complexity measures, providing new insight on the generation and characterization of random networks. Some theoretical and computational results illustrate the utility of the proposed framework.

  4. A new model of Random Regret Minimization

    NARCIS (Netherlands)

    Chorus, C.G.

    2010-01-01

    A new choice model is derived, rooted in the framework of Random Regret Minimization (RRM). The proposed model postulates that when choosing, people anticipate and aim to minimize regret. Whereas previous regret-based discrete choice-models assume that regret is experienced with respect to only the

  5. A Generalized Random Regret Minimization Model

    NARCIS (Netherlands)

    Chorus, C.G.

    2013-01-01

    This paper presents, discusses and tests a generalized Random Regret Minimization (G-RRM) model. The G-RRM model is created by replacing a fixed constant in the attribute-specific regret functions of the RRM model, by a regret-weight variable. Depending on the value of the regret-weights, the G-RRM

  6. The Western Way? Democracy and the Media Assistance Model

    Directory of Open Access Journals (Sweden)

    Daire Higgins

    2015-01-01

    Full Text Available International media assistance took off during a time where the ideological extremes of USA vs. USSR were set to disappear. Following the Cold War, international relations focused on democracy building, and nurturing independent media was embraced as a key part of this strategy. Fukayama called it the ‘End of History’, the fact that all other ideologies had fallen and Western style democracy was set to become the one common ideology. The US and UK led the way in media assistance, with their liberal ideas of a free press, bolstered by free market capitalism. America was the superpower, and forged the way around the globe with its beacon of democracy. Under that guiding light they would bring truth, accuracy, freedom of expression and independent reporting to the countries which had so long lived under the shadow of communism, or authoritarian media systems. This is what propelled and justified American foreign policy, and their media assistance, for many years. Much work was thus carried out in Eastern Europe and the former Soviet satellites, but many now question the impact and legacy of these projects. When the US and UK spoke of media assistance they seemed to mean ‘free market’. These days, the ‘democracy promoters’ focus has turned more to Africa and the Middle East. The ideology is apparently the same: to help establish and support democracy with a stronger and more independent media. But with Western economies, and their media systems, in crisis, the relevance of this media assistance model is questioned. This essay looks at the history of media assistance and the ongoing debate on the impact of media assistance over the long term, its motives and the new balance of power appearing in international media development.

  7. Permeability and porosity models of bi-fractal porous media

    Science.gov (United States)

    Tan, Xiao-Hua; Kui, Ming-Qing; Li, Xiao-Ping; Mao, Zheng-Lin; Xiao, Heng

    2017-11-01

    In previous studies, it is found that the frame and pore in porous media both possess the fractal geometric character. So the permeability and porosity models of bi-fractal porous media are derived based on the assumption that a porous media consists of fractal solid clusters and capillary bundles. The expressions of presented models are constituted by the fractal parameters of solid cluster and those of capillary bundle. Good agreement between model predictions and experimental data is obtained. This verifies the validity of the permeability and porosity models for bi-fractal porous media. The sensitive parameters that influence the permeability and porosity are specified, and their effects on the relationship between permeability and porosity are discussed.

  8. Optimal control of a social epidemic model with media coverage.

    Science.gov (United States)

    Huo, Hai-Feng; Huang, Shui-Rong; Wang, Xun-Yang; Xiang, Hong

    2017-12-01

    A new social epidemic model to depict alcoholism with media coverage is proposed in this paper. Some fundamental properties of the model including existence and positivity as well as boundedness of equilibria are investigated. Stability of all equilibria are studied. The existence of the optimal control pair and mathematical expressions of optimal control are obtained by Pontryagin's maximum principle. Numerical simulations are also performed to illustrate our results. Our results show that media coverage is an effective measure to quit drinking.

  9. Statistics of resonances and delay times in random media: beyond random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Kottos, Tsampikos [Department of Physics, Wesleyan University, Middletown, CT 06459-0155 (United States); Max-Planck-Institute for Dynamics and Self-Organization, Bunsenstrasse 10, D-37073 Goettingen (Germany)

    2005-12-09

    We review recent developments in quantum scattering from mesoscopic systems. Various spatial geometries whose closed analogues show diffusive, localized or critical behaviour are considered. These are the features that cannot be described by the universal random matrix theory results. Instead, one has to go beyond this approximation and incorporate them in a non-perturbative way. Here, we pay particular attention to the traces of these non-universal characteristics, in the distribution of the Wigner delay times and resonance widths. The former quantity captures time-dependent aspects of quantum scattering while the latter is associated with the poles of the scattering matrix.

  10. Nonlinear spatial focusing in random layered media by spectral pulse shaping

    Science.gov (United States)

    Han, Alex C.; Milner, Valery

    2016-02-01

    We demonstrate numerically a method of focusing two-photon fields inside one-dimensional random media. The approach is based on coherent control of backscattering achieved by adaptive spectral pulse shaping. The spectral phases of a femtosecond laser pulse are adjusted for the constructive interference of its backward-traveling components, resulting in an enhanced reflection from within the random system. A delayed forward-propagating second pulse overlaps with the controlled reflection, increasing the interpulse multiphoton field at a location determined by the delay between the two pulses. The technique is shown to be robust against the variations of the disorder and to work with realistic pulse-shaping parameters, hence enabling applications in controlling random lasing and multiphoton imaging in scattering materials.

  11. Effective Elliptic Models for Efficient Wavefield Extrapolation in Anisotropic Media

    KAUST Repository

    Waheed, Umair bin

    2014-05-01

    Wavefield extrapolation operator for elliptically anisotropic media offers significant cost reduction compared to that of transversely isotropic media (TI), especially when the medium exhibits tilt in the symmetry axis (TTI). However, elliptical anisotropy does not provide accurate focusing for TI media. Therefore, we develop effective elliptically anisotropic models that correctly capture the kinematic behavior of the TTI wavefield. Specifically, we use an iterative elliptically anisotropic eikonal solver that provides the accurate traveltimes for a TI model. The resultant coefficients of the elliptical eikonal provide the effective models. These effective models allow us to use the cheaper wavefield extrapolation operator for elliptic media to obtain approximate wavefield solutions for TTI media. Despite the fact that the effective elliptic models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including the frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy tradeoff for wavefield computations in TTI media, considering the cost prohibitive nature of the problem. We demonstrate the applicability of the proposed approach on the BP TTI model.

  12. RMBNToolbox: random models for biochemical networks

    Directory of Open Access Journals (Sweden)

    Niemi Jari

    2007-05-01

    Full Text Available Abstract Background There is an increasing interest to model biochemical and cell biological networks, as well as to the computational analysis of these models. The development of analysis methodologies and related software is rapid in the field. However, the number of available models is still relatively small and the model sizes remain limited. The lack of kinetic information is usually the limiting factor for the construction of detailed simulation models. Results We present a computational toolbox for generating random biochemical network models which mimic real biochemical networks. The toolbox is called Random Models for Biochemical Networks. The toolbox works in the Matlab environment, and it makes it possible to generate various network structures, stoichiometries, kinetic laws for reactions, and parameters therein. The generation can be based on statistical rules and distributions, and more detailed information of real biochemical networks can be used in situations where it is known. The toolbox can be easily extended. The resulting network models can be exported in the format of Systems Biology Markup Language. Conclusion While more information is accumulating on biochemical networks, random networks can be used as an intermediate step towards their better understanding. Random networks make it possible to study the effects of various network characteristics to the overall behavior of the network. Moreover, the construction of artificial network models provides the ground truth data needed in the validation of various computational methods in the fields of parameter estimation and data analysis.

  13. Echinacea purpurea and osteopathic manipulative treatment in children with recurrent otitis media: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Worden Katherine A

    2008-10-01

    Full Text Available Abstract Background Recurrent otitis media is a common problem in young children. Echinacea and osteopathic manipulative treatment have been proposed as preventive measures, but have been inadequately studied. This study was designed to assess the efficacy of Echinacea purpurea and/or osteopathic manipulative treatment (OMT for prevention of acute otitis media in otitis-prone children. Methods A randomized, placebo-controlled, two-by-two factorial trial with 6-month follow-up, conducted 1999 – 2002 in Tucson, Arizona. Patients were aged 12–60 months with recurrent otitis media, defined as three or more separate episodes of acute otitis media within six months, or at least four episodes in one year. Ninety children (44% white non-Hispanic, 39% Hispanic, 57% male were enrolled, of which 84 had follow-up for at least 3 months. Children were randomly assigned to one of four protocol groups: double placebo, echinacea plus sham OMT, true OMT (including cranial manipulation plus placebo echinacea, or true echinacea plus OMT. An alcohol extract of Echinacea purpurea roots and seeds (or placebo was administered for 10 days at the first sign of each common cold. Five OMT visits (or sham treatments were offered over 3 months. Results No interaction was found between echinacea and OMT. Echinacea was associated with a borderline increased risk of having at least one episode of acute otitis media during 6-month follow-up compared to placebo (65% versus 41%; relative risk, 1.59, 95% CI 1.04, 2.42. OMT did not significantly affect risk compared to sham (44% versus 61%; relative risk, 0.72, 95% CI 0.48, 1.10. Conclusion In otitis-prone young children, treating colds with this form of echinacea does not decrease the risk of acute otitis media, and may in fact increase risk. A regimen of up to five osteopathic manipulative treatments does not significantly decrease the risk of acute otitis media. Trial registration ClinicalTrials.gov Identifier: NCT00010465

  14. Echinacea purpurea and osteopathic manipulative treatment in children with recurrent otitis media: a randomized controlled trial

    Science.gov (United States)

    Wahl, Richard A; Aldous, Michael B; Worden, Katherine A; Grant, Kathryn L

    2008-01-01

    Background Recurrent otitis media is a common problem in young children. Echinacea and osteopathic manipulative treatment have been proposed as preventive measures, but have been inadequately studied. This study was designed to assess the efficacy of Echinacea purpurea and/or osteopathic manipulative treatment (OMT) for prevention of acute otitis media in otitis-prone children. Methods A randomized, placebo-controlled, two-by-two factorial trial with 6-month follow-up, conducted 1999 – 2002 in Tucson, Arizona. Patients were aged 12–60 months with recurrent otitis media, defined as three or more separate episodes of acute otitis media within six months, or at least four episodes in one year. Ninety children (44% white non-Hispanic, 39% Hispanic, 57% male) were enrolled, of which 84 had follow-up for at least 3 months. Children were randomly assigned to one of four protocol groups: double placebo, echinacea plus sham OMT, true OMT (including cranial manipulation) plus placebo echinacea, or true echinacea plus OMT. An alcohol extract of Echinacea purpurea roots and seeds (or placebo) was administered for 10 days at the first sign of each common cold. Five OMT visits (or sham treatments) were offered over 3 months. Results No interaction was found between echinacea and OMT. Echinacea was associated with a borderline increased risk of having at least one episode of acute otitis media during 6-month follow-up compared to placebo (65% versus 41%; relative risk, 1.59, 95% CI 1.04, 2.42). OMT did not significantly affect risk compared to sham (44% versus 61%; relative risk, 0.72, 95% CI 0.48, 1.10). Conclusion In otitis-prone young children, treating colds with this form of echinacea does not decrease the risk of acute otitis media, and may in fact increase risk. A regimen of up to five osteopathic manipulative treatments does not significantly decrease the risk of acute otitis media. Trial registration ClinicalTrials.gov Identifier: NCT00010465 PMID:18831749

  15. Nonparametric estimation in random sum models

    Directory of Open Access Journals (Sweden)

    Hassan S. Bakouch

    2013-05-01

    Full Text Available Let X1,X2,…,XN be independent, identically distributed, non-negative, integervalued random variables and let N be a non-negative, integer-valued random variable independent of X1,X2,…,XN . In this paper, we consider two nonparametric estimation problems for the random sum variable. The first is the estimation of the means of Xi and N based on the second-moment assumptions on distributions of Xi and N . The second is the nonparametric estimation of the distribution of Xi given a parametric model for the distribution of N . Some asymptotic properties of the proposed estimators are discussed.

  16. Modelling complex networks by random hierarchical graphs

    Directory of Open Access Journals (Sweden)

    M.Wróbel

    2008-06-01

    Full Text Available Numerous complex networks contain special patterns, called network motifs. These are specific subgraphs, which occur oftener than in randomized networks of Erdős-Rényi type. We choose one of them, the triangle, and build a family of random hierarchical graphs, being Sierpiński gasket-based graphs with random "decorations". We calculate the important characteristics of these graphs - average degree, average shortest path length, small-world graph family characteristics. They depend on probability of decorations. We analyze the Ising model on our graphs and describe its critical properties using a renormalization-group technique.

  17. Infinite Random Graphs as Statistical Mechanical Models

    DEFF Research Database (Denmark)

    Durhuus, Bergfinnur Jøgvan; Napolitano, George Maria

    2011-01-01

    We discuss two examples of infinite random graphs obtained as limits of finite statistical mechanical systems: a model of two-dimensional dis-cretized quantum gravity defined in terms of causal triangulated surfaces, and the Ising model on generic random trees. For the former model we describe...... a relation to the so-called uniform infinite tree and results on the Hausdorff and spectral dimension of two-dimensional space-time obtained in B. Durhuus, T. Jonsson, J.F. Wheater, J. Stat. Phys. 139, 859 (2010) are briefly outlined. For the latter we discuss results on the absence of spontaneous...

  18. Modeling microbial processes in porous media

    Science.gov (United States)

    Murphy, Ellyn M.; Ginn, Timothy R.

    The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu

  19. Parent-child interactions during traditional and interactive media settings: A pilot randomized control study.

    Science.gov (United States)

    Skaug, Silje; Englund, Kjellrun T; Saksvik-Lehouillier, Ingvild; Lydersen, Stian; Wichstrøm, Lars

    2017-12-15

    Parent-child interactions are pivotal for children's socioemotional development, yet might suffer with increased attention to screen media, as research has suggested. In response, we hypothesized that parent-child play on a tablet computer, as representative of interactive media, would generate higher-quality parent-child interactions than toy play or watching TV. We examined the emotional availability of mothers and their 2-year-old child during the previous three contexts using a randomized crossover design (n = 22) in a laboratory room. Among other results, mothers were more sensitive and structuring during joint gaming on a tablet than when engaged in toy play or watching TV. In addition, mothers were more hostile toward their children during play with traditional toys than during joint tablet gaming and television co-viewing. Such findings provide new insights into the impact of new media on parent-child interactions, chiefly by demonstrating that interactive media devices such as tablets can afford growth-enhancing parent-child interactions. © 2017 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

  20. A Dexterous Optional Randomized Response Model

    Science.gov (United States)

    Tarray, Tanveer A.; Singh, Housila P.; Yan, Zaizai

    2017-01-01

    This article addresses the problem of estimating the proportion Pi[subscript S] of the population belonging to a sensitive group using optional randomized response technique in stratified sampling based on Mangat model that has proportional and Neyman allocation and larger gain in efficiency. Numerically, it is found that the suggested model is…

  1. Stable lattice Boltzmann model for Maxwell equations in media

    Science.gov (United States)

    Hauser, A.; Verhey, J. L.

    2017-12-01

    The present work shows a method for stable simulations via the lattice Boltzmann (LB) model for electromagnetic waves (EM) transiting homogeneous media. LB models for such media were already presented in the literature, but they suffer from numerical instability when the media transitions are sharp. We use one of these models in the limit of pure vacuum derived from Liu and Yan [Appl. Math. Model. 38, 1710 (2014), 10.1016/j.apm.2013.09.009] and apply an extension that treats the effects of polarization and magnetization separately. We show simulations of simple examples in which EM waves travel into media to quantify error scaling, stability, accuracy, and time scaling. For conductive media, we use the Strang splitting and check the simulations accuracy at the example of the skin effect. Like pure EM propagation, the error for the static limits, which are constructed with a current density added in a first-order scheme, can be less than 1 % . The presented method is an easily implemented alternative for the stabilization of simulation for EM waves propagating in spatially complex structured media properties and arbitrary transitions.

  2. Role of quenching on superdiffusive transport in two-dimensional random media

    Science.gov (United States)

    Barthelemy, Pierre; Bertolotti, Jacopo; Vynck, Kevin; Lepri, Stefano; Wiersma, Diederik S.

    2010-07-01

    Transport in random media is known to be affected by quenched disorder. From the point of view of random walks, quenching induces correlations between steps that may alter the dynamical properties of the medium. This paper is intended to provide more insight into the role of quenched disorder on superdiffusive transport in two-dimensional random media. The systems under consideration are disordered materials called Lévy glasses that exhibit large spatial fluctuations in the density of scattering elements. We show that in an ideal Lévy glass the influence of quenching can be neglected, in the sense that transport follows to very good approximation that of a standard Lévy walk. We also show that, by changing sample parameters, quenching effects can be increased intentionally, thereby making it possible to investigate systematically diverse regimes of transport. In particular, we find that strong quenching induces local trapping effects which slow down superdiffusion and lead to a transient subdiffusivelike transport regime close to the truncation time of the system.

  3. Examining Asphaltene Solubility on Deposition in Model Porous Media

    OpenAIRE

    Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Yap, Yit-Fatt; Chai, John; Goharzadeh, Ashfin; Vargas, F. M.; Biswal, S.L.

    2016-01-01

    Asphaltenes are known to cause severe flow\\ud assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a k...

  4. An inventory model with random demand

    Science.gov (United States)

    Mitsel, A. A.; Kritski, O. L.; Stavchuk, LG

    2017-01-01

    The article describes a three-product inventory model with random demand at equal frequencies of delivery. A feature of this model is that the additional purchase of resources required is carried out within the scope of their deficit. This fact allows reducing their storage costs. A simulation based on the data on arrival of raw and materials at an enterprise in Kazakhstan has been prepared. The proposed model is shown to enable savings up to 40.8% of working capital.

  5. Fractional White-Noise Limit and Paraxial Approximation for Waves in Random Media

    Science.gov (United States)

    Gomez, Christophe; Pinaud, Olivier

    2017-12-01

    This work is devoted to the asymptotic analysis of high frequency wave propagation in random media with long-range dependence. We are interested in two asymptotic regimes, that we investigate simultaneously: the paraxial approximation, where the wave is collimated and propagates along a privileged direction of propagation, and the white-noise limit, where random fluctuations in the background are well approximated in a statistical sense by a fractional white noise. The fractional nature of the fluctuations is reminiscent of the long-range correlations in the underlying random medium. A typical physical setting is laser beam propagation in turbulent atmosphere. Starting from the high frequency wave equation with fast non-Gaussian random oscillations in the velocity field, we derive the fractional Itô-Schrödinger equation, that is, a Schrödinger equation with potential equal to a fractional white noise. The proof involves a fine analysis of the backscattering and of the coupling between the propagating and evanescent modes. Because of the long-range dependence, classical diffusion-approximation theorems for equations with random coefficients do not apply, and we therefore use moment techniques to study the convergence.

  6. Fractional White-Noise Limit and Paraxial Approximation for Waves in Random Media

    Science.gov (United States)

    Gomez, Christophe; Pinaud, Olivier

    2017-07-01

    This work is devoted to the asymptotic analysis of high frequency wave propagation in random media with long-range dependence. We are interested in two asymptotic regimes, that we investigate simultaneously: the paraxial approximation, where the wave is collimated and propagates along a privileged direction of propagation, and the white-noise limit, where random fluctuations in the background are well approximated in a statistical sense by a fractional white noise. The fractional nature of the fluctuations is reminiscent of the long-range correlations in the underlying random medium. A typical physical setting is laser beam propagation in turbulent atmosphere. Starting from the high frequency wave equation with fast non-Gaussian random oscillations in the velocity field, we derive the fractional Itô-Schrödinger equation, that is, a Schrödinger equation with potential equal to a fractional white noise. The proof involves a fine analysis of the backscattering and of the coupling between the propagating and evanescent modes. Because of the long-range dependence, classical diffusion-approximation theorems for equations with random coefficients do not apply, and we therefore use moment techniques to study the convergence.

  7. Boundary effects on effective conductivity of random heterogeneous media with spherical inclusions

    Science.gov (United States)

    Rabinovich, A.; Dagan, G.; Miloh, T.

    2012-10-01

    It is common to determine the effective conductivity of heterogeneous media by assuming stationarity of the random local properties. This assumption is not obeyed in a boundary layer of a body of finite size. The effect of different types of boundaries is examined for a two-phase medium with spherical inclusions of given conductivity distributed randomly in a matrix of a different conductivity. Exact solutions are derived for the apparent conductivity and the boundary layer thickness. The interaction between the spheres and the boundaries is fully incorporated in the solutions using a spherical harmonics expansion and the method of images. As applications, the corrections for the effective conductivity are given for two cases of finite bodies: the Maxwell sphere and a cylinder of flow parallel to the axis.

  8. Analysis and Computation of Acoustic and Elastic Wave Equations in Random Media

    KAUST Repository

    Motamed, Mohammad

    2014-01-06

    We propose stochastic collocation methods for solving the second order acoustic and elastic wave equations in heterogeneous random media and subject to deterministic boundary and initial conditions [1, 4]. We assume that the medium consists of non-overlapping sub-domains with smooth interfaces. In each sub-domain, the materials coefficients are smooth and given or approximated by a finite number of random variable. One important example is wave propagation in multi-layered media with smooth interfaces. The numerical scheme consists of a finite difference or finite element method in the physical space and a collocation in the zeros of suitable tensor product orthogonal polynomials (Gauss points) in the probability space. We provide a rigorous convergence analysis and demonstrate different types of convergence of the probability error with respect to the number of collocation points under some regularity assumptions on the data. In particular, we show that, unlike in elliptic and parabolic problems [2, 3], the solution to hyperbolic problems is not in general analytic with respect to the random variables. Therefore, the rate of convergence is only algebraic. A fast spectral rate of convergence is still possible for some quantities of interest and for the wave solutions with particular types of data. We also show that the semi-discrete solution is analytic with respect to the random variables with the radius of analyticity proportional to the grid/mesh size h. We therefore obtain an exponential rate of convergence which deteriorates as the quantity h p gets smaller, with p representing the polynomial degree in the stochastic space. We have shown that analytical results and numerical examples are consistent and that the stochastic collocation method may be a valid alternative to the more traditional Monte Carlo method. Here we focus on the stochastic acoustic wave equation. Similar results are obtained for stochastic elastic equations.

  9. Optimal Allocation in Stratified Randomized Response Model

    Directory of Open Access Journals (Sweden)

    Javid Shabbir

    2005-07-01

    Full Text Available A Warner (1965 randomized response model based on stratification is used to determine the allocation of samples. Both linear and log-linear cost functions are discussed under uni and double stratification. It observed that by using a log-linear cost function, one can get better allocations.

  10. Random effect selection in generalised linear models

    DEFF Research Database (Denmark)

    Denwood, Matt; Houe, Hans; Forkman, Björn

    We analysed abattoir recordings of meat inspection codes with possible relevance to onfarm animal welfare in cattle. Random effects logistic regression models were used to describe individual-level data obtained from 461,406 cattle slaughtered in Denmark. Our results demonstrate that the largest ...

  11. A New Model of Foreign Media Sense-Making

    Science.gov (United States)

    Yang, Linda Hui

    2016-01-01

    This paper introduces a new model to represent how individuals can develop a deepened understanding of both a foreign culture and of their own culture as a result of viewing and engaging with foreign media, and in particular foreign films and television series. The model emerged from data collected in a study of how Chinese university students…

  12. Modeling a Library Media-Classroom Integrated Instructional Process.

    Science.gov (United States)

    Bhalla, Pam

    1987-01-01

    Describes a model for the design, implementation, and evaluation of classroom instruction in which the teacher and media specialist work together and students produce a research paper, oral report, or audiovisual presentation. Both single-facet and multi-facet interdisciplinary approaches to the application of the model are described. (CLB)

  13. Bacterial otitis media: a new non-invasive rat model.

    NARCIS (Netherlands)

    Tonnaer, E.L.G.M.; Sanders, E.A.M.; Curfs, J.H.A.J.

    2003-01-01

    This study describes the development of a physiological rat model for otitis media. The model is based on the assumption that bacteria, intranasally introduced into the nasopharynx, will be transferred into the middle ear cavity during swallowing provided that the ambient air pressure is higher than

  14. Improving randomness characterization through Bayesian model selection.

    Science.gov (United States)

    Díaz Hernández Rojas, Rafael; Solís, Aldo; Angulo Martínez, Alí M; U'Ren, Alfred B; Hirsch, Jorge G; Marsili, Matteo; Pérez Castillo, Isaac

    2017-06-08

    Random number generation plays an essential role in technology with important applications in areas ranging from cryptography to Monte Carlo methods, and other probabilistic algorithms. All such applications require high-quality sources of random numbers, yet effective methods for assessing whether a source produce truly random sequences are still missing. Current methods either do not rely on a formal description of randomness (NIST test suite) on the one hand, or are inapplicable in principle (the characterization derived from the Algorithmic Theory of Information), on the other, for they require testing all the possible computer programs that could produce the sequence to be analysed. Here we present a rigorous method that overcomes these problems based on Bayesian model selection. We derive analytic expressions for a model's likelihood which is then used to compute its posterior distribution. Our method proves to be more rigorous than NIST's suite and Borel-Normality criterion and its implementation is straightforward. We applied our method to an experimental device based on the process of spontaneous parametric downconversion to confirm it behaves as a genuine quantum random number generator. As our approach relies on Bayesian inference our scheme transcends individual sequence analysis, leading to a characterization of the source itself.

  15. THE EFFECT OF INQUIRY TRAINING MODEL USE THE MEDIA PHET AGAINST SCIENCE PROCESS SKILLS AND LOGICAL THINKING SKILLS STUDENTS

    Directory of Open Access Journals (Sweden)

    Fajrul Wahdi Ginting

    2015-12-01

    Full Text Available The Purpose of The study: science process skills and logical thinking ability of students who use inquiry learning model training using PhET media; science process skills and logical thinking ability of students who use conventional learning model; and the difference science process skills and logical thinking ability of students to use learning model Inquiry Training using PhET media and conventional learning models. This research is a quasi experimental. Sample selection is done by cluster random sampling are two classes of classes VIII-E and class VIII-B, where the class VIII-E is taught by inquiry training model using media PhET and VIII-B with conventional learning model. The instrument used consisted of tests science process skills such as essay tests and tests of the ability to think logically in the form of multiple-choice tests. The data were analyzed using t test. The results showed that physics science process skills use Inquiry Training models using PhET media is different and showed better results compared with conventional learning model, and logical thinking skills students use Inquiry Training model using PhET media is different and show better results compared with conventional learning, and there is a difference between the ability to think logically and science process skills of students who use Inquiry Training model using PhET media and conventional learning models.

  16. Diffusion in time-dependent random media and the Kardar-Parisi-Zhang equation

    Science.gov (United States)

    Le Doussal, Pierre; Thiery, Thimothée

    2017-07-01

    Although time-dependent random media with short-range correlations lead to (possibly biased) normal tracer diffusion, anomalous fluctuations occur away from the most probable direction. This was pointed out recently in one-dimensional (1D) lattice random walks, where statistics related to the 1D Kardar-Parisi-Zhang (KPZ) universality class, i.e., the Gaussian unitary ensemble Tracy-Widom distribution, were shown to arise. Here, we provide a simple picture for this correspondence, directly in the continuum, which allows one to study arbitrary space dimensions and to predict a variety of universal distributions. In d =1 , we predict and verify numerically the emergence of the Gaussian orthogonal ensemble Tracy-Widom distribution for fluctuations of the transition probability. In d =3 , we predict a phase transition from Gaussian fluctuations to three-dimensional KPZ-type fluctuations as the bias is increased. We predict KPZ universal distributions for the arrival time of a first particle from a cloud diffusing in such media.

  17. Bayesian and variational Bayesian approaches for flows in heterogeneous random media

    Science.gov (United States)

    Yang, Keren; Guha, Nilabja; Efendiev, Yalchin; Mallick, Bani K.

    2017-09-01

    In this paper, we study porous media flows in heterogeneous stochastic media. We propose an efficient forward simulation technique that is tailored for variational Bayesian inversion. As a starting point, the proposed forward simulation technique decomposes the solution into the sum of separable functions (with respect to randomness and the space), where each term is calculated based on a variational approach. This is similar to Proper Generalized Decomposition (PGD). Next, we apply a multiscale technique to solve for each term (as in [1]) and, further, decompose the random function into 1D fields. As a result, our proposed method provides an approximation hierarchy for the solution as we increase the number of terms in the expansion and, also, increase the spatial resolution of each term. We use the hierarchical solution distributions in a variational Bayesian approximation to perform uncertainty quantification in the inverse problem. We conduct a detailed numerical study to explore the performance of the proposed uncertainty quantification technique and show the theoretical posterior concentration.

  18. Reference-free path length interferometry of random media with the intensity moments analysis.

    Science.gov (United States)

    Zimnyakov, Dmitry A; Yuvchenko, Sergey A; Pavlova, Maria V; Alonova, Marina V

    2017-06-26

    Stochastic interference of partially coherent light multiple scattered by a random medium is considered. The relationship between the second- and third-order moments of intensity fluctuations in random interference patterns, the coherence function of probe radiation, and the probability density of path differences for the interfering partial waves in the medium are established. The obtained relationships were verified using the statistical analysis of spectrally selected fluorescence radiation emitted by the laser-pumped dye-doped random medium. Rhodamine 6G water solution was applied as the doping agent for the ensembles of densely packed silica grains which were pumped by the CW radiation (532 nm) from the diode-pumped solid state laser. Experimentally observed abrupt decay of the second- and third-order moments of fluorescence intensity fluctuations for the wavelengths ranging from 620 nm to 680 nm is interpreted in terms of amplification of spontaneous emission at large dye concentrations. This paper discusses the new optical probe of random media defined as "the reference-free path length interferometry with the intensity moments analysis".

  19. Web-based Social Media Intervention to Increase Vaccine Acceptance: A Randomized Controlled Trial.

    Science.gov (United States)

    Glanz, Jason M; Wagner, Nicole M; Narwaney, Komal J; Kraus, Courtney R; Shoup, Jo Ann; Xu, Stanley; O'Leary, Sean T; Omer, Saad B; Gleason, Kathy S; Daley, Matthew F

    2017-12-01

    Interventions to address vaccine hesitancy and increase vaccine acceptance are needed. This study sought to determine if a Web-based, social media intervention increases early childhood immunization. A 3-arm, randomized controlled trial was conducted in Colorado from September 2013 to July 2016. Participants were pregnant women, randomly assigned (3:2:1) to a Web site with vaccine information and interactive social media components (VSM), a Web site with vaccine information (VI), or usual care (UC). Vaccination was assessed in infants of participants from birth to age 200 days. The primary outcome was days undervaccinated, measured as a continuous and dichotomous variable. Infants of 888 participants were managed for 200 days. By using a nonparametric rank-based analysis, mean ranks for days undervaccinated were significantly lower in the VSM arm versus UC (P = .02) but not statistically different between the VI and UC (P = .08) or between VSM and VI arms (P = .63). The proportions of infants up-to-date at age 200 days were 92.5, 91.3, and 86.6 in the VSM, VI, and UC arms, respectively. Infants in the VSM arm were more likely to be up-to-date than infants in the UC arm (odds ratio [OR] = 1.92; 95% confidence interval [CI], 1.07-3.47). Up-to-date status was not statistically different between VI and UC arms (OR = 1.62; 95% CI, 0.87-3.00) or between the VSM and VI arms (OR = 1.19, 95% CI, 0.70-2.03). Providing Web-based vaccine information with social media applications during pregnancy can positively influence parental vaccine behaviors. Copyright © 2017 by the American Academy of Pediatrics.

  20. Averaged Description of Flow (Steady and Transient) and Nonreactive Solute Transport in Random Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Schvidler, M.; Karasaki, K.

    2011-06-15

    In previous papers (Shvidler and Karasaki, 1999, 2001, 2005, and 2008) we presented and analyzed an approach for finding the general forms of exactly averaged equations of flow and transport in porous media. We studied systems of basic equations for steady flow with sources in unbounded domains with stochastically homogeneous conductivity fields. A brief analysis of exactly averaged equations of nonsteady flow and nonreactive solute transport was also presented. At the core of this approach is the existence of appropriate random Green's functions. For example, we showed that in the case of a 3-dimensional unbounded domain the existence of appropriate random Green's functions is sufficient for finding the exact nonlocal averaged equations for flow velocity using the operator with a unique kernel-vector. Examination of random fields with global symmetry (isotropy, transversal isotropy and orthotropy) makes it possible to describe significantly different types of averaged equations with nonlocal unique operators. It is evident that the existence of random Green's functions for physical linear processes is equivalent to assuming the existence of some linear random operators for appropriate stochastic equations. If we restricted ourselves to this assumption only, as we have done in this paper, we can study the processes in any dimensional bounded or unbounded fields and in addition, cases in which the random fields of conductivity and porosity are stochastically nonhomogeneous, nonglobally symmetrical, etc.. It is clear that examining more general cases involves significant difficulty and constricts the analysis of structural types for the processes being studied. Nevertheless, we show that we obtain the essential information regarding averaged equations for steady and transient flow, as well as for solute transport.

  1. Modelling of radon transport in porous media

    NARCIS (Netherlands)

    van der Graaf, E.R.; de Meijer, R.J.; Katase, A; Shimo, M

    1998-01-01

    This paper aims to describe the state of the art of modelling radon transport in soil on basis of multiphase radon transport equations. Emphasis is given to methods to obtain a consistent set of input parameters needed For such models. Model-measurement comparisons with the KVI radon transport

  2. Permeability model of sintered porous media: analysis and experiments

    Science.gov (United States)

    Flórez Mera, Juan Pablo; Chiamulera, Maria E.; Mantelli, Marcia B. H.

    2017-11-01

    In this paper, the permeability of porous media fabricated from copper powder sintering process was modeled and measured, aiming the use of the porosity as input parameter for the prediction of the permeability of sintering porous media. An expression relating the powder particle mean diameter with the permeability was obtained, based on an elementary porous media cell, which is physically represented by a duct formed by the arrangement of spherical particles forming a simple or orthorhombic packing. A circular duct with variable section was used to model the fluid flow within the porous media, where the concept of the hydraulic diameter was applied. Thus, the porous is modeled as a converging-diverging duct. The electrical circuit analogy was employed to determine two hydraulic resistances of the cell: based on the Navier-Stokes equation and on the Darcýs law. The hydraulic resistances are compared between themselves and an expression to determine the permeability as function of average particle diameter is obtained. The atomized copper powder was sifted to reduce the size dispersion of the particles. The porosities and permeabilities of sintered media fabricated from powders with particle mean diameters ranging from 20 to 200 microns were measured, by means of the image analysis method and using an experimental apparatus. The permeability data of a porous media, made of copper powder and saturated with distilled water, was used to compare with the permeability model. Permeability literature models, which considers that powder particles have the same diameter and include porosity data as input parameter, were compared with the present model and experimental data. This comparison showed to be quite good.

  3. Permeability model of sintered porous media: analysis and experiments

    Science.gov (United States)

    Flórez Mera, Juan Pablo; Chiamulera, Maria E.; Mantelli, Marcia B. H.

    2017-04-01

    In this paper, the permeability of porous media fabricated from copper powder sintering process was modeled and measured, aiming the use of the porosity as input parameter for the prediction of the permeability of sintering porous media. An expression relating the powder particle mean diameter with the permeability was obtained, based on an elementary porous media cell, which is physically represented by a duct formed by the arrangement of spherical particles forming a simple or orthorhombic packing. A circular duct with variable section was used to model the fluid flow within the porous media, where the concept of the hydraulic diameter was applied. Thus, the porous is modeled as a converging-diverging duct. The electrical circuit analogy was employed to determine two hydraulic resistances of the cell: based on the Navier-Stokes equation and on the Darcýs law. The hydraulic resistances are compared between themselves and an expression to determine the permeability as function of average particle diameter is obtained. The atomized copper powder was sifted to reduce the size dispersion of the particles. The porosities and permeabilities of sintered media fabricated from powders with particle mean diameters ranging from 20 to 200 microns were measured, by means of the image analysis method and using an experimental apparatus. The permeability data of a porous media, made of copper powder and saturated with distilled water, was used to compare with the permeability model. Permeability literature models, which considers that powder particles have the same diameter and include porosity data as input parameter, were compared with the present model and experimental data. This comparison showed to be quite good.

  4. A random walk model to evaluate autism

    Science.gov (United States)

    Moura, T. R. S.; Fulco, U. L.; Albuquerque, E. L.

    2018-02-01

    A common test administered during neurological examination in children is the analysis of their social communication and interaction across multiple contexts, including repetitive patterns of behavior. Poor performance may be associated with neurological conditions characterized by impairments in executive function, such as the so-called pervasive developmental disorders (PDDs), a particular condition of the autism spectrum disorders (ASDs). Inspired in these diagnosis tools, mainly those related to repetitive movements and behaviors, we studied here how the diffusion regimes of two discrete-time random walkers, mimicking the lack of social interaction and restricted interests developed for children with PDDs, are affected. Our model, which is based on the so-called elephant random walk (ERW) approach, consider that one of the random walker can learn and imitate the microscopic behavior of the other with probability f (1 - f otherwise). The diffusion regimes, measured by the Hurst exponent (H), is then obtained, whose changes may indicate a different degree of autism.

  5. Interactive media as a tool for reducing waiting anxiety at paediatric rehabilitation hospitals: a randomized controlled trial.

    Science.gov (United States)

    Biddiss, Elaine; Knibbe, Tara Joy; Fehlings, Darcy; Mckeever, Patricia; Cohen, Ashley; Mcpherson, Amy

    2017-12-15

    To investigate the efficacy of waiting room media for reducing anxiety and increasing satisfaction at a paediatric rehabilitation hospital. In this clustered, parallel, randomized controlled trial, 310 young people with disabilities (age range 5-19y) and their parents attending outpatient clinics were assigned to interactive media (n=113), a silent nature video (n=97), or media-free comparison (n=100) groups. Young person and parent anxiety was reported using the State-Trait Anxiety Inventory (STAI) on arrival and after 10 minutes in the waiting space. Questionnaires measured young person, parent, and staff satisfaction. Young people exposed to interactive media reported a postexposure state anxiety that was 1.1 raw points (2.7 standardized points) lower on the STAI than the comparison group (95% confidence interval [CI] -1.9 to -0.22). There was no difference in postexposure state anxiety between the passive media and comparison groups (95% CI -0.64 to 1.1). Parents' state anxiety did not differ between conditions, but interactive media were associated with greater satisfaction (p=0.009). Of 120 staff, 119 reported that interactive media improved the clinic experience for families. Interactive media designed for accessible, hands-free play mitigate waiting anxiety and increases satisfaction. This paper provides evidence to guide design and decision-making around the use of interactive media in health care spaces. Interactive media reduced preclinic waiting anxiety for young people with disabilities. Interactive media were accessible to young people with a range of mobility. Interactive media increased parental and staff satisfaction in the clinic. Guidelines for the design of hands-free, inclusive interactive media for health care facilities are presented. © 2017 Mac Keith Press.

  6. A volume-balance model for flow on porous media

    Science.gov (United States)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2015-11-01

    Volume-balance models are used by petroleum engineers for simulating multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Numerical tests for phase separation under gravity are presented for multiphase three dimensional flow in heterogeneous porous media. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER grant number 42536 (DGAJ-SPI-34-170412-217).

  7. The Cross-media Publishing Data Model of Map

    Directory of Open Access Journals (Sweden)

    WEN Jianlong

    2015-08-01

    Full Text Available Aiming at the problem of repeated map production and differences of visual expression effect appeared when the same spatial data are published across different media, the concept of cross-media publishing of map is proposed. Through analyzing the existing map data models and deeply mining the potential advantages of PDF page content objects such as mark content object, logic structure object, optional content object and so on in PDF structure, the point is around the feature object code, the feature object structure and the feature layered structure launched the design of the cross-media publishing data model of map. The model breached the past limit that the map data which satisfies the printing request and geographic spatial data only can be described on different stages or with different models. It creates the conditions for storage and management of the cross-media publishing data of map. After the experimental tests the results show that the model is feasible and effective.

  8. Mathematical modeling courses for Media technology students

    DEFF Research Database (Denmark)

    Timcenko, Olga

    2009-01-01

    This paper addresses curriculum development for Mathematical Modeling course at Medialogy education. Medialogy as a study line was established in 2002 at Faculty for Engineering and Natural Sciences at Aalborg University, and mathematics curriculum has already been revised three times, Mathematical...... Modeling on 6th semester being the latest addition. Some of the reasoning behind curriculum development, lessons learned and remaining issues are presented and discussed.  ...

  9. Engaging Moms on Teen Indoor Tanning Through Social Media: Protocol of a Randomized Controlled Trial

    Science.gov (United States)

    Baker, Katie; Griffith, Julia; Oleski, Jessica L; Palumbo, Ashley; Walkosz, Barbara J; Hillhouse, Joel; Henry, Kimberly L; Buller, David B

    2016-01-01

    anticipate completing this study by October 2019. Conclusions This trial will deliver social media content grounded in theory and will test it in a randomized design with state-of-the-art measures. This will contribute much needed insights on how to employ social media for health behavior change and disease prevention both for indoor tanning and other health risk behaviors and inform future social media efforts by public health and health care organizations. ClinicalTrial Clinicaltrials.gov NCT02835807; https://clinicaltrials.gov/ct2/show/NCT02835807 (Archived by WebCite at http://www.webcitation.org/6mDMICcCE). PMID:27899339

  10. Engaging Moms on Teen Indoor Tanning Through Social Media: Protocol of a Randomized Controlled Trial.

    Science.gov (United States)

    Pagoto, Sherry L; Baker, Katie; Griffith, Julia; Oleski, Jessica L; Palumbo, Ashley; Walkosz, Barbara J; Hillhouse, Joel; Henry, Kimberly L; Buller, David B

    2016-11-29

    . This trial will deliver social media content grounded in theory and will test it in a randomized design with state-of-the-art measures. This will contribute much needed insights on how to employ social media for health behavior change and disease prevention both for indoor tanning and other health risk behaviors and inform future social media efforts by public health and health care organizations. Clinicaltrials.gov NCT02835807; https://clinicaltrials.gov/ct2/show/NCT02835807 (Archived by WebCite at http://www.webcitation.org/6mDMICcCE).

  11. Media

    National Research Council Canada - National Science Library

    Emily Wexler

    2010-01-01

    .... Tradigital allows us to use online behaviour to track the effectiveness of online and offline media, not simply the correlation of TV airings with search activity, but also by employing a bevy...

  12. Media Use and Source Trust among Muslims in Seven Countries: Results of a Large Random Sample Survey

    Directory of Open Access Journals (Sweden)

    Steven R. Corman

    2013-12-01

    Full Text Available Despite the perceived importance of media in the spread of and resistance against Islamist extremism, little is known about how Muslims use different kinds of media to get information about religious issues, and what sources they trust when doing so. This paper reports the results of a large, random sample survey among Muslims in seven countries Southeast Asia, West Africa and Western Europe, which helps fill this gap. Results show a diverse set of profiles of media use and source trust that differ by country, with overall low trust in mediated sources of information. Based on these findings, we conclude that mass media is still the most common source of religious information for Muslims, but that trust in mediated information is low overall. This suggests that media are probably best used to persuade opinion leaders, who will then carry anti-extremist messages through more personal means.

  13. Viscoelastic flow simulations in model porous media

    Science.gov (United States)

    De, S.; Kuipers, J. A. M.; Peters, E. A. J. F.; Padding, J. T.

    2017-05-01

    We investigate the flow of unsteadfy three-dimensional viscoelastic fluid through an array of symmetric and asymmetric sets of cylinders constituting a model porous medium. The simulations are performed using a finite-volume methodology with a staggered grid. The solid-fluid interfaces of the porous structure are modeled using a second-order immersed boundary method [S. De et al., J. Non-Newtonian Fluid Mech. 232, 67 (2016), 10.1016/j.jnnfm.2016.04.002]. A finitely extensible nonlinear elastic constitutive model with Peterlin closure is used to model the viscoelastic part. By means of periodic boundary conditions, we model the flow behavior for a Newtonian as well as a viscoelastic fluid through successive contractions and expansions. We observe the presence of counterrotating vortices in the dead ends of our geometry. The simulations provide detailed insight into how flow structure, viscoelastic stresses, and viscoelastic work change with increasing Deborah number De. We observe completely different flow structures and different distributions of the viscoelastic work at high De in the symmetric and asymmetric configurations, even though they have the exact same porosity. Moreover, we find that even for the symmetric contraction-expansion flow, most energy dissipation is occurring in shear-dominated regions of the flow domain, not in extensional-flow-dominated regions.

  14. Models for seismic wave propagation in periodically layered porous media

    NARCIS (Netherlands)

    Kudarova, A.; Van Dalen, K.N.; Drijkoningen, G.G.

    2014-01-01

    Several models are discussed for seismic wave propagation in periodically layered poroelastic media where layers represent mesoscopic-scale heterogeneities that are larger than the pore and grain sizes but smaller than the wavelength. The layers behave according to Biot’s theory. Wave propagation

  15. Effective ellipsoidal models for wavefield extrapolation in tilted orthorhombic media

    KAUST Repository

    Waheed, Umair Bin

    2016-04-22

    Wavefield computations using the ellipsoidally anisotropic extrapolation operator offer significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate wavefield representation or imaging for media of orthorhombic symmetry. Therefore, we propose the use of ‘effective ellipsoidally anisotropic’ models that correctly capture the kinematic behaviour of wavefields for tilted orthorhombic (TOR) media. We compute effective velocities for the ellipsoidally anisotropic medium using kinematic high-frequency representation of the TOR wavefield, obtained by solving the TOR eikonal equation. The effective model allows us to use the cheaper ellipsoidally anisotropic wave extrapolation operators. Although the effective models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including frequency dependency and caustics, if present, with reasonable accuracy. The proposed methodology offers a much better cost versus accuracy trade-off for wavefield computations in TOR media, particularly for media of low to moderate anisotropic strength. Furthermore, the computed wavefield solution is free from shear-wave artefacts as opposed to the conventional finite-difference based TOR wave extrapolation scheme. We demonstrate applicability and usefulness of our formulation through numerical tests on synthetic TOR models. © 2016 Institute of Geophysics of the ASCR, v.v.i

  16. Ossicular bone modeling in acute otitis media

    DEFF Research Database (Denmark)

    Salomonsen, Rasmus Lysholdt; Hermansson, Ann; Cayé-Thomasen, Per

    2010-01-01

    A number of middle ear diseases are associated with pathologic bone modeling, either formative or resorptive. As such, the pathogenesis of a sclerotic mastoid has been controversial for decades. Experimental studies on acute middle ear infection have shown progressive osteoneogenesis in the bone ...

  17. Ossicular bone modeling in acute otitis media

    DEFF Research Database (Denmark)

    Salomonsen, Rasmus Lysholdt; Hermansson, Ann; Cayé-Thomasen, Per

    2010-01-01

    A number of middle ear diseases are associated with pathologic bone modeling, either formative or resorptive. As such, the pathogenesis of a sclerotic mastoid has been controversial for decades. Experimental studies on acute middle ear infection have shown progressive osteoneogenesis in the bone...

  18. Social Media and Peer-Reviewed Medical Journal Readership: A Randomized Prospective Controlled Trial.

    Science.gov (United States)

    Hawkins, C Matthew; Hunter, Makeba; Kolenic, Giselle E; Carlos, Ruth C

    2017-05-01

    To prospectively evaluate the impact of increasing levels of social media engagement on page visits and web-link clicks for content published in the Journal of the American College of Radiology. A three-arm prospective trial was designed using a control group, a basic Twitter intervention group (using only the Journal's @JACRJournal Twitter account), and an enhanced Twitter intervention group (using the personal Twitter accounts of editorial board members and trainees). Overall, 428 articles published between June 2013 and July 2015 were randomly assigned to the three groups. Article-specific tweets for both intervention arms were sent between September 14, 2015, and October 28, 2015. Primary end points included article-specific weekly and monthly page visits on the journal's Elsevier website (Amsterdam, Netherlands). For the two intervention groups, additional end points included 7-day and 30-day Twitter link clicks. Weekly page visits for the enhanced Twitter arm (mean 18.2; 95% confidence interval [CI] 15.6-20.7) were significantly higher when compared with the weekly page visits for the control arm (mean 7.6; 95% CI 1.7-13.6). However, there was no demonstrable increase in weekly page visits (mean 9.4; 95% CI 7.4-11.5) for the basic Twitter arm compared with the control arm. No intervention effects over control, regardless of Twitter arm assignment, were demonstrated for monthly page visits. The enhanced Twitter intervention resulted in a statistically significant increase in both 7-day and 30-day Twitter link clicks compared with the basic Twitter intervention group. An organized social media strategy, with focused social media activity from editorial board members, increased engagement with content published in a peer-reviewed radiology journal. Copyright © 2016 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  19. Multiple Volume Scattering in Random Media and Periodic Structures with Applications in Microwave Remote Sensing and Wave Functional Materials

    Science.gov (United States)

    Tan, Shurun

    The objective of my research is two-fold: to study wave scattering phenomena in dense volumetric random media and in periodic wave functional materials. For the first part, the goal is to use the microwave remote sensing technique to monitor water resources and global climate change. Towards this goal, I study the microwave scattering behavior of snow and ice sheet. For snowpack scattering, I have extended the traditional dense media radiative transfer (DMRT) approach to include cyclical corrections that give rise to backscattering enhancements, enabling the theory to model combined active and passive observations of snowpack using the same set of physical parameters. Besides DMRT, a fully coherent approach is also developed by solving Maxwell's equations directly over the entire snowpack including a bottom half space. This revolutionary new approach produces consistent scattering and emission results, and demonstrates backscattering enhancements and coherent layer effects. The birefringence in anisotropic snow layers is also analyzed by numerically solving Maxwell's equation directly. The effects of rapid density fluctuations in polar ice sheet emission in the 0.5˜2.0 GHz spectrum are examined using both fully coherent and partially coherent layered media emission theories that agree with each other and distinct from incoherent approaches. For the second part, the goal is to develop integral equation based methods to solve wave scattering in periodic structures such as photonic crystals and metamaterials that can be used for broadband simulations. Set upon the concept of modal expansion of the periodic Green's function, we have developed the method of broadband Green's function with low wavenumber extraction (BBGFL), where a low wavenumber component is extracted and results a non-singular and fast-converging remaining part with simple wavenumber dependence. We've applied the technique to simulate band diagrams and modal solutions of periodic structures, and to

  20. Examining Asphaltene Solubility on Deposition in Model Porous Media.

    Science.gov (United States)

    Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C; Goharzadeh, Afshin; Vargas, Francisco M; Biswal, Sibani Lisa

    2016-08-30

    Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection-diffusion effects on deposition.

  1. Mathematical and numerical modeling in porous media applications in geosciences

    CERN Document Server

    Diaz Viera, Martin A; Coronado, Manuel; Ortiz Tapia, Arturo

    2012-01-01

    Porous media are broadly found in nature and their study is of high relevance in our present lives. In geosciences porous media research is fundamental in applications to aquifers, mineral mines, contaminant transport, soil remediation, waste storage, oil recovery and geothermal energy deposits. Despite their importance, there is as yet no complete understanding of the physical processes involved in fluid flow and transport. This fact can be attributed to the complexity of the phenomena which include multicomponent fluids, multiphasic flow and rock-fluid interactions. Since its formulation in 1856, Darcy's law has been generalized to describe multi-phase compressible fluid flow through anisotropic and heterogeneous porous and fractured rocks. Due to the scarcity of information, a high degree of uncertainty on the porous medium properties is commonly present. Contributions to the knowledge of modeling flow and transport, as well as to the characterization of porous media at field scale are of great relevance. ...

  2. Adjunctive social media for more effective contraceptive counseling: a randomized controlled trial.

    Science.gov (United States)

    Kofinas, Jason D; Varrey, Aneesha; Sapra, Katherine J; Kanj, Rula V; Chervenak, Frank A; Asfaw, Tirsit

    2014-04-01

    To determine whether social media, specifically Facebook, is an effective tool for improving contraceptive knowledge. English-speaking women aged 18-45 years receiving care at an urban academic center obstetrics and gynecology clinic were included and randomized to a trial of standard contraceptive education and pamphlet (n=74) compared with standard contraceptive education and Facebook (n=69) information for contraception counseling. Contraceptive knowledge was evaluated preintervention and postintervention by the Contraceptive Knowledge Inventory. We evaluated the effect of the intervention by raw score and percent increase in Contraceptive Knowledge Inventory score, participant satisfaction with counseling method, and contraceptive preference postintervention. All analyses were stratified by age group. The median raw postintervention Contraceptive Knowledge Inventory score was significantly higher in the Facebook compared with the pamphlet group (15 compared with 12, Phigher in the Facebook group (median 10 compared with 6, Phigher in the Facebook compared with the pamphlet group (48% compared with 33%, P=.19). Social media as an adjunct to traditional in-office counseling improves patient contraceptive knowledge and increases patient preference for LARCs. ClinicalTrials.gov, www.clinicaltrials.gov, NCT5327714500.

  3. A randomized crossover study of web-based media literacy to prevent smoking.

    Science.gov (United States)

    Shensa, Ariel; Phelps-Tschang, Jane; Miller, Elizabeth; Primack, Brian A

    2016-02-01

    Feasibly implemented Web-based smoking media literacy (SML) programs have been associated with improving SML skills among adolescents. However, prior evaluations have generally had weak experimental designs. We aimed to examine program efficacy using a more rigorous crossover design. Seventy-two ninth grade students completed a Web-based SML program based on health behavior theory and implemented using a two-group two-period crossover design. Students were randomly assigned by classroom to receive media literacy or control interventions in different sequences. They were assessed three times, at baseline (T0), an initial follow-up after the first intervention (T1) and a second follow-up after the second intervention (T2). Crossover analysis using analysis of variance demonstrated significant intervention coefficients, indicating that the SML condition was superior to control for the primary outcome of total SML (F = 11.99; P < 0.001) and for seven of the nine individual SML items. Results were consistent in sensitivity analyses conducted using non-parametric methods. There were changes in some exploratory theory-based outcomes including attitudes and normative beliefs but not others. In conclusion, while strength of the design of this study supports and extends prior findings around effectiveness of SML programs, influences on theory-based mediators of smoking should be further explored. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  4. Trust, but verify: social media models for disaster management.

    Science.gov (United States)

    Mehta, Amisha M; Bruns, Axel; Newton, Judith

    2017-07-01

    A lack of trust in the information exchanged via social media may significantly hinder decisionmaking by community members and emergency services during disasters. The need for timely information at such times, though, challenges traditional ways of establishing trust. This paper, building on a multi-year research project that combined social media data analysis and participant observation within an emergency management organisation and in-depth engagement with stakeholders across the sector, pinpoints and examines assumptions governing trust and trusting relationships in social media disaster management. It assesses three models for using social media in disaster management-information gathering, quasi-journalistic verification, and crowdsourcing-in relation to the guardianship of trust to highlight the verification process for content and source and to identify the role of power and responsibilities. The conclusions contain important implications for emergency management organisations seeking to enhance their mechanisms for incorporating user-generated information from social media sources in their disaster response efforts. © 2017 The Author(s). Disasters © Overseas Development Institute, 2017.

  5. Modelling of Electrodynamic Phenomena in Slowly Moving Media

    Science.gov (United States)

    Rozov, Andrey Leonidovich

    2017-08-01

    We discuss the feasibility of using, along with Minkowski equations obtained on the basis of the theory of relativity and used at present in electrodynamics, alternative methods of describing the processes of interaction between electromagnetic fields and moving media. In this article, a way of describing electromagnetic fields in terms of classical mechanics is offered. A system of electrodynamic equations for slowly moving media was derived on the basis of Maxwell's theory within the framework of classical mechanics using Wilsons' experimental data with dielectrics in a previous article [A. Rozov, Z. Naturforsch. 70, 1019 (2015)]. This article puts forward a physical model that explains the features of the derived equations. The offered model made it possible to suggest a new approach to the derivation of electrodynamic equations for slowly moving media. A variant of Galileo's relativity principle, in accordance with which the electrodynamic equations for slowly moving media should be considered as Galilean-invariant, is laid down on the basis of both the interpretation of Galileo's concept following from Galileo's works and Pauli's concept of postulate of relativity within the framework of the represented physical model.

  6. Stochastic Models Predict User Behavior in Social Media

    OpenAIRE

    Hogg, Tad; Lerman, Kristina; Smith, Laura M.

    2013-01-01

    User response to contributed content in online social media depends on many factors. These include how the site lays out new content, how frequently the user visits the site, how many friends the user follows, how active these friends are, as well as how interesting or useful the content is to the user. We present a stochastic modeling framework that relates a user's behavior to details of the site's user interface and user activity and describe a procedure for estimating model parameters fro...

  7. Mass media destabilizes the cultural homogeneous regime in Axelrod's model

    OpenAIRE

    Peres, Lucas R.; Fontanari, José F.

    2009-01-01

    An important feature of Axelrod's model for culture dissemination or social influence is the emergence of many multicultural absorbing states, despite the fact that the local rules that specify the agents interactions are explicitly designed to decrease the cultural differences between agents. Here we re-examine the problem of introducing an external, global interaction -- the mass media -- in the rules of Axelrod's model: in addition to their nearest-neighbors, each agent has a certain proba...

  8. Addressing dental fear in children with autism spectrum disorders: a randomized controlled pilot study using electronic screen media.

    Science.gov (United States)

    Isong, Inyang A; Rao, Sowmya R; Holifield, Chloe; Iannuzzi, Dorothea; Hanson, Ellen; Ware, Janice; Nelson, Linda P

    2014-03-01

    Dental care is a significant unmet health care need for children with autism spectrum disorders (ASD). Many children with ASD do not receive dental care because of fear associated with dental procedures; oftentimes they require general anesthesia for regular dental procedures, placing them at risk of associated complications. Many children with ASD have a strong preference for visual stimuli, particularly electronic screen media. The use of visual teaching materials is a fundamental principle in designing educational programs for children with ASD. To determine if an innovative strategy using 2 types of electronic screen media was feasible and beneficial in reducing fear and uncooperative behaviors in children with ASD undergoing dental visits. We conducted a randomized controlled trial at Boston Children's Hospital dental clinic. Eighty (80) children aged 7 to 17 years with a known diagnosis of ASD and history of dental fear were enrolled in the study. Each child completed 2 preventive dental visits that were scheduled 6 months apart (visit 1 and visit 2). After visit 1, subjects were randomly assigned to 1 of 4 groups: (1) group A, control (usual care); (2) group B, treatment (video peer modeling that involved watching a DVD recording of a typically developing child undergoing a dental visit); (3) group C, treatment (video goggles that involved watching a favorite movie during the dental visit using sunglass-style video eyewear); and (4) group D, treatment (video peer modeling plus video goggles). Subjects who refused or were unable to wear the goggles watched the movie using a handheld portable DVD player. During both visits, the subject's level of anxiety and behavior were measured using the Venham Anxiety and Behavior Scales. Analyses of variance and Fisher's exact tests compared baseline characteristics across groups. Using intention to treat approach, repeated measures analyses were employed to test whether the outcomes differed significantly: (1) between

  9. Fracture of Cellular Media: A Foam Model

    Science.gov (United States)

    Hilgenfeldt, S.; Arif, S.; Tsai, J.

    2008-12-01

    Aqueous foam, almost entirely made of a Newtonian liquid and an ideal gas, shows surprisingly rich rheological behavior, including viscoelasticity and power-law shear thinning. The bubble mesostructure of the foam (seen as a cellular medium) is at the heart of the nontrivial rheology. Quantitative constitutive relations can be derived when properly accounting for the bubble geometry. Beyond linear and nonlinear rheology, we have investigated fracture in a quasi-two-dimensional foam sample as induced by the injection of additional fluid (gas). Depending on the rate and magnitude of applied pressure, the foam yields by either brittle or ductile fracture. The former is characterized by breaking thin films and small strains, the latter involves defect formation and motion (T1 transitions) without cell breakage. The experiments can be interpreted in two ways, both as a model of fracture in (regular, crystalline) atomic solids and as a model of failure in an (irregular, disordered) solid with heterogeneous domains, depending on the foam preparation and scale of the experiment. The latter view offers strong analogies to fracture of soil and its dependence on grain structure and water content.

  10. Discovering health topics in social media using topic models.

    Science.gov (United States)

    Paul, Michael J; Dredze, Mark

    2014-01-01

    By aggregating self-reported health statuses across millions of users, we seek to characterize the variety of health information discussed in Twitter. We describe a topic modeling framework for discovering health topics in Twitter, a social media website. This is an exploratory approach with the goal of understanding what health topics are commonly discussed in social media. This paper describes in detail a statistical topic model created for this purpose, the Ailment Topic Aspect Model (ATAM), as well as our system for filtering general Twitter data based on health keywords and supervised classification. We show how ATAM and other topic models can automatically infer health topics in 144 million Twitter messages from 2011 to 2013. ATAM discovered 13 coherent clusters of Twitter messages, some of which correlate with seasonal influenza (r = 0.689) and allergies (r = 0.810) temporal surveillance data, as well as exercise (r =  .534) and obesity (r =  -.631) related geographic survey data in the United States. These results demonstrate that it is possible to automatically discover topics that attain statistically significant correlations with ground truth data, despite using minimal human supervision and no historical data to train the model, in contrast to prior work. Additionally, these results demonstrate that a single general-purpose model can identify many different health topics in social media.

  11. Discovering health topics in social media using topic models.

    Directory of Open Access Journals (Sweden)

    Michael J Paul

    Full Text Available By aggregating self-reported health statuses across millions of users, we seek to characterize the variety of health information discussed in Twitter. We describe a topic modeling framework for discovering health topics in Twitter, a social media website. This is an exploratory approach with the goal of understanding what health topics are commonly discussed in social media. This paper describes in detail a statistical topic model created for this purpose, the Ailment Topic Aspect Model (ATAM, as well as our system for filtering general Twitter data based on health keywords and supervised classification. We show how ATAM and other topic models can automatically infer health topics in 144 million Twitter messages from 2011 to 2013. ATAM discovered 13 coherent clusters of Twitter messages, some of which correlate with seasonal influenza (r = 0.689 and allergies (r = 0.810 temporal surveillance data, as well as exercise (r =  .534 and obesity (r =  -.631 related geographic survey data in the United States. These results demonstrate that it is possible to automatically discover topics that attain statistically significant correlations with ground truth data, despite using minimal human supervision and no historical data to train the model, in contrast to prior work. Additionally, these results demonstrate that a single general-purpose model can identify many different health topics in social media.

  12. Particle filters for random set models

    CERN Document Server

    Ristic, Branko

    2013-01-01

    “Particle Filters for Random Set Models” presents coverage of state estimation of stochastic dynamic systems from noisy measurements, specifically sequential Bayesian estimation and nonlinear or stochastic filtering. The class of solutions presented in this book is based  on the Monte Carlo statistical method. The resulting  algorithms, known as particle filters, in the last decade have become one of the essential tools for stochastic filtering, with applications ranging from  navigation and autonomous vehicles to bio-informatics and finance. While particle filters have been around for more than a decade, the recent theoretical developments of sequential Bayesian estimation in the framework of random set theory have provided new opportunities which are not widely known and are covered in this book. These recent developments have dramatically widened the scope of applications, from single to multiple appearing/disappearing objects, from precise to imprecise measurements and measurement models. This book...

  13. Effects of Mass Media and Cultural Drift in a Model for Social Influence

    Science.gov (United States)

    Mazzitello, Karina I.; Candia, Julián; Dossetti, Víctor

    In the context of an extension of Axelrod's model for social influence, we study the interplay and competition between the cultural drift, represented as random perturbations, and mass media, introduced by means of an external homogeneous field. Unlike previous studies [J. C. González-Avella et al., Phys. Rev. E 72, 065102(R) (2005)], the mass media coupling proposed here is capable of affecting the cultural traits of any individual in the society, including those who do not share any features with the external message. A noise-driven transition is found: for large noise rates, both the ordered (culturally polarized) phase and the disordered (culturally fragmented) phase are observed, while, for lower noise rates, the ordered phase prevails. In the former case, the external field is found to induce cultural ordering, a behavior opposite to that reported in previous studies using a different prescription for the mass media interaction. We compare the predictions of this model to statistical data measuring the impact of a mass media vasectomy promotion campaign in Brazil.

  14. Mathematical models of a diffusion-convection in porous media

    Directory of Open Access Journals (Sweden)

    Anvarbek M. Meirmanov

    2012-06-01

    Full Text Available Mathematical models of a diffusion-convection in porous media are derived from the homogenization theory. We start with the mathematical model on the microscopic level, which consist of the Stokes system for a weakly compressible viscous liquid occupying a pore space, coupled with a diffusion-convection equation for the admixture. We suppose that the viscosity of the liquid depends on a concentration of the admixture and for this nonlinear system we prove the global in time existence of a weak solution. Next we rigorously fulfil the homogenization procedure as the dimensionless size of pores tends to zero, while the porous body is geometrically periodic. As a result, we derive new mathematical models of a diffusion-convection in absolutely rigid porous media.

  15. Spartan random processes in time series modeling

    Science.gov (United States)

    Žukovič, M.; Hristopulos, D. T.

    2008-06-01

    A Spartan random process (SRP) is used to estimate the correlation structure of time series and to predict (interpolate and extrapolate) the data values. SRPs are motivated from statistical physics, and they can be viewed as Ginzburg-Landau models. The temporal correlations of the SRP are modeled in terms of ‘interactions’ between the field values. Model parameter inference employs the computationally fast modified method of moments, which is based on matching sample energy moments with the respective stochastic constraints. The parameters thus inferred are then compared with those obtained by means of the maximum likelihood method. The performance of the Spartan predictor (SP) is investigated using real time series of the quarterly S&P 500 index. SP prediction errors are compared with those of the Kolmogorov-Wiener predictor. Two predictors, one of which is explicit, are derived and used for extrapolation. The performance of the predictors is similarly evaluated.

  16. Simulating propagation of coherent light in random media using the Fredholm type integral equation

    Science.gov (United States)

    Kraszewski, Maciej; Pluciński, Jerzy

    2017-06-01

    Studying propagation of light in random scattering materials is important for both basic and applied research. Such studies often require usage of numerical method for simulating behavior of light beams in random media. However, if such simulations require consideration of coherence properties of light, they may become a complex numerical problems. There are well established methods for simulating multiple scattering of light (e.g. Radiative Transfer Theory and Monte Carlo methods) but they do not treat coherence properties of light directly. Some variations of these methods allows to predict behavior of coherent light but only for an averaged realization of the scattering medium. This limits their application in studying many physical phenomena connected to a specific distribution of scattering particles (e.g. laser speckle). In general, numerical simulation of coherent light propagation in a specific realization of random medium is a time- and memory-consuming problem. The goal of the presented research was to develop new efficient method for solving this problem. The method, presented in our earlier works, is based on solving the Fredholm type integral equation, which describes multiple light scattering process. This equation can be discretized and solved numerically using various algorithms e.g. by direct solving the corresponding linear equations system, as well as by using iterative or Monte Carlo solvers. Here we present recent development of this method including its comparison with well-known analytical results and a finite-difference type simulations. We also present extension of the method for problems of multiple scattering of a polarized light on large spherical particles that joins presented mathematical formalism with Mie theory.

  17. Effectiveness of trimethoprim/sulfamethoxazole for children with chronic active otitis media: a randomized, placebo-controlled trial.

    NARCIS (Netherlands)

    van der Veen, E.L.; Rovers, M.M.; Albers, F.W.J.; Sanders, E.A.M.; Schilder, A.G.M.

    2007-01-01

    OBJECTIVE: The goal was to determine the clinical effectiveness of prolonged outpatient treatment with trimethoprim/sulfamethoxazole for children with chronic active otitis media. METHODS: We performed a randomized, placebo-controlled trial with 101 children (1-12 years of age) with chronic active

  18. Learning Quantum Chemical Model with Learning Media Concept Map and Power Point Viewed from Memory and Creativity Skills Students

    Directory of Open Access Journals (Sweden)

    Agus Wahidi

    2017-03-01

    Full Text Available This research is experimental, using first class learning a quantum model of learning with concept maps media and the second media using real environments by power point presentation. The population is all class XI Science, number 2 grade. The sampling technique is done by purposive random sampling. Data collection techniques to test for cognitive performance and memory capabilities, with a questionnaire for creativity. Hypothesis testing using three-way ANOVA different cells with the help of software Minitab 15.Based on the results of data processing, concluded: (1 there is no influence of the quantum model of learning with media learning concept maps and real environments for learning achievement chemistry, (2 there is a high impact memory ability and low on student achievement, (3 there is no the effect of high and low creativity in student performance, (4 there is no interaction learning model quantum media learning concept maps and real environments with memory ability on student achievement, (5 there is no interaction learning model quantum media learning concept maps and real environments with creativity of student achievement, (6 there is no interaction memory skills and creativity of student achievement, (7 there is no interaction learning model quantum media learning concept maps and real environments, memory skills, and creativity on student achievement.

  19. A Peer-Led, Social Media-Delivered, Safer Sex Intervention for Chinese College Students: Randomized Controlled Trial

    Science.gov (United States)

    Sun, Wai Han; Wong, Carlos King Ho

    2017-01-01

    Background The peer-led, social media-delivered intervention is an emerging method in sexual health promotion. However, no research has yet investigated its effectiveness as compared with other online channels or in an Asian population. Objective The objective of this study is to compare a peer-led, social media-delivered, safer sex intervention with a sexual health website. Both conditions target Chinese college students in Hong Kong. Methods A randomized controlled trial was conducted with a peer-led, safer sex Facebook group as the intervention and an existing online sexual health website as the control. The intervention materials were developed with peer input and followed the information-motivation-behavioral skills model; the intervention was moderated by peer educators. The participants filled out the online questionnaires before and after the 6-week intervention period. Outcome evaluations included safer sex attitudes, behavioral skills, and behaviors, while process evaluation focused on online experience, online-visiting frequency, and online engagement. The effect of online-visiting frequency and online engagement on outcome variables was investigated. Results Of 196 eligible participants—100 in the control group and 96 in the intervention group—who joined the study, 2 (1.0%) control participants joined the Facebook group and 24 of the remaining 194 participants (12.4%) were lost to follow-up. For the process evaluation, participants in the intervention group reported more satisfying online experiences (Psocial media-delivered, safer sex intervention was found to be feasible and effective in improving attitudes toward condom use and behavioral skills, but was not significantly more effective than a website. Future research may focus on the long-term effectiveness and cost-effectiveness of this popular method, as well as the potential cultural differences of using social media between different countries. Trial Registration Chinese Clinical Trial

  20. A Peer-Led, Social Media-Delivered, Safer Sex Intervention for Chinese College Students: Randomized Controlled Trial.

    Science.gov (United States)

    Sun, Wai Han; Wong, Carlos King Ho; Wong, William Chi Wai

    2017-08-09

    The peer-led, social media-delivered intervention is an emerging method in sexual health promotion. However, no research has yet investigated its effectiveness as compared with other online channels or in an Asian population. The objective of this study is to compare a peer-led, social media-delivered, safer sex intervention with a sexual health website. Both conditions target Chinese college students in Hong Kong. A randomized controlled trial was conducted with a peer-led, safer sex Facebook group as the intervention and an existing online sexual health website as the control. The intervention materials were developed with peer input and followed the information-motivation-behavioral skills model; the intervention was moderated by peer educators. The participants filled out the online questionnaires before and after the 6-week intervention period. Outcome evaluations included safer sex attitudes, behavioral skills, and behaviors, while process evaluation focused on online experience, online-visiting frequency, and online engagement. The effect of online-visiting frequency and online engagement on outcome variables was investigated. Of 196 eligible participants-100 in the control group and 96 in the intervention group-who joined the study, 2 (1.0%) control participants joined the Facebook group and 24 of the remaining 194 participants (12.4%) were lost to follow-up. For the process evaluation, participants in the intervention group reported more satisfying online experiences (Pdifference was found. After adjusting for demographic data, increased online-visiting frequency was associated with better contraceptive use behavioral intention (P=.05), better behavioral skills (P=.02), and more frequent condom use (P=.04). A peer-led, social media-delivered, safer sex intervention was found to be feasible and effective in improving attitudes toward condom use and behavioral skills, but was not significantly more effective than a website. Future research may focus on the

  1. Inverse random source scattering for the Helmholtz equation in inhomogeneous media

    Science.gov (United States)

    Li, Ming; Chen, Chuchu; Li, Peijun

    2018-01-01

    This paper is concerned with an inverse random source scattering problem in an inhomogeneous background medium. The wave propagation is modeled by the stochastic Helmholtz equation with the source driven by additive white noise. The goal is to reconstruct the statistical properties of the random source such as the mean and variance from the boundary measurement of the radiated random wave field at multiple frequencies. Both the direct and inverse problems are considered. We show that the direct problem has a unique mild solution by a constructive proof. For the inverse problem, we derive Fredholm integral equations, which connect the boundary measurement of the radiated wave field with the unknown source function. A regularized block Kaczmarz method is developed to solve the ill-posed integral equations. Numerical experiments are included to demonstrate the effectiveness of the proposed method.

  2. P-adic model of transport in porous disordered media

    Science.gov (United States)

    Khrennikov, Adrei Yu.; Oleschko, Klaudia

    2014-05-01

    The soil porosity and permeability are the most important quantitative indicators of soil dynamics under the land-use change. The main problema in the modeling of this dynamic is still poor correlation between the real measuring data and the mathematical and computer simulation models. In order to overpassed this deep divorce we have designed a new technique, able to compare the data arised from the multiscale image analices and time series of the basic physical properties dynamics in porous media studied in time and space. We present a model of the diffusion reaction type describing transport in disordered porous media, e.g., water or oil flow in a complex network of pores. Our model is based on p-adic representation of such networks. This is a kind of fractal representation. We explore advantages of p- adic representation, namely, the possibility to endow p-adic trees with an algebraic structure and ultrametric topology and, hence, to apply analysis which have (at least some) similarities with ordinary real analysis on the straight line. We present the system of two diffusion reaction equations describing propagation of particles in networks of pores in disordered media. As an application, one can consider water transport through the soil pore Networks, or oil flow through capillaries nets. Under some restrictions on potentials and rate coefficients we found the stationary regime corresponding to water content or concentration of oil in a cluster of capillaries. Usage of p-adic analysis (in particular, p-adic wavelets) gives a possibility to find the stationary solution in the analytic form which makes possible to present a clear pedological or geological picture of the process. The mathematical model elaborated in this paper (Khrennikov, 2013) can be applied to variety of problems from water concentration in aquifers to the problem of formation of oil reservoirs in disordered media with porous structures. Another possible application may have real practical

  3. Development of a restricted state space stochastic differential equation model for bacterial growth in rich media

    DEFF Research Database (Denmark)

    Møller, Jan Kloppenborg; Philipsen, Kirsten Riber; Christiansen, Lasse Engbo

    2012-01-01

    In the present study, bacterial growth in a rich media is analysed in a Stochastic Differential Equation (SDE) framework. It is demonstrated that the SDE formulation and smoothened state estimates provide a systematic framework for data driven model improvements, using random walk hidden states....... Bacterial growth is limited by the available substrate and the inclusion of diffusion must obey this natural restriction. By inclusion of a modified logistic diffusion term it is possible to introduce a diffusion term flexible enough to capture both the growth phase and the stationary phase, while...... to capture the random behaviour of the growth model. Further, it is concluded that the Monod effect is not needed to capture the dynamics of bacterial growth in the data presented....

  4. Kinetic Models with Randomly Perturbed Binary Collisions

    Science.gov (United States)

    Bassetti, Federico; Ladelli, Lucia; Toscani, Giuseppe

    2011-02-01

    We introduce a class of Kac-like kinetic equations on the real line, with general random collisional rules which, in some special cases, identify models for granular gases with a background heat bath (Carrillo et al. in Discrete Contin. Dyn. Syst. 24(1):59-81, 2009), and models for wealth redistribution in an agent-based market (Bisi et al. in Commun. Math. Sci. 7:901-916, 2009). Conditions on these collisional rules which guarantee both the existence and uniqueness of equilibrium profiles and their main properties are found. The characterization of these stationary states is of independent interest, since we show that they are stationary solutions of different evolution problems, both in the kinetic theory of rarefied gases (Cercignani et al. in J. Stat. Phys. 105:337-352, 2001; Villani in J. Stat. Phys. 124:781-822, 2006) and in the econophysical context (Bisi et al. in Commun. Math. Sci. 7:901-916, 2009).

  5. Bridges in the random-cluster model

    Directory of Open Access Journals (Sweden)

    Eren Metin Elçi

    2016-02-01

    Full Text Available The random-cluster model, a correlated bond percolation model, unifies a range of important models of statistical mechanics in one description, including independent bond percolation, the Potts model and uniform spanning trees. By introducing a classification of edges based on their relevance to the connectivity we study the stability of clusters in this model. We prove several exact relations for general graphs that allow us to derive unambiguously the finite-size scaling behavior of the density of bridges and non-bridges. For percolation, we are also able to characterize the point for which clusters become maximally fragile and show that it is connected to the concept of the bridge load. Combining our exact treatment with further results from conformal field theory, we uncover a surprising behavior of the (normalized variance of the number of (non-bridges, showing that it diverges in two dimensions below the value 4cos2⁡(π/3=0.2315891⋯ of the cluster coupling q. Finally, we show that a partial or complete pruning of bridges from clusters enables estimates of the backbone fractal dimension that are much less encumbered by finite-size corrections than more conventional approaches.

  6. Random graph models for dynamic networks

    Science.gov (United States)

    Zhang, Xiao; Moore, Cristopher; Newman, Mark E. J.

    2017-10-01

    Recent theoretical work on the modeling of network structure has focused primarily on networks that are static and unchanging, but many real-world networks change their structure over time. There exist natural generalizations to the dynamic case of many static network models, including the classic random graph, the configuration model, and the stochastic block model, where one assumes that the appearance and disappearance of edges are governed by continuous-time Markov processes with rate parameters that can depend on properties of the nodes. Here we give an introduction to this class of models, showing for instance how one can compute their equilibrium properties. We also demonstrate their use in data analysis and statistical inference, giving efficient algorithms for fitting them to observed network data using the method of maximum likelihood. This allows us, for example, to estimate the time constants of network evolution or infer community structure from temporal network data using cues embedded both in the probabilities over time that node pairs are connected by edges and in the characteristic dynamics of edge appearance and disappearance. We illustrate these methods with a selection of applications, both to computer-generated test networks and real-world examples.

  7. Effect of (social) media on the political figure fever model: Jokowi-fever model

    Science.gov (United States)

    Yong, Benny; Samat, Nor Azah

    2016-02-01

    In recent years, political figures begin to utilize social media as one of alternative to engage in communication with their supporters. Publics referred to Jokowi, one of the candidates in Indonesia presidential election in 2014, as the first politician in Indonesia to truly understand the power of social media. Social media is very important in shaping public opinion. In this paper, effect of social media on the Jokowi-fever model in a closed population will be discussed. Supporter population is divided into three class sub-population, i.e susceptible supporters, Jokowi infected supporters, and recovered supporters. For case no positive media, there are two equilibrium points; the Jokowi-fever free equilibrium point in which it locally stable if basic reproductive ratio less than one and the Jokowi-fever endemic equilibrium point in which it locally stable if basic reproductive ratio greater than one. For case no negative media, there is only the Jokowi-fever endemic equilibrium point in which it locally stable if the condition is satisfied. Generally, for case positive media proportion is positive, there is no Jokowi-fever free equilibrium point. The numerical result shows that social media gives significantly effect on Jokowi-fever model, a sharp increase or a sharp decrease in the number of Jokowi infected supporters. It is also shown that the boredom rate is one of the sensitive parameters in the Jokowi-fever model; it affects the number of Jokowi infected supporters.

  8. 3D Modeling Techniques for Print and Digital Media

    Science.gov (United States)

    Stephens, Megan Ashley

    In developing my thesis, I looked to gain skills using ZBrush to create 3D models, 3D scanning, and 3D printing. The models created compared the hearts of several vertebrates and were intended for students attending Comparative Vertebrate Anatomy. I used several resources to create a model of the human heart and was able to work from life while creating heart models from other vertebrates. I successfully learned ZBrush and 3D scanning, and successfully printed 3D heart models. ZBrush allowed me to create several intricate models for use in both animation and print media. The 3D scanning technique did not fit my needs for the project, but may be of use for later projects. I was able to 3D print using two different techniques as well.

  9. Efficacy of a randomized trial of a community and school-based anti-violence media intervention among small-town middle school youth.

    Science.gov (United States)

    Swaim, Randall C; Kelly, Kathleen

    2008-09-01

    In a community randomized controlled trial, intervention middle school students from small towns were exposed to a community and school-based anti-violence intervention ("Resolve It, Solve It"). The primary intervention was a media campaign in which local high school students served as models in print, radio, and television PSAs and spearheaded local school and community activities. The media campaign was supported with school and community events that reinforced campaign messages. Tests of recognition and recall indicated widespread exposure to the media intervention. Multiple group latent growth models indicated that relative to control students, intervention students reported significant differences in rates of growth for intent for violence, physical assault against people, verbal victimization, and perceived safety at school. No differences were found for verbal assault, physical assault against objects, physical victimization, or self-efficacy for avoiding violence. When examined by sex, it was determined that results for physical assault against people were obtained only among female students, and changes in verbal victimization and perceived school safety were observed only among male students. These results suggest that a media and reinforcing community intervention led by older peers can alter rates of growth for some measures of violence and associated factors among small-town youth. Further research is indicated to determine how different campaign messages influence students by sex.

  10. Comparison of Media Literacy and Usual Education to Prevent Tobacco Use: A Cluster-Randomized Trial

    Science.gov (United States)

    Primack, Brian A.; Douglas, Erika L.; Land, Stephanie R.; Miller, Elizabeth; Fine, Michael J.

    2014-01-01

    Background: Media literacy programs have shown potential for reduction of adolescent tobacco use. We aimed to determine if an anti-smoking media literacy curriculum improves students' media literacy and affects factors related to adolescent smoking. Methods: We recruited 1170 9th-grade students from 64 classrooms in 3 public urban high…

  11. Modelling information dissemination under privacy concerns in social media

    Science.gov (United States)

    Zhu, Hui; Huang, Cheng; Lu, Rongxing; Li, Hui

    2016-05-01

    Social media has recently become an important platform for users to share news, express views, and post messages. However, due to user privacy preservation in social media, many privacy setting tools are employed, which inevitably change the patterns and dynamics of information dissemination. In this study, a general stochastic model using dynamic evolution equations was introduced to illustrate how privacy concerns impact the process of information dissemination. Extensive simulations and analyzes involving the privacy settings of general users, privileged users, and pure observers were conducted on real-world networks, and the results demonstrated that user privacy settings affect information differently. Finally, we also studied the process of information diffusion analytically and numerically with different privacy settings using two classic networks.

  12. Reach/frequency for printed media: Personal probabilities or models

    DEFF Research Database (Denmark)

    Mortensen, Peter Stendahl

    2000-01-01

    that, in order to prevent bias, ratings per group must be used as reading probabilities. Nevertheless, in most cases, the estimates are still biased compared with panel data, thus overestimating net ´reach. Models with the same assumptions as with assignments of reading probabilities are presented......The author evaluates two different ways of estimating reach and frequency of plans for printed media. The first assigns reading probabilities to groups of respondents and calculates reach and frequency by simulation. the second estimates parameters to a model for reach/frequency. It is concluded...

  13. Illicit drugs and the media: models of media effects for use in drug policy research.

    Science.gov (United States)

    Lancaster, Kari; Hughes, Caitlin E; Spicer, Bridget; Matthew-Simmons, Francis; Dillon, Paul

    2011-07-01

    Illicit drugs are never far from the media gaze and although identified almost a decade ago as 'a new battleground' for the alcohol and other drug (AOD) field there has been limited research examining the role of the news media and its effects on audiences and policy. This paper draws together media theories from communication literature to examine media functions. We illustrate how each function is relevant for media and drugs research by drawing upon the existing literature examining Australian media coverage during the late 1990s of escalating heroin-related problems and proposed solutions. Media can influence audiences in four key ways: by setting the agenda and defining public interest; framing issues through selection and salience; indirectly shaping individual and community attitudes towards risk; and feeding into political debate and decision making. Each has relevance for the AOD field. For example, media coverage of the escalating heroin-related problems in Australia played a strong role in generating interest in heroin overdoses, framing public discourse in terms of a health and/or criminal issue and affecting political decisions. Implications AND CONCLUSION: Media coverage in relation to illicit drugs can have multifarious effects. Incorporating media communication theories into future research and actions is critical to facilitate understanding of the short- and long-term impacts of media coverage on illicit drugs and the avenues by which the AOD field can mitigate or inform future media debates on illicit drugs. © 2010 Australasian Professional Society on Alcohol and other Drugs.

  14. Equivalent Continuum Modeling for Shock Wave Propagation in Jointed Media

    Energy Technology Data Exchange (ETDEWEB)

    Vorobiev, O; Antoun, T

    2009-12-11

    This study presents discrete and continuum simulations of shock wave propagating through jointed media. The simulations were performed using the Lagrangian hydrocode GEODYN-L with joints treated explicitly using an advanced contact algorithm. They studied both isotropic and anisotropic joint representations. For an isotropically jointed geologic medium, the results show that the properties of the joints can be combined with the properties of the intact rock to develop an equivalent continuum model suitable for analyzing wave propagation through the jointed medium. For an anisotropically jointed geologic medium, they found it difficult to develop an equivalent continuum (EC) model that matches the response derived from mesoscopic simulation. They also performed simulations of wave propagation through jointed media. Two appraoches are suggested for modeling the rock mass. In one approach, jointed are modeled explicitly in a Lagrangian framework with appropriate contact algorithms used to track motion along the interfaces. In the other approach, the effect of joints is taken into account using a constitutive model derived from mesoscopic simulations.

  15. Random Search with Memory in Patchy Media: Exploration-Exploitation Tradeoff

    CERN Document Server

    Chupeau, M; Redner, S

    2016-01-01

    How to best exploit patchy resources? This long-standing question belongs to the extensively studied class of explore/exploit problems that arise in a wide range of situations, from animal foraging, to robotic exploration, and to human decision processes. Despite its broad relevance, the issue of optimal exploitation has previously only been tackled through two paradigmatic limiting models---patch-use and random search---that do not account for the interplay between searcher motion within patches and resource depletion. Here, we bridge this gap by introducing a minimal patch exploitation model that incorporates this coupling: the searcher depletes the resources along its random-walk trajectory within a patch and travels to a new patch after it takes $\\mathcal{S}$ consecutive steps without finding resources. We compute the distribution of the amount of resources $F_t$ consumed by time $t$ for this non-Markovian random walker and show that exploring multiple patches is beneficial. In one dimension, we analytica...

  16. In situ bioremediation: A network model of diffusion and flow in granular porous media

    Energy Technology Data Exchange (ETDEWEB)

    Griffiths, S.K.; Nilson, R.H.; Bradshaw, R.W.

    1997-04-01

    In situ bioremediation is a potentially expedient, permanent and cost- effective means of waste site decontamination. However, permeability reductions due to the transport and deposition of native fines or due to excessive microorganism populations may severely inhibit the injection of supplemental oxygen in the contamination zone. To help understand this phenomenon, we have developed a micro-mechanical network model of flow, diffusion and particle transport in granular porous materials. The model differs from most similar models in that the network is defined by particle positions in a numerically-generated particle array. The model is thus widely applicable to computing effective transport properties for both ordered and realistic random porous media. A laboratory-scale apparatus to measure permeability reductions has also been designed, built and tested.

  17. Physical modelling of elastic anisotropy in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Furre, Anne-Kari

    1997-12-31

    During the last decades, anisotropy has become increasingly interesting in hydrocarbon prospecting. Knowledge of anisotropy in the subsurface can improve reservoir production and data interpretation. This thesis presents experimental studies of three different artificial anisotropic media: layered materials, isotropic matrix with stress-induced fractures, and layered media with controlled crack patterns at an oblique angle relative to layering. Layered media were constructed by varying grain size distributions for different layers, which resulted in acoustic and permeability anisotropy. The thin layer materials could be described by Backus modelling provided the wavelength was much larger than the layer periods. Frequency dependent scattering was observed for waves travelling normal to the layers. Saturated wave velocities were consistent with transverse isotropic Biot theory, but because the permeability anisotropy was small, no flow dependent attenuation anisotropy was observed. When sandstones were cemented under stress and then released, to simulate a vertical core or uplift process, predominantly horizontal cracks developed in the samples. On reloading to the cementing stress level, the velocities were below the initial values, which supports the theories of crack growth. In further triaxial tests on the same material a stress-dependent anisotropy occurred similar to what is often seen in natural samples taken from large depths. 70 refs., 200 figs., 56 tabs.

  18. Meso-Scale Stochastic Model for Flow and Transport in Porous Media

    Science.gov (United States)

    Tartakovsky, A. M.; Tartakovsky, D. M.; Meakin, P.

    2008-12-01

    In a homogeneous porous medium, dispersive mixing is the result of a combination of molecular diffusion (diffusive mixing) and spreading due to variations in the fluid velocity (advective mixing). In traditional Darcy(continuum)-scale models this combination is treated as a Fickian diffusion process with a macro-scale effective diffusion coefficient (the dispersion coefficient). However, dispersive mixing is very different from purely diffusive mixing and there is ample evidence that the advection-dispersion equations significantly over-predict the extent of reactions in mixing induced chemical transformations. We have developed a new meso-scale stochastic Lagrangian particle model that treats advective mixing and diffusive mixing separately. We assume that fluid flow in homogeneous porous media is governed by a stochastic Langevin equation that is obtained by adding white noise fluctuations to the momentum conservation equation. The noise represents the random interactions between the fluid and the disordered porous medium, which forces fluid flow paths to deviate from the smooth flow paths predicted by the Darcy scale continuum flow equations. The molecular diffusion of solutes carried by the fluid is governed by the classical advection-diffusion equation, which becomes stochastic due to random advection. The stochastic meso-scale model and deterministic advection-dispersion theory were used to simulate the reactive mixing of two solutions injected in parallel into a flow domain. IN the stochastic model, the transport equations were numerically solved using smoothed particle hydrodynamics (SPH), a Lagrangian particle method that has been previously applied to both deterministic and stochastic transport problems. Comparison of the two solutions revealed that the Langevin model gives better estimates of concentrations than the Darcy scale advection-dispersion model, and that the Darcy scale model significantly overestimates the amount of product in mixing induced

  19. PENGEMBANGAN MODEL PEER COUNSELING SEBAGAI MEDIA PENGALAMAN PRAKTIK KONSELING

    Directory of Open Access Journals (Sweden)

    muslikah muslikah

    2017-03-01

    Full Text Available Practical experience is an important component of counselor education program. Through the experience student counseling practice, counselor candidate  given the experience to apply the skills and knowledge they acquired in the lecture. Peer Counseling in this research defined as the involvement of youth in peer groups to provide particular input for the development of personality and social of adolescents. Thus, peer counseling can be utilized in the process of lectures, so counselors candidate can be optimized to obtain practical experience supervised by a professional counselor. This research aims to develop a peer counseling model as an experience counseling practice media in basic skills counseling subject. The design used is research and development. Subjects were students of BK FIP UNNES. Data collected through in-depth interviews, questionnaires and  document studies. Data analysis technique used is  interactive model of Miles and Huberman. Results of the research is a model of peer counseling as an experience counseling practice media in basic skills of counseling subject include: (a rational, (b Definition, (c Interest, (d assuming, (e materials, (f the stages of peer counseling implementation, (g the evaluation and succes indicators, and function of group members, (h the phase of the service, (i the evaluation and follow-up. Based on  results expert validation obtained that the model is feasible and can be applied.

  20. Media models and objectification of men and women

    Directory of Open Access Journals (Sweden)

    Chiara Rollero

    2013-06-01

    Full Text Available Literature on objectification has largely demonstrated the relationship between exposure to objectified media models and body dissatisfaction for women. The aim of the research presented here is to extend the study of the consequences of such exposure - examining both male and female models - in relation to psychological well-being, self-esteem and endorsement of sexist attitudes. 166 university students (51.8% male participated in the study. Results showed that exposure to objectified male models decreases men’s well-being, while exposure to objectified female models not only decreases women’s well-being but also their perception of attractiveness and social esteem. Furthermore, female objectification influences men’s sexism, increasing hostility towards women and at the same time reducing the hostility toward their own gender. The implications are discussed.

  1. Stencil method: a Markov model for transport in porous media

    Science.gov (United States)

    Delgoshaie, A. H.; Tchelepi, H.; Jenny, P.

    2016-12-01

    In porous media the transport of fluid is dominated by flow-field heterogeneity resulting from the underlying transmissibility field. Since the transmissibility is highly uncertain, many realizations of a geological model are used to describe the statistics of the transport phenomena in a Monte Carlo framework. One possible way to avoid the high computational cost of physics-based Monte Carlo simulations is to model the velocity field as a Markov process and use Markov Chain Monte Carlo. In previous works multiple Markov models for discrete velocity processes have been proposed. These models can be divided into two general classes of Markov models in time and Markov models in space. Both of these choices have been shown to be effective to some extent. However some studies have suggested that the Markov property cannot be confirmed for a temporal Markov process; Therefore there is not a consensus about the validity and value of Markov models in time. Moreover, previous spacial Markov models have only been used for modeling transport on structured networks and can not be readily applied to model transport in unstructured networks. In this work we propose a novel approach for constructing a Markov model in time (stencil method) for a discrete velocity process. The results form the stencil method are compared to previously proposed spacial Markov models for structured networks. The stencil method is also applied to unstructured networks and can successfully describe the dispersion of particles in this setting. Our conclusion is that both temporal Markov models and spacial Markov models for discrete velocity processes can be valid for a range of model parameters. Moreover, we show that the stencil model can be more efficient in many practical settings and is suited to model dispersion both on structured and unstructured networks.

  2. Calculation Of Effective Fluid Permeability In Porous Media With Quenched Random Disorder Using The Coherent Potential Approximation

    Science.gov (United States)

    Hristopulos, Dionissios

    2001-03-01

    Quenched random disorder models represent the heterogeneity of the saturated fluid permeability of porous media in steady-state flow conditions. The effective permeability is based on the stochastic average of local fluctuations and measures large-scale effects of the disorder. Explicit calculations of effective permeability require various restrictive assumptions on the disorder distribution, and numerical methods are computationally intensive. We propose a semianalytical approach based on the coherent potential approximation (CPA), used for electronic band structure calculations in disordered semiconductors. The PCPA does not require the restrictions of explicit methods and admits efficient numerical solutions. The PCPA equations yield the exact effective permeability (the harmonic mean), in one spatial dimension. The leading order solution in higher dimensions agrees with the standard perturbation expansion. It is known that the effective permeability of a two-dimensional medium with lognormal disorder is given exactly by the geometric mean. We show that the numerical solutions of the PCPA are in good agreement with the exact expression.

  3. Local radial basis function meshless scheme for vector radiative transfer in participating media with randomly oriented axisymmetric particles.

    Science.gov (United States)

    Sun, Jie; Yi, Hong-Liang; Tan, He-Ping

    2016-02-20

    A local radial basis function meshless scheme (LRBFM) is developed to solve polarized radiative transfer in participating media containing randomly oriented axisymmetric particles in which radial basis functions augmented with polynomial basis are employed to construct the trial functions, and the vector radiative-transfer equation based on the discrete-ordinates approach is discretized directly by collocation method. The LRBFM belongs to a class of truly meshless methods that do not need any mesh or any numerical integration scheme. Performances of the LRBFM are verified with analytical solutions and other numerical results reported earlier in the literature via five various test cases. The predicted angular distribution of brightness temperature and Stokes vector by the LRBFM agree very well with the benchmark. It is demonstrated that the LRBFM is accurate to solve vector radiative transfer in participating media with randomly oriented axisymmetric particles.

  4. Quantum correlation of fiber-based telecom-band photon pairs through standard loss and random media.

    Science.gov (United States)

    Sua, Yong Meng; Malowicki, John; Lee, Kim Fook

    2014-08-15

    We study quantum correlation and interference of fiber-based telecom-band photon pairs with one photon of the pair experiencing multiple scattering in a random medium. We measure joint probability of two-photon detection for signal photon in a normal channel and idler photon in a channel, which is subjected to two independent conditions: standard loss (neutral density filter) and random media. We observe that both conditions degrade the correlation of signal and idler photons, and depolarization of the idler photon in random medium can enhance two-photon interference at certain relative polarization angles. Our theoretical calculation on two-photon polarization correlation and interference as a function of mean free path is in agreement with our experiment data. We conclude that quantum correlation of a polarization-entangled photon pair is better preserved than a polarization-correlated photon pair as one photon of the pair scatters through a random medium.

  5. Social media-delivered sexual health intervention: a cluster randomized controlled trial.

    Science.gov (United States)

    Bull, Sheana S; Levine, Deborah K; Black, Sandra R; Schmiege, Sarah J; Santelli, John

    2012-11-01

    Youth are using social media regularly and represent a group facing substantial risk for sexually transmitted infection (STI). Although there is evidence that the Internet can be used effectively in supporting healthy sexual behavior, this has not yet extended to social networking sites. To determine whether STI prevention messages delivered via Facebook are efficacious in preventing increases in sexual risk behavior at 2 and 6 months. Cluster RCT, October 2010-May 2011. Individuals (seeds) recruited in multiple settings (online, via newspaper ads and face-to-face) were asked to recruit three friends, who in turn recruited additional friends, extending three waves from the seed. Seeds and waves of friends were considered networks and exposed to either the intervention or control condition. Exposure to Just/Us, a Facebook page developed with youth input, or to control content on 18-24 News, a Facebook page with current events for 2 months. Condom use at last sex and proportion of sex acts protected by condoms. Repeated measures of nested data were used to model main effects of exposure to Just/Us and time by treatment interaction. A total of 1578 participants enrolled, with 14% Latino and 35% African-American; 75% of participants completed at least one study follow-up. Time by treatment effects were observed at 2 months for condom use (intervention 68% vs control 56%, p=0.04) and proportion of sex acts protected by condoms (intervention 63% vs control 57%, p=0.03) where intervention participation reduced the tendency for condom use to decrease over time. No effects were seen at 6 months. Social networking sites may be venues for efficacious health education interventions. More work is needed to understand what elements of social media are compelling, how network membership influences effects, and whether linking social media to clinical and social services can be beneficial. This study is registered at www.clinicaltrials.govNCT00725959. Copyright © 2012 American

  6. Numerical modeling of bubble dynamics in viscoelastic media with relaxation

    Science.gov (United States)

    Warnez, M. T.; Johnsen, E.

    2015-01-01

    Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller–Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin–Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time. PMID:26130967

  7. Numerical modeling of bubble dynamics in viscoelastic media with relaxation

    Science.gov (United States)

    Warnez, M. T.; Johnsen, E.

    2015-06-01

    Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.

  8. Single realization stochastic FDTD for weak scattering waves in biological random media.

    Science.gov (United States)

    Tan, Tengmeng; Taflove, Allen; Backman, Vadim

    2013-02-01

    This paper introduces an iterative scheme to overcome the unresolved issues presented in S-FDTD (stochastic finite-difference time-domain) for obtaining ensemble average field values recently reported by Smith and Furse in an attempt to replace the brute force multiple-realization also known as Monte-Carlo approach with a single-realization scheme. Our formulation is particularly useful for studying light interactions with biological cells and tissues having sub-wavelength scale features. Numerical results demonstrate that such a small scale variation can be effectively modeled with a random medium problem which when simulated with the proposed S-FDTD indeed produces a very accurate result.

  9. Randomized Controlled Trial of a Computerized Interactive Media-Based Problem Solving Treatment for Depression.

    Science.gov (United States)

    Sandoval, Luis R; Buckey, Jay C; Ainslie, Ricardo; Tombari, Martin; Stone, William; Hegel, Mark T

    2017-05-01

    This study evaluated the efficacy of an interactive media-based, computer-delivered depression treatment program (imbPST) compared to a no-treatment control condition (NTC) in a parallel-group, randomized, controlled trial conducted in an outpatient psychiatric research clinic. 45 adult participants with major depressive disorder or dysthymia were randomized to receive either 6 weekly sessions of imbPST or no treatment (No Treatment Control; NTC). The primary outcome measure was the Beck Depression Inventory II (BDI-II). There was a significant Group x Time interaction effect [F (1.73, 43)= 58.78; p<.001; η2=.58, Cohens d=1.94], such that the patients receiving imbPST had a significantly greater reduction in depressive symptoms compared to the patients in the NTC condition. Participants in the imbPST group improved their depression symptoms significantly from moderate (BDI-II=21.9±4.20) to mild levels of depression (BDI-II=17.9±4.0) after receiving 3 weekly sessions of imbPST (p<0.001), and progressed to still milder levels of depression after six weekly sessions (BDI-II=14.5±3.7, p<0.001). NTC participants showed no significant reduction in BDI-II scores (BDI-II=21.8±4.2 pre, BDI-II=21.5±5.2 post, N.S.). Additionally, 40% of the imbPST group showed a clinically significant and reliable change in depression levels while none of the NTC group met this criterion. imbPST participants rated the program highly usable on the system usability scale (SUS) after the first session (SUS Session 1=74.6±7.2) and usability scores increased significantly by the last session (SUS Session 6=85.4±5.6). We conclude that imbPST is an effective, engaging, and easily used depression treatment program that warrants further evaluation with heterogeneous depressed populations in a stand-alone, self-administered fashion. Copyright © 2016. Published by Elsevier Ltd.

  10. Renal Insufficiency Following Contrast Media Administration Trial (REMEDIAL): a randomized comparison of 3 preventive strategies.

    Science.gov (United States)

    Briguori, Carlo; Airoldi, Flavio; D'Andrea, Davide; Bonizzoni, Erminio; Morici, Nuccia; Focaccio, Amelia; Michev, Iassen; Montorfano, Matteo; Carlino, Mauro; Cosgrave, John; Ricciardelli, Bruno; Colombo, Antonio

    2007-03-13

    Volume supplementation by saline infusion combined with N-acetylcysteine (NAC) represents an effective strategy to prevent contrast agent-induced nephrotoxicity (CIN). Preliminary data support the concept that sodium bicarbonate and ascorbic acid also may be effective in preventing CIN. Three hundred twenty-six consecutive patients with chronic kidney disease, referred to our institutions for coronary and/or peripheral procedures, were randomly assigned to prophylactic administration of 0.9% saline infusion plus NAC (n=111), sodium bicarbonate infusion plus NAC (n=108), and 0.9% saline plus ascorbic acid plus NAC (n=107). All enrolled patients had serum creatinine > or = 2.0 mg/dL and/or estimated glomerular filtration rate or = 25% in the creatinine concentration 48 hours after the procedure (CIN). The amount of contrast media administered (179+/-102, 169+/-92, and 169+/-94 mL, respectively; P=0.69) and risk scores (9.1+/-3.4, 9.5+/-3.6, and 9.3+/-3.6; P=0.21) were similar in the 3 groups. CIN occurred in 11 of 111 patients (9.9%) in the saline plus NAC group, in 2 of 108 (1.9%) in the bicarbonate plus NAC group (P=0.019 by Fisher exact test versus saline plus NAC group), and in 11 of 107 (10.3%) in the saline plus ascorbic acid plus NAC group (P=1.00 versus saline plus NAC group). The strategy of volume supplementation by sodium bicarbonate plus NAC seems to be superior to the combination of normal saline with NAC alone or with the addition of ascorbic acid in preventing CIN in patients at medium to high risk.

  11. Modeling Flow in Porous Media with Double Porosity/Permeability.

    Science.gov (United States)

    Seyed Joodat, S. H.; Nakshatrala, K. B.; Ballarini, R.

    2016-12-01

    Although several continuum models are available to study the flow of fluids in porous media with two pore-networks [1], they lack a firm theoretical basis. In this poster presentation, we will present a mathematical model with firm thermodynamic basis and a robust computational framework for studying flow in porous media that exhibit double porosity/permeability. The mathematical model will be derived by appealing to the maximization of rate of dissipation hypothesis, which ensures that the model is in accord with the second law of thermodynamics. We will also present important properties that the solutions under the model satisfy, along with an analytical solution procedure based on the Green's function method. On the computational front, a stabilized mixed finite element formulation will be derived based on the variational multi-scale formalism. The equal-order interpolation, which is computationally the most convenient, is stable under this formulation. The performance of this formulation will be demonstrated using patch tests, numerical convergence study, and representative problems. It will be shown that the pressure and velocity profiles under the double porosity/permeability model are qualitatively and quantitatively different from the corresponding ones under the classical Darcy equations. Finally, it will be illustrated that the surface pore-structure is not sufficient in characterizing the flow through a complex porous medium, which pitches a case for using advanced characterization tools like micro-CT. References [1] G. I. Barenblatt, I. P. Zheltov, and I. N. Kochina, "Basic concepts in the theory of seepage of homogeneous liquids in fissured rocks [strata]," Journal of Applied Mathematics and Mechanics, vol. 24, pp. 1286-1303, 1960.

  12. Multiscale model reduction for shale gas transport in fractured media

    KAUST Repository

    Akkutlu, I. Y.

    2016-05-18

    In this paper, we develop a multiscale model reduction technique that describes shale gas transport in fractured media. Due to the pore-scale heterogeneities and processes, we use upscaled models to describe the matrix. We follow our previous work (Akkutlu et al. Transp. Porous Media 107(1), 235–260, 2015), where we derived an upscaled model in the form of generalized nonlinear diffusion model to describe the effects of kerogen. To model the interaction between the matrix and the fractures, we use Generalized Multiscale Finite Element Method (Efendiev et al. J. Comput. Phys. 251, 116–135, 2013, 2015). In this approach, the matrix and the fracture interaction is modeled via local multiscale basis functions. In Efendiev et al. (2015), we developed the GMsFEM and applied for linear flows with horizontal or vertical fracture orientations aligned with a Cartesian fine grid. The approach in Efendiev et al. (2015) does not allow handling arbitrary fracture distributions. In this paper, we (1) consider arbitrary fracture distributions on an unstructured grid; (2) develop GMsFEM for nonlinear flows; and (3) develop online basis function strategies to adaptively improve the convergence. The number of multiscale basis functions in each coarse region represents the degrees of freedom needed to achieve a certain error threshold. Our approach is adaptive in a sense that the multiscale basis functions can be added in the regions of interest. Numerical results for two-dimensional problem are presented to demonstrate the efficiency of proposed approach. © 2016 Springer International Publishing Switzerland

  13. A Systems Thinking Model for Open Source Software Development in Social Media

    OpenAIRE

    Mustaquim, Moyen

    2010-01-01

    In this paper a social media model, based on systems thinking methodology is proposed to understand the behavior of the open source software development community working in social media.The proposed model is focused on relational influences of two different systems- social media and the open source community. This model can be useful for taking decisions which are complicated and where solutions are not apparent.Based on the proposed model, an efficient way of working in open source developm...

  14. A mixing model to predict selected parameters in mixing container media

    NARCIS (Netherlands)

    Blok, C.; Withagen, J.C.M.

    2009-01-01

    The aim of the study was to get accurate data on the effects of mixing container media components and to match these data against models for mixing container media. It was accepted that the mixing of two container media components was related linearly to the amounts of material mixed, for parameters

  15. A data-driven model for influenza transmission incorporating media effects.

    Science.gov (United States)

    Mitchell, Lewis; Ross, Joshua V

    2016-10-01

    Numerous studies have attempted to model the effect of mass media on the transmission of diseases such as influenza; however, quantitative data on media engagement has until recently been difficult to obtain. With the recent explosion of 'big data' coming from online social media and the like, large volumes of data on a population's engagement with mass media during an epidemic are becoming available to researchers. In this study, we combine an online dataset comprising millions of shared messages relating to influenza with traditional surveillance data on flu activity to suggest a functional form for the relationship between the two. Using this data, we present a simple deterministic model for influenza dynamics incorporating media effects, and show that such a model helps explain the dynamics of historical influenza outbreaks. Furthermore, through model selection we show that the proposed media function fits historical data better than other media functions proposed in earlier studies.

  16. Induced Monoculture in Axelrod Model with Clever Mass Media

    Science.gov (United States)

    Rodríguez, Arezky H.; Del Castillo-Mussot, M.; Vázquez, G. J.

    A new model is proposed, in the context of Axelrod's model for the study of cultural dissemination, to include an external vector field (VF) which describes the effects of mass media on social systems. The VF acts over the whole system and it is characterized by two parameters: a nonnull overlap with each agent in the society and a confidence value of its information. Beyond a threshold value of the confidence, there is induced monocultural globalization of the system lined up with the VF. Below this value, the multicultural states are unstable and certain homogenization of the system is obtained in opposite line up according to that we have called negative publicity effect. Three regimes of behavior for the spread process of the VF information as a function of time are reported.

  17. Design of control adaptability system model for TV media organization structure

    Institute of Scientific and Technical Information of China (English)

    WANG Dong-dong; WANG Ya-lin; MA Tao

    2008-01-01

    To resolve the control adaptability problem of TV media in complex competitive environment, a con-trol system model of TV media organization structure was designed. Based on the designed system model for TV media organization structure, the relations among the main factors of the system constitution, missions, organi-zing decision entity, and carrying bodies were analyzed. By means of applying multi-objective decision method and complex control system theory, and combining the integration model of TV media organization structure, the basic model was concluded and the corresponding parameters were designed. The current organization process of TV media is analyzed by this model, which comes to the adaptability appearance with different parameters. The results indicate that the model can estimate current TV media organization structure for the chain appearance of communications and the correlation between platforms and policy-making agencies.

  18. Modelling News Media Use. Positing and applying the MC/GC model to the analysis of media use in everyday life and crisis situations

    DEFF Research Database (Denmark)

    Westlund, Oscar; Ghersetti, Marina

    2014-01-01

    The contemporary mediascape offers a plethora of news media and social media, which people can turn to in everyday life and during a crisis. The characteristics of media vary, providing different logics and affordances, and occupying different niches in time and space (medium-centric (MC) approach......). Generations develop routinized media usage patterns in the formative phases of their lives, which they often maintain in their daily habits in everyday life (generation-centric (GC) approach). Crisis events in the vicinity, such as gas emissions, terrorist attacks, pandemics and earthquakes, presumably ignite...... an augmented interest for information and news on the events that may cause a destabilization of established media usage routines. This article aims to conceptualize, describe and explain how four generations envision their media use during such crises. The article posits the MC/GC-model, a 2x2 matrix...

  19. Modeling of flow in faulted and fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Oeian, Erlend

    2004-03-01

    The work on this thesis has been done as part of a collaborative and inter disciplinary effort to improve the understanding of oil recovery mechanisms in fractured reservoirs. This project has been organized as a Strategic University Program (SUP) at the University of Bergen, Norway. The complex geometries of fractured reservoirs combined with flow of several fluid phases lead to difficult mathematical and numerical problems. In an effort to try to decrease the gap between the geological description and numerical modeling capabilities, new techniques are required. Thus, the main objective has been to improve the ATHENA flow simulator and utilize it within a fault modeling context. Specifically, an implicit treatment of the advection dominated mass transport equations within a domain decomposition based local grid refinement framework has been implemented. Since large computational tasks may arise, the implicit formulation has also been included in a parallel version of the code. Within the current limits of the simulator, appropriate up scaling techniques has also been considered. Part I of this thesis includes background material covering the basic geology of fractured porous media, the mathematical model behind the in-house flow simulator ATHENA and the additions implemented to approach simulation of flow through fractured and faulted porous media. In Part II, a set of research papers stemming from Part I is presented. A brief outline of the thesis follows below. In Chapt. 1 important aspects of the geological description and physical parameters of fractured and faulted porous media is presented. Based on this the scope of this thesis is specified having numerical issues and consequences in mind. Then, in Chapt. 2, the mathematical model and discretizations in the flow simulator is given followed by the derivation of the implicit mass transport formulation. In order to be fairly self-contained, most of the papers in Part II also includes the mathematical model

  20. Space-time mesh adaptation for solute transport in randomly heterogeneous porous media.

    Science.gov (United States)

    Dell'Oca, Aronne; Porta, Giovanni Michele; Guadagnini, Alberto; Riva, Monica

    2017-07-05

    We assess the impact of an anisotropic space and time grid adaptation technique on our ability to solve numerically solute transport in heterogeneous porous media. Heterogeneity is characterized in terms of the spatial distribution of hydraulic conductivity, whose natural logarithm, Y, is treated as a second-order stationary random process. We consider nonreactive transport of dissolved chemicals to be governed by an Advection Dispersion Equation at the continuum scale. The flow field, which provides the advective component of transport, is obtained through the numerical solution of Darcy's law. A suitable recovery-based error estimator is analyzed to guide the adaptive discretization. We investigate two diverse strategies guiding the (space-time) anisotropic mesh adaptation. These are respectively grounded on the definition of the guiding error estimator through the spatial gradients of: (i) the concentration field only; (ii) both concentration and velocity components. We test the approach for two-dimensional computational scenarios with moderate and high levels of heterogeneity, the latter being expressed in terms of the variance of Y. As quantities of interest, we key our analysis towards the time evolution of section-averaged and point-wise solute breakthrough curves, second centered spatial moment of concentration, and scalar dissipation rate. As a reference against which we test our results, we consider corresponding solutions associated with uniform space-time grids whose level of refinement is established through a detailed convergence study. We find a satisfactory comparison between results for the adaptive methodologies and such reference solutions, our adaptive technique being associated with a markedly reduced computational cost. Comparison of the two adaptive strategies tested suggests that: (i) defining the error estimator relying solely on concentration fields yields some advantages in grasping the key features of solute transport taking place within

  1. A Note on the Correlated Random Coefficient Model

    DEFF Research Database (Denmark)

    Kolodziejczyk, Christophe

    In this note we derive the bias of the OLS estimator for a correlated random coefficient model with one random coefficient, but which is correlated with a binary variable. We provide set-identification to the parameters of interest of the model. We also show how to reduce the bias of the estimator...

  2. The Analysis of Random Effects in Modeling Studies.

    Science.gov (United States)

    Scheirer, C. James; Geller, Sanford E.

    1979-01-01

    Argues that in research on the effects of modeling, models must be analyzed as a random factor in order to avoid a positive bias in the results. The concept of a random factor is discussed, worked examples are provided, and a practical solution to the problem is proposed. (JMB)

  3. Compensatory and non-compensatory multidimensional randomized item response models

    NARCIS (Netherlands)

    Fox, J.P.; Entink, R.K.; Avetisyan, M.

    2014-01-01

    Randomized response (RR) models are often used for analysing univariate randomized response data and measuring population prevalence of sensitive behaviours. There is much empirical support for the belief that RR methods improve the cooperation of the respondents. Recently, RR models have been

  4. A random energy model for size dependence : recurrence vs. transience

    NARCIS (Netherlands)

    Külske, Christof

    1998-01-01

    We investigate the size dependence of disordered spin models having an infinite number of Gibbs measures in the framework of a simplified 'random energy model for size dependence'. We introduce two versions (involving either independent random walks or branching processes), that can be seen as

  5. Discrete Network Modeling for Field-Scale Flow and Transport Through Porous Media

    National Research Council Canada - National Science Library

    Howington, Stacy

    1997-01-01

    .... Specifically, a stochastic, high-resolution, discrete network model is developed and explored for simulating macroscopic flow and conservative transport through macroscopic porous media Networks...

  6. How Managers' Shared Mental Models of Business–Customer Interactions Create Different Sensemaking of Social Media

    DEFF Research Database (Denmark)

    Rydén, Pernille; Ringberg, Torsten; Wilke, Ricky

    2015-01-01

    Building on empirical research, we identify four mental models of business–customer interactions and show how each uniquely affects how managers conceptualize and use social media. The four models are “business-to-customers,” “business-from-customers,” “business-with-customers,” and “business......-for-customers.” The mental model approach helps explain why managers' use of social media does not necessarily lead to radical changes in their interaction with customers, despite the opportunities facilitated by these media. We provide a conceptual framework that enables managers to introspectively investigate their own...... mental models and thereby revise their sensemaking and use of social media....

  7. Efficient algorithms for multiscale modeling in porous media

    KAUST Repository

    Wheeler, Mary F.

    2010-09-26

    We describe multiscale mortar mixed finite element discretizations for second-order elliptic and nonlinear parabolic equations modeling Darcy flow in porous media. The continuity of flux is imposed via a mortar finite element space on a coarse grid scale, while the equations in the coarse elements (or subdomains) are discretized on a fine grid scale. We discuss the construction of multiscale mortar basis and extend this concept to nonlinear interface operators. We present a multiscale preconditioning strategy to minimize the computational cost associated with construction of the multiscale mortar basis. We also discuss the use of appropriate quadrature rules and approximation spaces to reduce the saddle point system to a cell-centered pressure scheme. In particular, we focus on multiscale mortar multipoint flux approximation method for general hexahedral grids and full tensor permeabilities. Numerical results are presented to verify the accuracy and efficiency of these approaches. © 2010 John Wiley & Sons, Ltd.

  8. Toward An Ontology of Mutual Recursion: Models, Mind and Media

    Directory of Open Access Journals (Sweden)

    Mat Wall-Smith

    2008-01-01

    Full Text Available In Parables for the Virtual Massumi describes 'The Autonomy of Affect' in our ecology of thought (Massumi 2002 : 35. The object of Stiegler's Technics and Time is 'technics apprehended as the horizon of all possibility to come and all possibility of a future' (Stiegler 1998 : ix. The ecological dynamic described by the recursion between this 'affective autonomy' and a 'technical horizon of possibility' describes a metamodel of the relation between body and world, between perception and expression. I argue that this metamodel allows for the technical architectures that enshrine media processes and models as both the manifestation and modulation of the 'industry' or vitality of mind. I argue that these technical architectures are crucial to the creation and maintenance of dynamic ecologies of living.

  9. Sensitivity of Effective Thermal Conductivity Models on Temperature Distribution of Heterogeneous media of Fully Ceramic Micro-encapsulated Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Hyuk; Kim, S. J.; Hwang, D. H.; Lee, W. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    A TRISO fuel particle consists of a spherical fuel kernel with four coating layers such as buffer, Inner PyC, SiC, Outer PyC. A FCM fuel pellet contains randomly distributed 36 in a SiC matrix. Such heterogeneous and complicated structure adds difficulty in calculating the realistic temperature distributions in the FCM fuel. General practice is to use a homogenized model using an effective thermal conductivity model. For these difficulties, a realistic temperature profile on a heterogeneous media is generally calculated on a homogenization model. In this study, we investigate the influence of effective thermal conductivity models on the temperature distribution in a heterogeneous media on FCM fuel pellet. Feasibility of Single Domain Homogenization(SDH) model has been estimated for a heterogeneous media like FCM fuel. From the study, it is found that the effective thermal conductivity is a crucial parameter in analyzing the temperature distributions in SDH approach. Sensitivity of the effective thermal conductivity models indicates that the Maxwell model or an optimized conductivity models are adequate in modeling the heterogeneous FCM fuel.

  10. The Ising model on random lattices in arbitrary dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Bonzom, Valentin, E-mail: vbonzom@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, 31 Caroline St. N, ON N2L 2Y5, Waterloo (Canada); Gurau, Razvan, E-mail: rgurau@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, 31 Caroline St. N, ON N2L 2Y5, Waterloo (Canada); Rivasseau, Vincent, E-mail: vincent.rivasseau@gmail.com [Laboratoire de Physique Theorique, CNRS UMR 8627, Universite Paris XI, F-91405 Orsay Cedex (France)

    2012-05-01

    We study analytically the Ising model coupled to random lattices in dimension three and higher. The family of random lattices we use is generated by the large N limit of a colored tensor model generalizing the two-matrix model for Ising spins on random surfaces. We show that, in the continuum limit, the spin system does not exhibit a phase transition at finite temperature, in agreement with numerical investigations. Furthermore we outline a general method to study critical behavior in colored tensor models.

  11. Efektivitas Model Pembelajaran Clis Berbantuan Media Slide Powerpoint Terhadap Hasil Belajar IPA

    Directory of Open Access Journals (Sweden)

    Riska Fajar Ayu Kusuma Wardani

    2017-12-01

    Full Text Available Penelitian ini didasari fakta bahwa siswa kelas V SDN Pulerejo jarang melakukan percobaan sehingga hasil belajar IPA rendah. Penelitian ini bertujuan untuk mengetahui efektivitas model pembelajaran CLIS berbantuan media slide powerpoint terhadap hasil belajar IPA siswa kelas V SDN Pulerejo. Jenis penelitian ini adalah kuantitatif dengan metode Quasy Eksperimental Design dan desain penelitian posttest only control design. Populasi penelitian adalah siswa kelas V SDN Pulerejo dengan sampel 22 siswa sebagai kelas eksperimen dan 20 siswa sebagai kelas kontrol. Sampel ditentukan menggunakan simple random sampling dengan teknik lotre. Teknik pengumpulan data menggunakan tes dan dokumentasi. Analisis data menggunakan metode statistik rumus uji-t dengan taraf signifikan 5% dan dk=40. Hasil penelitian menunjukkan nilai thitung lebih besar dari ttabel=2,340>1,68385 sehingga H0 ditolak dan H1 diterima dan nilai rata-rata posttest kelas eksperimen 82,36 lebih besar dari kelas kontrol 74,20. Dapat disimpulkan bahwa ada efektivitas model pembelajaran CLIS  berbantuan media slide powerpoint terhadap hasil belajar IPA siswa kelas V SDN Pulerejo Kecamatan Pilangkenceng Kabupaten Madiun Tahun Pelajaran 2016/2017.

  12. Stochastic representations of seismic anisotropy: transversely isotropic effective media models

    Science.gov (United States)

    Song, Xin; Jordan, Thomas H.

    2017-06-01

    We apply Jordan's self-consistent, second-order Born theory to compute the effective stiffness tensor for spatially stationary, stochastic models of 3-D elastic heterogeneity. The effects of local anisotropy can be separated from spatially extended geometric anisotropy by factoring the covariance of the moduli into a one-point variance tensor and a two-point correlation function. The latter is incorporated into the rescaled Kneer tensor, which is contracted against the one-point variance tensor to yield a second-order perturbation to the Voigt average. The theory can handle heterogeneity with orthotropic stochastic symmetry, but the calculations presented here are restricted to media with transversely isotropic (TI) statistics. We thoroughly investigate TI stochastic media that are locally isotropic. If the heterogeneity aspect ratio η is unity, the effective medium is isotropic, and the main effect of the scattering is to reduce the moduli. The two limiting regimes are a 2-D vertical stochastic bundle (η → 0), where the P and S anisotropy ratios are negative, and a 1-D horizontal stochastic laminate (η → ∞), where they are positive. The effective-medium equations for the latter yield the second-order approximation to Backus's exact solution, demonstrating the connection between Backus theory and self-consistent effective-media theory. Comparisons of the exact and second-order results for non-Gaussian laminates indicate that the approximation should be adequate for moduli heterogeneities less than about 30 per cent and thus valid for most seismological purposes. We apply the locally isotropic theory to data from the Los Angeles Basin to illustrate how it can be used to explain shallow seismic anisotropy. To assess the relative contributions of geometric and local anisotropy to the effective anisotropy, we consider a rotational model for stochastic anisotropic variability proposed by Jordan. In this model, the axis of a hexagonally symmetric stiffness

  13. A didactical structural model – linking analysis of teaching and analysis of educational media

    DEFF Research Database (Denmark)

    Graf, Stefan Ting

    1. Gap between general didactics and textbook/media research There seems to be a gap between general didactics (theory of teaching) and research in textbooks or educational media in general at least in the Nordic and German speaking countries. General didactic and their models seem to underestimate...... related questions (e.g. readability) without establishing a link to what is useful for the teacher’s tasks both on the level of preparation, practice and reflection, i.e. without an explicit theory of teaching. 2. Media in general didactics I will discuss the status of media in some current models...... of reflection in general didactics (Hiim/Hippe, Meyer, Klafki) and present a reconstruction of a didactical model of structure (Strukturmodel), whose counterstones are ‘intentional content’, ‘media/expression’ and ‘teaching method/activity’. The inclusion of media/expression in the model resumes a seemingly...

  14. Blastocyst utilization rates after continuous culture in two commercial single-step media: a prospective randomized study with sibling oocytes.

    Science.gov (United States)

    Sfontouris, Ioannis A; Kolibianakis, Efstratios M; Lainas, George T; Venetis, Christos A; Petsas, George K; Tarlatzis, Basil C; Lainas, Tryfon G

    2017-10-01

    The aim of this study is to determine whether blastocyst utilization rates are different after continuous culture in two different commercial single-step media. This is a paired randomized controlled trial with sibling oocytes conducted in infertility patients, aged ≤40 years with ≥10 oocytes retrieved assigned to blastocyst culture and transfer. Retrieved oocytes were randomly allocated to continuous culture in either Sage one-step medium (Origio) or Continuous Single Culture (CSC) medium (Irvine Scientific) without medium renewal up to day 5 post oocyte retrieval. Main outcome measure was the proportion of embryos suitable for clinical use (utilization rate). A total of 502 oocytes from 33 women were randomly allocated to continuous culture in either Sage one-step medium (n = 250) or CSC medium (n = 252). Fertilization was performed by either in vitro fertilization or intracytoplasmic sperm injection, and embryo transfers were performed on day 5. Two patients had all blastocysts frozen due to the occurrence of severe ovarian hyperstimulation syndrome. Fertilization and cleavage rates, as well as embryo quality on day 3, were similar in the two media. Blastocyst utilization rates (%, 95% CI) [55.4% (46.4-64.1) vs 54.7% (44.9-64.6), p = 0.717], blastocyst formation rates [53.6% (44.6-62.5) vs 51.9 (42.2-61.6), p = 0.755], and proportion of good quality blastocysts [36.8% (28.1-45.4) vs 36.1% (27.2-45.0), p = 0.850] were similar in Sage one-step and CSC media, respectively. Continuous culture of embryos in Sage one-step and CSC media is associated with similar blastocyst development and utilization rates. Both single-step media appear to provide adequate support during in vitro preimplantation embryo development. Whether these observations are also valid for other continuous single medium protocols remains to be determined. NCT02302638.

  15. Phase field modeling of partially saturated deformable porous media

    Science.gov (United States)

    Sciarra, Giulio

    2016-09-01

    A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).

  16. SHIR competitive information diffusion model for online social media

    Science.gov (United States)

    Liu, Yun; Diao, Su-Meng; Zhu, Yi-Xiang; Liu, Qing

    2016-11-01

    In online social media, opinion divergences and differentiations generally exist as a result of individuals' extensive participation and personalization. In this paper, a Susceptible-Hesitated-Infected-Removed (SHIR) model is proposed to study the dynamics of competitive dual information diffusion. The proposed model extends the classical SIR model by adding hesitators as a neutralized state of dual information competition. It is both hesitators and stable spreaders that facilitate information dissemination. Researching on the impacts of diffusion parameters, it is found that the final density of stiflers increases monotonically as infection rate increases and removal rate decreases. And the advantage information with larger stable transition rate takes control of whole influence of dual information. The density of disadvantage information spreaders slightly grows with the increase of its stable transition rate, while whole spreaders of dual information and the relaxation time remain almost unchanged. Moreover, simulations imply that the final result of competition is closely related to the ratio of stable transition rates of dual information. If the stable transition rates of dual information are nearly the same, a slightly reduction of the smaller one brings out a significant disadvantage in its propagation coverage. Additionally, the relationship of the ratio of final stiflers versus the ratio of stable transition rates presents power characteristic.

  17. The Adoption of Social Media to Recruit Participants for the Cool Runnings Randomized Controlled Trial in Australia.

    Science.gov (United States)

    Burgess, Jacqueline D; Kimble, Roy M; Watt, Kerrianne; Cameron, Cate M

    2017-10-24

    Using social media to recruit specific populations for research studies is gaining popularity. Given that mothers of young children are the most active on social media, and young children are the most at risk of preventable burn injuries, social media was used to recruit mothers of young children to a burn prevention intervention. The aim of this paper was to describe the social media recruitment methods used to enroll mothers of young children to the app-based burn prevention intervention Cool Runnings. Participants were recruited via paid Facebook and Instagram advertisements to a 2-group, parallel, single-blinded, randomized controlled trial (RCT). The advertisements were targeted at women 18 years and older, living in Queensland, Australia, with at least 1 child aged 5 to 12 months at the time of recruitment. Over the 30-day recruitment period from January to February 2016, Facebook and Instagram advertisements reached 65,268 people, generating 2573 link clicks, 1161 app downloads, and 498 enrolled participants to the Cool Runnings RCT. The cost per enrolled participant was Aus $13.08. Saturdays were the most effective day of the week for advertising results. The most popular time of day for enrolments was between 5 to 11 PM. This recruitment strategy campaign resulted in a broad reach of participants from regional, rural, and remote Queensland. Participants were representative of the population in regard to age and education levels. To our knowledge, this is the first use of social media recruitment for an injury prevention campaign. This recruitment method resulted in the rapid and cost-effective recruitment of participants with social, geographic, and economic diversity that were largely representative of the population.

  18. Efficient Modeling and Migration in Anisotropic Media Based on Prestack Exploding Reflector Model and Effective Anisotropy

    KAUST Repository

    Wang, Hui

    2014-05-01

    This thesis addresses the efficiency improvement of seismic wave modeling and migration in anisotropic media. This improvement becomes crucial in practice as the process of imaging complex geological structures of the Earth\\'s subsurface requires modeling and migration as building blocks. The challenge comes from two aspects. First, the underlying governing equations for seismic wave propagation in anisotropic media are far more complicated than that in isotropic media which demand higher computational costs to solve. Second, the usage of whole prestack seismic data still remains a burden considering its storage volume and the existing wave equation solvers. In this thesis, I develop two approaches to tackle the challenges. In the first part, I adopt the concept of prestack exploding reflector model to handle the whole prestack data and bridge the data space directly to image space in a single kernel. I formulate the extrapolation operator in a two-way fashion to remove he restriction on directions that waves propagate. I also develop a generic method for phase velocity evaluation within anisotropic media used in this extrapolation kernel. The proposed method provides a tool for generating prestack images without wavefield cross correlations. In the second part of this thesis, I approximate the anisotropic models using effective isotropic models. The wave phenomena in these effective models match that in anisotropic models both kinematically and dynamically. I obtain the effective models through equating eikonal equations and transport equations of anisotropic and isotropic models, thereby in the high frequency asymptotic approximation sense. The wavefields extrapolation costs are thus reduced using isotropic wave equation solvers while the anisotropic effects are maintained through this approach. I benchmark the two proposed methods using synthetic datasets. Tests on anisotropic Marmousi model and anisotropic BP2007 model demonstrate the applicability of my

  19. Ultrasonic Modeling of Bounded Beam Reflection from Anisotropic Media

    Science.gov (United States)

    Schmitt, D. R.; Malehmir, R.; Kazemi, N.

    2016-12-01

    In this contribution, we try to physically model and understand the physics behind directional dependency of reflectivity from an anisotropic medium as a test of existing theory. One aspect of this is to motivate researchers to look beyond the simplifying assumptions that have been widely employed in the analysis of azimuthally varying seismic reflectivity. To do this, we are making laboratory measurements of the acoustic reflectivity from an orthorhombic medium cut at a variety of orientations in order to expose surfaces with differing anisotropy. The laboratory experiments employ a large aperture transmitter and a small, near-point-source, receiver placed within a goniometer that allows for rotation of the transducers and of the sample, this system was developed in earlier studies of reflectivity from porous media. This enables us to measure reflectivity from any azimuth and over a large range of incidence angles. We used Aluminum with known elastic properties for calibration and comparing the reflectivity results with Zoepprtiz solution. The successful correlation with reflectivity data enables us to go one step ahead and replace the sample with any anisotropic sample. The samples are machined from a `phenolic' material created with fibre cloth layers embedded within an epoxy resin, this material is known to be weakly orthorhombic. Blocks fo this material are cut such that the reflecting surfaces lie at a variety of angles with respect to the layering. These results suggest that some care should be employed in azimuthal seismic studies as it may be difficult to detect the differences in the reflectivity before the P-wave critical angle. However, this critical angle displays substantial change with azimuth and may provide important information for seismic investigations.The reflectivity variations are being modelled using a code called ARTc (Anisotropic Reflection and Transmission code) that provides the plane-wave reflectivity and transmissivity for the general

  20. Social Media Success for Academic Knowledge Sharing in Indonesia (Conceptual Model Development)

    Science.gov (United States)

    Assegaff, Setiawan

    2017-04-01

    The aim of this study is to investigate how success is the social media as a tool for knowledge sharing among scholars in Indonesia. To evaluate the success of social media we develop a model base on Delone and McLeane IS Success Model. In this article, we would like discuss the process of developing the research model. In developing the model, we conduct literature review from knowledge management, social media and IS Success Model area from previous study. This study resulted in the social success model for academic knowledge sharing in Indonesia.

  1. A local model of light interaction with transparent crystalline media.

    Science.gov (United States)

    Debelov, Victor A; Kozlov, Dmitry S

    2013-08-01

    The paper is devoted to the derivation of a bidirectional distribution function for crystals, which specifies all outgoing rays for a ray coming to the boundary of two transparent crystalline media with different optical properties, i.e., a particular mineral, directions of optical axes if they exist, and other features. A local model of interaction based on the notion of polarized light ray is introduced, which is specified by a geometric ray, its polarization state, light intensity, and so on. The computational algorithm that is suggested allows computing the directions and other properties of all (up to four) outgoing rays. In this paper, isotropic, uniaxial, and biaxial crystals are processed in a similar manner. The correctness of the model is validated by comparison of photos of real uniaxial crystals with corresponding computed images. The case of biaxial crystals is validated by testing the effect of conical refraction. Specifications of a series of tests devoted to rendering of optically different objects is presented also.

  2. Cyberbullying behavior and adolescents' use of media with antisocial content: A cyclic process model

    NARCIS (Netherlands)

    den Hamer, A.H.; Konijn, E.A.; Keijer, M.G.

    2014-01-01

    The present study examined the role of media use in adolescents' cyberbullying behavior. Following previous research, we propose a Cyclic Process Model of face-to-face victimization and cyberbullying through two mediating processes of anger/frustration and antisocial media content. This model was

  3. Weight information labels on media models reduce body dissatisfaction in adolescent girls

    NARCIS (Netherlands)

    Veldhuis, Jolanda; Konijn, Elly A; Seidell, Jacob C

    2012-01-01

    PURPOSE: To examine how weight information labels on variously sized media models affect (pre)adolescent girls' body perceptions and how they compare themselves with media models. METHODS: We used a three (body shape: extremely thin vs. thin vs. normal weight) × three (information label: 6-kg

  4. Adolescents and Music Media: Toward an Involvement-Mediational Model of Consumption and Self-Concept

    Science.gov (United States)

    Kistler, Michelle; Rodgers, Kathleen Boyce; Power, Thomas; Austin, Erica Weintraub; Hill, Laura Griner

    2010-01-01

    Using social cognitive theory and structural regression modeling, we examined pathways between early adolescents' music media consumption, involvement with music media, and 3 domains of self-concept (physical appearance, romantic appeal, and global self-worth; N=124). A mediational model was supported for 2 domains of self-concept. Music media…

  5. Community media research : a quest for theoretically-grounded models

    NARCIS (Netherlands)

    Jankowski, N.W.

    2003-01-01

    This article provides a panoramic sketch of the characteristics of community media and focuses on three forms: community television, community radio and community networks. The author contends, after a review of research conducted around these media, that much of this work has contributed little to

  6. Semantically Enhanced Topic Modeling and Its Applications in Social Media

    Science.gov (United States)

    Guo, Lifan

    2013-01-01

    As we witness the prosperity of the social media in the past few years, and feel the explosion of "user-generated content" on the Internet, there is little question that we have entered an era of Big Data. Those social media sites, such as Facebook, LinkedIn, Quora and Twitter have been important sources for a wide spectrum of users.…

  7. Multiphysical modelling of fluid transport through osteo-articular media

    Directory of Open Access Journals (Sweden)

    Thibault Lemaire

    2010-03-01

    Full Text Available In this study, a multiphysical description of fluid transport through osteo-articular porous media is presented. Adapted from the model of Moyne and Murad, which is intended to describe clayey materials behaviour, this multiscale modelling allows for the derivation of the macroscopic response of the tissue from microscopical information. First the model is described. At the pore scale, electrohydrodynamics equations governing the electrolyte movement are coupled with local electrostatics (Gauss-Poisson equation, and ionic transport equations. Using a change of variables and an asymptotic expansion method, the macroscopic description is carried out. Results of this model are used to show the importance of couplings effects on the mechanotransduction of compact bone remodelling.Neste estudo uma descrição multifísica do transporte de fluidos em meios porosos osteo articulares é apresentada. Adaptado a partir do modelo de Moyne e Murad proposto para descrever o comportamento de materiais argilosos a modelagem multiescala permite a derivação da resposta macroscópica do tecido a partir da informação microscópica. Na primeira parte o modelo é apresentado. Na escala do poro as equações da eletro-hidrodinâmica governantes do movimento dos eletrolitos são acopladas com a eletrostática local (equação de Gauss-Poisson e as equações de transporte iônico. Usando uma mudança de variáveis e o método de expansão assintótica a derivação macroscópica é conduzida. Resultados do modelo proposto são usados para salientar a importância dos efeitos de acoplamento sobre a transdução mecânica da remodelagem de ossos compactados.

  8. Mean-intercept anisotropy analysis of porous media. I. Analytic formulae for anisotropic Boolean models.

    Science.gov (United States)

    Klatt, Michael A; Schröder-Turk, Gerd E; Mecke, Klaus

    2017-07-01

    Structure-property relations, which relate the shape of the microstructure to physical properties such as transport or mechanical properties, need sensitive measures of structure. What are suitable fabric tensors that quantify the shape of anisotropic heterogeneous materials? The mean intercept length is among the most commonly used characteristics of anisotropy in porous media, for example, of trabecular bone in medical physics. We analyze the orientation-biased Boolean model, a versatile stochastic model that represents microstructures as overlapping grains with an orientation bias towards a preferred direction. This model is an extension of the isotropic Boolean model, which has been shown to truthfully reproduce multi-functional properties of isotropic porous media. We explain the close relationship between the concept of intersections with test lines to the elaborate mathematical theory of queues, and how explicit results from the latter can be directly applied to characterize microstructures. In this series of two papers, we provide analytic formulas for the anisotropic Boolean model and demonstrate often overlooked conceptual shortcomings of this approach. Queuing theory is used to derive simple and illustrative formulas for the mean intercept length. It separates into an intensity-dependent and an orientation-dependent factor. The global average of the mean intercept length can be expressed by local characteristics of a single grain alone. We thus identify which shape information about the random process the mean intercept length contains. The connection between global and local quantities helps to interpret observations and provides insights into the possibilities and limitations of the analysis. In the second paper of this series, we discuss, based on the findings in this paper, short-comings of the mean intercept analysis for (bone-)microstructure characterization. We will suggest alternative and better defined sensitive anisotropy measures from integral

  9. Learning from and with Customers with Social Media: A Model for Social Customer Learning

    Directory of Open Access Journals (Sweden)

    Hannu Kärkkäinen

    2012-01-01

    Full Text Available Social media can enable and significantly increase the collaboration andlearning from customers in various ways, for instance by novel social waysof providing and receiving feedback from new products and concepts. Wehave created a model that can support managers and researchers to betteranalyse and understand the possibilities of social media approaches especiallyfrom the business-to-business (B2B customer interface standpoint. Weused the model to analyse found various types of business-to-business relatedsocial media approaches to create new understanding of the scarcelyresearched field of social media in the customer learning and the customerinterface of B2B innovation.

  10. Hierarchical multiscale modeling for flows in fractured media using generalized multiscale finite element method

    KAUST Repository

    Efendiev, Yalchin R.

    2015-06-05

    In this paper, we develop a multiscale finite element method for solving flows in fractured media. Our approach is based on generalized multiscale finite element method (GMsFEM), where we represent the fracture effects on a coarse grid via multiscale basis functions. These multiscale basis functions are constructed in the offline stage via local spectral problems following GMsFEM. To represent the fractures on the fine grid, we consider two approaches (1) discrete fracture model (DFM) (2) embedded fracture model (EFM) and their combination. In DFM, the fractures are resolved via the fine grid, while in EFM the fracture and the fine grid block interaction is represented as a source term. In the proposed multiscale method, additional multiscale basis functions are used to represent the long fractures, while short-size fractures are collectively represented by a single basis functions. The procedure is automatically done via local spectral problems. In this regard, our approach shares common concepts with several approaches proposed in the literature as we discuss. We would like to emphasize that our goal is not to compare DFM with EFM, but rather to develop GMsFEM framework which uses these (DFM or EFM) fine-grid discretization techniques. Numerical results are presented, where we demonstrate how one can adaptively add basis functions in the regions of interest based on error indicators. We also discuss the use of randomized snapshots (Calo et al. Randomized oversampling for generalized multiscale finite element methods, 2014), which reduces the offline computational cost.

  11. Modeling Gene Regulation in Liver Hepatocellular Carcinoma with Random Forests

    National Research Council Canada - National Science Library

    Hilal Kazan

    2016-01-01

    .... We developed a random forest model that incorporates copy-number variation, DNA methylation, transcription factor, and microRNA binding information as features to predict gene expression in HCC...

  12. Superstatistical analysis and modelling of heterogeneous random walks

    Science.gov (United States)

    Metzner, Claus; Mark, Christoph; Steinwachs, Julian; Lautscham, Lena; Stadler, Franz; Fabry, Ben

    2015-06-01

    Stochastic time series are ubiquitous in nature. In particular, random walks with time-varying statistical properties are found in many scientific disciplines. Here we present a superstatistical approach to analyse and model such heterogeneous random walks. The time-dependent statistical parameters can be extracted from measured random walk trajectories with a Bayesian method of sequential inference. The distributions and correlations of these parameters reveal subtle features of the random process that are not captured by conventional measures, such as the mean-squared displacement or the step width distribution. We apply our new approach to migration trajectories of tumour cells in two and three dimensions, and demonstrate the superior ability of the superstatistical method to discriminate cell migration strategies in different environments. Finally, we show how the resulting insights can be used to design simple and meaningful models of the underlying random processes.

  13. Event-Based Media Enrichment Using an Adaptive Probabilistic Hypergraph Model.

    Science.gov (United States)

    Liu, Xueliang; Wang, Meng; Yin, Bao-Cai; Huet, Benoit; Li, Xuelong

    2015-11-01

    Nowadays, with the continual development of digital capture technologies and social media services, a vast number of media documents are captured and shared online to help attendees record their experience during events. In this paper, we present a method combining semantic inference and multimodal analysis for automatically finding media content to illustrate events using an adaptive probabilistic hypergraph model. In this model, media items are taken as vertices in the weighted hypergraph and the task of enriching media to illustrate events is formulated as a ranking problem. In our method, each hyperedge is constructed using the K-nearest neighbors of a given media document. We also employ a probabilistic representation, which assigns each vertex to a hyperedge in a probabilistic way, to further exploit the correlation among media data. Furthermore, we optimize the hypergraph weights in a regularization framework, which is solved as a second-order cone problem. The approach is initiated by seed media and then used to rank the media documents using a transductive inference process. The results obtained from validating the approach on an event dataset collected from EventMedia demonstrate the effectiveness of the proposed approach.

  14. Evidence-based management of otitis media: a 5S model approach.

    Science.gov (United States)

    Wasson, J D; Yung, M W

    2015-02-01

    The 5S model proposes five hierarchical levels (systems, summaries, synopses, syntheses and studies) of pre-appraised evidence to guide evidence-based practice. This review aimed to identify and summarise pre-appraised evidence at the highest available 5S level for the management of different subsets of otitis media: acute otitis media, otitis media with effusion, chronic suppurative otitis media and cholesteatoma in both adults and children. Data sources were pre-appraised evidence resources. Evidence freely available from sources at the highest available level of the 5S model were summarised for this review. System level evidence exists for acute otitis media and otitis media with effusion. Summary level evidence exists for recurrent acute otitis media and medical management of chronic suppurative otitis media. There is an absence of randomised controlled trials to prove the efficacy of surgical management of chronic suppurative otitis media and cholesteatoma. Until randomised controlled trial data are generated, consensus publications on the surgical management of chronic suppurative otitis media and cholesteatoma should be used to guide best practice.

  15. Oil drainage in model porous media by viscoelastic fluids

    Science.gov (United States)

    Beaumont, Julien; Bodiguel, Hugues; Colin, Annie

    2012-11-01

    Crude oil recovery efficiency has been shown to depend directly on the capillary number (Ca). If the capillary phenomenon is well described for Newtonian fluids, the consequences of non linear rheology and viscoelasticity require more experimental work at the pore scale. In this work we take advantage of microfluidic to revisit this field. We carried out oil drainage experiments through a micromodel made up with photoresist resin. The wetting phase trapped is a model oil. The invading phases used are aqueous solutions of high molecular weight hydrolyzed polyacrylamide (HPAM) and surfactant. Qualitatively, we observed a transition between a capillary fingering at low flow rates and a stable front at high flow rates for the drainage experiments with HPAM and surfactant solutions as it happened for drainage with Newtonian fluids. From movies of the filling of the device, we determine the local velocity of all menisci in the porous media. Thus, we quantify the capillary fingering. Surprisingly, local velocities are not significantly different from those measured using water, whereas the HPAM solutions are much more viscous. With betaine solutions, we observed an emulsification of the oil clusters trapped during the invasion leading to a very high oil recovery after percolation.

  16. A conceptual model for the use of social media in companies

    OpenAIRE

    Nistor, Cristian

    2013-01-01

    Social media is currently an evolving “wave” in online business marketing. Marketers are beginning to drive the use of social media as a component in their marketing strategy and campaigns to reach out to customers and fans. Within the subdisciplines of marketing that may use social media include promotions, marketing intelligence, sentiments research, public relations, marketing communications and product and customer management. This paper will try to find a conceptual model to examine peop...

  17. Cyberbullying behavior and adolescents' use of media with antisocial content: a cyclic process model.

    Science.gov (United States)

    den Hamer, Anouk; Konijn, Elly A; Keijer, Micha G

    2014-02-01

    The present study examined the role of media use in adolescents' cyberbullying behavior. Following previous research, we propose a Cyclic Process Model of face-to-face victimization and cyberbullying through two mediating processes of anger/frustration and antisocial media content. This model was tested utilizing a cross-sectional design with adolescent participants (N=892). Exposure to antisocial media content was measured with a newly developed content-based scale (i.e., the C-ME), showing good psychometric qualities. Results of structural equation modeling showed that adolescents' exposure to antisocial media content was significantly associated with cyberbullying behavior, especially in adolescents who experienced anger and frustration due to face-to-face victimization. Goodness of fit indices demonstrated a good fit of the theoretical model to the data and indicated that exposure to antisocial media content acts as an amplifier in a cyclic process of victimization-related anger and cyberbullying behavior.

  18. The Importance of Social Media in Business Models on Internet

    OpenAIRE

    Nicodim Liliana; Negoi Eugen Remus; Tileaga Cosmin

    2012-01-01

    Social media is a term that reflects the rapid development of technology and the skills and knowledge users, a complex concept for which there is no universally accepted definition. The term defines generic, a set of online communication channels, social networks and transmission of information, including social networks, groups, forums, blogs and various content platforms that facilitate transmission and instant communication (Safko, L., The Social Media Bible, John Willey & Sons, New Jersey...

  19. Random-Field Model of a Cooper Pair Insulator

    Science.gov (United States)

    Proctor, Thomas; Chudnovsky, Eugene; Garanin, Dmitry

    2013-03-01

    The model of a disordered superconducting film with quantum phase fluctuations is mapped on a random-field XY spin model in 2+1 dimensions. Analytical studies within continuum field theory, supported by our recent numerical calculations on discrete lattices, show the onset of the low-temperature Cooper pair insulator phase. The constant external field in the random-field spin model maps on the Josephson coupling between the disordered film and a bulk superconductor. Such a coupling, if sufficiently strong, restores superconductivity in the film. This provides an experimental test for the quantum fluctuation model of a superinsulator.

  20. Weight information labels on media models reduce body dissatisfaction in adolescent girls.

    Science.gov (United States)

    Veldhuis, Jolanda; Konijn, Elly A; Seidell, Jacob C

    2012-06-01

    To examine how weight information labels on variously sized media models affect (pre)adolescent girls' body perceptions and how they compare themselves with media models. We used a three (body shape: extremely thin vs. thin vs. normal weight) × three (information label: 6-kg underweight vs. 3-kg underweight vs. normal weight) experimental design in three age-groups (9-10 years, 12-13 years, and 15-16 years; n = 184). The girls completed questionnaires after exposure to media models. Weight information labels affected girls' body dissatisfaction, social comparison with media figures, and objectified body consciousness. Respondents exposed to an extremely thin body shape labeled to be of "normal weight" were most dissatisfied with their own bodies and showed highest levels of objectified body consciousness and comparison with media figures. An extremely thin body shape combined with a corresponding label (i.e., 6-kg underweight), however, induced less body dissatisfaction and less comparison with the media model. Age differences were also found to affect body perceptions: adolescent girls showed more negative body perceptions than preadolescents. Weight information labels may counteract the generally media-induced thin-body ideal. That is, when the weight labels appropriately informed the respondents about the actual thinness of the media model's body shape, girls were less affected. Weight information labels also instigated a normalization effect when a "normal-weight" label was attached to underweight-sized media models. Presenting underweight as a normal body shape, clearly increased body dissatisfaction in girls. Results also suggest age between preadolescence and adolescence as a critical criterion in responding to media models' body shape. Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  1. Critical media pedagogy - theoretical underpinning and contribution to media education

    OpenAIRE

    Valenta, Petr

    2016-01-01

    Critical media pedagogy - theoretical underpinnigs and contribution to media education Dissertation Mgr. Petr Valenta Keywords critical theory, critical media pedagogy, media literacy, critical pedagogy, media, ideology, discourse, power, symbolic power, knowledge Abstract The theoretical dissertation analyzes the traditional media education model issues, which derives from the orientation of media literacy on the dominant paradigm of media effects research in media studies. Media education t...

  2. A generalized model via random walks for information filtering

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhuo-Ming, E-mail: zhuomingren@gmail.com [Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700, Fribourg (Switzerland); Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, ChongQing, 400714 (China); Kong, Yixiu [Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700, Fribourg (Switzerland); Shang, Ming-Sheng, E-mail: msshang@cigit.ac.cn [Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, ChongQing, 400714 (China); Zhang, Yi-Cheng [Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700, Fribourg (Switzerland)

    2016-08-06

    There could exist a simple general mechanism lurking beneath collaborative filtering and interdisciplinary physics approaches which have been successfully applied to online E-commerce platforms. Motivated by this idea, we propose a generalized model employing the dynamics of the random walk in the bipartite networks. Taking into account the degree information, the proposed generalized model could deduce the collaborative filtering, interdisciplinary physics approaches and even the enormous expansion of them. Furthermore, we analyze the generalized model with single and hybrid of degree information on the process of random walk in bipartite networks, and propose a possible strategy by using the hybrid degree information for different popular objects to toward promising precision of the recommendation. - Highlights: • We propose a generalized recommendation model employing the random walk dynamics. • The proposed model with single and hybrid of degree information is analyzed. • A strategy with the hybrid degree information improves precision of recommendation.

  3. A model of using social media for collaborative learning to enhance learners’ performance on learning

    Directory of Open Access Journals (Sweden)

    Waleed Mugahed Al-Rahmi

    2017-10-01

    Full Text Available Social media has been always described as the channel through which knowledge is transmitted between communities and learners. This social media has been utilized by colleges in a way to encourage collaborative learning and social interaction. This study explores the use of social media in the process of collaborative learning through learning Quran and Hadith. Through this investigation, different factors enhancing collaborative learning in learning Quran and Hadith in the context of using social media are going to be examined. 340 respondents participated in this study. The structural equation modeling (SEM was used to analyze the data obtained. Upon analysis and structural model validities, the study resulted in a model used for measuring the influences of the different variables. The study reported direct and indirect significant impacts of these variables on collaborative learning through the use of social media which might lead to a better performance by learners.

  4. A Moderated Mediation Model of the Relationship between Media, Social Capital, and Cancer Knowledge.

    Science.gov (United States)

    Lee, Chul-Joo; Kim, Kwanho; Kang, Bee-Ah

    2018-01-24

    We combined insights from various theories and models of media learning, and advanced an indirect model accounting for the mechanisms underlying the media influences on knowledge acquisition. Our model was largely supported by the data from a two-wave longitudinal panel survey with a nationwide sample of Korean adults. It was found that both personal cancer history and cancer worry were positively associated with exposure to stomach cancer information from the media. In turn, exposure to media information was positively related to reflective integration of that information, which ultimately leads to stomach cancer knowledge only among people with high levels of social capital. These findings suggest that media uses and effects are not only an individual but also a contextually dependent experience.

  5. Detecting Rumors Through Modeling Information Propagation Networks in a Social Media Environment.

    Science.gov (United States)

    Liu, Yang; Xu, Songhua; Tourassi, Georgia

    2015-01-01

    In the midst of today's pervasive influence of social media content and activities, information credibility has increasingly become a major issue. Accordingly, identifying false information, e.g. rumors circulated in social media environments, attracts expanding research attention and growing interests. Many previous studies have exploited user-independent features for rumor detection. These prior investigations uniformly treat all users relevant to the propagation of a social media message as instances of a generic entity. Such a modeling approach usually adopts a homogeneous network to represent all users, the practice of which ignores the variety across an entire user population in a social media environment. Recognizing this limitation of modeling methodologies, this study explores user-specific features in a social media environment for rumor detection. The new approach hypothesizes that whether a user tends to spread a rumor is dependent upon specific attributes of the user in addition to content characteristics of the message itself. Under this hypothesis, information propagation patterns of rumors versus those of credible messages in a social media environment are systematically differentiable. To explore and exploit this hypothesis, we develop a new information propagation model based on a heterogeneous user representation for rumor recognition. The new approach is capable of differentiating rumors from credible messages through observing distinctions in their respective propagation patterns in social media. Experimental results show that the new information propagation model based on heterogeneous user representation can effectively distinguish rumors from credible social media content.

  6. An Investigation of the Mental Models of Social Media in the Minds of Managers

    DEFF Research Database (Denmark)

    Rydén, Pernille; Ringberg, Torsten; Wilke, Ricky

    The paper empirically illustrates how managers’ use of social media in business is constrained by socio-mental models (mindsets) of business-consumer interaction. As such, it counters the rationalist argument that the use social media relies on an analysis of opportunities in the market and capab...

  7. Using the Integrative Model to Explain How Exposure to Sexual Media Content Influences Adolescent Sexual Behavior

    Science.gov (United States)

    Bleakley, Amy; Hennessy, Michael; Fishbein, Martin; Jordan, Amy

    2011-01-01

    Published research demonstrates an association between exposure to media sexual content and a variety of sex-related outcomes for adolescents. What is not known is the mechanism through which sexual content produces this "media effect" on adolescent beliefs, attitudes, and behavior. Using the Integrative Model of Behavioral Prediction, this…

  8. Online revenue models in the media sector : an exploratory study on their success factors and adoption

    NARCIS (Netherlands)

    Stienstra, Martin R.; Ruel, Hubertus Johannes Maria; Boerrigter, Thomas

    2010-01-01

    Especially for companies in the media sector such as publishers, the Internet has created new strategic and commercial opportunities. However, many companies in the media sector are struggling with how to adapt their business and revenue model for doing profitable business online. This exploratory

  9. Exploring Use of New Media in Environmental Education Contexts: Introducing Visitors' Technology Use in Zoos Model

    Science.gov (United States)

    Yocco, Victor; Danter, Elizabeth H.; Heimlich, Joseph E.; Dunckel, Betty A.; Myers, Chris

    2011-01-01

    Modern zoological gardens have invested substantial resources in technology to deliver environmental education concepts to visitors. Investment in these media reflects a currently unsubstantiated belief that visitors will both use and learn from these media alongside more traditional and less costly displays. This paper proposes a model that…

  10. Model C critical dynamics of random anisotropy magnets

    Energy Technology Data Exchange (ETDEWEB)

    Dudka, M [Institute for Condensed Matter Physics, National Acad. Sci. of Ukraine, UA-79011 Lviv (Ukraine); Folk, R [Institut fuer Theoretische Physik, Johannes Kepler Universitaet Linz, A-4040 Linz (Austria); Holovatch, Yu [Institute for Condensed Matter Physics, National Acad. Sci. of Ukraine, UA-79011 Lviv (Ukraine); Moser, G [Institut fuer Physik und Biophysik, Universitaet Salzburg, A-5020 Salzburg (Austria)

    2007-07-20

    We study the relaxational critical dynamics of the three-dimensional random anisotropy magnets with the non-conserved n-component order parameter coupled to a conserved scalar density. In the random anisotropy magnets, the structural disorder is present in the form of local quenched anisotropy axes of random orientation. When the anisotropy axes are randomly distributed along the edges of the n-dimensional hypercube, asymptotical dynamical critical properties coincide with those of the random-site Ising model. However the structural disorder gives rise to considerable effects for non-asymptotic critical dynamics. We investigate this phenomenon by a field-theoretical renormalization group analysis in the two-loop order. We study critical slowing down and obtain quantitative estimates for the effective and asymptotic critical exponents of the order parameter and scalar density. The results predict complex scenarios for the effective critical exponent approaching the asymptotic regime.

  11. Distance learning strategies for weight management utilizing social media: A comparison of phone conference call versus social media platform. Rationale and design for a randomized study.

    Science.gov (United States)

    Willis, Erik A; Szabo-Reed, Amanda N; Ptomey, Lauren T; Steger, Felicia L; Honas, Jeffery J; Al-Hihi, Eyad M; Lee, Robert; Vansaghi, Lisa; Washburn, Richard A; Donnelly, Joseph E

    2016-03-01

    Management of obesity in the context of the primary care physician visit is of limited efficacy in part because of limited ability to engage participants in sustained behavior change between physician visits. Therefore, healthcare systems must find methods to address obesity that reach beyond the walls of clinics and hospitals and address the issues of lifestyle modification in a cost-conscious way. The dramatic increase in technology and online social networks may present healthcare providers with innovative ways to deliver weight management programs that could have an impact on health care at the population level. A randomized study will be conducted on 70 obese adults (BMI 30.0-45.0 kg/m(2)) to determine if weight loss (6 months) is equivalent between weight management interventions utilizing behavioral strategies by either a conference call or social media approach. The primary outcome, body weight, will be assessed at baseline and 6 months. Secondary outcomes including waist circumference, energy and macronutrient intake, and physical activity will be assessed on the same schedule. In addition, a cost analysis and process evaluation will be completed. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. A proposal on alternative sampling-based modeling method of spherical particles in stochastic media for Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Song Hyun Kim

    2015-08-01

    Full Text Available Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

  13. Random matrix model for disordered conductors

    Indian Academy of Sciences (India)

    1. Introduction. Matrix models are being successfully employed in a variety of domains of physics includ- ing studies on heavy nuclei [1], mesoscopic disordered conductors [2,3], two-dimensional quantum gravity [4], and chaotic quantum systems [5]. Universal conductance fluctuations in metals [6] and spectral fluctuations in ...

  14. Anderson localization of electromagnetic waves in randomly-stratified magnetodielectric media with uniform impedance.

    Science.gov (United States)

    Kim, Kihong

    2015-06-01

    The propagation and the Anderson localization of electromagnetic waves in a randomly-stratified slab, where both the dielectric permittivity and the magnetic permeability depend on one spatial coordinate in a random manner, is theoretically studied. The case where the wave impedance is uniform, while the refractive index is random, is considered in detail. The localization length and the disorder-averaged transmittance of s and p waves incident obliquely on the slab are calculated as a function of the incident angle θ and the strength of randomness in a numerically precise manner, using the invariant imbedding method. It is found that the waves incident perpendicularly on the slab are delocalized, while those incident obliquely are localized. As the incident angle increases from zero, the localization length decreases from infinity monotonically to some finite value. The localization length is found to depend on the incident angle as θ-4 and a simple analytical formula, which works quite well for weak disorder and small incident angles, is derived. The localization length does not depend on the wave polarization, but the disorder-averaged transmittance generally does.

  15. Localization of transverse waves in randomly layered media at oblique incidence

    NARCIS (Netherlands)

    Bliokh, K.Yu.; Freilikher, V.D.

    2004-01-01

    We investigate the oblique incidence of electromagnetic waves on a randomly layered medium in the limit of strong disorder. An approximate method for calculating the inverse localization length based on the assumptions of zero-energy flux and complete phase stochastization is presented. Two effects

  16. Munich case, some decisions make great stories: Business Model innovation by means of Social Media

    OpenAIRE

    Rodríguez Donaire, Silvia; Olivé Tomàs, Antoni

    2012-01-01

    The main objective of this article is to identify how Social Media influences the way the business is managed and/or innovated. To evaluate this Business Model Innovation we have conducted a case study that assesses how strategic choices made by managers, due to the implementation of Social Media, influences Business Model Innovation. The contribution of this article throughout the company’s history, Munich case, allows us to see how Munich’s Business Model has been innovated, and how Social ...

  17. Surface Roughness Impacts on Granular Media Filtration at Favorable Deposition Conditions: Experiments and Modeling.

    Science.gov (United States)

    Jin, Chao; Normani, Stefano D; Emelko, Monica B

    2015-07-07

    Column tests were conducted to investigate media roughness impacts on particle deposition in absence of an energy barrier (i.e., high ionic strength). Media/collector surface roughness consistently influenced colloid deposition in a nonlinear, nonmonotonic manner such that a critical roughness size associated with minimum particle deposition could be identified; this was confirmed using a convection-diffusion model. The results demonstrate that media surface roughness size alone is inadequate for predicting media roughness impacts on particle deposition; rather, the relative size relationship between the particles and media/collectors must also be considered. A model that quantitatively considers media surface roughness was developed that described experimental outcomes well and consistently with classic colloid filtration theory (CFT) for smooth surfaces. Dimensionless-scaling factors froughness and fPCIF were introduced and used to develop a model describing particle deposition rate (kd) and colloid attachment efficiency (α). The model includes fitting parameters that reflect the impact of critical system characteristics such as ionic strength, loading rate, hydrophobicity. Excellent agreement was found not only between the modeled outcomes for colloid attachment efficiency (α) and experimental results from the column tests, but also with experimental outcomes reported elsewhere. The model developed herein provides a framework for describing media surface roughness impacts on colloid deposition.

  18. Single-cluster dynamics for the random-cluster model

    NARCIS (Netherlands)

    Deng, Y.; Qian, X.; Blöte, H.W.J.

    We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

  19. Single-cluster dynamics for the random-cluster model

    NARCIS (Netherlands)

    Deng, Y.; Qian, X.; Blöte, H.W.J.

    2009-01-01

    We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

  20. Simulating intrafraction prostate motion with a random walk model

    Directory of Open Access Journals (Sweden)

    Tobias Pommer, PhD

    2017-07-01

    Conclusions: Random walk modeling is feasible and recreated the characteristics of the observed prostate motion. Introducing artificial transient motion did not improve the overall agreement, although the first 30 seconds of the traces were better reproduced. The model provides a simple estimate of prostate motion during delivery of radiation therapy.

  1. Model of two-temperature convective transfer in porous media

    Science.gov (United States)

    Gruais, Isabelle; Poliševski, Dan

    2017-12-01

    In this paper, we study the asymptotic behaviour of the solution of a convective heat transfer boundary problem in an ɛ -periodic domain which consists of two interwoven phases, solid and fluid, separated by an interface. The fluid flow and its dependence with respect to the temperature are governed by the Boussinesq approximation of the Stokes equations. The tensors of thermal diffusion of both phases are ɛ -periodic, as well as the heat transfer coefficient which is used to describe the first-order jump condition on the interface. We find by homogenization that the two-scale limits of the solutions verify the most common system used to describe local thermal non-equilibrium phenomena in porous media (see Nield and Bejan in Convection in porous media, Springer, New York, 1999; Rees and Pop in Transport phenomena in porous media III, Elsevier, Oxford, 2005). Since now, this system was justified only by volume averaging arguments.

  2. Stakeholder Models for Social and Mobile Media CSR Projects

    DEFF Research Database (Denmark)

    Kampf, Constance Elizabeth

    2014-01-01

    This paper is intended to demonstrate current uses of smartphone and social media technology by consumers. The three cases discussed show ways in which consumers have built communities through social and mobile media for a range of purposes—1) to organize their purchasing activities to get...... businesses to reduce their ecological footprint in immediate and concrete ways, 2) define consumer point of purchase information sources about product goodness for health, community and the environment, or 3) to push their agendas for using corporate resources for aid purposes. These consumers organize...... now have the ability to engage with knowledge resources related to CSR made available through innovative uses of smartphone and social media technology. In these cases of consumer initiated sustainability-on-the go—the Good Guide, CarrotMob and Colalife— organizations founded by activist individuals...

  3. Microscopic imaging through turbid media Monte Carlo modeling and applications

    CERN Document Server

    Gu, Min; Deng, Xiaoyuan

    2015-01-01

    This book provides a systematic introduction to the principles of microscopic imaging through tissue-like turbid media in terms of Monte-Carlo simulation. It describes various gating mechanisms based on the physical differences between the unscattered and scattered photons and method for microscopic image reconstruction, using the concept of the effective point spread function. Imaging an object embedded in a turbid medium is a challenging problem in physics as well as in biophotonics. A turbid medium surrounding an object under inspection causes multiple scattering, which degrades the contrast, resolution and signal-to-noise ratio. Biological tissues are typically turbid media. Microscopic imaging through a tissue-like turbid medium can provide higher resolution than transillumination imaging in which no objective is used. This book serves as a valuable reference for engineers and scientists working on microscopy of tissue turbid media.

  4. A note on moving average models for Gaussian random fields

    DEFF Research Database (Denmark)

    Hansen, Linda Vadgård; Thorarinsdottir, Thordis L.

    The class of moving average models offers a flexible modeling framework for Gaussian random fields with many well known models such as the Matérn covariance family and the Gaussian covariance falling under this framework. Moving average models may also be viewed as a kernel smoothing of a Lévy...... basis, a general modeling framework which includes several types of non-Gaussian models. We propose a new one-parameter spatial correlation model which arises from a power kernel and show that the associated Hausdorff dimension of the sample paths can take any value between 2 and 3. As a result...

  5. Application of Poisson random effect models for highway network screening.

    Science.gov (United States)

    Jiang, Ximiao; Abdel-Aty, Mohamed; Alamili, Samer

    2014-02-01

    In recent years, Bayesian random effect models that account for the temporal and spatial correlations of crash data became popular in traffic safety research. This study employs random effect Poisson Log-Normal models for crash risk hotspot identification. Both the temporal and spatial correlations of crash data were considered. Potential for Safety Improvement (PSI) were adopted as a measure of the crash risk. Using the fatal and injury crashes that occurred on urban 4-lane divided arterials from 2006 to 2009 in the Central Florida area, the random effect approaches were compared to the traditional Empirical Bayesian (EB) method and the conventional Bayesian Poisson Log-Normal model. A series of method examination tests were conducted to evaluate the performance of different approaches. These tests include the previously developed site consistence test, method consistence test, total rank difference test, and the modified total score test, as well as the newly proposed total safety performance measure difference test. Results show that the Bayesian Poisson model accounting for both temporal and spatial random effects (PTSRE) outperforms the model that with only temporal random effect, and both are superior to the conventional Poisson Log-Normal model (PLN) and the EB model in the fitting of crash data. Additionally, the method evaluation tests indicate that the PTSRE model is significantly superior to the PLN model and the EB model in consistently identifying hotspots during successive time periods. The results suggest that the PTSRE model is a superior alternative for road site crash risk hotspot identification. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Statistics of highly heterogeneous flow fields confined to three-dimensional random porous media

    Science.gov (United States)

    Jin, C.; Langston, P. A.; Pavlovskaya, G. E.; Hall, M. R.; Rigby, S. P.

    2016-01-01

    We present a strong relationship between the microstructural characteristics of, and the fluid velocity fields confined to, three-dimensional random porous materials. The relationship is revealed through simultaneously extracting correlation functions Ru u(r ) of the spatial (Eulerian) velocity fields and microstructural two-point correlation functions S2(r ) of the random porous heterogeneous materials. This demonstrates that the effective physical transport properties depend on the characteristics of complex pore structure owing to the relationship between Ru u(r ) and S2(r ) revealed in this study. Further, the mean excess plot was used to investigate the right tail of the streamwise velocity component that was found to obey light-tail distributions. Based on the mean excess plot, a generalized Pareto distribution can be used to approximate the positive streamwise velocity distribution.

  7. Crossing probability for directed polymers in random media. II. Exact tail of the distribution.

    Science.gov (United States)

    De Luca, Andrea; Le Doussal, Pierre

    2016-03-01

    We study the probability p ≡ p(η)(t) that two directed polymers in a given random potential η and with fixed and nearby endpoints do not cross until time t. This probability is itself a random variable (over samples η), which, as we show, acquires a very broad probability distribution at large time. In particular, the moments of p are found to be dominated by atypical samples where p is of order unity. Building on a formula established by us in a previous work using nested Bethe ansatz and Macdonald process methods, we obtain analytically the leading large time behavior of all moments p(m) ≃ γ(m)/t. From this, we extract the exact tail ∼ρ(p)/t of the probability distribution of the noncrossing probability at large time. The exact formula is compared to numerical simulations, with excellent agreement.

  8. Lightwave Propagation in the Presence of Random Turbulent Media and Pointing Jitter in Optical Space Communications

    OpenAIRE

    Toyoshima, Morio

    2003-01-01

    This study is devoted to lightwave propagation in the presence of random pointing jitter and atmospheric turbulence. The intrinsic narrow beam/high gain nature of free-space laser communications produces several extremely valuable advantages when compared to microwaves, but also requires a very high tracking and pointing accuracy. Furthermore, space-to-ground optical communications are strongly affected by scintillation effects due to the turbulent atmosphere. The purpose of this study is to ...

  9. Noninferiority, randomized, controlled trial comparing embryo development using media developed for sequential or undisturbed culture in a time-lapse setup.

    Science.gov (United States)

    Hardarson, Thorir; Bungum, Mona; Conaghan, Joe; Meintjes, Marius; Chantilis, Samuel J; Molnar, Laszlo; Gunnarsson, Kristina; Wikland, Matts

    2015-12-01

    To study whether a culture medium that allows undisturbed culture supports human embryo development to the blastocyst stage equivalently to a well-established sequential media. Randomized, double-blinded sibling trial. Independent in vitro fertilization (IVF) clinics. One hundred twenty-eight patients, with 1,356 zygotes randomized into two study arms. Embryos randomly allocated into two study arms to compare embryo development on a time-lapse system using a single-step medium or sequential media. Percentage of good-quality blastocysts on day 5. Percentage of day 5 good-quality blastocysts was 21.1% (standard deviation [SD] ± 21.6%) and 22.2% (SD ± 22.1%) in the single-step time-lapse medium (G-TL) and the sequential media (G-1/G-2) groups, respectively. The mean difference (-1.2; 95% CI, -6.0; 3.6) between the two media systems for the primary end point was less than the noninferiority margin of -8%. There was a statistically significantly lower number of good-quality embryos on day 3 in the G-TL group [50.7% (SD ± 30.6%) vs. 60.8% (SD ± 30.7%)]. Four out of the 11 measured morphokinetic parameters were statistically significantly different for the two media used. The mean levels of ammonium concentration in the media at the end of the culture period was statistically significantly lower in the G-TL group as compared with the G-2 group. We have shown that a single-step culture medium supports blastocyst development equivalently to established sequential media. The ammonium concentrations were lower in the single-step media, and the measured morphokinetic parameters were modified somewhat. NCT01939626. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  10. E-Learning and Social Media Motivation Factor Model

    Science.gov (United States)

    Rosli, Mohd Shafie; Saleh, Nor Shela; Aris, Baharuddin; Ahmad, Maizah Hura; Sejzi, Abbas Abjoli; Shamsudin, Nur Amalina

    2016-01-01

    The aims of this study are to probe into the motivational factors toward the usage of e-learning and social media among educational technology postgraduate students in the Faculty of Education, Universiti Teknologi Malaysia. This study had involved 70 respondents via the means of a questionnaire. Four factors have been studied, named, the factor…

  11. Statistical Models for Linguistic Variation in Online Media

    Science.gov (United States)

    Kulkarni, Vivek

    2017-01-01

    Language on the Internet and social media varies due to time, geography, and social factors. For example, consider an online chat forum where people from different regions across the world interact. In such scenarios, it is important to track and detect regional variation in language. A person from the UK, who is in conversation with someone from…

  12. Mentoring a New Library Media Specialist: A Model Relationship

    Science.gov (United States)

    Creighton, Peggy Milam

    2007-01-01

    In this article, the author discusses her experiences mentoring new library media specialists for each of the past three years. She discusses the following topics: (1) What is a mentor?; (2) What exactly is the purpose of a mentor?; (3) Why mentor?; (4) What are the professional practices of a good mentor; (5) Building a professional toolbox; (6)…

  13. Fractal and Multifractal Models Applied to Porous Media - Editorial

    Science.gov (United States)

    Given the current high level of interest in the use of fractal geometry to characterize natural porous media, a special issue of the Vadose Zone Journal was organized in order to expose established fractal analysis techniques and cutting-edge new developments to a wider Earth science audience. The ...

  14. The Laugh Model: Reframing and Rebranding Public Health Through Social Media

    National Research Council Canada - National Science Library

    Lister, Cameron; Royne, Marla; Payne, Hannah E; Cannon, Ben; Hanson, Carl; Barnes, Michael

    2015-01-01

    We examined the use of low-cost social media platforms in communicating public health messages and outline the laugh model, a framework through which public health organizations can reach and engage communities...

  15. Weight information labels on media models reduce body dissatisfaction in adolescent girls

    National Research Council Canada - National Science Library

    Veldhuis, Jolanda; Konijn, Elly A; Seidell, Jacob C

    2012-01-01

    ...)adolescent girls' body perceptions and how they compare themselves with media models. METHODS: We used a three (body shape: extremely thin vs. thin vs. normal weight) × three (information label: 6-kg underweight vs...

  16. Audit Komunikasi Pemasaran Motion Radio: Analisis Media Organizational Model melalui Metode Sostac

    National Research Council Canada - National Science Library

    Anathasia Citra

    2011-01-01

    This research is about the marketing communication audit of Otomotion FM that re-branding into Motion Radio by analyzing Media Organizational Model through SOSTAC method, Situation-Objective-Strategy...

  17. FEFLOW finite element modeling of flow, mass and heat transport in porous and fractured media

    CERN Document Server

    Diersch, Hans-Jörg G

    2013-01-01

    Placing advanced theoretical and numerical methods in the hands of modeling practitioners and scientists, this book explores the FEFLOW system for solving flow, mass and heat transport processes in porous and fractured media. Offers applications and exercises.

  18. Random Multi-Hopper Model. Super-Fast Random Walks on Graphs

    OpenAIRE

    Estrada, Ernesto; Delvenne, Jean-Charles; Hatano, Naomichi; Mateos, José L.; Metzler, Ralf; Riascos ( Universidad Mariana, Pasto, Colombia), Alejandro P; Schaub, Michael T.

    2016-01-01

    We develop a model for a random walker with long-range hops on general graphs. This random multi-hopper jumps from a node to any other node in the graph with a probability that decays as a function of the shortest-path distance between the two nodes. We consider here two decaying functions in the form of the Laplace and Mellin transforms of the shortest-path distances. Remarkably, when the parameters of these transforms approach zero asymptotically, the multi-hopper's hitting times between an...

  19. Semiparametric Bayesian Estimation of Random Coefficients Discrete Choice Models

    OpenAIRE

    Tchumtchoua, Sylvie; Dey, Dipak

    2007-01-01

    Heterogeneity in choice models is typically assumed to have a normal distribution in both Bayesian and classical setups. In this paper, we propose a semiparametric Bayesian framework for the analysis of random coefficients discrete choice models that can be applied to both individual as well as aggregate data. Heterogeneity is modeled using a Dirichlet process prior which varies with consumers characteristics through covariates. We develop a Markov chain Monte Carlo algorithm for fitting such...

  20. RANDOM CLOSED SET MODELS: ESTIMATING AND SIMULATING BINARY IMAGES

    Directory of Open Access Journals (Sweden)

    Ángeles M Gallego

    2011-05-01

    Full Text Available In this paper we show the use of the Boolean model and a class of RACS models that is a generalization of it to obtain simulations of random binary images able to imitate natural textures such as marble or wood. The different tasks required, parameter estimation, goodness-of-fit test and simulation, are reviewed. In addition to a brief review of the theory, simulation studies of each model are included.

  1. Effects of random noise in a dynamical model of love

    Energy Technology Data Exchange (ETDEWEB)

    Xu Yong, E-mail: hsux3@nwpu.edu.cn [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); Gu Rencai; Zhang Huiqing [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2011-07-15

    Highlights: > We model the complexity and unpredictability of psychology as Gaussian white noise. > The stochastic system of love is considered including bifurcation and chaos. > We show that noise can both suppress and induce chaos in dynamical models of love. - Abstract: This paper aims to investigate the stochastic model of love and the effects of random noise. We first revisit the deterministic model of love and some basic properties are presented such as: symmetry, dissipation, fixed points (equilibrium), chaotic behaviors and chaotic attractors. Then we construct a stochastic love-triangle model with parametric random excitation due to the complexity and unpredictability of the psychological system, where the randomness is modeled as the standard Gaussian noise. Stochastic dynamics under different three cases of 'Romeo's romantic style', are examined and two kinds of bifurcations versus the noise intensity parameter are observed by the criteria of changes of top Lyapunov exponent and shape of stationary probability density function (PDF) respectively. The phase portraits and time history are carried out to verify the proposed results, and the good agreement can be found. And also the dual roles of the random noise, namely suppressing and inducing chaos are revealed.

  2. Validity of "Hi_Science" as instructional media based-android refer to experiential learning model

    Science.gov (United States)

    Qamariah, Jumadi, Senam, Wilujeng, Insih

    2017-08-01

    Hi_Science is instructional media based-android in learning science on material environmental pollution and global warming. This study is aimed: (a) to show the display of Hi_Science that will be applied in Junior High School, and (b) to describe the validity of Hi_Science. Hi_Science as instructional media created with colaboration of innovative learning model and development of technology at the current time. Learning media selected is based-android and collaborated with experiential learning model as an innovative learning model. Hi_Science had adapted student worksheet by Taufiq (2015). Student worksheet had very good category by two expert lecturers and two science teachers (Taufik, 2015). This student worksheet is refined and redeveloped in android as an instructional media which can be used by students for learning science not only in the classroom, but also at home. Therefore, student worksheet which has become instructional media based-android must be validated again. Hi_Science has been validated by two experts. The validation is based on assessment of meterials aspects and media aspects. The data collection was done by media assessment instrument. The result showed the assessment of material aspects has obtained the average value 4,72 with percentage of agreement 96,47%, that means Hi_Science on the material aspects is in excellent category or very valid category. The assessment of media aspects has obtained the average value 4,53 with percentage of agreement 98,70%, that means Hi_Science on the media aspects is in excellent category or very valid category. It was concluded that Hi_Science as instructional media can be applied in the junior high school.

  3. Positive random fields for modeling material stiffness and compliance

    DEFF Research Database (Denmark)

    Hasofer, Abraham Michael; Ditlevsen, Ove Dalager; Tarp-Johansen, Niels Jacob

    1998-01-01

    with material properties modeled in terms of the considered random fields.The paper addsthe gamma field, the Fisher field, the beta field, and their reciprocal fields to the catalogue. These fields are all defined on the basis of sums of squares of independent standard Gaussian random variables.All the existing......Positive random fields with known marginal properties and known correlation function are not numerous in the literature. The most prominent example is the log\\-normal field for which the complete distribution is known and for which the reciprocal field is also lognormal. It is of interest...... to supplement the catalogue of positive fields beyond the class of those obtained by simple marginal transformation of a Gaussian field, this class containing the lognormal field.As a minimum for a random field to be included in the catalogue itis required that an algorithm for simulation of realizations can...

  4. Elliptic equation for random walks. Application to transport in microporous media

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    2007-01-01

    We consider a process of random walks with arbitrary residence time distribution. We show that in many cases this process may not be described by the classical (Fick) parabolic diffusion equation, but an elliptic equation. An additional term proportional to the second time derivative takes...... into account the distribution of the residence times of molecules ill pores. The new elliptic diffusion equation is strictly derived by the operator approach. A criterion showing where the new equation should be applied instead of the standard diffusion equation is obtained. Boundary conditions are studied...

  5. Wave propagation through random media: A local method of small perturbations based on the Helmholtz equation

    Science.gov (United States)

    Grosse, Ralf

    1990-01-01

    Propagation of sound through the turbulent atmosphere is a statistical problem. The randomness of the refractive index field causes sound pressure fluctuations. Although no general theory to predict sound pressure statistics from given refractive index statistics exists, there are several approximate solutions to the problem. The most common approximation is the parabolic equation method. Results obtained by this method are restricted to small refractive index fluctuations and to small wave lengths. While the first condition is generally met in the atmosphere, it is desirable to overcome the second. A generalization of the parabolic equation method with respect to the small wave length restriction is presented.

  6. Using Random Forest Models to Predict Organizational Violence

    Science.gov (United States)

    Levine, Burton; Bobashev, Georgly

    2012-01-01

    We present a methodology to access the proclivity of an organization to commit violence against nongovernment personnel. We fitted a Random Forest model using the Minority at Risk Organizational Behavior (MAROS) dataset. The MAROS data is longitudinal; so, individual observations are not independent. We propose a modification to the standard Random Forest methodology to account for the violation of the independence assumption. We present the results of the model fit, an example of predicting violence for an organization; and finally, we present a summary of the forest in a "meta-tree,"

  7. Porous Media and Immersed Boundary Hybrid-Modelling for Simulating Flow in Stone Cover-Layers

    DEFF Research Database (Denmark)

    Jensen, Bjarne; Liu, Xiaofeng; Christensen, Erik Damgaard

    In this paper we present a new numerical modelling approach for coastal and marine applications where a porous media conceptual model was combined with a free surface volume-of-fluid (VOF) model and an immersed boundary method (IBM). The immersed boundary model covers the method of describing a s...

  8. Porous Media and Immersed Boundary Hybrid-Modelling for Simulating Flow in Stone Cover-Layers

    DEFF Research Database (Denmark)

    Jensen, Bjarne; Liu, Xiaofeng; Christensen, Erik Damgaard

    2017-01-01

    In this paper we present a new numerical modelling approach for coastal and marine applications where a porous media conceptual model was combined with a free surface volume-of-fluid (VOF) model and an immersed boundary method (IBM). The immersed boundary model covers the method of describing a s...

  9. Direct Simulation of Multiple Scattering by Discrete Random Media Illuminated by Gaussian Beams

    Science.gov (United States)

    Mackowski, Daniel W.; Mishchenko, Michael I.

    2011-01-01

    The conventional orientation-averaging procedure developed in the framework of the superposition T-matrix approach is generalized to include the case of illumination by a Gaussian beam (GB). The resulting computer code is parallelized and used to perform extensive numerically exact calculations of electromagnetic scattering by volumes of discrete random medium consisting of monodisperse spherical particles. The size parameters of the scattering volumes are 40, 50, and 60, while their packing density is fixed at 5%. We demonstrate that all scattering patterns observed in the far-field zone of a random multisphere target and their evolution with decreasing width of the incident GB can be interpreted in terms of idealized theoretical concepts such as forward-scattering interference, coherent backscattering (CB), and diffuse multiple scattering. It is shown that the increasing violation of electromagnetic reciprocity with decreasing GB width suppresses and eventually eradicates all observable manifestations of CB. This result supplements the previous demonstration of the effects of broken reciprocity in the case of magneto-optically active particles subjected to an external magnetic field.

  10. Are Discrepancies in RANS Modeled Reynolds Stresses Random?

    CERN Document Server

    Xiao, Heng; Wang, Jian-xun; Paterson, Eric G

    2016-01-01

    In the turbulence modeling community, significant efforts have been made to quantify the uncertainties in the Reynolds-Averaged Navier--Stokes (RANS) models and to improve their predictive capabilities. Of crucial importance in these efforts is the understanding of the discrepancies in the RANS modeled Reynolds stresses. However, to what extent these discrepancies can be predicted or whether they are completely random remains a fundamental open question. In this work we used a machine learning algorithm based on random forest regression to predict the discrepancies. The success of the regression--prediction procedure indicates that, to a large extent, the discrepancies in the modeled Reynolds stresses can be explained by the mean flow feature, and thus they are universal quantities that can be extrapolated from one flow to another, at least among different flows sharing the same characteristics such as separation. This finding has profound implications to the future development of RANS models, opening up new ...

  11. An iterative fullwave simulation approach to multiple scattering in media with randomly distributed microbubbles

    Science.gov (United States)

    Joshi, Aditya; Lindsey, Brooks D.; Dayton, Paul A.; Pinton, Gianmarco; Muller, Marie

    2017-05-01

    Ultrasound contrast agents (UCA), such as microbubbles, enhance the scattering properties of blood, which is otherwise hypoechoic. The multiple scattering interactions of the acoustic field with UCA are poorly understood due to the complexity of the multiple scattering theories and the nonlinear microbubble response. The majority of bubble models describe the behavior of UCA as single, isolated microbubbles suspended in infinite medium. Multiple scattering models such as the independent scattering approximation can approximate phase velocity and attenuation for low scatterer volume fractions. However, all current models and simulation approaches only describe multiple scattering and nonlinear bubble dynamics separately. Here we present an approach that combines two existing models: (1) a full-wave model that describes nonlinear propagation and scattering interactions in a heterogeneous attenuating medium and (2) a Paul-Sarkar model that describes the nonlinear interactions between an acoustic field and microbubbles. These two models were solved numerically and combined with an iterative approach. The convergence of this combined model was explored in silico for 0.5 × 106 microbubbles ml-1, 1% and 2% bubble concentration by volume. The backscattering predicted by our modeling approach was verified experimentally with water tank measurements performed with a 128-element linear array transducer. An excellent agreement in terms of the fundamental and harmonic acoustic fields is shown. Additionally, our model correctly predicts the phase velocity and attenuation measured using through transmission and predicted by the independent scattering approximation.

  12. Buffalos milk yield analysis using random regression models

    Directory of Open Access Journals (Sweden)

    A.S. Schierholt

    2010-02-01

    Full Text Available Data comprising 1,719 milk yield records from 357 females (predominantly Murrah breed, daughters of 110 sires, with births from 1974 to 2004, obtained from the Programa de Melhoramento Genético de Bubalinos (PROMEBUL and from records of EMBRAPA Amazônia Oriental - EAO herd, located in Belém, Pará, Brazil, were used to compare random regression models for estimating variance components and predicting breeding values of the sires. The data were analyzed by different models using the Legendre’s polynomial functions from second to fourth orders. The random regression models included the effects of herd-year, month of parity date of the control; regression coefficients for age of females (in order to describe the fixed part of the lactation curve and random regression coefficients related to the direct genetic and permanent environment effects. The comparisons among the models were based on the Akaike Infromation Criterion. The random effects regression model using third order Legendre’s polynomials with four classes of the environmental effect were the one that best described the additive genetic variation in milk yield. The heritability estimates varied from 0.08 to 0.40. The genetic correlation between milk yields in younger ages was close to the unit, but in older ages it was low.

  13. MEDIA AND INCREASING PUBLIC TRUST IN MODERN IRAN: A CONCEPTUAL MODEL

    Directory of Open Access Journals (Sweden)

    Habib Ebrahimpour

    2012-06-01

    Full Text Available Public trust is one of the social capitals that can lead to integration in social systems. Trust links the citizens to organizations and institutions which represent them and in this way it increases the government’s legitimacy and effectiveness. In industrial communications nothing is more important than establishing public trust in media. Therefore, building trust and reflecting the facts on social, political, and economical issues are the essentials of media work. Hence, this study set out to investigate the effective factors which contribute to increasing public trust toward media and giving a conceptual model for them in Iran. Based on the five effective factors of public trust in media, some suggestions are finally given which can be manipulated in order to enhance media trust in modern Iran.

  14. Media, Gadgets.

    Science.gov (United States)

    Journal of Chemical Education, 1981

    1981-01-01

    Summarizes papers presented at the Sixth Biennial Conference on Chemical Education describing new media and gadgets, particularly models, computers, and other media. A bibliography of 15 presented papers on these topics is attached. (CS)

  15. Thermodynamic Modelling of Dolomite Behavior in Aqueous Media

    OpenAIRE

    Tadeusz Michałowski; Agustin G. Asuero

    2012-01-01

    The compact thermodynamic approach to the systems containing calcium, magnesium, and carbonate species is referred to dissolution of dolomite, as an example of nonequilibrium ternary salt when introduced into aqueous media. The study of dolomite is based on all attainable physicochemical knowledge, involved in expressions for equilibrium constants, where the species of the system are interrelated. The species are also involved in charge and concentration balances, considered as constraints pu...

  16. Electromagnetic Models for Remote Sensing of Layered Rough Media

    OpenAIRE

    Imperatore, Pasquale; Iodice, Antonio; Riccio, Daniele

    2010-01-01

    A quantitative mathematical analysis of wave propagation in three-dimensional layered rough media is fundamental in understanding intriguing scattering phenomena in such structures, especially in the perspective of remote sensing applications. The results of the Boundary Perturbation Theory (BPT), as introduced by P. Imperatore and his coauthors in many different papers, essentially constitutes the content of this chapter in which the theoretical body of results is presented in organized mann...

  17. (YIP) Detecting, Analyzing, Modeling Adversarial Propaganda in Social Media

    Science.gov (United States)

    2015-10-26

    James Caverlee Department of Computer Science and Engineering Texas A&M University College Station, TX 77843-3112 email: caverlee@cse.tamu.edu 1 Summary...This project has investigated strategic manipulation and adversarial propaganda in social media through a multi-faceted campaign-oriented framework. A...The overall research goals of this project have been threefold: • Detection: Can we detect campaigns engaging in strategic manipulation efficiently

  18. Modeling approaches to natural convection in porous media

    CERN Document Server

    Su, Yan

    2015-01-01

    This book provides an overview of the field of flow and heat transfer in porous medium and focuses on presentation of a generalized approach to predict drag and convective heat transfer within porous medium of arbitrary microscopic geometry, including reticulated foams and packed beds. Practical numerical methods to solve natural convection problems in porous media will be presented with illustrative applications for filtrations, thermal storage and solar receivers.

  19. Radiative Heat Transfer Modeling in Fibrous Porous Media

    Science.gov (United States)

    Sobhani, Sadaf; Panerai, Francesco; Borner, Arnaud; Ferguson, Joseph C.; Wray, Alan; Mansour, Nagi N.

    2017-01-01

    Phenolic-Impregnated Carbon Ablator (PICA) was developed at NASA Ames Research Center as a lightweight thermal protection system material for successful atmospheric entries. The objective of the current work is to compute the effective radiative conductivity of fibrous porous media, such as preforms used to make PICA, to enable the efficient design of materials that can meet the thermal performance goals of forthcoming space exploration missions.

  20. Anomaly detection in random heterogeneous media Feynman-Kac formulae, stochastic homogenization and statistical inversion

    CERN Document Server

    Simon, Martin

    2015-01-01

    This monograph is concerned with the analysis and numerical solution of a stochastic inverse anomaly detection problem in electrical impedance tomography (EIT). Martin Simon studies the problem of detecting a parameterized anomaly in an isotropic, stationary and ergodic conductivity random field whose realizations are rapidly oscillating. For this purpose, he derives Feynman-Kac formulae to rigorously justify stochastic homogenization in the case of the underlying stochastic boundary value problem. The author combines techniques from the theory of partial differential equations and functional analysis with probabilistic ideas, paving the way to new mathematical theorems which may be fruitfully used in the treatment of the problem at hand. Moreover, the author proposes an efficient numerical method in the framework of Bayesian inversion for the practical solution of the stochastic inverse anomaly detection problem.   Contents Feynman-Kac formulae Stochastic homogenization Statistical inverse problems  Targe...

  1. Application of Random-Effects Probit Regression Models.

    Science.gov (United States)

    Gibbons, Robert D.; Hedeker, Donald

    1994-01-01

    Develops random-effects probit model for case in which outcome of interest is series of correlated binary responses, obtained as product of longitudinal response process where individual is repeatedly classified on binary outcome variable or in multilevel or clustered problems in which individuals within groups are considered to share…

  2. Asthma Self-Management Model: Randomized Controlled Trial

    Science.gov (United States)

    Olivera, Carolina M. X.; Vianna, Elcio Oliveira; Bonizio, Roni C.; de Menezes, Marcelo B.; Ferraz, Erica; Cetlin, Andrea A.; Valdevite, Laura M.; Almeida, Gustavo A.; Araujo, Ana S.; Simoneti, Christian S.; de Freitas, Amanda; Lizzi, Elisangela A.; Borges, Marcos C.; de Freitas, Osvaldo

    2016-01-01

    Information for patients provided by the pharmacist is reflected in adhesion to treatment, clinical results and patient quality of life. The objective of this study was to assess an asthma self-management model for rational medicine use. This was a randomized controlled trial with 60 asthmatic patients assigned to attend five modules presented by…

  3. First principles modeling of magnetic random access memory devices (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Butler, W.H.; Zhang, X.; Schulthess, T.C.; Nicholson, D.M.; Oparin, A.B. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); MacLaren, J.M. [Department of Physics, Tulane University, New Orleans, Louisiana 70018 (United States)

    1999-04-01

    Giant magnetoresistance (GMR) and spin-dependent tunneling may be used to make magnetic random access memory devices. We have applied first-principles based electronic structure techniques to understand these effects and in the case of GMR to model the transport properties of the devices. {copyright} {ital 1999 American Institute of Physics.}

  4. Performance of Random Effects Model Estimators under Complex Sampling Designs

    Science.gov (United States)

    Jia, Yue; Stokes, Lynne; Harris, Ian; Wang, Yan

    2011-01-01

    In this article, we consider estimation of parameters of random effects models from samples collected via complex multistage designs. Incorporation of sampling weights is one way to reduce estimation bias due to unequal probabilities of selection. Several weighting methods have been proposed in the literature for estimating the parameters of…

  5. Scale-free random graphs and Potts model

    Indian Academy of Sciences (India)

    real-world networks such as the world-wide web, the Internet, the coauthorship, the protein interaction networks and so on display power-law behaviors in the degree ... in this paper, we study the evolution of SF random graphs from the perspective of equilibrium statistical physics. The formulation in terms of the spin model ...

  6. Modeling fiber type grouping by a binary Markov random field

    NARCIS (Netherlands)

    Venema, H. W.

    1992-01-01

    A new approach to the quantification of fiber type grouping is presented, in which the distribution of histochemical type in a muscle cross section is regarded as a realization of a binary Markov random field (BMRF). Methods for the estimation of the parameters of this model are discussed. The first

  7. Quantum random oracle model for quantum digital signature

    Science.gov (United States)

    Shang, Tao; Lei, Qi; Liu, Jianwei

    2016-10-01

    The goal of this work is to provide a general security analysis tool, namely, the quantum random oracle (QRO), for facilitating the security analysis of quantum cryptographic protocols, especially protocols based on quantum one-way function. QRO is used to model quantum one-way function and different queries to QRO are used to model quantum attacks. A typical application of quantum one-way function is the quantum digital signature, whose progress has been hampered by the slow pace of the experimental realization. Alternatively, we use the QRO model to analyze the provable security of a quantum digital signature scheme and elaborate the analysis procedure. The QRO model differs from the prior quantum-accessible random oracle in that it can output quantum states as public keys and give responses to different queries. This tool can be a test bed for the cryptanalysis of more quantum cryptographic protocols based on the quantum one-way function.

  8. THE EFFECT OF MODEL SCIENTIFIC INQUIRY USING MEDIA PhET TOWARD SKILLS PROCESS OF SCIENCE VIEWED FROM CRITICAL THINKING SKILLS

    Directory of Open Access Journals (Sweden)

    Nanda Safarati

    2017-06-01

    Full Text Available The purpose of research to analyse: the science process skills that are taught in a model of scientific inquiry using the media PhET better than students taught by learning direct instruction, science process skills of physics students who has the critical thinking skills using a model of scientific inquiry than average -rata better than students who have critical thinking skills using a direct model of instruction above average, the interaction of scientific inquiry learning model using PhET media with critical thinking skills of students in improving students' science process skills. This research is quasi experimental. Technique that used to gain a sample is random cluster sampling. The instrument used is the science process skills test and test critical thinking skills. The results of this study concluded that: the science process skills of students who are taught by the model of scientific inquiry using the media PhET better than students taught by learning direct instruction, science process skills of physics students who have the critical thinking skills using a model of scientific inquiry over average better than students who have critical thinking skills using a direct model of instruction above average, there is interaction scientific inquiry model using the media PhET with critical thinking skills of students in improving students' science process skills.

  9. TV, Social Media, and College Students' Binge Drinking Intentions: Moderated Mediation Models.

    Science.gov (United States)

    Yang, Bo; Zhao, Xinyan

    2017-12-21

    Many studies to date have examined how media influence health-related behavior through social norms. However, most studies focused on traditional media. In the era of traditional and social media integration, our study advances health and mass communication scholarship by examining the influence of both traditional and social media mediated through social norms. Also, we examined a boundary condition for the norms-mediated media influence process. Namely, in the context of college binge drinking, we predict that exposure to TV and social media prodrinking messages can influence college students' binge drinking intentions through perceived peer descriptive and injunctive norms. We also predict that group identification will moderate this indirect effect. Our moderated mediation models were tested via structural equation modeling (N = 609). We found that college students' exposure to social media prodrinking messages indirectly influenced their binge drinking intentions via perceived injunctive norms, and students' identification with their peers moderated this indirect effect. However, neither descriptive nor injunctive norms mediated the influence of students' exposure to TV prodrinking messages on their binge drinking intentions. Theoretical and practical implications of the findings are discussed.

  10. Setting the agenda: Different strategies of a Mass Media in a model of cultural dissemination

    Science.gov (United States)

    Pinto, Sebastián; Balenzuela, Pablo; Dorso, Claudio O.

    2016-09-01

    Day by day, people exchange opinions about news with relatives, friends, and coworkers. In most cases, they get informed about a given issue by reading newspapers, listening to the radio, or watching TV, i.e., through a Mass Media (MM). However, the importance of a given new can be stimulated by the Media by assigning newspaper's pages or time in TV programs. In this sense, we say that the Media has the power to "set the agenda", i.e., it decides which new is important and which is not. On the other hand, the Media can know people's concerns through, for instance, websites or blogs where they express their opinions, and then it can use this information in order to be more appealing to an increasing number of people. In this work, we study different scenarios in an agent-based model of cultural dissemination, in which a given Mass Media has a specific purpose: To set a particular topic of discussion and impose its point of view to as many social agents as it can. We model this by making the Media has a fixed feature, representing its point of view in the topic of discussion, while it tries to attract new consumers, by taking advantage of feedback mechanisms, represented by adaptive features. We explore different strategies that the Media can adopt in order to increase the affinity with potential consumers and then the probability to be successful in imposing this particular topic.

  11. Evolution of the concentration PDF in random environments modeled by global random walk

    Science.gov (United States)

    Suciu, Nicolae; Vamos, Calin; Attinger, Sabine; Knabner, Peter

    2013-04-01

    The evolution of the probability density function (PDF) of concentrations of chemical species transported in random environments is often modeled by ensembles of notional particles. The particles move in physical space along stochastic-Lagrangian trajectories governed by Ito equations, with drift coefficients given by the local values of the resolved velocity field and diffusion coefficients obtained by stochastic or space-filtering upscaling procedures. A general model for the sub-grid mixing also can be formulated as a system of Ito equations solving for trajectories in the composition space. The PDF is finally estimated by the number of particles in space-concentration control volumes. In spite of their efficiency, Lagrangian approaches suffer from two severe limitations. Since the particle trajectories are constructed sequentially, the demanded computing resources increase linearly with the number of particles. Moreover, the need to gather particles at the center of computational cells to perform the mixing step and to estimate statistical parameters, as well as the interpolation of various terms to particle positions, inevitably produce numerical diffusion in either particle-mesh or grid-free particle methods. To overcome these limitations, we introduce a global random walk method to solve the system of Ito equations in physical and composition spaces, which models the evolution of the random concentration's PDF. The algorithm consists of a superposition on a regular lattice of many weak Euler schemes for the set of Ito equations. Since all particles starting from a site of the space-concentration lattice are spread in a single numerical procedure, one obtains PDF estimates at the lattice sites at computational costs comparable with those for solving the system of Ito equations associated to a single particle. The new method avoids the limitations concerning the number of particles in Lagrangian approaches, completely removes the numerical diffusion, and

  12. New Didactical Models in Open and Online Learning based on Social Media

    NARCIS (Netherlands)

    Rothkrantz, L.J.M.

    2016-01-01

    In this paper we present a new didactical model for open online learning using social media. Ideas underlying this model are discussed in recent literature. The innovative part of the model is that students are connected and cooperate via a social network of study friends for example via Facebook or

  13. Laser Beam Propagation Through Inhomogeneous Media with Shock-Like Profiles: Modeling and Computing

    Science.gov (United States)

    Adamovsky, Grigory; Ida, Nathan

    1997-01-01

    Wave propagation in inhomogeneous media has been studied for such diverse applications as propagation of radiowaves in atmosphere, light propagation through thin films and in inhomogeneous waveguides, flow visualization, and others. In recent years an increased interest has been developed in wave propagation through shocks in supersonic flows. Results of experiments conducted in the past few years has shown such interesting phenomena as a laser beam splitting and spreading. The paper describes a model constructed to propagate a laser beam through shock-like inhomogeneous media. Numerical techniques are presented to compute the beam through such media. The results of computation are presented, discussed, and compared with experimental data.

  14. The Efficacy of a Walking Intervention Using Social Media to Increase Physical Activity: A Randomized Trial.

    Science.gov (United States)

    Rote, Aubrianne E; Klos, Lori A; Brondino, Michael J; Harley, Amy E; Swartz, Ann M

    2015-06-16

    Facebook may be a useful tool to provide a social support group to encourage increases in physical activity. This study examines the efficacy of a Facebook social support group to increase steps/day in young women. Female college freshmen (N = 63) were randomized to one of two 8-week interventions: a Facebook Social Support Group (n = 32) or a Standard Walking Intervention (n = 31). Participants in both groups received weekly step goals and tracked steps/day with a pedometer. Women in the Facebook Social Support Group were also enrolled in a Facebook group and asked to post information about their steps/day and provide feedback to one another. Women in both intervention arms significantly increased steps/day pre- to postintervention (F(8,425) = 94.43, P Social Support Group increased steps/day significantly more (F(1,138) = 11.34, P social support group to increase physical activity in young women. Women in the Facebook Social Support Group increased walking by approximately 1.5 miles/day more than women in the Standard Walking Intervention which, if maintained, could have a profound impact on their future health.

  15. Numerical modeling of contaminant transport in fractured porous media using mixed finite-element and finitevolume methods

    KAUST Repository

    Dong, Chen

    2011-01-01

    A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods; i.e., the mixed finite-element (MFE) method and the finite-volume method. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocity fields for both the fractures and matrix, which are crucial to the convection part of the transport equation. The finite-volume method and the standard MFE method are used to approximate the convection and dispersion terms, respectively. The temporary evolution for the pressure distributions, streamline fields, and concentration profiles are obtained for six different arrangements of fractures. The results clearly show the distorted concentration effects caused by the ordered and disordered (random) patterns of the fractures and illustrate the robustness and efficiency of the proposed numerical model. © 2011 by Begell House Inc.

  16. A monoecious and diploid Moran model of random mating.

    Science.gov (United States)

    Hössjer, Ola; Tyvand, Peder A

    2016-04-07

    An exact Markov chain is developed for a Moran model of random mating for monoecious diploid individuals with a given probability of self-fertilization. The model captures the dynamics of genetic variation at a biallelic locus. We compare the model with the corresponding diploid Wright-Fisher (WF) model. We also develop a novel diffusion approximation of both models, where the genotype frequency distribution dynamics is described by two partial differential equations, on different time scales. The first equation captures the more slowly varying allele frequencies, and it is the same for the Moran and WF models. The other equation captures departures of the fraction of heterozygous genotypes from a large population equilibrium curve that equals Hardy-Weinberg proportions in the absence of selfing. It is the distribution of a continuous time Ornstein-Uhlenbeck process for the Moran model and a discrete time autoregressive process for the WF model. One application of our results is to capture dynamics of the degree of non-random mating of both models, in terms of the fixation index fIS. Although fIS has a stable fixed point that only depends on the degree of selfing, the normally distributed oscillations around this fixed point are stochastically larger for the Moran than for the WF model. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Experimentally validated microstructural 3D constitutive model of coronary arterial media.

    Science.gov (United States)

    Hollander, Yaniv; Durban, David; Lu, Xiao; Kassab, Ghassan S; Lanir, Yoram

    2011-03-01

    Accurate modeling of arterial response to physiological or pathological loads may shed light on the processes leading to initiation and progression of a number of vascular diseases and may serve as a tool for prediction and diagnosis. In this study, a microstructure based hyperelastic constitutive model is developed for passive media of porcine coronary arteries. The most general model contains 12 independent parameters representing the three-dimensional inner fibrous structure of the media and includes the effects of residual stresses and osmotic swelling. Parameter estimation and model validation were based on mechanical data of porcine left anterior descending (LAD) media under radial inflation, axial extension, and twist tests. The results show that a reduced four parameter model is sufficient to reliably predict the passive mechanical properties. These parameters represent the stiffness and the helical orientation of each lamellae fiber and the stiffness of the interlamellar struts interconnecting these lamellae. Other structural features, such as orientational distribution of helical fibers and anisotropy of the interlamellar network, as well as possible transmural distribution of structural features, were found to have little effect on the global media mechanical response. It is shown that the model provides good predictions of the LAD media twist response based on parameters estimated from only biaxial tests of inflation and extension. In addition, good predictive capabilities are demonstrated for the model behavior at high axial stretch ratio based on data of law stretches.

  18. Modeling flow in porous media with double porosity/permeability: Mathematical model, properties, and analytical solutions

    CERN Document Server

    Nakshatrala, K B; Ballarini, R

    2016-01-01

    Geo-materials such as vuggy carbonates are known to exhibit multiple spatial scales. A common manifestation of spatial scales is the presence of (at least) two different scales of pores, which is commonly referred to as double porosity. To complicate things, the pore-network at each scale exhibits different permeability, and these networks are connected through fissure and conduits. Although some models are available in the literature, they lack a strong theoretical basis. This paper aims to fill this lacuna by providing the much needed theoretical foundations of the flow in porous media which exhibit double porosity/permeability. We first obtain a mathematical model for double porosity/permeability using the maximization of rate of dissipation hypothesis, and thereby providing a firm thermodynamic underpinning. We then present, along with mathematical proofs, several important mathematical properties that the solutions to the double porosity/permeability model satisfy. These properties are important in their...

  19. The Development of Mind Mapping Media in Flood Material using ADDIE Model

    Directory of Open Access Journals (Sweden)

    Sri Adelila Sari

    2016-02-01

    Full Text Available This study aimed to develop a media mind mapping through ADDIE model in teaching the flooding material. The samples that used were students of class X-3 Madrasah Aliyah (MA Darul Ulum totaling 30 students. This type of study was the Research and Development (R & D by using ADDIE models. Data collected by using mind mapping sheets that students' work. Data was analyzed by descriptive statistics. Results of this study found that in developing mind mapping media through five stages, namely: analysis, design, development, implementation and evaluation. The study concluded that the media mind mapping that have been developed and validated could be a viable and effective media used in the learning process. 

  20. PENGARUH MODEL TEAM GAMES TOURNAMENT MEDIA TOURNAMENTQUESTION CARDS TERHADAP HASIL BELAJAR SISWA PADA MATERI HIDROKARBON

    Directory of Open Access Journals (Sweden)

    Armynda Dewi Cita Sari

    2015-11-01

    Full Text Available This study was conducted to find out the effect of Team Games Tournament teaching model using Tournament-Question Cards, toward the learning outcomes of a Senior High School (SHS in Semarang on hydrocarbon and crude oil subjects. The initial observation result showed that their learning outcomes was still low as 55,78%. The population was X grader of a SHS in Semarang for the academic years 2011/2012. The sample was X-3 grader students as the control and X-4 grader as the experimental, which were selected using cluster random sampling method. Team Games Tournament teaching model using Tournament-Question Cards were applied in the  experimental class, while the conventional teaching model were used in the control class. Based on the facts, the average of post test result from the experiment class was 83,96 and the control class was 75,56. The experiment class and the control class post test grades were distributed normally and had the same variants, whereas on the one-sample t-test result was t count (3,61 > t table (2,02  which mean the average grade of experiment was better than the control class. Hypothesis testing used were biserial correlation coefficient and coefficient of determination obtained rb =0,618 and the influence 38,15%. It can be concluded that there is a significant correlation between Team Games Tournament teaching model using Tournament-Question Cards toward the learning outcomes of X grader of SHS in Semarang on hydrocarbon and crude oil subjects, with influence 38,15%.Key Words: Tournament-Question Cards media 

  1. Random matrices as models for the statistics of quantum mechanics

    Science.gov (United States)

    Casati, Giulio; Guarneri, Italo; Mantica, Giorgio

    1986-05-01

    Random matrices from the Gaussian unitary ensemble generate in a natural way unitary groups of evolution in finite-dimensional spaces. The statistical properties of this time evolution can be investigated by studying the time autocorrelation functions of dynamical variables. We prove general results on the decay properties of such autocorrelation functions in the limit of infinite-dimensional matrices. We discuss the relevance of random matrices as models for the dynamics of quantum systems that are chaotic in the classical limit. Permanent address: Dipartimento di Fisica, Via Celoria 16, 20133 Milano, Italy.

  2. Stochastic geometry, spatial statistics and random fields models and algorithms

    CERN Document Server

    2015-01-01

    Providing a graduate level introduction to various aspects of stochastic geometry, spatial statistics and random fields, this volume places a special emphasis on fundamental classes of models and algorithms as well as on their applications, for example in materials science, biology and genetics. This book has a strong focus on simulations and includes extensive codes in Matlab and R, which are widely used in the mathematical community. It can be regarded as a continuation of the recent volume 2068 of Lecture Notes in Mathematics, where other issues of stochastic geometry, spatial statistics and random fields were considered, with a focus on asymptotic methods.

  3. Stochastic persistence and stationary distribution in an SIS epidemic model with media coverage

    Science.gov (United States)

    Guo, Wenjuan; Cai, Yongli; Zhang, Qimin; Wang, Weiming

    2018-02-01

    This paper aims to study an SIS epidemic model with media coverage from a general deterministic model to a stochastic differential equation with environment fluctuation. Mathematically, we use the Markov semigroup theory to prove that the basic reproduction number R0s can be used to control the dynamics of stochastic system. Epidemiologically, we show that environment fluctuation can inhibit the occurrence of the disease, namely, in the case of disease persistence for the deterministic model, the disease still dies out with probability one for the stochastic model. So to a great extent the stochastic perturbation under media coverage affects the outbreak of the disease.

  4. Large scale flow visualization and anemometry applied to lab on chip models of porous media

    CERN Document Server

    Paiola, Johan; Bodiguel, Hugues

    2016-01-01

    The following is a report on an experimental technique allowing to quantify and map the velocity field with a very high resolution and a simple equipment in large 2D devices. A simple Shlieren technique is proposed to reinforce the contrast in the images and allow you to detect seeded particles that are pixel-sized or even inferior to it. The velocimetry technique that we have reported on is based on auto-correlation functions of the pixel intensity, which we have shown are directly related to the magnitude of the local average velocity. The characteristic time involved in the decorrelation of the signal is proportional to the tracer size and inversely proportional to the average velocity. We have reported on a detailed discussion about the optimization of relevant involved parameters, the spatial resolution and the accuracy of the method. The technique is then applied to a model porous media made of a random channel network. We show that it is highly efficient to determine the magnitude of the flow in each o...

  5. Stability and bifurcation for an SEIS epidemic model with the impact of media

    Science.gov (United States)

    Huo, Hai-Feng; Yang, Peng; Xiang, Hong

    2018-01-01

    A novel SEIS epidemic model with the impact of media is introduced. By analyzing the characteristic equation of equilibrium, the basic reproduction number is obtained and the stability of the steady states is proved. The occurrence of a forward, backward and Hopf bifurcation is derived. Numerical simulations and sensitivity analysis are performed. Our results manifest that media can regard as a good indicator in controlling the emergence and spread of the epidemic disease.

  6. A generalized model via random walks for information filtering

    Science.gov (United States)

    Ren, Zhuo-Ming; Kong, Yixiu; Shang, Ming-Sheng; Zhang, Yi-Cheng

    2016-08-01

    There could exist a simple general mechanism lurking beneath collaborative filtering and interdisciplinary physics approaches which have been successfully applied to online E-commerce platforms. Motivated by this idea, we propose a generalized model employing the dynamics of the random walk in the bipartite networks. Taking into account the degree information, the proposed generalized model could deduce the collaborative filtering, interdisciplinary physics approaches and even the enormous expansion of them. Furthermore, we analyze the generalized model with single and hybrid of degree information on the process of random walk in bipartite networks, and propose a possible strategy by using the hybrid degree information for different popular objects to toward promising precision of the recommendation.

  7. Connectivity properties of the random-cluster model

    Science.gov (United States)

    Weigel, Martin; Metin Elci, Eren; Fytas, Nikolaos G.

    2016-02-01

    We investigate the connectivity properties of the random-cluster model mediated by bridge bonds that, if removed, lead to the generation of new connected components. We study numerically the density of bridges and the fragmentation kernel, i.e., the relative sizes of the generated fragments, and find that these quantities follow a scaling description. The corresponding scaling exponents are related to well known equilibrium critical exponents of the model. Using the Russo-Margulis formalism, we derive an exact relation between the expected density of bridges and the number of active edges. The same approach allows us to study the fluctuations in the numbers of bridges, thereby uncovering a new singularity in the random- cluster model as q clusters connected by bridges and candidate-bridges play a pivotal role. We discuss several different implementations of the necessary connectivity algorithms and assess their relative performance.

  8. An efficient wave extrapolation method for tilted orthorhombic media using effective ellipsoidal models

    KAUST Repository

    Waheed, Umair bin

    2014-08-01

    The wavefield extrapolation operator for ellipsoidally anisotropic (EA) media offers significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate focusing for media of orthorhombic anisotropy. Therefore, we develop effective EA models that correctly capture the kinematic behavior of the wavefield for tilted orthorhombic (TOR) media. Specifically, we compute effective source-dependent velocities for the EA model using kinematic high-frequency representation of the TOR wavefield. The effective model allows us to use the cheaper EA wavefield extrapolation operator to obtain approximate wavefield solutions for a TOR model. Despite the fact that the effective EA models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including the frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy tradeoff for wavefield computations in TOR media, particularly for media of low to moderate complexity. We demonstrate applicability of the proposed approach on a layered TOR model.

  9. Generalized random sign and alert delay models for imperfect maintenance.

    Science.gov (United States)

    Dijoux, Yann; Gaudoin, Olivier

    2014-04-01

    This paper considers the modelling of the process of Corrective and condition-based Preventive Maintenance, for complex repairable systems. In order to take into account the dependency between both types of maintenance and the possibility of imperfect maintenance, Generalized Competing Risks models have been introduced in "Doyen and Gaudoin (J Appl Probab 43:825-839, 2006)". In this paper, we study two classes of these models, the Generalized Random Sign and Generalized Alert Delay models. A Generalized Competing Risks model can be built as a generalization of a particular Usual Competing Risks model, either by using a virtual age framework or not. The models properties are studied and their parameterizations are discussed. Finally, simulation results and an application to real data are presented.

  10. A Social Media Peer Group for Mothers To Prevent Obesity from Infancy: The Grow2Gether Randomized Trial.

    Science.gov (United States)

    Fiks, Alexander G; Gruver, Rachel S; Bishop-Gilyard, Chanelle T; Shults, Justine; Virudachalam, Senbagam; Suh, Andrew W; Gerdes, Marsha; Kalra, Gurpreet K; DeRusso, Patricia A; Lieberman, Alexandra; Weng, Daniel; Elovitz, Michal A; Berkowitz, Robert I; Power, Thomas J

    2017-10-01

    Few studies have addressed obesity prevention among low-income families whose infants are at increased obesity risk. We tested a Facebook peer-group intervention for low-income mothers to foster behaviors promoting healthy infant growth. In this randomized controlled trial, 87 pregnant women (Medicaid insured, BMI ≥25 kg/m2) were randomized to the Grow2Gether intervention or text message appointment reminders. Grow2Gether participants joined a private Facebook group of 9-13 women from 2 months before delivery until infant age 9 months. A psychologist facilitated groups featuring a curriculum of weekly videos addressing feeding, sleep, parenting, and maternal well-being. Feasibility was assessed using the frequency and content of participation, and acceptability using surveys. Maternal beliefs and behaviors and infant growth were assessed at birth, 2, 4, 6, and 9 months. Differences in infant growth between study arms were explored. We conducted intention-to-treat analyses using quasi-least-squares regression. Eighty-eight percent (75/85) of intervention participants (42% (36/85) food insecure, 88% (75/85) black) reported the group was helpful. Participants posted 30 times/group/week on average. At 9 months, the intervention group had significant improvement in feeding behaviors (Infant Feeding Style Questionnaire) compared to the control group (p = 0.01, effect size = 0.45). Intervention group mothers were significantly less likely to pressure infants to finish food and, at age 6 months, give cereal in the bottle. Differences were not observed for other outcomes, including maternal feeding beliefs or infant weight-for-length. A social media peer-group intervention was engaging and significantly impacted certain feeding behaviors in families with infants at high risk of obesity.

  11. Driven interfaces in random media at finite temperature: existence of an anomalous zero-velocity phase at small external force.

    Science.gov (United States)

    Monthus, Cécile; Garel, Thomas

    2008-10-01

    The motion of driven interfaces in random media at finite temperature T and small external force F is usually described by a linear displacement h{G}(t) approximately V(F,T)t at large times, where the velocity vanishes according to the creep formula as V(F,T) approximately e;{-K(T)F;{mu}} for F-->0 . In this paper, we question this picture on the specific example of the directed polymer in a two-dimensional random medium. We have recently shown [C. Monthus and T. Garel, J. Phys. A 41, 255002 (2008)] that its dynamics for F=0 can be analyzed in terms of a strong disorder renormalization procedure, where the distribution of renormalized barriers flows towards some "infinite disorder fixed point." In the present paper, we obtain that for small F , this "infinite disorder fixed point" becomes a "strong disorder fixed point" with an exponential distribution of renormalized barriers. The corresponding distribution of trapping times then only decays as a power law P(tau) approximately 1tau;{1+alpha} , where the exponent alpha(F,T) vanishes as alpha(F,T) proportional, variant F micro as F-->0 . Our conclusion is that in the small force region alpha(F,T)infinity induces strong non-self-averaging effects that invalidate the usual creep formula obtained by replacing all trapping times by the typical value. We find instead that the motion is only sublinearly in time h{G}(t) approximately t;{alpha(F,T)} , i.e., the asymptotic velocity vanishes V=0 . This analysis is confirmed by numerical simulations of a directed polymer with a metric constraint driven in a traps landscape. We moreover obtain that the roughness exponent, which is governed by the equilibrium value zeta{eq}=23 up to some large scale, becomes equal to zeta=1 at the largest scales.

  12. A social media-based physical activity intervention: a randomized controlled trial.

    Science.gov (United States)

    Cavallo, David N; Tate, Deborah F; Ries, Amy V; Brown, Jane D; DeVellis, Robert F; Ammerman, Alice S

    2012-11-01

    Online social networks, such as Facebook™, have extensive reach, and they use technology that could enhance social support, an established determinant of physical activity. This combination of reach and functionality makes online social networks a promising intervention platform for increasing physical activity. To test the efficacy of a physical activity intervention that combined education, physical activity monitoring, and online social networking to increase social support for physical activity compared to an education-only control. RCT. Students (n=134) were randomized to two groups: education-only controls receiving access to a physical activity-focused website (n=67) and intervention participants receiving access to the same website with physical activity self-monitoring and enrollment in a Facebook group (n=67). Recruitment and data collection occurred in 2010 and 2011; data analyses were performed in 2011. Female undergraduate students at a large southeastern public university. Intervention participants were encouraged through e-mails, website instructions, and moderator communications to solicit and provide social support related to increasing physical activity through a physical activity-themed Facebook group. Participants received access to a dedicated website with educational materials and a physical activity self-monitoring tool. The primary outcome was perceived social support for physical activity; secondary outcomes included self-reported physical activity. Participants experienced increases in social support and physical activity over time but there were no differences in perceived social support or physical activity between groups over time. Facebook participants posted 259 times to the group. Two thirds (66%) of intervention participants completing a post-study survey indicated that they would recommend the program to friends. Use of an online social networking group plus self-monitoring did not produce greater perceptions of social support or

  13. Media coverage of celebrity DUIs: teachable moments or problematic social modeling?

    Science.gov (United States)

    Smith, Katherine Clegg; Twum, Denise; Gielen, Andrea Carlson

    2009-01-01

    Alcohol in the media influences norms around use, particularly for young people. A recent spate of celebrity arrests for drinking and driving (DUI) has received considerable media attention. We asked whether these newsworthy events serve as teachable moments or problematic social modeling for young women. Qualitative analysis of US media coverage of four female celebrities (Michelle Rodriguez, Paris Hilton, Nicole Richie and Lindsay Lohan) was conducted over the year following their DUI arrest (December 2005 through June 2008). The media sample included five television and three print sources and resulted in 150 print and 16 television stories. Stories were brief, episodic and focused around glamorous celebrity images. They included routine discussion of the consequences of the DUI for the individual celebrities without much evidence of a consideration of the public health dimensions of drinking and driving or possible prevention measures. Our analysis found little material in the media coverage that dealt with preventing injury or promoting individual and collective responsibility for ensuring such protection. Media attention to such newsworthy events is a missed opportunity that can and should be addressed through media advocacy efforts.

  14. Shape modelling using Markov random field restoration of point correspondences.

    Science.gov (United States)

    Paulsen, Rasmus R; Hilger, Klaus B

    2003-07-01

    A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized shapes and improves the capability of reconstruction of the training data. Furthermore, the method leads to an overall reduction in the total variance of the point distribution model. Thus, it finds correspondence between semi-landmarks that are highly correlated in the shape tangent space. The method is demonstrated on a set of human ear canals extracted from 3D-laser scans.

  15. Many-body localization in the quantum random energy model

    Science.gov (United States)

    Laumann, Chris; Pal, Arijeet

    2014-03-01

    The quantum random energy model is a canonical toy model for a quantum spin glass with a well known phase diagram. We show that the model exhibits a many-body localization-delocalization transition at finite energy density which significantly alters the interpretation of the statistical ``frozen'' phase at lower temperature in isolated quantum systems. The transition manifests in many-body level statistics as well as the long time dynamics of on-site observables. CRL thanks the Perimeter Institute for hospitality and support.

  16. Shape Modelling Using Markov Random Field Restoration of Point Correspondences

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Hilger, Klaus Baggesen

    2003-01-01

    A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized...... shapes and improves the capability of reconstruction of the training data. Furthermore, the method leads to an overall reduction in the total variance of the point distribution model. Thus, it finds correspondence between semilandmarks that are highly correlated in the shape tangent space. The method...

  17. A Random Dot Product Model for Weighted Networks

    CERN Document Server

    DeFord, Daryl R

    2016-01-01

    This paper presents a generalization of the random dot product model for networks whose edge weights are drawn from a parametrized probability distribution. We focus on the case of integer weight edges and show that many previously studied models can be recovered as special cases of this generalization. Our model also determines a dimension--reducing embedding process that gives geometric interpretations of community structure and centrality. The dimension of the embedding has consequences for the derived community structure and we exhibit a stress function for determining appropriate dimensions. We use this approach to analyze a coauthorship network and voting data from the U.S. Senate.

  18. Modeling random combustion of lycopodium particles and gas

    Directory of Open Access Journals (Sweden)

    M Bidabadi

    2016-06-01

    Full Text Available The random modeling combustion of lycopodium particles has been researched by many authors. In this paper, we extend this model and we also generate a different method by analyzing the effect of random distributed sources of combustible mixture. The flame structure is assumed to consist of a preheat-vaporization zone, a reaction zone and finally a post flame zone. We divide the preheat zone to different parts. We assumed that there is different distribution of particles in sections which are really random. Meanwhile, it is presumed that the fuel particles vaporize first to yield gaseous fuel. In other words, most of the fuel particles are vaporized at the end of the preheat zone. It is assumed that the Zel’dovich number is large; therefore, the reaction term in preheat zone is negligible. In this work, the effect of random distribution of particles in the preheat zone on combustion characteristics such as burning velocity, flame temperature for different particle radius is obtained.

  19. Blastocyst culture using single versus sequential media in clinical IVF: a systematic review and meta-analysis of randomized controlled trials.

    Science.gov (United States)

    Sfontouris, Ioannis A; Martins, Wellington P; Nastri, Carolina O; Viana, Iara G R; Navarro, Paula A; Raine-Fenning, Nick; van der Poel, Sheryl; Rienzi, Laura; Racowsky, Catherine

    2016-10-01

    The purpose of this study was to undertake a review of the available evidence comparing the use of a single medium versus sequential media for embryo culture to the blastocyst stage in clinical IVF. We searched the Cochrane Central, PubMed, Scopus, ClinicalTrials.gov, Current Controlled Trials and WHO International Clinical Trials Registry Platform to identify randomized controlled trials comparing single versus sequential media for blastocyst culture and ongoing pregnancy rate. Included studies randomized either oocytes/zygotes or women. Eligible oocyte/zygote studies were analyzed to assess the risk difference (RD) and 95 % confidence intervals (CI) between the two media systems; eligible woman-based studies were analyzed to assess the risk ratio (RR) and 95 % CI for clinical pregnancy rate. No differences were observed between single and sequential media for either ongoing pregnancy per randomized woman (relative risk (RR) = 0.9, 95 % CI = 0.7 to 1.3, two studies including 246 women, I 2  = 0 %) or clinical pregnancy per randomized woman (RR = 1.0, 95 % CI = 0.7 to 1.4, one study including 100 women); or miscarriage per clinical pregnancy: RR = 1.3, 95 % CI = 0.4 to 4.3, two studies including 246 participants, I 2  = 0 %). Single media use was associated with an increase blastocyst formation per randomized oocyte/zygote (relative distribution (RD) = +0.06, 95 % CI = +0.01 to +0.12, ten studies including 7455 oocytes/zygotes, I 2  = 83 %) but not top/high blastocyst formation (RD = +0.05, 95 % CI = -0.01 to +0.11, five studies including 3879 oocytes/zygotes, I 2  = 93 %). The overall quality of the evidence was very low for all these four outcomes. Although using a single medium for extended culture has some practical advantages and blastocyst formation rates appear to be higher, there is insufficient evidence to recommend either sequential or single-step media as being superior for the culture of

  20. Thermodynamic Modelling of Dolomite Behavior in Aqueous Media

    Directory of Open Access Journals (Sweden)

    Tadeusz Michałowski

    2012-01-01

    Full Text Available The compact thermodynamic approach to the systems containing calcium, magnesium, and carbonate species is referred to dissolution of dolomite, as an example of nonequilibrium ternary salt when introduced into aqueous media. The study of dolomite is based on all attainable physicochemical knowledge, involved in expressions for equilibrium constants, where the species of the system are interrelated. The species are also involved in charge and concentration balances, considered as constraints put on a closed system, separated from the environment by diathermal walls. The inferences are gained from calculations performed with use of an iterative computer program. The simulated quasistatic processes occurred under isothermal conditions, started at a preassumed pH0 value of the solution where dolomite was introduced, and are usually involved with formation of other solid phases. None simplifying assumptions in the calculations were made.

  1. Spatially random models, estimation theory, and robot arm dynamics

    Science.gov (United States)

    Rodriguez, G.

    1987-01-01

    Spatially random models provide an alternative to the more traditional deterministic models used to describe robot arm dynamics. These alternative models can be used to establish a relationship between the methodologies of estimation theory and robot dynamics. A new class of algorithms for many of the fundamental robotics problems of inverse and forward dynamics, inverse kinematics, etc. can be developed that use computations typical in estimation theory. The algorithms make extensive use of the difference equations of Kalman filtering and Bryson-Frazier smoothing to conduct spatial recursions. The spatially random models are very easy to describe and are based on the assumption that all of the inertial (D'Alembert) forces in the system are represented by a spatially distributed white-noise model. The models can also be used to generate numerically the composite multibody system inertia matrix. This is done without resorting to the more common methods of deterministic modeling involving Lagrangian dynamics, Newton-Euler equations, etc. These methods make substantial use of human knowledge in derivation and minipulation of equations of motion for complex mechanical systems.

  2. Prediction models for clustered data: comparison of a random intercept and standard regression model.

    Science.gov (United States)

    Bouwmeester, Walter; Twisk, Jos W R; Kappen, Teus H; van Klei, Wilton A; Moons, Karel G M; Vergouwe, Yvonne

    2013-02-15

    When study data are clustered, standard regression analysis is considered inappropriate and analytical techniques for clustered data need to be used. For prediction research in which the interest of predictor effects is on the patient level, random effect regression models are probably preferred over standard regression analysis. It is well known that the random effect parameter estimates and the standard logistic regression parameter estimates are different. Here, we compared random effect and standard logistic regression models for their ability to provide accurate predictions. Using an empirical study on 1642 surgical patients at risk of postoperative nausea and vomiting, who were treated by one of 19 anesthesiologists (clusters), we developed prognostic models either with standard or random intercept logistic regression. External validity of these models was assessed in new patients from other anesthesiologists. We supported our results with simulation studies using intra-class correlation coefficients (ICC) of 5%, 15%, or 30%. Standard performance measures and measures adapted for the clustered data structure were estimated. The model developed with random effect analysis showed better discrimination than the standard approach, if the cluster effects were used for risk prediction (standard c-index of 0.69 versus 0.66). In the external validation set, both models showed similar discrimination (standard c-index 0.68 versus 0.67). The simulation study confirmed these results. For datasets with a high ICC (≥15%), model calibration was only adequate in external subjects, if the used performance measure assumed the same data structure as the model development method: standard calibration measures showed good calibration for the standard developed model, calibration measures adapting the clustered data structure showed good calibration for the prediction model with random intercept. The models with random intercept discriminate better than the standard model only

  3. Multiscale modeling of high contrast brinkman equations with applications to deformable porous media

    KAUST Repository

    Brown, Donald

    2013-06-18

    Simulating porous media flows has a wide range of applications. Often, these applications involve many scales and multi-physical processes. A useful tool in the analysis of such problems in that of homogenization as an averaged description is derived circumventing the need for complicated simulation of the fine scale features. In this work, we recall recent developments of homogenization techniques in the application of flows in deformable porous media. In addition, homogenization of media with high-contrast. In particular, we recall the main ideas of the homogenization of slowly varying Stokes flow and summarize the results of [4]. We also present the ideas for extending these techniques to high-contrast deformable media [3]. These ideas are connected by the modeling of multiscale fluid-structure interaction problems. © 2013 American Society of Civil Engineers.

  4. Emerging Media Crisis Value Model: A Comparison of Relevant, Timely Message Strategies for Emergency Events

    Directory of Open Access Journals (Sweden)

    Sabrina Page

    2013-01-01

    Full Text Available Communication during an emergency or crisis event is essential for emergency responders, the community involved, and those watching on television as well as receiving information via social media from family members, friends or other community members. The evolution of communication during an emergency/crisis event now includes utilizing social media. To better understand this evolution the Emerging Media Crisis Value Model (EMCVM is used in comparing two emergency events; Hurricane Irene (2011, a natural disaster, and the theater shooting in Aurora, Colorado (2012, a man-made crisis. The EMCVM provides a foundation for future studies focusing on the use of social media, emergency responders at the local, state and national levels are better prepared to educate a community thus, counteracting public uncertainty, fear, while providing timely, accurate information.

  5. Setting the Agenda: Different strategies of a Mass Media in a model of cultural dissemination

    CERN Document Server

    Pinto, Sebastián; Dorso, Claudio O

    2015-01-01

    Day by day, people exchange opinions about a given new with relatives, friends, and coworkers. In most cases, they get informed about a given issue by reading newspapers, listening to the radio, or watching TV, i.e., through a Mass Media (MM). However, the importance of a given new can be stimulated by the Media by assigning newspaper's pages or time in TV programs. In this sense, we say that the Media has the power to "set the agenda", i.e., it decides which new is important and which is not. On the other hand, the Media can know people's concerns through, for instance, websites or blogs where they express their opinions, and then it can use this information in order to be more appealing to an increasing number of people. In this work, we study different scenarios in an agent-based model of cultural dissemination, in which a given Mass Media has a specific purpose: To set a particular topic of discussion and impose its point of view to as many social agents as it can. We model this by making the Media has a ...

  6. Least squares estimation in a simple random coefficient autoregressive model

    DEFF Research Database (Denmark)

    Johansen, Søren; Lange, Theis

    2013-01-01

    we prove the curious result that View the MathML source. The proof applies the notion of a tail index of sums of positive random variables with infinite variance to find the order of magnitude of View the MathML source and View the MathML source and hence the limit of View the MathML source......The question we discuss is whether a simple random coefficient autoregressive model with infinite variance can create the long swings, or persistence, which are observed in many macroeconomic variables. The model is defined by yt=stρyt−1+εt,t=1,…,n, where st is an i.i.d. binary variable with p...

  7. Random unitary evolution model of quantum Darwinism with pure decoherence

    Science.gov (United States)

    Balanesković, Nenad

    2015-10-01

    We study the behavior of Quantum Darwinism [W.H. Zurek, Nat. Phys. 5, 181 (2009)] within the iterative, random unitary operations qubit-model of pure decoherence [J. Novotný, G. Alber, I. Jex, New J. Phys. 13, 053052 (2011)]. We conclude that Quantum Darwinism, which describes the quantum mechanical evolution of an open system S from the point of view of its environment E, is not a generic phenomenon, but depends on the specific form of input states and on the type of S-E-interactions. Furthermore, we show that within the random unitary model the concept of Quantum Darwinism enables one to explicitly construct and specify artificial input states of environment E that allow to store information about an open system S of interest with maximal efficiency.

  8. Statistical Modeling of Robotic Random Walks on Different Terrain

    Science.gov (United States)

    Naylor, Austin; Kinnaman, Laura

    Issues of public safety, especially with crowd dynamics and pedestrian movement, have been modeled by physicists using methods from statistical mechanics over the last few years. Complex decision making of humans moving on different terrains can be modeled using random walks (RW) and correlated random walks (CRW). The effect of different terrains, such as a constant increasing slope, on RW and CRW was explored. LEGO robots were programmed to make RW and CRW with uniform step sizes. Level ground tests demonstrated that the robots had the expected step size distribution and correlation angles (for CRW). The mean square displacement was calculated for each RW and CRW on different terrains and matched expected trends. The step size distribution was determined to change based on the terrain; theoretical predictions for the step size distribution were made for various simple terrains. It's Dr. Laura Kinnaman, not sure where to put the Prefix.

  9. Towards a social media-based model of trust and its application

    NARCIS (Netherlands)

    Boertjes, E.M.; Gerrits, B.M.; Kooij, R.E.; Maanen, P.P. van; Raaijmakers, S.A.; Wit, J.J. de

    2012-01-01

    In this paper we describe the development of a model for measuring consumer trust in certain topics on the basis of social media. Specifically, we propose a model for trust that takes into account both textually expressed sentiment and source authority, and illustrate it on a specific case: the

  10. Modeling the co-transport of viruses and colloids in unsaturated porous media

    NARCIS (Netherlands)

    Seetha, N.; Mohan Kumar, M. S.; Hassanizadeh, S. Majid

    2015-01-01

    A mathematical model is developed to simulate the co-transport of viruses and colloids in unsaturated porous media under steady-state flow conditions. The virus attachment to the mobile and immobile colloids is described using a linear reversible kinetic model. Colloid transport is assumed to be

  11. Presenting Thin Media Models Affects Women's Choice of Diet or Normal Snacks

    Science.gov (United States)

    Krahe, Barbara; Krause, Christina

    2010-01-01

    Our study explored the influence of thin- versus normal-size media models and of self-reported restrained eating behavior on women's observed snacking behavior. Fifty female undergraduates saw a set of advertisements for beauty products showing either thin or computer-altered normal-size female models, allegedly as part of a study on effective…

  12. Social aggregation in pea aphids: experiment and random walk modeling.

    Directory of Open Access Journals (Sweden)

    Christa Nilsen

    Full Text Available From bird flocks to fish schools and ungulate herds to insect swarms, social biological aggregations are found across the natural world. An ongoing challenge in the mathematical modeling of aggregations is to strengthen the connection between models and biological data by quantifying the rules that individuals follow. We model aggregation of the pea aphid, Acyrthosiphon pisum. Specifically, we conduct experiments to track the motion of aphids walking in a featureless circular arena in order to deduce individual-level rules. We observe that each aphid transitions stochastically between a moving and a stationary state. Moving aphids follow a correlated random walk. The probabilities of motion state transitions, as well as the random walk parameters, depend strongly on distance to an aphid's nearest neighbor. For large nearest neighbor distances, when an aphid is essentially isolated, its motion is ballistic with aphids moving faster, turning less, and being less likely to stop. In contrast, for short nearest neighbor distances, aphids move more slowly, turn more, and are more likely to become stationary; this behavior constitutes an aggregation mechanism. From the experimental data, we estimate the state transition probabilities and correlated random walk parameters as a function of nearest neighbor distance. With the individual-level model established, we assess whether it reproduces the macroscopic patterns of movement at the group level. To do so, we consider three distributions, namely distance to nearest neighbor, angle to nearest neighbor, and percentage of population moving at any given time. For each of these three distributions, we compare our experimental data to the output of numerical simulations of our nearest neighbor model, and of a control model in which aphids do not interact socially. Our stochastic, social nearest neighbor model reproduces salient features of the experimental data that are not captured by the control.

  13. Information inefficiency in a random linear economy model

    CERN Document Server

    Jerico, Joao Pedro

    2016-01-01

    We study the effects of introducing information inefficiency in a model for a random linear economy with a representative consumer. This is done by considering statistical, instead of classical, economic general equilibria. Employing two different approaches we show that inefficiency increases the consumption set of a consumer but decreases her expected utility. In this scenario economic activity grows while welfare shrinks, that is the opposite of the behavior obtained by considering a rational consumer.

  14. Predictors for contrast media-induced nephropathy and long-term survival: Prospectively assessed data from the randomized controlled Dialysis-Versus-Diuresis (DVD) trial

    Science.gov (United States)

    Hölscher, Birgit; Heitmeyer, Christine; Fobker, Manfred; Breithardt, Günter; Schaefer, Roland M; Reinecke, Holger

    2008-01-01

    BACKGROUND: Among the numerous studies concerning contrast media-induced nephropathy (CIN), there was no prospective trial that provided data on the long-term outcomes. OBJECTIVES: To prospectively assess predictors of CIN and long-term outcomes of affected patients. METHODS: Four hundred twelve consecutive patients with serum creatinine levels of 115 μmol/L to 309 μmol/L (1.3 mg/dL to 3.5 mg/dL) undergoing elective coronary angiography were included. Patients were randomly assigned to periprocedural hydration alone, hydration plus onetime hemodialysis or hydration plus N-acetylcysteine. RESULTS: Multivariate logistic regression identified the following as predictors of CIN within 72 h (equivalent to an increase in creatinine 44.2 μmol/L [0.5 mg/dL] or more) : prophylactic postprocedural hemodialysis (OR 2.86, 95% CI 1.07 to 7.69), use of angiotensin-converting enzyme inhibitors (OR 6.16, 95% CI 2.01 to 18.93), baseline glomerular filtration rate (OR 0.94, 95% CI 0.90 to 0.98) and the amount of contrast media given (OR 1.01, 95% CI 1.00 to 1.01). With regard to long-term outcome (mean follow-up 649 days), multivariate Cox regression models found elevated creatinine levels at 30 days (hazard rate ratio [HRR] 5.48, 95% CI 2.85 to 10.53), but not CIN within 72 h (HRR 1.12, 95% CI 0.63 to 2.02), to be associated with increased mortality. In addition, independent predictors for death during follow-up included left ventricular ejection fraction lower than 35% (HRR 4.01, 95% CI 2.22 to 7.26), serum phosphate (HRR 1.64, 95% CI 1.10 to 2.43) and hemoglobin (HRR 0.80, 95% CI 0.67 to 0.96). CONCLUSION: From the present prospective trial, performance of post-procedural hemodialysis, use of angiotensin-converting enzyme inhibitors, reduced baseline glomerular filtration rate and amount of contrast media were independent predictors of CIN within 72 h after catheterization. Assessing renal function after 30 days, rather than within 72 h, seemed to be more predictive for

  15. Reactive transport in porous media: Pore-network model approach compared to pore-scale model

    Science.gov (United States)

    Varloteaux, Clément; Vu, Minh Tan; Békri, Samir; Adler, Pierre M.

    2013-02-01

    Accurate determination of three macroscopic parameters governing reactive transport in porous media, namely, the apparent solute velocity, the dispersion, and the apparent reaction rate, is of key importance for predicting solute migration through reservoir aquifers. Two methods are proposed to calculate these parameters as functions of the Péclet and the Péclet-Dahmköhler numbers. In the first method called the pore-scale model (PSM), the porous medium is discretized by the level set method; the Stokes and convection-diffusion equations with reaction at the wall are solved by a finite-difference scheme. In the second method, called the pore-network model (PNM), the void space of the porous medium is represented by an idealized geometry of pore bodies joined by pore throats; the flow field is computed by solving Kirchhoff's laws and transport calculations are performed in the asymptotic regime where the solute concentration undergoes an exponential evolution with time. Two synthetic geometries of porous media are addressed by using both numerical codes. The first geometry is constructed in order to validate the hypotheses implemented in PNM. PSM is also used for a better understanding of the various reaction patterns observed in the asymptotic regime. Despite the PNM approximations, a very good agreement between the models is obtained, which shows that PNM is an accurate description of reactive transport. PNM, which can address much larger pore volumes than PSM, is used to evaluate the influence of the concentration distribution on macroscopic properties of a large irregular network reconstructed from microtomography images. The role of the dimensionless numbers and of the location and size of the largest pore bodies is highlighted.

  16. An Investigation of How Managers’ Mental Models of Business-Consumer Interaction Influence the Implementation and Use of Social Media

    DEFF Research Database (Denmark)

    Rydén, Pernille; Ringberg, Torsten; Wilke, Ricky

    2014-01-01

    The paper empirically illustrates how mental models influence how managers implement social media in their businesses. We posit that managers’ use of social media is constrained by four mental models of business-consumer interaction and question the rational decision process that often is assumed...... to play a major part of introducing new technology. Based on twenty interviews with managers we identify four mental models,each of which uniquely influences how managers implement social media within the service and retailing industries....

  17. Portable Video Media Versus Standard Verbal Communication in Surgical Information Delivery to Nurses: A Prospective Multicenter, Randomized Controlled Crossover Trial.

    Science.gov (United States)

    Kam, Jonathan; Ainsworth, Hannah; Handmer, Marcus; Louie-Johnsun, Mark; Winter, Matthew

    2016-10-01

    Continuing education of health professionals is important for delivery of quality health care. Surgical nurses are often required to understand surgical procedures. Nurses need to be aware of the expected outcomes and recognize potential complications of such procedures during their daily work. Traditional educational methods, such as conferences and tutorials or informal education at the bedside, have many drawbacks for delivery of this information in a universal, standardized, and timely manner. The rapid uptake of portable media devices makes portable video media (PVM) a potential alternative to current educational methods. To compare PVM to standard verbal communication (SVC) for surgical information delivery and educational training for nurses and evaluate its impact on knowledge acquisition and participant satisfaction. Prospective, multicenter, randomized controlled crossover trial. Two hospitals: Gosford District Hospital and Wyong Hospital. Seventy-two nursing staff (36 at each site). Information delivery via PVM--7-minute video compared to information delivered via SVC. Knowledge acquisition was measured by a 32-point questionnaire, and satisfaction with the method of education delivery was measured using the validated Client Satisfaction Questionnaire (CSQ-8). Knowledge acquisition was higher via PVM compared to SVC 25.9 (95% confidence interval [CI] 25.2-26.6) versus 24.3 (95% CI 23.5-25.1), p = .004. Participant satisfaction was higher with PVM 29.5 (95% CI 28.3-30.7) versus 26.5 (95% CI 25.1-27.9), p = .003. Following information delivery via SVC, participants had a 6% increase in knowledge scores, 24.3 (95% CI 23.5-25.1) versus 25.7 (95% CI 24.9-26.5) p = .001, and a 13% increase in satisfaction scores, 26.5 (95% CI 25.1-27.9) versus 29.9 (95% CI 28.8-31.0) p < .001, when they crossed-over to information delivery via PVM. PVM provides a novel method for providing education to nurses that improves knowledge retention and satisfaction with the

  18. Social media to supplement point-of-care ultrasound courses: the "sandwich e-learning" approach. A randomized trial.

    Science.gov (United States)

    Hempel, Dorothea; Haunhorst, Stephanie; Sinnathurai, Sivajini; Seibel, Armin; Recker, Florian; Heringer, Frank; Michels, Guido; Breitkreutz, Raoul

    2016-12-01

    Point-of-care ultrasound (POC-US) is gaining importance in almost all specialties. E-learning has been used to teach theoretical knowledge and pattern recognition. As social media are universally available, they can be utilized for educational purposes. We wanted to evaluate the utility of the sandwich e-learning approach defined as a pre-course e-learning and a post-course learning activity using Facebook after a one-day point-of-care ultrasound (POC-US) course and its effect on the retention of knowledge. A total of 62 medial students were recruited for this study and randomly assigned to one of four groups. All groups received an identical hands-on training and performed several tests during the study period. The hands-on training was performed in groups of five students per instructor with the students scanning each other. Group 1 had access to pre-course e-learning, but not to post-course e-learning. Instead of a pre-course e-learning, group 2 listened to presentations at the day of the course (classroom teaching) and had access to the post-course learning activity using Facebook. Group 3 had access to both pre- and post-course e-learning (sandwich e-learning) activities, while group 4 listened classroom presentations only (classroom teaching only). Therefore only groups 2 and 3 had access to post-course learning via Facebook by joining a secured group. Posts containing ultrasound pictures and videos were published to this group. The students were asked to "like" the posts to monitor attendance. Knowledge retention was assessed 6 weeks after the course. After 6 weeks, group 3 achieved comparable results when compared to group 2 (82.2 % + -8.2 vs. 84.3 + -8.02) (p = 0.3). Students who participated in the post-course activity were more satisfied with the overall course than students without post-course learning (5.5 vs. 5.3 on a range from 1 to 6). In this study, the sandwich e-learning approach led to equal rates of knowledge retention compared to

  19. An online randomized controlled trial evaluating HIV prevention digital media interventions for men who have sex with men.

    Directory of Open Access Journals (Sweden)

    Sabina Hirshfield

    Full Text Available As HIV infection continues unabated, there is a need for effective interventions targeting at-risk men who have sex with men (MSM. Engaging MSM online where they meet sexual partners is critical for HIV prevention efforts.A randomized controlled trial (RCT conducted online among U.S. MSM recruited from several gay sexual networking websites assessed the impact of 2 HIV prevention videos and an HIV prevention webpage compared to a control condition for the study outcomes HIV testing, serostatus disclosure, and unprotected anal intercourse (UAI at 60-day follow-up. Video conditions were pooled due to reduced power from low retention (53%, n = 1,631. No participant incentives were provided.Follow-up was completed by 1,631 (53% of 3,092 eligible men. In the 60 days after the intervention, men in the pooled video condition were significantly more likely than men in the control to report full serostatus disclosure ('asked and told' with their last sexual partner (OR 1.32, 95% CI 1.01-1.74. Comparing baseline to follow-up, HIV-negative men in the pooled video (OR 0.70, 95% CI 0.54-0.91 and webpage condition (OR 0.43, 95% CI 0.25-0.72 significantly reduced UAI at follow-up. HIV-positive men in the pooled video condition significantly reduced UAI (OR 0.38, 95% CI 0.20-0.67 and serodiscordant UAI (OR 0.53, 95% CI 0.28-0.96 at follow-up.Findings from this online RCT of MSM recruited from sexual networking websites suggest that a low cost, brief digital media intervention designed to engage critical thinking can increase HIV disclosure to sexual partners and decrease sexual risk. Effective, brief HIV prevention interventions featuring digital media that are made widely available may serve as a complementary part of an overall behavioral and biomedical strategy for reducing sexual risk by addressing the specific needs and circumstances of the target population, and by changing individual knowledge, motivations, and community norms.ClinicalTrials.gov NCT

  20. An online randomized controlled trial evaluating HIV prevention digital media interventions for men who have sex with men.

    Science.gov (United States)

    Hirshfield, Sabina; Chiasson, Mary Ann; Joseph, Heather; Scheinmann, Roberta; Johnson, Wayne D; Remien, Robert H; Shaw, Francine Shuchat; Emmons, Reed; Yu, Gary; Margolis, Andrew D

    2012-01-01

    As HIV infection continues unabated, there is a need for effective interventions targeting at-risk men who have sex with men (MSM). Engaging MSM online where they meet sexual partners is critical for HIV prevention efforts. A randomized controlled trial (RCT) conducted online among U.S. MSM recruited from several gay sexual networking websites assessed the impact of 2 HIV prevention videos and an HIV prevention webpage compared to a control condition for the study outcomes HIV testing, serostatus disclosure, and unprotected anal intercourse (UAI) at 60-day follow-up. Video conditions were pooled due to reduced power from low retention (53%, n = 1,631). No participant incentives were provided. Follow-up was completed by 1,631 (53%) of 3,092 eligible men. In the 60 days after the intervention, men in the pooled video condition were significantly more likely than men in the control to report full serostatus disclosure ('asked and told') with their last sexual partner (OR 1.32, 95% CI 1.01-1.74). Comparing baseline to follow-up, HIV-negative men in the pooled video (OR 0.70, 95% CI 0.54-0.91) and webpage condition (OR 0.43, 95% CI 0.25-0.72) significantly reduced UAI at follow-up. HIV-positive men in the pooled video condition significantly reduced UAI (OR 0.38, 95% CI 0.20-0.67) and serodiscordant UAI (OR 0.53, 95% CI 0.28-0.96) at follow-up. Findings from this online RCT of MSM recruited from sexual networking websites suggest that a low cost, brief digital media intervention designed to engage critical thinking can increase HIV disclosure to sexual partners and decrease sexual risk. Effective, brief HIV prevention interventions featuring digital media that are made widely available may serve as a complementary part of an overall behavioral and biomedical strategy for reducing sexual risk by addressing the specific needs and circumstances of the target population, and by changing individual knowledge, motivations, and community norms. ClinicalTrials.gov NCT00649701.

  1. An Online Randomized Controlled Trial Evaluating HIV Prevention Digital Media Interventions for Men Who Have Sex with Men

    Science.gov (United States)

    Hirshfield, Sabina; Chiasson, Mary Ann; Joseph, Heather; Scheinmann, Roberta; Johnson, Wayne D.; Remien, Robert H.; Shaw, Francine Shuchat; Emmons, Reed; Yu, Gary; Margolis, Andrew D.

    2012-01-01

    Background As HIV infection continues unabated, there is a need for effective interventions targeting at-risk men who have sex with men (MSM). Engaging MSM online where they meet sexual partners is critical for HIV prevention efforts. Methods A randomized controlled trial (RCT) conducted online among U.S. MSM recruited from several gay sexual networking websites assessed the impact of 2 HIV prevention videos and an HIV prevention webpage compared to a control condition for the study outcomes HIV testing, serostatus disclosure, and unprotected anal intercourse (UAI) at 60-day follow-up. Video conditions were pooled due to reduced power from low retention (53%, n = 1,631). No participant incentives were provided. Principal Findings Follow-up was completed by 1,631 (53%) of 3,092 eligible men. In the 60 days after the intervention, men in the pooled video condition were significantly more likely than men in the control to report full serostatus disclosure (‘asked and told’) with their last sexual partner (OR 1.32, 95% CI 1.01–1.74). Comparing baseline to follow-up, HIV-negative men in the pooled video (OR 0.70, 95% CI 0.54–0.91) and webpage condition (OR 0.43, 95% CI 0.25–0.72) significantly reduced UAI at follow-up. HIV-positive men in the pooled video condition significantly reduced UAI (OR 0.38, 95% CI 0.20–0.67) and serodiscordant UAI (OR 0.53, 95% CI 0.28–0.96) at follow-up. Conclusions/Significance Findings from this online RCT of MSM recruited from sexual networking websites suggest that a low cost, brief digital media intervention designed to engage critical thinking can increase HIV disclosure to sexual partners and decrease sexual risk. Effective, brief HIV prevention interventions featuring digital media that are made widely available may serve as a complementary part of an overall behavioral and biomedical strategy for reducing sexual risk by addressing the specific needs and circumstances of the target population, and by changing

  2. Calibration of stormwater quality regression models: a random process?

    Science.gov (United States)

    Dembélé, A; Bertrand-Krajewski, J-L; Barillon, B

    2010-01-01

    Regression models are among the most frequently used models to estimate pollutants event mean concentrations (EMC) in wet weather discharges in urban catchments. Two main questions dealing with the calibration of EMC regression models are investigated: i) the sensitivity of models to the size and the content of data sets used for their calibration, ii) the change of modelling results when models are re-calibrated when data sets grow and change with time when new experimental data are collected. Based on an experimental data set of 64 rain events monitored in a densely urbanised catchment, four TSS EMC regression models (two log-linear and two linear models) with two or three explanatory variables have been derived and analysed. Model calibration with the iterative re-weighted least squares method is less sensitive and leads to more robust results than the ordinary least squares method. Three calibration options have been investigated: two options accounting for the chronological order of the observations, one option using random samples of events from the whole available data set. Results obtained with the best performing non linear model clearly indicate that the model is highly sensitive to the size and the content of the data set used for its calibration.

  3. Richly parameterized linear models additive, time series, and spatial models using random effects

    CERN Document Server

    Hodges, James S

    2013-01-01

    A First Step toward a Unified Theory of Richly Parameterized Linear ModelsUsing mixed linear models to analyze data often leads to results that are mysterious, inconvenient, or wrong. Further compounding the problem, statisticians lack a cohesive resource to acquire a systematic, theory-based understanding of models with random effects.Richly Parameterized Linear Models: Additive, Time Series, and Spatial Models Using Random Effects takes a first step in developing a full theory of richly parameterized models, which would allow statisticians to better understand their analysis results. The aut

  4. High-temperature series expansions for random Potts models

    Directory of Open Access Journals (Sweden)

    M.Hellmund

    2005-01-01

    Full Text Available We discuss recently generated high-temperature series expansions for the free energy and the susceptibility of random-bond q-state Potts models on hypercubic lattices. Using the star-graph expansion technique, quenched disorder averages can be calculated exactly for arbitrary uncorrelated coupling distributions while keeping the disorder strength p as well as the dimension d as symbolic parameters. We present analyses of the new series for the susceptibility of the Ising (q=2 and 4-state Potts model in three dimensions up to the order 19 and 18, respectively, and compare our findings with results from field-theoretical renormalization group studies and Monte Carlo simulations.

  5. The Effect of Health Beliefs, Media Perceptions, and Communicative Behaviors on Health Behavioral Intention: An Integrated Health Campaign Model on Social Media.

    Science.gov (United States)

    Yoo, Sun-Wook; Kim, Jarim; Lee, Yeunjae

    2018-01-01

    Social media have recently gained attention as a potential health campaign tool. This study examines this line of expectation concerning the role social media may play in health campaigns by testing an integrated health campaign model that combines insights from research on social media-specific perceptions and communicative behaviors in order to predict health behaviors. Specifically, this study aims to (a) develop a more holistic social media campaign model for predicting health behaviors in the social media context, (b) investigate how social media channel-related perceptions affect preventive health behaviors, and (c) investigate how communicative behaviors mediate perceptions and behavioral intention. The study conducted an online survey of 498 females who followed the Purple Ribbon Twitter campaign (@pprb), a cervical cancer prevention campaign. The results indicated that information acquisition mediated perceived risk's effect on intention. Information acquisition also mediated the relationships between intention and information selection and information transmission. On the other hand, social media-related perceptions indirectly impacted behavioral intention through communicative behaviors. The findings' theoretical and practical implications are discussed.

  6. Marginal and Random Intercepts Models for Longitudinal Binary Data with Examples from Criminology

    Science.gov (United States)

    Long, Jeffrey D.; Loeber, Rolf; Farrington, David P.

    2009-01-01

    Two models for the analysis of longitudinal binary data are discussed: the marginal model and the random intercepts model. In contrast to the linear mixed model (LMM), the two models for binary data are not subsumed under a single hierarchical model. The marginal model provides group-level information whereas the random intercepts model provides…

  7. Modeling the state dependent impulse control for computer virus propagation under media coverage

    Science.gov (United States)

    Liang, Xiyin; Pei, Yongzhen; Lv, Yunfei

    2018-02-01

    A state dependent impulsive control model is proposed to model the spread of computer virus incorporating media coverage. By the successor function, the sufficient conditions for the existence and uniqueness of order-1 periodic solution are presented first. Secondly, for two classes of periodic solutions, the geometric property of successor function and the analogue of the Poincaré criterion are employed to obtain the stability results. These results show that the number of the infective computers is under the threshold all the time. Finally, the theoretic and numerical analysis show that media coverage can delay the spread of computer virus.

  8. Retrieving quantifiable social media data from human sensor networks for disaster modeling and crisis mapping

    Science.gov (United States)

    Aulov, Oleg

    This dissertation presents a novel approach that utilizes quantifiable social media data as a human aware, near real-time observing system, coupled with geophysical predictive models for improved response to disasters and extreme events. It shows that social media data has the potential to significantly improve disaster management beyond informing the public, and emphasizes the importance of different roles that social media can play in management, monitoring, modeling and mitigation of natural and human-caused extreme disasters. In the proposed approach Social Media users are viewed as "human sensors" that are "deployed" in the field, and their posts are considered to be "sensor observations", thus different social media outlets all together form a Human Sensor Network. We utilized the "human sensor" observations, as boundary value forcings, to show improved geophysical model forecasts of extreme disaster events when combined with other scientific data such as satellite observations and sensor measurements. Several recent extreme disasters are presented as use case scenarios. In the case of the Deepwater Horizon oil spill disaster of 2010 that devastated the Gulf of Mexico, the research demonstrates how social media data from Flickr can be used as a boundary forcing condition of GNOME oil spill plume forecast model, and results in an order of magnitude forecast improvement. In the case of Hurricane Sandy NY/NJ landfall impact of 2012, we demonstrate how the model forecasts, when combined with social media data in a single framework, can be used for near real-time forecast validation, damage assessment and disaster management. Owing to inherent uncertainties in the weather forecasts, the NOAA operational surge model only forecasts the worst-case scenario for flooding from any given hurricane. Geolocated and time-stamped Instagram photos and tweets allow near real-time assessment of the surge levels at different locations, which can validate model forecasts, give

  9. Using the Integrative Model to Explain How Exposure to Sexual Media Content Influences Adolescent Sexual Behavior

    Science.gov (United States)

    Bleakley, Amy; Hennessy, Michael; Fishbein, Martin; Jordan, Amy

    2017-01-01

    Published research demonstrates an association between exposure to media sexual content and a variety of sex-related outcomes for adolescents. What is not known is the mechanism through which sexual content produces this “media effect” on adolescent beliefs, attitudes, and behavior. Using the Integrative Model of Behavioral Prediction, this paper uses data from a longitudinal study of adolescents ages 16–18 (n=460) to determine how exposure to sexual media content influences sexual behavior. Path analysis and structural equation modeling demonstrated that intention to engage in sexual intercourse is determined by a combination of attitudes, normative pressure, and self efficacy but that exposure to sexual media content only affects normative pressure beliefs. By applying the Integrative Model, we are able to identify which beliefs are influenced by exposure to media sex and improve the ability of health educators, researchers, and others to design effective messages for health communication campaigns and messages pertaining to adolescents’ engaging in sexual intercourse. PMID:21606378

  10. Random Predictor Models for Rigorous Uncertainty Quantification: Part 1

    Science.gov (United States)

    Crespo, Luis G.; Kenny, Sean P.; Giesy, Daniel P.

    2015-01-01

    This and a companion paper propose techniques for constructing parametric mathematical models describing key features of the distribution of an output variable given input-output data. By contrast to standard models, which yield a single output value at each value of the input, Random Predictors Models (RPMs) yield a random variable at each value of the input. Optimization-based strategies for calculating RPMs having a polynomial dependency on the input and a linear dependency on the parameters are proposed. These formulations yield RPMs having various levels of fidelity in which the mean and the variance of the model's parameters, thus of the predicted output, are prescribed. As such they encompass all RPMs conforming to these prescriptions. The RPMs are optimal in the sense that they yield the tightest predictions for which all (or, depending on the formulation, most) of the observations are less than a fixed number of standard deviations from the mean prediction. When the data satisfies mild stochastic assumptions, and the optimization problem(s) used to calculate the RPM is convex (or, when its solution coincides with the solution to an auxiliary convex problem), the model's reliability, which is the probability that a future observation would be within the predicted ranges, can be bounded tightly and rigorously.

  11. Random matrices and the six-vertex model

    CERN Document Server

    Bleher, Pavel

    2013-01-01

    This book provides a detailed description of the Riemann-Hilbert approach (RH approach) to the asymptotic analysis of both continuous and discrete orthogonal polynomials, and applications to random matrix models as well as to the six-vertex model. The RH approach was an important ingredient in the proofs of universality in unitary matrix models. This book gives an introduction to the unitary matrix models and discusses bulk and edge universality. The six-vertex model is an exactly solvable two-dimensional model in statistical physics, and thanks to the Izergin-Korepin formula for the model with domain wall boundary conditions, its partition function matches that of a unitary matrix model with nonpolynomial interaction. The authors introduce in this book the six-vertex model and include a proof of the Izergin-Korepin formula. Using the RH approach, they explicitly calculate the leading and subleading terms in the thermodynamic asymptotic behavior of the partition function of the six-vertex model with domain wa...

  12. Modeling of the dielectric permittivity of porous soil media with water using statistical-physical models

    Science.gov (United States)

    Usowicz, Boguslaw; Marczewski, Wojciech; Usowicz, Jerzy B.; Łukowski, Mateusz; Lipiec, Jerzy; Stankiewicz, Krystyna

    2013-04-01

    Radiometric observations with SMOS rely on the Radiation Transfer Equations (RTE) determining the Brightness Temperature (BT) in two linear polarization components (H, V) satisfying Fresnel principle of propagation in horizontally layered target media on the ground. RTE involve variables which bound the equations expressed in Electro-Magnetic (EM) terms of the intensity BT to the physical reality expressed by non-EM variables (Soil Moisture (SM), vegetation indexes, fractional coverage with many different properties, and the boundary conditions like optical thickness, layer definitions, roughness, etc.) bridging the EM domain to other physical aspects by means of the so called tau-omega methods. This method enables joining variety of different valuable models, including specific empirical estimation of physical properties in relation to the volumetric water content. The equations of RTE are in fact expressed by propagation, reflection and losses or attenuation existing on a considered propagation path. The electromagnetic propagation is expressed in the propagation constant. For target media on the ground the dielectric constant is a decisive part for effects of propagation. Therefore, despite of many various physical parameters involved, one must effectively and dominantly rely on the dielectric constant meant as a complex variable. The real part of the dielectric constant represents effect of apparent shortening the propagation path and the refraction, while the imaginary part is responsible for the attenuation or losses. This work engages statistical-physical modeling of soil properties considering the media as a mixture of solid grains, and gas or liquid filling of pores and contact bridges between compounds treated statistically. The method of this modeling provides an opportunity of characterizing the porosity by general statistical means, and is applicable to various physical properties (thermal, electrical conductivity and dielectric properties) which

  13. Randomized pilot trial measuring knowledge acquisition of opioid education in emergency department patients using a novel media platform.

    Science.gov (United States)

    Chakravarthy, Bharath; Somasundaram, Shashank; Mogi, Jennifer; Burns, Roshan; Hoonpongsimanont, Wirachin; Wiechmann, Warren; Lotfipour, Shahram

    2017-09-05

    The number of active opioid analgesic prescriptions has risen steadily, causing increases in nonmedical opioid use, addiction, and overdose. Insufficient focus on patient discharge instructions has contributed to lack of patient awareness regarding dangers of opioids. This study examines whether an educational Khan Academy-style animation discharge instruction on the dangers and safe usage of opioid analgesics elicits higher knowledge acquisition than current standard of care. Additionally, it measures the feasibility of implementing this video discharge instruction in the emergency department (ED). Fifty-two English-speaking patients aged 18 years or older receiving an opioid prescription were enrolled in this study. Patients were randomized into 2 groups. The standard of care group received verbal instruction and an informational sheet, whereas the video animation group received a 6-minute video on proper usage of opioids in addition to standard of care. Video content was sourced from samhsa.gov and administered within the ED prior to discharge. Both groups received a 26-question test regarding the dangers and safe usage of opioids immediately after education. An unpaired t test compared knowledge acquisition between the 2 groups. Fifty-four patients were approached, 52 patients enrolled; 27 in the standard group and 25 in the animation group. The standard of care group averaged 65% knowledge acquisition (16.8/26 correct), whereas the animation group averaged 82% acquisition (21.2/26 correct). The video animation significantly increased patient knowledge acquisition about opioid medications' risks and proper usage and disposal (P = .001). It can be concluded that medical knowledge acquisition is improved in the video animation group compared with the current standard of care (P = .001). It can also be concluded that it is feasible to implement a novel media platform to educate patients receiving opioid analgesics in the ED (96.1%).

  14. Nutritional Online Information for Cancer Patients: a Randomized Trial of an Internet Communication Plus Social Media Intervention.

    Science.gov (United States)

    Gnagnarella, Patrizia; Misotti, Alessandro Maria; Santoro, Luigi; Akoumianakis, Demosthenes; Del Campo, Laura; De Lorenzo, Francesco; Lombardo, Claudio; Milolidakis, Giannis; Sullivan, Richard; McVie, John Gordon

    2016-09-01

    We hypothesized that cancer patients using an Internet website would show an improvement in the knowledge about healthy eating habits, and this might be enhanced by social media interaction. A 6-month randomized intervention was set up. Eligible subjects were allocated in intervention (IG) and control groups (CG). IG had access to the website, and CG was provided with printed versions. All enrolled participants filled in Nutrition Questionnaire (NQ), Quality of Life Questionnaire (QoL) and Psychological Distress Inventory (PDI), at baseline and after 6 months. The difference between post- vs pre-questionnaires was calculated. Seventy-four subjects (CG 39; IG 35) completed the study. There was an increase in the score after the intervention in both groups for the NQ, even if not statistically significant. Dividing the IG into three categories, no (NI), low (LI) and high interactions (HI), we found a decreased score (improvement) in the CG (-0.2) and in the HI (-1.7), and an increased score (worsening) in the NI (+3.3) (p = NS) analysing the PDI. We found an increased score in the QoL both in CG and IG (adjusted LSMeans +3.5 and +2.8 points, respectively; p = NS). This study represents an example for support cancer patients. Despite the lack of significant effects, critical points and problems encountered may be of interest to researchers and organization working in the cancer setting. Intervention strategies to support patients during the care process are needed in order to attain the full potential of patient-centred care on cancer outcomes.

  15. Nonparametric Estimation of Distributions in Random Effects Models

    KAUST Repository

    Hart, Jeffrey D.

    2011-01-01

    We propose using minimum distance to obtain nonparametric estimates of the distributions of components in random effects models. A main setting considered is equivalent to having a large number of small datasets whose locations, and perhaps scales, vary randomly, but which otherwise have a common distribution. Interest focuses on estimating the distribution that is common to all datasets, knowledge of which is crucial in multiple testing problems where a location/scale invariant test is applied to every small dataset. A detailed algorithm for computing minimum distance estimates is proposed, and the usefulness of our methodology is illustrated by a simulation study and an analysis of microarray data. Supplemental materials for the article, including R-code and a dataset, are available online. © 2011 American Statistical Association.

  16. Statistical Downscaling of Temperature with the Random Forest Model

    Directory of Open Access Journals (Sweden)

    Bo Pang

    2017-01-01

    Full Text Available The issues with downscaling the outputs of a global climate model (GCM to a regional scale that are appropriate to hydrological impact studies are investigated using the random forest (RF model, which has been shown to be superior for large dataset analysis and variable importance evaluation. The RF is proposed for downscaling daily mean temperature in the Pearl River basin in southern China. Four downscaling models were developed and validated by using the observed temperature series from 61 national stations and large-scale predictor variables derived from the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis dataset. The proposed RF downscaling model was compared to multiple linear regression, artificial neural network, and support vector machine models. Principal component analysis (PCA and partial correlation analysis (PAR were used in the predictor selection for the other models for a comprehensive study. It was shown that the model efficiency of the RF model was higher than that of the other models according to five selected criteria. By evaluating the predictor importance, the RF could choose the best predictor combination without using PCA and PAR. The results indicate that the RF is a feasible tool for the statistical downscaling of temperature.

  17. How do you perceive this author? Understanding and modeling authors' communication quality in social media.

    Science.gov (United States)

    Han, Kyungsik

    2018-01-01

    In this study, we leverage human evaluations, content analysis, and computational modeling to generate a comprehensive analysis of readers' evaluations of authors' communication quality in social media with respect to four factors: author credibility, interpersonal attraction, communication competence, and intent to interact. We review previous research on the human evaluation process and highlight its limitations in providing sufficient information for readers to assess authors' communication quality. From our analysis of the evaluations of 1,000 Twitter authors' communication quality from 300 human evaluators, we provide empirical evidence of the impact of the characteristics of the reader (demographic, social media experience, and personality), author (profile and social media engagement), and content (linguistic, syntactic, similarity, and sentiment) on the evaluation of an author's communication quality. In addition, based on the author and message characteristics, we demonstrate the potential for building accurate models that can indicate an author's communication quality.

  18. How do you perceive this author? Understanding and modeling authors’ communication quality in social media

    Science.gov (United States)

    2018-01-01

    In this study, we leverage human evaluations, content analysis, and computational modeling to generate a comprehensive analysis of readers’ evaluations of authors’ communication quality in social media with respect to four factors: author credibility, interpersonal attraction, communication competence, and intent to interact. We review previous research on the human evaluation process and highlight its limitations in providing sufficient information for readers to assess authors’ communication quality. From our analysis of the evaluations of 1,000 Twitter authors’ communication quality from 300 human evaluators, we provide empirical evidence of the impact of the characteristics of the reader (demographic, social media experience, and personality), author (profile and social media engagement), and content (linguistic, syntactic, similarity, and sentiment) on the evaluation of an author’s communication quality. In addition, based on the author and message characteristics, we demonstrate the potential for building accurate models that can indicate an author’s communication quality. PMID:29389979

  19. The impact of media on a new product innovation diffusion: a mathematical model

    Directory of Open Access Journals (Sweden)

    Joydip Dhar

    2015-05-01

    to discuss the influence of media coverage in spreading and controlling of adopter of a particular product in a region. The model exhibits two equilibria:(i a adopter-free and (ii unique interior equilibrium. Stability analysis of the model shows that the adopter-free equilibrium is always locally asymptotically stable if the influence number of adopter $(R_0$, which depends on parameters of the system is less than unity. Otherwise if $R_0>1$, a unique interior equilibrium exists, it is locally asymptotically stable under some set of conditions. Further analytically and numerically it is observed that the region for backward bifurcation of adopter population increases with the decrease of the valid contact rate before media alert. Finally, numerically experimentations are presented to establish the effect of different media alert rate on adopter and non adopter population.

  20. Global stability of a two-mediums rumor spreading model with media coverage

    Science.gov (United States)

    Huo, Liang'an; Wang, Li; Song, Guoxiang

    2017-09-01

    Rumor spreading is a typical form of social communication and plays a significant role in social life, and media coverage has a great influence on the spread of rumor. In this paper, we present a new model with two media coverage to investigate the impact of the different mediums on rumor spreading. Then, we calculate the equilibria of the model and construct the reproduction number ℜ0. And we prove the global asymptotic stability of equilibria by using Lyapunov functions. Finally, we can conclude that the transition rate of the ignorants between two mediums has a direct effect on the scale of spreaders, and different media coverage has significant effects on the dynamics behaviors of rumor spreading.

  1. Grayscale lattice Boltzmann model for multiphase heterogeneous flow through porous media.

    Science.gov (United States)

    Pereira, Gerald G

    2016-06-01

    The grayscale lattice Boltzmann (LB) model has been recently developed to model single-phase fluid flow through heterogeneous porous media. Flow is allowed in each voxel but the degree of flow depends on that voxel's resistivity to fluid motion. Here we extend the grayscale LB model to multiphase, immiscible flow. The new model is outlined and then applied to a number of test cases, which show good agreement with theory. This method is subsequently used to model the important case where each voxel may have a different resistance to each particular fluid that is passing through it. Finally, the method is applied to model fluid flow through real porous media to demonstrate its capability. Both the capillary and viscous flow regimes are recovered in these simulations.

  2. Relations between Lagrangian models and synthetic random velocity fields.

    Science.gov (United States)

    Olla, Piero; Paradisi, Paolo

    2004-10-01

    The authors propose an alternative interpretation of Markovian transport models based on the well-mixed condition, in terms of the properties of a random velocity field with second order structure functions scaling linearly in the space-time increments. This interpretation allows direct association of the drift and noise terms entering the model, with the geometry of the turbulent fluctuations. In particular, the well-known nonuniqueness problem in the well-mixed approach is solved in terms of the antisymmetric part of the velocity correlations; its relation with the presence of nonzero mean helicity and other geometrical properties of the flow is elucidated. The well-mixed condition appears to be a special case of the relation between conditional velocity increments of the random field and the one-point Eulerian velocity distribution, allowing generalization of the approach to the transport of nontracer quantities. Application to solid particle transport leads to a model satisfying, in the homogeneous isotropic turbulence case, all the conditions on the behavior of the correlation times for the fluid velocity sampled by the particles. In particular, correlation times in the gravity and in the inertia dominated case, respectively, longer and shorter than in the passive tracer case; in the gravity dominated case, correlation times longer for velocity components along gravity, than for the perpendicular ones. The model produces, in channel flow geometry, particle deposition rates in agreement with experiments.

  3. Genetic evaluation of European quails by random regression models

    Directory of Open Access Journals (Sweden)

    Flaviana Miranda Gonçalves

    2012-09-01

    Full Text Available The objective of this study was to compare different random regression models, defined from different classes of heterogeneity of variance combined with different Legendre polynomial orders for the estimate of (covariance of quails. The data came from 28,076 observations of 4,507 female meat quails of the LF1 lineage. Quail body weights were determined at birth and 1, 14, 21, 28, 35 and 42 days of age. Six different classes of residual variance were fitted to Legendre polynomial functions (orders ranging from 2 to 6 to determine which model had the best fit to describe the (covariance structures as a function of time. According to the evaluated criteria (AIC, BIC and LRT, the model with six classes of residual variances and of sixth-order Legendre polynomial was the best fit. The estimated additive genetic variance increased from birth to 28 days of age, and dropped slightly from 35 to 42 days. The heritability estimates decreased along the growth curve and changed from 0.51 (1 day to 0.16 (42 days. Animal genetic and permanent environmental correlation estimates between weights and age classes were always high and positive, except for birth weight. The sixth order Legendre polynomial, along with the residual variance divided into six classes was the best fit for the growth rate curve of meat quails; therefore, they should be considered for breeding evaluation processes by random regression models.

  4. Mortar Methods for Pore-to-Continuum Modeling of Flow and Transport in Porous Media

    Science.gov (United States)

    Balhoff, M.

    2014-12-01

    Pore-scale network modeling has become an effective method for accurate prediction and upscaling of macroscopic properties in porous media. Computational and imaging restrictions generally limit the network size to the order of 1.0 mm3 (few thousand pores). For extremely heterogeneous media these models are not large enough to capture the petrophysical properties of the entire medium and inaccurate results can be obtained when upscaling to the continuum scale. Moreover, the boundary conditions imposed are artificial; a pressure gradient is imposed in one dimension so the influence of flow behavior in the surrounding media is not included. Here we model flow and transport at the pore scale but develop hybrid multiscale techniques to bridge the pore and macro-scales. Novel domain decomposition methods are used for upscaling; finite element mortars are used as a mathematical tool to ensure interfacial pressures and fluxes are matched at the interfaces of the networks boundaries. The results compare favorably to the more computationally intensive (and impractical) approach of upscaling the media as a single model. Moreover, the results are much more accurate than traditional hierarchal upscaling methods. This upscaling technique has important implications for using pore-scale models directly in reservoir simulators in a multiscale setting.

  5. Using Culturally Sensitive Media Messages to Reduce HIV-associated Sexual Behavior in High-risk African-American Adolescents: Results from a Randomized Trial

    Science.gov (United States)

    Sznitman, Sharon; Vanable, Peter A.; Carey, Michael P.; Hennessy, Michael; Brown, Larry K.; Valois, Robert F.; Stanton, Bonita F.; Salazar, Laura F.; DiClemente, Ralph; Farber, Naomi; Romer, Daniel

    2010-01-01

    Purpose To test the long-term effects of a mass media intervention that used culturally and developmentally appropriate messages to enhance HIV-preventive beliefs and behavior of high-risk African-American adolescents. Methods Television and radio messages were delivered over three years in two cities (Syracuse, NY and Macon, GA) that were randomly selected within each of two regionally matched city pairs with the other cities (Providence, RI and Columbia, SC) serving as controls. African American adolescents ages 14 to 17 (N = 1710), recruited in the four cities over a 16-month period, completed audio computer-assisted self-interviews at recruitment and again at 3, 6, 12 and 18-months post-recruitment to assess the long-term effects of the media program. To identify the unique effects of the media intervention, youth who completed at least one follow-up and who did not test positive for any of three sexually transmitted infections at recruitment or at 6 and 12-month follow-up were retained for analysis (N=1346). Results The media intervention reached virtually all of the adolescents in the trial and produced a range of effects including improved normative condom-use negotiation expectancies and increased sex refusal self-efficacy. Most importantly, older adolescents (ages 16-17) exposed to the media program exhibited a less risky age trajectory of unprotected sex than those in the non-media cities. Conclusions Culturally tailored mass media messages delivered consistently over time have the potential to reach a large audience of high-risk adolescents, to support changes in HIV-preventive beliefs, and to reduce HIV-associated risk behaviors among older youth. PMID:21856515

  6. Homogenization of a double porosity model in deformable media

    Directory of Open Access Journals (Sweden)

    Abdelhamid Ainouz

    2013-04-01

    Full Text Available The article addresses the homogenization of a family of micro-models for the flow of a slightly compressible fluid in a poroelastic matrix containing periodically distributed poroelastic inclusions, with low permeabilities and with imperfect contact on the interface. The micro-models are based on Biot's system for consolidation processes in each phase, with interfacial barrier formulation. Using the two-scale convergence technique, it is shown that the derived system is a general model of that proposed by Aifantis, plus an extra memory term.

  7. Computational fluid dynamics (CFD) using porous media modeling predicts recurrence after coiling of cerebral aneurysms.

    Science.gov (United States)

    Umeda, Yasuyuki; Ishida, Fujimaro; Tsuji, Masanori; Furukawa, Kazuhiro; Shiba, Masato; Yasuda, Ryuta; Toma, Naoki; Sakaida, Hiroshi; Suzuki, Hidenori

    2017-01-01

    This study aimed to predict recurrence after coil embolization of unruptured cerebral aneurysms with computational fluid dynamics (CFD) using porous media modeling (porous media CFD). A total of 37 unruptured cerebral aneurysms treated with coiling were analyzed using follow-up angiograms, simulated CFD prior to coiling (control CFD), and porous media CFD. Coiled aneurysms were classified into stable or recurrence groups according to follow-up angiogram findings. Morphological parameters, coil packing density, and hemodynamic variables were evaluated for their correlations with aneurysmal recurrence. We also calculated residual flow volumes (RFVs), a novel hemodynamic parameter used to quantify the residual aneurysm volume after simulated coiling, which has a mean fluid domain > 1.0 cm/s. Follow-up angiograms showed 24 aneurysms in the stable group and 13 in the recurrence group. Mann-Whitney U test demonstrated that maximum size, dome volume, neck width, neck area, and coil packing density were significantly different between the two groups (P CFD and larger RFVs in the porous media CFD. Multivariate logistic regression analyses demonstrated that RFV was the only independently significant factor (odds ratio, 1.06; 95% confidence interval, 1.01-1.11; P = 0.016). The study findings suggest that RFV collected under porous media modeling predicts the recurrence of coiled aneurysms.

  8. Analysis of attenuation and dispersion of Rayleigh waves in viscoelastic media by finite-difference modeling

    Science.gov (United States)

    Yuan, Shichuan; Song, Xianhai; Cai, Wei; Hu, Ying

    2018-01-01

    Viscoelasticity of Earth media has an important influence on Rayleigh-wave propagation. Therefore, it is necessary to study the attenuation and dispersion of Rayleigh-wave by numerical modeling to better understand Rayleigh-wave behaviors in Earth media. Modeling adopts a staggered finite-difference (FD) scheme, which calculates the spatial derivatives by a 12th-order operator and the time derivatives by the fourth-order Runge-Kutta method. In time-space domain, the accuracy of FD method is demonstrated through comparing the modeling results with the analytical solution in an elastic half-space. In frequency-velocity domain, the correctness of modeling results is verified via comparing the dispersive images with the theoretical dispersion curves of Rayleigh-wave. The attenuation and dispersion of Rayleigh-wave are analyzed by comparisons between elastic and viscoelastic modeling results in the homogeneous half-space models in terms of the wave field snapshots, the synthetic seismograms, and the dispersive images, respectively. The two-layer models are also simulated to further investigate the attenuation and dispersion of Rayleigh-wave in viscoelastic layered media. Results show that the viscoelastic Rayleigh-wave presents substantial differences in amplitude and phase velocity compared with the elastic case. Viscoelasticity of media arouses amplitude attenuation of Rayleigh-wave. The high-frequency waves are attenuated more severely than the lower-frequency waves, and the attenuation degree is severe increasingly with offset increasing. Viscoelasticity of media also causes the phase velocity dispersion of Rayleigh-wave. The phase velocity ratio of viscoelastic Rayleigh-wave respecting to the corresponding elastic one increases with frequency, and the resolution of dispersion energy is lower than the elastic one. The attenuation and dispersion of Rayleigh-wave are prominent increasingly with Q decreasing.

  9. An improved porous media model for nuclear reactor analysis

    National Research Council Canada - National Science Library

    Roozbeh Vadi Kamran Sepanloo

    2016-01-01

    ...) for nuclear reactor analysis. In the conventional approach, whole reactor core simplifies to a single porous medium and also, the resis- tance coefficients that are essential to using this model are constant values...

  10. Improving degradation of emerging organic compounds by applying chaotic advection in Managed Aquifer Recharge in randomly heterogeneous porous media

    Science.gov (United States)

    Rodríguez-Escales, P.; Fernà ndez-Garcia, D.; Drechsel, J.; Folch, A.; Sanchez-Vila, X.

    2017-05-01

    Improving degradation rates of emerging organic compounds (EOCs) in groundwater is still a challenge. Although their degradation is not fully understood, it has been observed that some substances are preferably degraded under specific redox conditions. The coupling of Managed Aquifer Recharge with soil aquifer remediation treatment, by placing a reactive layer containing organic matter at the bottom of the infiltration pond, is a promising technology to improve the rate of degradation of EOCs. Its success is based on assuming that recharged water and groundwater get well mixed, which is not always true. It has been demonstrated that mixing can be enhanced by inducing chaotic advection through extraction-injection-engineering. In this work, we analyze how chaotic advection might enhance the spreading of redox conditions with the final aim of improving degradation of a mix of benzotriazoles: benzotriazole, 5-methyl-benzotriazole, and 5-chloro-benzotriazole. The degradation of the first two compounds was fastest under aerobic conditions whereas the third compound was best degraded under denitrification conditions. We developed a reactive transport model that describes how a recharged water rich in organic matter mixes with groundwater, how this organic matter is oxidized by different electron acceptors, and how the benzotriazoles are degraded attending for the redox state. The model was tested in different scenarios of recharge, both in homogenous and in heterogenous media. It was found that chaotic flow increases the spreading of the plume of recharged water. Consequently, different redox conditions coexist at a given time, facilitating the degradation of EOCs.

  11. Modelling bioaugmentation in unsaturated porous media: The linuron herbicide example

    DEFF Research Database (Denmark)

    Owsianiak, Mikolaj; Dechesne, Arnaud; Binning, Philip John

    2010-01-01

    To protect groundwater resources against pesticides, bioaugmentation with microorganisms immobilized in solid carriers has been considered as a soil remediation strategy. We have developed a mathematical model to assess this bioremediation approach to remove the pesticide linuron from soils...... at various water saturation levels. A bacterium mineralizing linuron is heterogeneously distributed within a 3-D model domain in spherical hotspots of 2-mm diameter size. Diffusion and advection due to infiltration are the transport processes, and microbial growth follows first order kinetics. Without...

  12. Estimating Random Regret Minimization models in the route choice context

    DEFF Research Database (Denmark)

    Prato, Carlo Giacomo

    The discrete choice paradigm of random regret minimization (RRM) has been recently proposed in several choice contexts. In the route choice context, the paradigm has been used to model the choice among three routes, to define regret-based equilibrium in risky conditions, and to formulate regret......-based stochastic user equilibrium. However, in the same context the RRM literature has not confronted three major challenges: (i) accounting for similarity across alternative routes, (ii) analyzing choice set composition effects on choice probabilities, and (iii) comparing the RRM model with advanced RUM...... counterparts. This paper looks into RRM-based route choice models from these three perspectives by (i) proposing utility-based and regret-based correction terms to account for similarity across alternatives, (ii) analyzing the variation of choice set probabilities with the choice set composition, and (iii...

  13. Super Yang-Mills theory as a random matrix model

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, W. [Institute for Theoretical Physics, State University of New York, Stony Brook, New York 11794-3840 (United States)

    1995-07-15

    We generalize the Gervais-Neveu gauge to four-dimensional {ital N}=1 superspace. The model describes an {ital N}=2 super Yang-Mills theory. All chiral superfields ({ital N}=2 matter and ghost multiplets) exactly cancel to all loops. The remaining Hermitian scalar superfield (matrix) has a renormalizable massive propagator and simplified vertices. These properties are associated with {ital N}=1 supergraphs describing a superstring theory on a random lattice world sheet. We also consider all possible finite matrix models, and find they have a universal large-color limit. These could describe gravitational strings if the matrix-model coupling is fixed to unity, for exact electric-magnetic self-duality.

  14. Exponential random graph models for networks with community structure.

    Science.gov (United States)

    Fronczak, Piotr; Fronczak, Agata; Bujok, Maksymilian

    2013-09-01

    Although the community structure organization is an important characteristic of real-world networks, most of the traditional network models fail to reproduce the feature. Therefore, the models are useless as benchmark graphs for testing community detection algorithms. They are also inadequate to predict various properties of real networks. With this paper we intend to fill the gap. We develop an exponential random graph approach to networks with community structure. To this end we mainly built upon the idea of blockmodels. We consider both the classical blockmodel and its degree-corrected counterpart and study many of their properties analytically. We show that in the degree-corrected blockmodel, node degrees display an interesting scaling property, which is reminiscent of what is observed in real-world fractal networks. A short description of Monte Carlo simulations of the models is also given in the hope of being useful to others working in the field.

  15. POD-Galerkin Model for Incompressible Single-Phase Flow in Porous Media

    KAUST Repository

    Wang, Yi

    2017-01-25

    Fast prediction modeling via proper orthogonal decomposition method combined with Galerkin projection is applied to incompressible single-phase fluid flow in porous media. Cases for different configurations of porous media, boundary conditions and problem scales are designed to examine the fidelity and robustness of the model. High precision (relative deviation 1.0 x 10(-4)% similar to 2.3 x 10(-1)%) and large acceleration (speed-up 880 similar to 98454 times) of POD model are found in these cases. Moreover, the computational time of POD model is quite insensitive to the complexity of problems. These results indicate POD model is especially suitable for large-scale complex problems in engineering.

  16. Measuring News Media Literacy

    Science.gov (United States)

    Maksl, Adam; Ashley, Seth; Craft, Stephanie

    2015-01-01

    News media literacy refers to the knowledge and motivations needed to identify and engage with journalism. This study measured levels of news media literacy among 500 teenagers using a new scale measure based on Potter's model of media literacy and adapted to news media specifically. The adapted model posits that news media literate individuals…

  17. Loyalty, Investment Model and New Media - A Correlation Study in Banking Services in Montenegro

    Directory of Open Access Journals (Sweden)

    Femić-Radosavović Bojana

    2017-01-01

    Full Text Available In this paper we perceived causal relationship between loyalty, satisfaction, quality of the alternatives, investment size, and new media through online word of mouth in banking services in Montenegro. Obtained empirical results substantiated validity of the set hypothetical frame, i.e. meaningfulness of the conceptual model that is set.

  18. Modelling Scattering of Electromagnetic Waves in Layered Media: An Up-to-Date Perspective

    Directory of Open Access Journals (Sweden)

    Pasquale Imperatore

    2017-01-01

    Full Text Available This paper addresses the subject of electromagnetic wave scattering in layered media, thus covering the recent progress achieved with different approaches. Existing theories and models are analyzed, classified, and summarized on the basis of their characteristics. Emphasis is placed on both theoretical and practical application. Finally, patterns and trends in the current literature are identified and critically discussed.

  19. Modelling and analysis of CVD processes in porous media for ceramic composite preparation

    NARCIS (Netherlands)

    Lin, Y.S.; Lin, Y.S.; Burggraaf, A.J.; Burggraaf, Anthonie

    1991-01-01

    A continuum phenomenological model is presented to describe chemical vapour deposition (CVD) of solid product inside porous substrate media for the preparation of reinforced ceramic-matrix composites [by the chemical vapour infiltration (CVI) process] and ceramic membrane composites (by a modified

  20. A Model for the Effect of Disturbances in the Optical Media on the OCT Image Quality

    NARCIS (Netherlands)

    Kok, Pauline H. B.; van Dijk, Hille W.; van den Berg, Thomas J. T. P.; Verbraak, Frank D.

    2009-01-01

    PURPOSE. The loss of quality of optical coherence tomography (OCT) images resulting from disturbances in the optical media has been modeled. METHODS. OCT measurements were performed in two healthy volunteers using time domain (TD)-OCT (StratusOCT; Carl Zeiss Meditec, Dublin, CA). Optical

  1. Variable effects of radiological contrast media on thrombus growth in a rabbit jugular vein thrombosis model

    NARCIS (Netherlands)

    Levi, M. [=Marcel M.; Biemond, B. J.; Sturk, A.; Hoek, J.; ten Cate, J. W.

    1991-01-01

    We studied the effect of an ionic high osmolar contrast medium (Ioxitalamate), an ionic low osmolar contrast medium (Ioxaglate) and various nonionic low osmolar contrast media (Iopamidol, Iopromide and Iohexol) on thrombus growth in a rabbit jugular vein thrombosis model. Thrombus growth was

  2. Coupled poroelastic waves and electromagnetic fields in layered media : Theory, Modeling, and Interferometric Synthesis

    NARCIS (Netherlands)

    Grobbe, N.

    2016-01-01

    In this thesis, I study coupled poroelastic waves and electromagnetic fields in layered media. The focus is two-fold:
    1. Increase the theoretical and physical understanding of the seismo-electromagnetic phenomenon by analytically-based numerical modeling.
    2. Investigate the potential of

  3. Pore-network modeling of solute transport and biofilm growth in porous media

    NARCIS (Netherlands)

    Qin, Chao Zhong; Hassanizadeh, S. Majid

    2015-01-01

    In this work, a pore-network (PN) model for solute transport and biofilm growth in porous media was developed. Compared to previous studies of biofilm growth, it has two new features. First, the constructed pore network gives a better representation of a porous medium. Second, instead of using a

  4. MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE FLUID PHASE POROUS MEDIA

    Science.gov (United States)

    A two-dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between nonaqueous phase liquid, water, gas and solid phases in porous media under the assumption of local chemical equilib...

  5. : The origins of the random walk model in financial theory

    OpenAIRE

    Walter, Christian

    2013-01-01

    Ce texte constitue le chapitre 2 de l'ouvrage Le modèle de marche au hasard en finance, de Christian Walter, à paraître chez Economica, collection " Audit, assurance, actuariat ", en juin 2013. Il est publié ici avec l'accord de l'éditeur.; Three main concerns pave the way for the birth of the random walk model in financial theory: an ethical issue with Jules Regnault (1834-1894), a scientific issue with Louis Bachelier (1870-1946) and a pratical issue with Alfred Cowles (1891-1984). Three to...

  6. Topic Modeling Based Image Clustering by Events in Social Media

    Directory of Open Access Journals (Sweden)

    Bin Xu

    2016-01-01

    Full Text Available Social event detection in large photo collections is very challenging and multimodal clustering is an effective methodology to deal with the problem. Geographic information is important in event detection. This paper proposed a topic model based approach to estimate the missing geographic information for photos. The approach utilizes a supervised multimodal topic model to estimate the joint distribution of time, geographic, content, and attached textual information. Then we annotate the missing geographic photos with a predicted geographic coordinate. Experimental results indicate that the clustering performance improved by annotated geographic information.

  7. Rigorously testing multialternative decision field theory against random utility models.

    Science.gov (United States)

    Berkowitsch, Nicolas A J; Scheibehenne, Benjamin; Rieskamp, Jörg

    2014-06-01

    Cognitive models of decision making aim to explain the process underlying observed choices. Here, we test a sequential sampling model of decision making, multialternative decision field theory (MDFT; Roe, Busemeyer, & Townsend, 2001), on empirical grounds and compare it against 2 established random utility models of choice: the probit and the logit model. Using a within-subject experimental design, participants in 2 studies repeatedly choose among sets of options (consumer products) described on several attributes. The results of Study 1 showed that all models predicted participants' choices equally well. In Study 2, in which the choice sets were explicitly designed to distinguish the models, MDFT had an advantage in predicting the observed choices. Study 2 further revealed the occurrence of multiple context effects within single participants, indicating an interdependent evaluation of choice options and correlations between different context effects. In sum, the results indicate that sequential sampling models can provide relevant insights into the cognitive process underlying preferential choices and thus can lead to better choice predictions. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  8. Development of collaborative-creative learning model using virtual laboratory media for instrumental analytical chemistry lectures

    Science.gov (United States)

    Zurweni, Wibawa, Basuki; Erwin, Tuti Nurian

    2017-08-01

    The framework for teaching and learning in the 21st century was prepared with 4Cs criteria. Learning providing opportunity for the development of students' optimal creative skills is by implementing collaborative learning. Learners are challenged to be able to compete, work independently to bring either individual or group excellence and master the learning material. Virtual laboratory is used for the media of Instrumental Analytical Chemistry (Vis, UV-Vis-AAS etc) lectures through simulations computer application and used as a substitution for the laboratory if the equipment and instruments are not available. This research aims to design and develop collaborative-creative learning model using virtual laboratory media for Instrumental Analytical Chemistry lectures, to know the effectiveness of this design model adapting the Dick & Carey's model and Hannafin & Peck's model. The development steps of this model are: needs analyze, design collaborative-creative learning, virtual laboratory media using macromedia flash, formative evaluation and test of learning model effectiveness. While, the development stages of collaborative-creative learning model are: apperception, exploration, collaboration, creation, evaluation, feedback. Development of collaborative-creative learning model using virtual laboratory media can be used to improve the quality learning in the classroom, overcome the limitation of lab instruments for the real instrumental analysis. Formative test results show that the Collaborative-Creative Learning Model developed meets the requirements. The effectiveness test of students' pretest and posttest proves significant at 95% confidence level, t-test higher than t-table. It can be concluded that this learning model is effective to use for Instrumental Analytical Chemistry lectures.

  9. A note on modeling vehicle accident frequencies with random-parameters count models.

    Science.gov (United States)

    Anastasopoulos, Panagiotis Ch; Mannering, Fred L

    2009-01-01

    In recent years there have been numerous studies that have sought to understand the factors that determine the frequency of accidents on roadway segments over some period of time, using count data models and their variants (negative binomial and zero-inflated models). This study seeks to explore the use of random-parameters count models as another methodological alternative in analyzing accident frequencies. The empirical results show that random-parameters count models have the potential to provide a fuller understanding of the factors determining accident frequencies.

  10. Calculating model of depolarization coefficient for microstructured media

    Science.gov (United States)

    Xu, Jiang; Qian, Weixian; Chen, Qian

    2017-11-01

    As a new analytical method to study the propagation of polarized light, the system to classify the microstructure of a surface had been established. In this paper, the Jones Matrix and Mueller Matrix had been used to set up the physical model. By using the propagation path theory of polarized light, the mechanism of the scattering of electromagnetic wave had been observed, the relationship between the characteristics of depolarization and mechanism of scattering had been analyzed, and the relation formula of Mueller matrix, Mueller-Jones matrix and Isotropic-Depolarizer matrix had been deduced. Then combined with Fresnel formula, the depolarization coefficients of samples had been obtain, which was described the ability of material to weaken the polarization attribute of incident light. Finally, the theoretical model had been verified by experiments. The results showed that, the depolarization coefficients of the samples were related to the surface microstructure and scattering characteristics, and this model was more effectively to analyze the microstructure of the surface. Therefore, the model had a great application value, and the paper had very important significance on the development of polarization measurement technique.

  11. Interpreting parameters in the logistic regression model with random effects

    DEFF Research Database (Denmark)

    Larsen, Klaus; Petersen, Jørgen Holm; Budtz-Jørgensen, Esben

    2000-01-01

    interpretation, interval odds ratio, logistic regression, median odds ratio, normally distributed random effects......interpretation, interval odds ratio, logistic regression, median odds ratio, normally distributed random effects...

  12. An unsupervised machine learning model for discovering latent infectious diseases using social media data.

    Science.gov (United States)

    Lim, Sunghoon; Tucker, Conrad S; Kumara, Soundar

    2017-02-01

    The authors of this work propose an unsupervised machine learning model that has the ability to identify real-world latent infectious diseases by mining social media data. In this study, a latent infectious disease is defined as a communicable disease that has not yet been formalized by national public health institutes and explicitly communicated to the general public. Most existing approaches to modeling infectious-disease-related knowledge discovery through social media networks are top-down approaches that are based on already known information, such as the names of diseases and their symptoms. In existing top-down approaches, necessary but unknown information, such as disease names and symptoms, is mostly unidentified in social media data until national public health institutes have formalized that disease. Most of the formalizing processes for latent infectious diseases are time consuming. Therefore, this study presents a bottom-up approach for latent infectious disease discovery in a given location without prior information, such as disease names and related symptoms. Social media messages with user and temporal information are extracted during the data preprocessing stage. An unsupervised sentiment analysis model is then presented. Users' expressions about symptoms, body parts, and pain locations are also identified from social media data. Then, symptom weighting vectors for each individual and time period are created, based on their sentiment and social media expressions. Finally, latent-infectious-disease-related information is retrieved from individuals' symptom weighting vectors. Twitter data from August 2012 to May 2013 are used to validate this study. Real electronic medical records for 104 individuals, who were diagnosed with influenza in the same period, are used to serve as ground truth validation. The results are promising, with the highest precision, recall, and F1 score values of 0.773, 0.680, and 0.724, respectively. This work uses individuals

  13. Mesoscopic modeling of multi-physicochemical transport phenomena in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Qinjin [Los Alamos National Laboratory; Wang, Moran [Los Alamos National Laboratory; Mukherjee, Partha P [Los Alamos National Laboratory; Lichtner, Peter C [Los Alamos National Laboratory

    2009-01-01

    We present our recent progress on mesoscopic modeling of multi-physicochemical transport phenomena in porous media based on the lattice Boltzmann method. Simulation examples include injection of CO{sub 2} saturated brine into a limestone rock, two-phase behavior and flooding phenomena in polymer electrolyte fuel cells, and electroosmosis in homogeneously charged porous media. It is shown that the lattice Boltzmann method can account for multiple, coupled physicochemical processes in these systems and can shed some light on the underlying physics occuning at the fundamental scale. Therefore, it can be a potential powerful numerical tool to analyze multi-physicochemical processes in various energy, earth, and environmental systems.

  14. INTRODUCTION: Theoretical Models as Mass Media Practice: Perspectives from the West

    DEFF Research Database (Denmark)

    Thomsen, Line

    2007-01-01

    What is journalism? How does it exist and why? How does journalism define itself and in what ways can we make use of looking theoretically at the practice of it? These were the central themes of our workshop; Theoretical Models as Mass Media Practice held at the ‘Minding the Gap’ conference...... at Reuters Institute in May 2007, from which this collection of papers has been selected. As with the other workshops during the conference, the majority of our panellists were themselves once media practitioners. It is my opinion that this background and inside knowledge of the field in itself can provide...

  15. Mobile news - a review and model of journalism in an age of mobile media

    DEFF Research Database (Denmark)

    Westlund, Oscar

    2012-01-01

    -related content and services began to flourish. Accessing mobile news has gained traction in the everyday life of the public. In parallel, legacy news media have in recent years developed news provision, by repurposing or customising journalistic content published for mobile sites and/or applications....... This article explores the production of mobile news, by discussing and synthesising the findings of the contemporary literature found in the nexus of journalism and mobile media. It posits a model of journalism focusing on the roles of humans and technology in activities characterised by customising...

  16. A Methodological Demonstration of Set-theoretical Approach to Social Media Maturity Models Using Necessary Condition Analysis

    DEFF Research Database (Denmark)

    Lasrado, Lester Allan; Vatrapu, Ravi; Andersen, Kim Normann

    2016-01-01

    by applying the Necessary Condition Analysis (NCA) technique to derive maturity stages and stage boundaries conditions. The ontology is to view stages (boundaries) in maturity models as a collection of necessary condition. Using social media maturity data, we demonstrate the strength of our approach...... and evaluate some of arguments presented by previous conceptual focused social media maturity models....

  17. Is gender still a predisposing factor in contrast-media associated adverse drug reactions? A systematic review and meta-analysis of randomized trials and observational studies.

    Science.gov (United States)

    Lee, Heeyoung; Song, Seungyeon; Oh, Yun-Kyoung; Kang, WonKu; Kim, Eunyoung

    2017-04-01

    To evaluate the role of gender as a risk factor for developing contrast media-associated adverse drug reactions (CM-ADRs) by comparing the incidence of CM-ADR between male and female patients according to study design, ADR type, and computed tomography (CT) examination. We systematically searched three electronic databases for eligible studies. In the studies included (n=18), we assessed effect estimates of the relative incidence of CM-ADR, analysed by experimental design, ADR type and CT examination. This was calculated by using a random effects model if clinical conditions showed heterogeneity; otherwise, a fixed effects model was used. We identified 10,776 patients administered CM. According to the designs, studies were classified into randomised controlled trials (RCTs) and observational studies. Results were as follows: risk ratio (RR)=1.07 (95% confidence interval (CI): 0.79-1.46, P=0.66) for RCTs, and RR=0.77 (95% CI: 0.58-1.04, P=0.09) for observational studies. The results of analysis according to ADR type and for undergoing CT demonstrated that the incidence of CM-ADR did not differ between males and females. We found no significant difference in the incidence of CM-ADRs between male and female patients according to study design, ADR type, or CT examination. Future studies to determine why gender has shown different roles as a risk factor between CM-ADRs and non-CM ADRs are needed. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Genetic parameters for various random regression models to describe the weight data of pigs

    NARCIS (Netherlands)

    Huisman, A.E.; Veerkamp, R.F.; Arendonk, van J.A.M.

    2002-01-01

    Various random regression models have been advocated for the fitting of covariance structures. It was suggested that a spline model would fit better to weight data than a random regression model that utilizes orthogonal polynomials. The objective of this study was to investigate which kind of random

  19. Genetic parameters for different random regression models to describe weight data of pigs

    NARCIS (Netherlands)

    Huisman, A.E.; Veerkamp, R.F.; Arendonk, van J.A.M.

    2001-01-01

    Various random regression models have been advocated for the fitting of covariance structures. It was suggested that a spline model would fit better to weight data than a random regression model that utilizes orthogonal polynomials. The objective of this study was to investigate which kind of random

  20. RIM: A Random Item Mixture Model to Detect Differential Item Functioning

    Science.gov (United States)

    Frederickx, Sofie; Tuerlinckx, Francis; De Boeck, Paul; Magis, David

    2010-01-01

    In this paper we present a new methodology for detecting differential item functioning (DIF). We introduce a DIF model, called the random item mixture (RIM), that is based on a Rasch model with random item difficulties (besides the common random person abilities). In addition, a mixture model is assumed for the item difficulties such that the…

  1. RIM: A random item mixture model to detect Differential Item Functioning

    NARCIS (Netherlands)

    Frederickx, S.; Tuerlinckx, T.; de Boeck, P.; Magis, D.

    2010-01-01

    In this paper we present a new methodology for detecting differential item functioning (DIF). We introduce a DIF model, called the random item mixture (RIM), that is based on a Rasch model with random item difficulties (besides the common random person abilities). In addition, a mixture model is

  2. A didactical structural model – linking analysis of teaching and analysis of educational media

    DEFF Research Database (Denmark)

    Graf, Stefan Ting

    2009-01-01

    1. Gap between general didactics and textbook/media research There seems to be a gap between general didactics (theory of teaching) and research in textbooks or educational media in general at least in the Nordic and German speaking countries. General didactic and their models seem to underestimate...... for teaching if the research or the analysis does not have an integrated concept of teaching? Concrete concepts of teaching could be very challenging for research serving both teacher education and media production. As a radical example for such a challenge I will present and discuss the concept of “Lehrkunst......” (Berg/Schulze) with the principles of exemplary content, genetic learning and dramaturgical teaching....

  3. A memory model for internet hits after media exposure

    Science.gov (United States)

    Chessa, Antonio G.; Murre, Jaap M. J.

    2004-02-01

    We present a cognitive model, based on the mathematical theory of point processes, which extends the results of two studies by Johansen (Physica A 276 (2000) 338; Physica A 296 (2001) 539) on download relaxation dynamics. Responses from subjects are considered as single events, which are received from original listeners or readers and from a network of social contacts, through which a message may propagate further. We collected data on the number of daily visits at our web site after a radio interview with the second author, in which the name of the web site was mentioned. A model based on an exponential hit time distribution and a homogeneous point process for regular visitors fits our data and Johansen's very well and is superior to both the power law and the logarithmic function. The fits suggest that hit data from different sources share the same cognitive mechanism, which are controlled merely by the encoding and retrieval of the target information memorised.

  4. A mixed damage model for unsaturated porous media

    Science.gov (United States)

    Arson, Chloé; Gatmiri, Behrouz

    2009-02-01

    The aim of this study is to present a framework for the modeling of damage in continuous unsaturated porous geomaterials. The damage variable is a second-order tensor. The model is formulated in net stress and suction independent state variables. Correspondingly, the strain tensor is split into two independent thermodynamic strain components. The proposed framework mixes micro-mechanical and phenomenological approaches. On the one hand, the effective stress concept of Continuum Damage Mechanics is used in order to compute the damaged rigidities. On the other hand, the concept of equivalent mechanical state is introduced in order to get a simple phenomenological formulation of the behavior laws. Cracking effects are also taken into account in the fluid transfer laws. To cite this article: C. Arson, B. Gatmiri, C. R. Mecanique 337 (2009).

  5. A Combustion and Heat Transfer Model for Porous Media

    Science.gov (United States)

    1982-06-01

    combustion process in two phases. During the initial phase, combustion occurs within the porous medium. The second phase occurs when the exo- thermic ...the combustion model. Specifically, there is a change in the behavior of combustion when insulated boundaries on the porous solid are changed to...represent insulated boundaries on the porous solid (i.e., no heat loss from the porous solid to the environment). Expressions III. 51 and III. 52 provide for

  6. Modeling Residual NAPL in Water-Wet Porous Media

    Directory of Open Access Journals (Sweden)

    R.J. Lenhard

    2002-06-01

    Full Text Available A model is outlined that predicts NAPL which is held in pore wedges and as films or lenses on solid and water surfaces and contributes negligibly to NAPL advection. This is conceptually referred to as residual NAPL. Since residual NAPL is immobile, it remains in the vadose zone after all free NAPL has drained. Residual NAPL is very important because it is a long-term source for groundwater contamination. Recent laboratory experiments have demonstrated that current models for predicting subsurface NAPL behavior are inadequate because they do not correctly predict residual NAPL. The main reason for the failure is a deficiency in the current constitutive theories for multiphase flow that are used in numerical simulators. Multiphase constitutive theory governs the relations among relative permeability, saturation, and pressure for fluid systems (i.e., air, NAPL, water. In this paper, we outline a model describing relations between fluid saturations and pressures that can be combined with existing multiphase constitutive theory to predict residual NAPL. We test the revised constitutive theory by applying it to a scenario involving NAPL imbibition and drainage, as well as water imbibition and drainage. The results suggest that the revised constitutive theory is able to predict the distribution of residual NAPL in the vadose zone as a function of saturation-path history. The revised model describing relations between fluid saturation and pressures will help toward developing or improving numerical multiphase flow simulators.

  7. The Laugh Model: Reframing and Rebranding Public Health Through Social Media.

    Science.gov (United States)

    Lister, Cameron; Royne, Marla; Payne, Hannah E; Cannon, Ben; Hanson, Carl; Barnes, Michael

    2015-11-01

    We examined the use of low-cost social media platforms in communicating public health messages and outline the laugh model, a framework through which public health organizations can reach and engage communities. In August 2014, we developed an online campaign (Web site and social media) to help promote healthy family meals in Utah in conjunction with the state and local health departments. By the end of September 2014, a total of 3641 individuals had visited the Utahfamilymeals.org Web site. Facebook ads reached a total of 29 078 people, and 56 900 people were reached through Twitter ads. The per-person price of the campaign was 0.2 cents, and the total estimated target population reach was between 10% and 12%. There are 3 key takeaways from our campaign: use of empowering and engaging techniques may be more effective than use of educational techniques; use of social media Web sites and online marketing tactics can enhance collaboration, interdisciplinary strategies, and campaign effectiveness; and use of social media as a communication platform is often preferable to use of mass media in terms of cost-effectiveness, more precise evaluations of campaign success, and increased sustainability.

  8. The Laugh Model: Reframing and Rebranding Public Health Through Social Media

    Science.gov (United States)

    Royne, Marla; Payne, Hannah E.; Cannon, Ben; Hanson, Carl; Barnes, Michael

    2015-01-01

    Objectives. We examined the use of low-cost social media platforms in communicating public health messages and outline the laugh model, a framework through which public health organizations can reach and engage communities. Methods. In August 2014, we developed an online campaign (Web site and social media) to help promote healthy family meals in Utah in conjunction with the state and local health departments. Results. By the end of September 2014, a total of 3641 individuals had visited the Utahfamilymeals.org Web site. Facebook ads reached a total of 29 078 people, and 56 900 people were reached through Twitter ads. The per-person price of the campaign was 0.2 cents, and the total estimated target population reach was between 10% and 12%. Conclusions. There are 3 key takeaways from our campaign: use of empowering and engaging techniques may be more effective than use of educational techniques; use of social media Web sites and online marketing tactics can enhance collaboration, interdisciplinary strategies, and campaign effectiveness; and use of social media as a communication platform is often preferable to use of mass media in terms of cost-effectiveness, more precise evaluations of campaign success, and increased sustainability. PMID:26378824

  9. An emotional contagion model for heterogeneous social media with multiple behaviors

    Science.gov (United States)

    Xiong, Xi; Li, Yuanyuan; Qiao, Shaojie; Han, Nan; Wu, Yue; Peng, Jing; Li, Binyong

    2018-01-01

    The emotion varies and propagates with the spatial and temporal information of individuals through social media, which uncovers several interaction mechanisms and features the community structure in order to facilitate individuals' communication and emotional contagion in social networks. Aiming to show the detailed process and characteristics of emotional contagion within social media, we propose an emotional independent cascade model in which individual emotion can affect the subsequent emotion of his/her friends. The transmissibility is introduced to measure the capability of propagating emotion with respect to an individual in social networks. By analyzing the patterns of emotional contagion on Twitter data, we find that the value of transmissibility differs on different layers and on different community structures. Extensive experiments were conducted and the results reveal that, the polar emotion of hub users can lead to the disappearance of opposite emotion, and the transmissibility makes no sense. The final emotional distribution depends on the initial emotional distribution and the transmissibilities. Individuals from a small community are more likely to change their mood by the influence of community leaders. In addition, we compared the proposed model with two other models, the emotion-based spreader-ignorant-stifler model and the standard independent cascade model. The results demonstrate that the proposed model can reflect the real-world situation of emotional contagion for heterogeneous social media while the computational complexities of all these three models are similar.

  10. Stochastic aggregation model (SAM) for DNAPL water displacement in porous media

    Science.gov (United States)

    Trantham, H.; Durnford, D.

    1999-03-01

    Source zone characterization of DNAPL in the subsurface is a necessary part of managing environmental risks. Modeling DNAPL-water displacement processes at the pore-scale can lead to greater insight and understanding of lateral spreading, the extent of vertical migration, and the final fluid distributions of dense non-aqueous phase liquids. A two-dimensional stochastic aggregation model is developed to study DNAPL-water displacement in porous media. The model is a modified diffusion limited aggregation model, and uses essential properties governing front stability as model input: DNAPL-water viscosity differences, DNAPL-water density differences, intrinsic permeability of the porous media, flow rate, and the inclination angle of the porous media from the horizontal. Due to the simplicity of the algorithm, this modeling technique can produce realistic DNAPL-water configurations much faster than conventional continuum approaches and allows for a Monte Carlo approach to be utilized. The model is validated through comparison to laboratory experiments involving 1,2-Dichloroethane, carbon tetrachloride, tetrachloroethylene, and mobile pyrogard 53. These experiments were performed at varying flow rates and angles of inclination from the horizontal.

  11. Three-dimensional magnetotelluric modeling in anisotropic media using edge-based finite element method

    Science.gov (United States)

    Xiao, Tiaojie; Liu, Yun; Wang, Yun; Fu, Li-Yun

    2018-02-01

    It is important to understand how magnetotelluric (MT) modeling can most effectively be performed in general anisotropic media. However, previous studies in this area have mainly focused on the use of one-dimensional (1D) and two-dimensional (2D) algorithms. Thus, building on earlier work, it is important to study the performance of three-dimensional (3D) modeling in arbitrary conductivity media; therefore, an edge-based finite element (FE) method has been developed for 3D MT modeling in arbitrary conductivity media. This approach is based on the initial derivation of a series of equivalent variational equations that are based on Maxwell equations, generated using the weighted residual method. Specific values were then obtained for coefficient matrixes of this edge-based FE method using hexahedral meshes, and the algorithm was verified by comparing its results with finite difference (FD) solutions generated using a 2D anisotropic model. Finally, the results of a 3D anisotropic model were analyzed detailed for three conditions; another 3D anisotropic model was designed and its results were compared with two isotropic models'.

  12. MODEL INFORMASI PUBLIK DI ERA MEDIA SOSIAL: KAJIAN GROUNDED TEORI DI PEMDA SUKOHARJO

    Directory of Open Access Journals (Sweden)

    Dian Purworini

    2017-01-01

    Full Text Available Model komunikasi yang diterapkan di instansi pemerintah daerah menarik untuk diteliti dari kajian public relations. Model komunikasi yang tampak dilakukan satu arah diyakini oleh banyak kalangan akan bergeser ke komunikasi dua arah seiring dengan maraknya perkembangan media sosial. Penelitian di bidang ini tentu sangat relevan mengingat humas secara ideal memiliki peran signifikan dalam mengelola komunikasi di instansi. Penelitian ini dilakukan di pemerintah daerah Sukoharjo. Penelitian dilakukan dengan yang teknik kualitatif dengan analisis data menggunakan grounded theory. Dari analisis yang dilakukan, dapat dijelaskan bahwa humas pemda Sukoharjo menganut model komunikasi satu arah, dimana model ini bertumpu pada diseminasi informasi kepada publik. Ini menjelaskan nilai utama yang melekat dalam komunikasi di humas pemda. Nilai utama termasuk pola komunikasi, tipe informasi dan media yang digunakan. Komunikasi satu arah terbentuk karena pengaruh SDM yang ada dan peraturan yang berlaku di instansi tersebut.

  13. Gaussian random bridges and a geometric model for information equilibrium

    Science.gov (United States)

    Mengütürk, Levent Ali

    2018-03-01

    The paper introduces a class of conditioned stochastic processes that we call Gaussian random bridges (GRBs) and proves some of their properties. Due to the anticipative representation of any GRB as the sum of a random variable and a Gaussian (T , 0) -bridge, GRBs can model noisy information processes in partially observed systems. In this spirit, we propose an asset pricing model with respect to what we call information equilibrium in a market with multiple sources of information. The idea is to work on a topological manifold endowed with a metric that enables us to systematically determine an equilibrium point of a stochastic system that can be represented by multiple points on that manifold at each fixed time. In doing so, we formulate GRB-based information diversity over a Riemannian manifold and show that it is pinned to zero over the boundary determined by Dirac measures. We then define an influence factor that controls the dominance of an information source in determining the best estimate of a signal in the L2-sense. When there are two sources, this allows us to construct information equilibrium as a functional of a geodesic-valued stochastic process, which is driven by an equilibrium convergence rate representing the signal-to-noise ratio. This leads us to derive price dynamics under what can be considered as an equilibrium probability measure. We also provide a semimartingale representation of Markovian GRBs associated with Gaussian martingales and a non-anticipative representation of fractional Brownian random bridges that can incorporate degrees of information coupling in a given system via the Hurst exponent.

  14. Modeling the adoption of innovations in the presence of geographic and media influences.

    Science.gov (United States)

    Toole, Jameson L; Cha, Meeyoung; González, Marta C

    2012-01-01

    While there is a large body of work examining the effects of social network structure on innovation adoption, models to date have lacked considerations of real geography or mass media. In this article, we show these features are crucial to making more accurate predictions of a social contagion and technology adoption at a city-to-city scale. Using data from the adoption of the popular micro-blogging platform, Twitter, we present a model of adoption on a network that places friendships in real geographic space and exposes individuals to mass media influence. We show that homophily both among individuals with similar propensities to adopt a technology and geographic location is critical to reproducing features of real spatiotemporal adoption. Furthermore, we estimate that mass media was responsible for increasing Twitter's user base two to four fold. To reflect this strength, we extend traditional contagion models to include an endogenous mass media agent that responds to those adopting an innovation as well as influencing agents to adopt themselves.

  15. Social Media Text Classification by Enhancing Well-Formed Text Trained Model

    Directory of Open Access Journals (Sweden)

    Phat Jotikabukkana

    2016-09-01

    Full Text Available Social media are a powerful communication tool in our era of digital information. The large amount of user-generated data is a useful novel source of data, even though it is not easy to extract the treasures from this vast and noisy trove. Since classification is an important part of text mining, many techniques have been proposed to classify this kind of information. We developed an effective technique of social media text classification by semi-supervised learning utilizing an online news source consisting of well-formed text. The computer first automatically extracts news categories, well-categorized by publishers, as classes for topic classification. A bag of words taken from news articles provides the initial keywords related to their category in the form of word vectors. The principal task is to retrieve a set of new productive keywords. Term Frequency-Inverse Document Frequency weighting (TF-IDF and Word Article Matrix (WAM are used as main methods. A modification of WAM is recomputed until it becomes the most effective model for social media text classification. The key success factor was enhancing our model with effective keywords from social media. A promising result of 99.50% accuracy was achieved, with more than 98.5% of Precision, Recall, and F-measure after updating the model three times.

  16. Modeling the adoption of innovations in the presence of geographic and media influences.

    Directory of Open Access Journals (Sweden)

    Jameson L Toole

    Full Text Available While there is a large body of work examining the effects of social network structure on innovation adoption, models to date have lacked considerations of real geography or mass media. In this article, we show these features are crucial to making more accurate predictions of a social contagion and technology adoption at a city-to-city scale. Using data from the adoption of the popular micro-blogging platform, Twitter, we present a model of adoption on a network that places friendships in real geographic space and exposes individuals to mass media influence. We show that homophily both among individuals with similar propensities to adopt a technology and geographic location is critical to reproducing features of real spatiotemporal adoption. Furthermore, we estimate that mass media was responsible for increasing Twitter's user base two to four fold. To reflect this strength, we extend traditional contagion models to include an endogenous mass media agent that responds to those adopting an innovation as well as influencing agents to adopt themselves.

  17. Modeling Dynamics of Diffusion Across Heterogeneous Social Networks: News Diffusion in Social Media

    Directory of Open Access Journals (Sweden)

    Peter Christen

    2013-10-01

    Full Text Available Diverse online social networks are becoming increasingly interconnected by sharing information. Accordingly, emergent macro-level phenomena have been observed, such as the synchronous spread of information across different types of social media. Attempting to analyze the emergent global behavior is impossible from the examination of a single social platform, and dynamic influences between different social networks are not negligible. Furthermore, the underlying structural property of networks is important, as it drives the diffusion process in a stochastic way. In this paper, we propose a macro-level diffusion model with a probabilistic approach by combining both the heterogeneity and structural connectivity of social networks. As real-world phenomena, we explore instances of news diffusion across different social media platforms from a dataset that contains over 386 million web documents covering a one-month period in early 2011. We find that influence between different media types is varied by the context of information. News media are the most influential in the arts and economy categories, while social networking sites (SNS and blog media are in the politics and culture categories, respectively. Furthermore, controversial topics, such as political protests and multiculturalism failure, tend to spread concurrently across social media, while entertainment topics, such as film releases and celebrities, are more likely driven by interactions within single social platforms. We expect that the proposed model applies to a wider class of diffusion phenomena in diverse fields and that it provides a way of interpreting the dynamics of diffusion in terms of the strength and directionality of influences among populations.

  18. What Factors Lead Companies to Adopt Social Media in their processes: Proposal and Test of a Measurement Model

    Directory of Open Access Journals (Sweden)

    Jozé Braz de Araújo

    2016-01-01

    Full Text Available The objective of this study was to understand which factors lead companies to use social media to achieve results. For that, a theoretical model was proposed and tested. Data was collected using a survey of 237 companies. In the analysis we analysis used the structural eq uation modeling technique. The results show that the social media relative advantage and its observability were important factors to social media organizational adoption. We also found that big companies with more formalized organizational structure (OS t end to adopt social media more than small ones with no formal OS. The companies studied showed strong organizational disposition for innovation adoption.

  19. Using culturally sensitive media messages to reduce HIV-associated sexual behavior in high-risk African American adolescents: results from a randomized trial.

    Science.gov (United States)

    Sznitman, Sharon; Vanable, Peter A; Carey, Michael P; Hennessy, Michael; Brown, Larry K; Valois, Robert F; Stanton, Bonita F; Salazar, Laura F; Diclemente, Ralph; Farber, Naomi; Romer, Daniel

    2011-09-01

    To test the long-term effects of a mass media intervention that used culturally and developmentally appropriate messages to enhance human immunodeficiency virus (HIV)-preventive beliefs and behavior of high-risk African American adolescents. Television and radio messages were delivered for more than 3 years in two cities (Syracuse, NY; and Macon, GA) that were randomly selected within each of the two regionally matched city pairs, with the other cities (Providence, RI; and Columbia, SC) serving as controls. African American adolescents, aged 14-17 years (N = 1,710), recruited in the four cities over a 16-month period, completed audio computer-assisted self-interviews at recruitment and again at 3, 6, 12, and 18-months postrecruitment to assess the long-term effects of the media program. To identify the unique effects of the media intervention, youth who completed at least one follow-up and who did not test positive for any of the three sexually transmitted infections at recruitment or at 6-and 12-month follow-up were retained for analysis (N = 1,346). The media intervention reached virtually all the adolescents in the trial and produced a range of effects including improved normative condom-use negotiation expectancies and increased sex refusal self-efficacy. Most importantly, older adolescents (aged 16-17 years) exposed to the media program showed a less risky age trajectory of unprotected sex than those in the nonmedia cities. Culturally tailored mass media messages that are delivered consistently over time have the potential to reach a large audience of high-risk adolescents, to support changes in HIV-preventive beliefs, and to reduce HIV-associated risk behaviors among older youth. Copyright © 2011 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  20. Auxiliary Parameter MCMC for Exponential Random Graph Models

    Science.gov (United States)

    Byshkin, Maksym; Stivala, Alex; Mira, Antonietta; Krause, Rolf; Robins, Garry; Lomi, Alessandro

    2016-11-01

    Exponential random graph models (ERGMs) are a well-established family of statistical models for analyzing social networks. Computational complexity has so far limited the appeal of ERGMs for the analysis of large social networks. Efficient computational methods are highly desirable in order to extend the empirical scope of ERGMs. In this paper we report results of a research project on the development of snowball sampling methods for ERGMs. We propose an auxiliary parameter Markov chain Monte Carlo (MCMC) algorithm for sampling from the relevant probability distributions. The method is designed to decrease the number of allowed network states without worsening the mixing of the Markov chains, and suggests a new approach for the developments of MCMC samplers for ERGMs. We demonstrate the method on both simulated and actual (empirical) network data and show that it reduces CPU time for parameter estimation by an order of magnitude compared to current MCMC methods.

  1. Modelling and analysis of CVD processes in porous media for ceramic composite preparation

    OpenAIRE

    Lin, Y S; Burggraaf, A.J.; Burggraaf, Anthonie

    1991-01-01

    A continuum phenomenological model is presented to describe chemical vapour deposition (CVD) of solid product inside porous substrate media for the preparation of reinforced ceramic-matrix composites [by the chemical vapour infiltration (CVI) process] and ceramic membrane composites (by a modified CVD process). The chemical reaction, intrapore diffusion, non-isobaric viscous flow and variation of substrate pore geometry during deposition are considered in the model which is readily solved by ...

  2. Peningkatan Kemampuan Mahasiswa dalam Membaca Gambar Proyeksi Menggunakan Pembelajaran Discovery Learning Dengan Media Model

    Directory of Open Access Journals (Sweden)

    Muhammad Khumaedi

    2016-02-01

    Full Text Available This experimental study aims at finding out whether discovery learning using model media improves students' ability in reading projection drawing. Utilizing pretest-posttest design, the study involved 30 students in each of the treatment and the control groups. Result of descriptive and t-test analyses reveal that discovery learning improves the students' ability in reading projection drawing and that it is a better learning model than reception learning.

  3. Prestack exploding reflector modelling and migration for anisotropic media

    KAUST Repository

    Alkhalifah, Tariq Ali

    2014-10-09

    The double-square-root equation is commonly used to image data by downward continuation using one-way depth extrapolation methods. A two-way time extrapolation of the double-square-root-derived phase operator allows for up and downgoing wavefields but suffers from an essential singularity for horizontally travelling waves. This singularity is also associated with an anisotropic version of the double-square-root extrapolator. Perturbation theory allows us to separate the isotropic contribution, as well as the singularity, from the anisotropic contribution to the operator. As a result, the anisotropic residual operator is free from such singularities and can be applied as a stand alone operator to correct for anisotropy. We can apply the residual anisotropy operator even if the original prestack wavefield was obtained using, for example, reverse-time migration. The residual correction is also useful for anisotropic parameter estimation. Applications to synthetic data demonstrate the accuracy of the new prestack modelling and migration approach. It also proves useful in approximately imaging the Vertical Transverse Isotropic Marmousi model.

  4. Applying risk and resilience models to predicting the effects of media violence on development.

    Science.gov (United States)

    Prot, Sara; Gentile, Douglas A

    2014-01-01

    Although the effects of media violence on children and adolescents have been studied for over 50 years, they remain controversial. Much of this controversy is driven by a misunderstanding of causality that seeks the cause of atrocities such as school shootings. Luckily, several recent developments in risk and resilience theories offer a way out of this controversy. Four risk and resilience models are described, including the cascade model, dose-response gradients, pathway models, and turning-point models. Each is described and applied to the existing media effects literature. Recommendations for future research are discussed with regard to each model. In addition, we examine current developments in theorizing that stressors have sensitizing versus steeling effects and recent interest in biological and gene by environment interactions. We also discuss several of the cultural aspects that have supported the polarization and misunderstanding of the literature, and argue that applying risk and resilience models to the theories and data offers a more balanced way to understand the subtle effects of media violence on aggression within a multicausal perspective.

  5. Smoldering of porous media: numerical model and comparison of calculations with experiment

    Science.gov (United States)

    Lutsenko, N. A.; Levin, V. A.

    2017-10-01

    Numerical modelling of smoldering in porous media under natural convection is considered. Smoldering can be defined as a flameless exothermic surface reaction; it is a type of heterogeneous combustion which can propagate in porous media. Peatbogs, landfills and other natural or man-made porous objects can sustain smoldering under natural (or free) convection, when the flow rate of gas passed through the porous object is unknown a priori. In the present work a numerical model is proposed for investigating smoldering in porous media under natural convection. The model is based on the assumption of interacting interpenetrating continua using classical approaches of the theory of filtration combustion and includes equations of state, continuity, momentum conservation and energy for solid and gas phases. Computational results obtained by means of the numerical model in one-dimensional case are compared with the experimental data of the smoldering combustion in polyurethane foam under free convection in the gravity field, which were described in literature. Calculations shows that when simulating both co-current combustion (when the smoldering wave moves upward) and counter-current combustion (when the smoldering wave moves downward), the numerical model can provide a good quantitative agreement with experiment if the parameters of the model are well defined.

  6. Joint modeling of ChIP-seq data via a Markov random field model

    NARCIS (Netherlands)

    Bao, Yanchun; Vinciotti, Veronica; Wit, Ernst; 't Hoen, Peter A C

    Chromatin ImmunoPrecipitation-sequencing (ChIP-seq) experiments have now become routine in biology for the detection of protein-binding sites. In this paper, we present a Markov random field model for the joint analysis of multiple ChIP-seq experiments. The proposed model naturally accounts for

  7. Anomalous solute transport in saturated porous media: Relating transport model parameters to electrical and nuclear magnetic resonance properties

    National Research Council Canada - National Science Library

    Swanson, Ryan D; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day‐Lewis, Frederick D; Singha, Kamini

    2015-01-01

    The advection‐dispersion equation (ADE) fails to describe commonly observed non‐Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual‐domain mass‐transfer (DDMT) model...

  8. An advective volume-balance model for flow in porous media

    Science.gov (United States)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2016-11-01

    Volume-balance models are used by petroleum engineers to simulate multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Preliminary numerical tests of phase separation due to gravity suggest the model reproduces qualitatively the physical phenomena. Fondo Sectorial CONACYT-SENER Grant Number 42536 (DGAJ-SPI-34-170412-217).

  9. Pseudospectral modeling and dispersion analysis of Rayleigh waves in viscoelastic media

    Science.gov (United States)

    Zhang, K.; Luo, Y.; Xia, J.; Chen, C.

    2011-01-01

    Multichannel Analysis of Surface Waves (MASW) is one of the most widely used techniques in environmental and engineering geophysics to determine shear-wave velocities and dynamic properties, which is based on the elastic layered system theory. Wave propagation in the Earth, however, has been recognized as viscoelastic and the propagation of Rayleigh waves presents substantial differences in viscoelastic media as compared with elastic media. Therefore, it is necessary to carry out numerical simulation and dispersion analysis of Rayleigh waves in viscoelastic media to better understand Rayleigh-wave behaviors in the real world. We apply a pseudospectral method to the calculation of the spatial derivatives using a Chebyshev difference operator in the vertical direction and a Fourier difference operator in the horizontal direction based on the velocity-stress elastodynamic equations and relations of linear viscoelastic solids. This approach stretches the spatial discrete grid to have a minimum grid size near the free surface so that high accuracy and resolution are achieved at the free surface, which allows an effective incorporation of the free surface boundary conditions since the Chebyshev method is nonperiodic. We first use an elastic homogeneous half-space model to demonstrate the accuracy of the pseudospectral method comparing with the analytical solution, and verify the correctness of the numerical modeling results for a viscoelastic half-space comparing the phase velocities of Rayleigh wave between the theoretical values and the dispersive image generated by high-resolution linear Radon transform. We then simulate three types of two-layer models to analyze dispersive-energy characteristics for near-surface applications. Results demonstrate that the phase velocity of Rayleigh waves in viscoelastic media is relatively higher than in elastic media and the fundamental mode increases by 10-16% when the frequency is above 10. Hz due to the velocity dispersion of P

  10. Φ -Ψ model for electrodynamics in dielectric media: exact quantisation in the Heisenberg representation

    Energy Technology Data Exchange (ETDEWEB)

    Belgiorno, Francesco [Politecnico di Milano, Dipartimento di Matematica, Milano (Italy); INdAM-GNFM, Milano (Italy); Cacciatori, Sergio L. [Universita dell' Insubria, Department of Science and High Technology, Como (Italy); INFN sezione di Milano, Milano (Italy); Dalla Piazza, Francesco [Universita ' ' La Sapienza' ' , Dipartimento di Matematica, Roma (Italy); Doronzo, Michele [Universita dell' Insubria, Department of Science and High Technology, Como (Italy)

    2016-06-15

    We investigate the quantisation in the Heisenberg representation of a model which represents a simplification of the Hopfield model for dielectric media, where the electromagnetic field is replaced by a scalar field φ and the role of the polarisation field is played by a further scalar field ψ. The model, which is quadratic in the fields, is still characterised by a non-trivial physical content, as the physical particles correspond to the polaritons of the standard Hopfield model of condensed matter physics. Causality is also taken into account and a discussion of the standard interaction representation is also considered. (orig.)

  11. Micro-poromechanics model of fluid-saturated chemically active fibrous media.

    Science.gov (United States)

    Misra, Anil; Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette

    2015-02-01

    We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete.

  12. Universal randomness

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, Viktor S [Landau Institute for Theoretical Physics, Russian Academy of Sciences, Moscow (Russian Federation)

    2011-03-31

    In the last two decades, it has been established that a single universal probability distribution function, known as the Tracy-Widom (TW) distribution, in many cases provides a macroscopic-level description of the statistical properties of microscopically different systems, including both purely mathematical ones, such as increasing subsequences in random permutations, and quite physical ones, such as directed polymers in random media or polynuclear crystal growth. In the first part of this review, we use a number of models to examine this phenomenon at a simple qualitative level and then consider the exact solution for one-dimensional directed polymers in a random environment, showing that free energy fluctuations in such a system are described by the universal TW distribution. The second part provides detailed appendix material containing the necessary mathematical background for the first part. (reviews of topical problems)

  13. Hedonic travel cost and random utility models of recreation

    Energy Technology Data Exchange (ETDEWEB)

    Pendleton, L. [Univ. of Southern California, Los Angeles, CA (United States); Mendelsohn, R.; Davis, E.W. [Yale Univ., New Haven, CT (United States). School of Forestry and Environmental Studies

    1998-07-09

    Micro-economic theory began as an attempt to describe, predict and value the demand and supply of consumption goods. Quality was largely ignored at first, but economists have started to address quality within the theory of demand and specifically the question of site quality, which is an important component of land management. This paper demonstrates that hedonic and random utility models emanate from the same utility theoretical foundation, although they make different estimation assumptions. Using a theoretically consistent comparison, both approaches are applied to examine the quality of wilderness areas in the Southeastern US. Data were collected on 4778 visits to 46 trails in 20 different forest areas near the Smoky Mountains. Visitor data came from permits and an independent survey. The authors limited the data set to visitors from within 300 miles of the North Carolina and Tennessee border in order to focus the analysis on single purpose trips. When consistently applied, both models lead to results with similar signs but different magnitudes. Because the two models are equally valid, recreation studies should continue to use both models to value site quality. Further, practitioners should be careful not to make simplifying a priori assumptions which limit the effectiveness of both techniques.

  14. Psychophysiological effects of a web-based stress management system: A prospective, randomized controlled intervention study of IT and media workers [ISRCTN54254861

    Directory of Open Access Journals (Sweden)

    Theorell Töres

    2005-07-01

    Full Text Available Abstract Background The aim of the present study was to assess possible effects on mental and physical well-being and stress-related biological markers of a web-based health promotion tool. Methods A randomized, prospectively controlled study was conducted with before and after measurements, involving 303 employees (187 men and 116 women, age 23–64 from four information technology and two media companies. Half of the participants were offered web-based health promotion and stress management training (intervention lasting for six months. All other participants constituted the reference group. Different biological markers were measured to detect possible physiological changes. Results After six months the intervention group had improved statistically significantly compared to the reference group on ratings of ability to manage stress, sleep quality, mental energy, concentration ability and social support. The anabolic hormone dehydroepiandosterone sulphate (DHEA-S decreased significantly in the reference group as compared to unchanged levels in the intervention group. Neuropeptide Y (NPY increased significantly in the intervention group compared to the reference group. Chromogranin A (CgA decreased significantly in the intervention group as compared to the reference group. Tumour necrosis factor α (TNFα decreased significantly in the reference group compared to the intervention group. Logistic regression analysis revealed that group (intervention vs. reference remained a significant factor in five out of nine predictive models. Conclusion The results indicate that an automatic web-based system might have short-term beneficial physiological and psychological effects and thus might be an opportunity in counteracting some clinically relevant and common stress and health issues of today.

  15. Psychophysiological effects of a web-based stress management system: a prospective, randomized controlled intervention study of IT and media workers [ISRCTN54254861].

    Science.gov (United States)

    Hasson, Dan; Anderberg, Ulla Maria; Theorell, Töres; Arnetz, Bengt B

    2005-07-25

    The aim of the present study was to assess possible effects on mental and physical well-being and stress-related biological markers of a web-based health promotion tool. A randomized, prospectively controlled study was conducted with before and after measurements, involving 303 employees (187 men and 116 women, age 23-64) from four information technology and two media companies. Half of the participants were offered web-based health promotion and stress management training (intervention) lasting for six months. All other participants constituted the reference group. Different biological markers were measured to detect possible physiological changes. After six months the intervention group had improved statistically significantly compared to the reference group on ratings of ability to manage stress, sleep quality, mental energy, concentration ability and social support. The anabolic hormone dehydroepiandosterone sulphate (DHEA-S) decreased significantly in the reference group as compared to unchanged levels in the intervention group. Neuropeptide Y (NPY) increased significantly in the intervention group compared to the reference group. Chromogranin A (CgA) decreased significantly in the intervention group as compared to the reference group. Tumour necrosis factor alpha (TNFalpha) decreased significantly in the reference group compared to the intervention group. Logistic regression analysis revealed that group (intervention vs. reference) remained a significant factor in five out of nine predictive models. The results indicate that an automatic web-based system might have short-term beneficial physiological and psychological effects and thus might be an opportunity in counteracting some clinically relevant and common stress and health issues of today.

  16. Using random walk in models specified by stochastic differential equations to determine the best expression for the bacterial growth rate

    DEFF Research Database (Denmark)

    In this presentation we consider a new method first introduced by Kristensen et al. [1] to improve the model for bacterial growth. Traditionally the substrate dependent growth rate μ(S) is modeled using the Monod expression, however it fails to describe the growth of bacteria in rich media. For P...... contains two state variables, the bacterial and substrate densities. To improve the growth model we initially allow the growth rate μ(S) to vary as a random walk, i.e. we reformulate the SDE model to include μ(S) as an extra state variable which change is described by the Wiener process. We use data from....... aeruginosa we observe a growth pattern far from Monod growth. Therefore a reformulation of the growth expression is necessary. Without any pre-knowledge about the functional dependence between the growth rate and the substrate content and with only limited experimental resources necessary, the proposed...

  17. The hydro-mechanical modeling of the fractured media; Modelisation hydromecanique des milieux fractures

    Energy Technology Data Exchange (ETDEWEB)

    Kadiri, I

    2002-10-15

    The hydro-mechanical modeling of the fractured media is quite complex. Simplifications are necessary for the modeling of such media, but, not always justified, Only permeable fractures are often considered. The rest of the network is approximated by an equivalent continuous medium. Even if we suppose that this approach is validated, the hydraulic and mechanical properties of the fractures and of the continuous medium are seldom known. Calibrations are necessary for the determination of these properties. Until now, one does not know very well the nature of measurements which must be carried out in order to carry on a modeling in discontinuous medium, nor elements of enough robust validation for this kind of modeling. For a better understanding of the hydro-mechanical phenomena in fractured media, two different sites have been selected for the work. The first is the site of Grimsel in Switzerland in which an underground laboratory is located at approximately 400 m of depth. The FEBEX experiment aims at the in-situ study of the consecutive phenomena due to the installation of a heat source representative of radioactive waste in the last 17 meters of the FEBEX tunnel in the laboratory of Grimsel. Only, the modeling of the hydro-mechanical of the excavation was model. The modeling of the Febex enabled us to establish a methodology of calibration of the hydraulic properties in the discontinuous media. However, this kind of study on such complex sites does not make possible to answer all the questions which arise on the hydro-mechanical behavior of the fractured media. We thus carried out modeling on an other site, smaller than the fist one and more accessible. The experimental site of Coaraze, in the Maritime Alps, is mainly constituted of limestone and fractures. Then the variation of water pressure along fractures is governed by the opening/closure sequence of a water gate. Normal displacement as well as the pore pressure along these fractures are recorded, and then

  18. Droplet localization in the random XXZ model and its manifestations

    Science.gov (United States)

    Elgart, A.; Klein, A.; Stolz, G.

    2018-01-01

    We examine many-body localization properties for the eigenstates that lie in the droplet sector of the random-field spin- \\frac 1 2 XXZ chain. These states satisfy a basic single cluster localization property (SCLP), derived in Elgart et al (2018 J. Funct. Anal. (in press)). This leads to many consequences, including dynamical exponential clustering, non-spreading of information under the time evolution, and a zero velocity Lieb–Robinson bound. Since SCLP is only applicable to the droplet sector, our definitions and proofs do not rely on knowledge of the spectral and dynamical characteristics of the model outside this regime. Rather, to allow for a possible mobility transition, we adapt the notion of restricting the Hamiltonian to an energy window from the single particle setting to the many body context.

  19. [Critical of the additive model of the randomized controlled trial].

    Science.gov (United States)

    Boussageon, Rémy; Gueyffier, François; Bejan-Angoulvant, Theodora; Felden-Dominiak, Géraldine

    2008-01-01

    Randomized, double-blind, placebo-controlled clinical trials are currently the best way to demonstrate the clinical effectiveness of drugs. Its methodology relies on the method of difference (John Stuart Mill), through which the observed difference between two groups (drug vs placebo) can be attributed to the pharmacological effect of the drug being tested. However, this additive model can be questioned in the event of statistical interactions between the pharmacological and the placebo effects. Evidence in different domains has shown that the placebo effect can influence the effect of the active principle. This article evaluates the methodological, clinical and epistemological consequences of this phenomenon. Topics treated include extrapolating results, accounting for heterogeneous results, demonstrating the existence of several factors in the placebo effect, the necessity to take these factors into account for given symptoms or pathologies, as well as the problem of the "specific" effect.

  20. Random field Ising model and community structure in complex networks

    Science.gov (United States)

    Son, S.-W.; Jeong, H.; Noh, J. D.

    2006-04-01

    We propose a method to determine the community structure of a complex network. In this method the ground state problem of a ferromagnetic random field Ising model is considered on the network with the magnetic field Bs = +∞, Bt = -∞, and Bi≠s,t=0 for a node pair s and t. The ground state problem is equivalent to the so-called maximum flow problem, which can be solved exactly numerically with the help of a combinatorial optimization algorithm. The community structure is then identified from the ground state Ising spin domains for all pairs of s and t. Our method provides a criterion for the existence of the community structure, and is applicable equally well to unweighted and weighted networks. We demonstrate the performance of the method by applying it to the Barabási-Albert network, Zachary karate club network, the scientific collaboration network, and the stock price correlation network. (Ising, Potts, etc.)

  1. Random Field Ising Models: Fractal Interfaces and their Implications

    Science.gov (United States)

    Bupathy, A.; Kumar, M.; Banerjee, V.; Puri, S.

    2017-10-01

    We use a computationally efficient graph-cut (GC) method to obtain exact ground-states of the d = 3 random field Ising model (RFIM) on simple cubic (SC), bodycentered cubic (BCC) and face-centered cubic (FCC) lattices with Gaussian, Uniform and Bimodal distributions for the disorder Δ. At small-r, the correlation function C(r; Δ) shows a cusp singularity characterised by a non-integer roughness exponent α signifying rough fractal interfaces with dimension d f = d – α. In the paramagnetic phase (Δ > Δ c ), α ≃ 0:5 for all lattice and disorder types. In the ferromagnetic phase (Δ Fractal interfaces have important implications on growth and relaxation.

  2. From Multi-Porosity to Multiple-Scale Permeability Models of Natural Fractured Media

    Science.gov (United States)

    De Dreuzy, J. R.; Davy, P.; Meheust, Y.; Bour, O.

    2014-12-01

    Classical dual-porosity models and homogenization approaches fail to represent the permeability scaling, the high flow channeling and the broad variability observed in natural fractured media. More critically, most modeling frameworks cannot restitute simultaneously the permeability increase with scale and the persistence of channeling. In fact, channeling enhances the impact of bottlenecks, reduces permeability, and increases permeability variability with scale. It is the case of percolation theory but also of more advanced large-range correlated theories including power-law scaling of some of the fracture properties including their length or their mutual distances. More generally, we show with extensive numerical studies on 3D Discrete Fracture Networks (DFNs) that hydraulic behaviors come from a number of local and global fracture characteristics. The concept of effective properties like effective permeability itself appears quite weak and should be replaced by new modeling frameworks. We propose three alternative approaches combining the specificies of fracture flow and transport of DFNs and the simplicity of continuum approaches: 1- Discrete dual porosity media for high flow localization in a subset of the fracture network. 2- Structured Interacting Continua for highly organized diffusive processes in poorly connected fracture structures. 3- Multiple-scale permeability models for hierarchically structured fractured media with 3D concurrent fracture percolating networks. These different approaches can be combined and specified with a limited number of parameters. They are also efficient in representing the potentially large hydraulic impact of minor modification of the fracture network geometry and local connectivity.

  3. Cluster-size entropy in the Axelrod model of social influence: small-world networks and mass media.

    Science.gov (United States)

    Gandica, Y; Charmell, A; Villegas-Febres, J; Bonalde, I

    2011-10-01

    We study the Axelrod's cultural adaptation model using the concept of cluster-size entropy S(c), which gives information on the variability of the cultural cluster size present in the system. Using networks of different topologies, from regular to random, we find that the critical point of the well-known nonequilibrium monocultural-multicultural (order-disorder) transition of the Axelrod model is given by the maximum of the S(c)(q) distributions. The width of the cluster entropy distributions can be used to qualitatively determine whether the transition is first or second order. By scaling the cluster entropy distributions we were able to obtain a relationship between the critical cultural trait q(c) and the number F of cultural features in two-dimensional regular networks. We also analyze the effect of the mass media (external field) on social systems within the Axelrod model in a square network. We find a partially ordered phase whose largest cultural cluster is not aligned with the external field, in contrast with a recent suggestion that this type of phase cannot be formed in regular networks. We draw a q-B phase diagram for the Axelrod model in regular networks.

  4. Asymptotic limits of some models for sound propagation in porous media and the assignment of the pore characteristic lengths.

    Science.gov (United States)

    Horoshenkov, Kirill V; Groby, Jean-Philippe; Dazel, Olivier

    2016-05-01

    Modeling of sound propagation in porous media requires the knowledge of several intrinsic material parameters, some of which are difficult or impossible to measure directly, particularly in the case of a porous medium which is composed of pores with a wide range of scales and random interconnections. Four particular parameters which are rarely measured non-acoustically, but used extensively in a number of acoustical models, are the viscous and thermal characteristic lengths, thermal permeability, and Pride parameter. The main purpose of this work is to show how these parameters relate to the pore size distribution which is a routine characteristic measured non-acoustically. This is achieved through the analysis of the asymptotic behavior of four analytical models which have been developed previously to predict the dynamic density and/or compressibility of the equivalent fluid in a porous medium. In this work the models proposed by Johnson, Koplik, and Dashn [J. Fluid Mech. 176, 379-402 (1987)], Champoux and Allard [J. Appl. Phys. 70(4), 1975-1979 (1991)], Pride, Morgan, and Gangi [Phys. Rev. B 47, 4964-4978 (1993)], and Horoshenkov, Attenborough, and Chandler-Wilde [J. Acoust. Soc. Am. 104, 1198-1209 (1998)] are compared. The findings are then used to compare the behavior of the complex dynamic density and compressibility of the fluid in a material pore with uniform and variable cross-sections.

  5. Cluster-size entropy in the Axelrod model of social influence: Small-world networks and mass media

    Science.gov (United States)

    Gandica, Y.; Charmell, A.; Villegas-Febres, J.; Bonalde, I.

    2011-10-01

    We study the Axelrod's cultural adaptation model using the concept of cluster-size entropy Sc, which gives information on the variability of the cultural cluster size present in the system. Using networks of different topologies, from regular to random, we find that the critical point of the well-known nonequilibrium monocultural-multicultural (order-disorder) transition of the Axelrod model is given by the maximum of the Sc(q) distributions. The width of the cluster entropy distributions can be used to qualitatively determine whether the transition is first or second order. By scaling the cluster entropy distributions we were able to obtain a relationship between the critical cultural trait qc and the number F of cultural features in two-dimensional regular networks. We also analyze the effect of the mass media (external field) on social systems within the Axelrod model in a square network. We find a partially ordered phase whose largest cultural cluster is not aligned with the external field, in contrast with a recent suggestion that this type of phase cannot be formed in regular networks. We draw a q-B phase diagram for the Axelrod model in regular networks.

  6. Teens, dating violence, and media use: a review of the literature and conceptual model for future research.

    Science.gov (United States)

    Manganello, Jennifer A

    2008-01-01

    Dating violence is highly prevalent among adolescents. Of importance, dating violence has been associated with negative physical and mental health outcomes for teens and high-risk behaviors such as unsafe sex practices. Although a growing body of research has examined the extent and nature of this problem, little research has considered aspects of the media that might be associated with risk for teen dating violence, such as time spent using media and effects of media content. This article provides an overview of the prevalence of teen dating violence, describes the potential for assessing media use as a risk factor, offers a conceptual model, and suggests ideas for future research.

  7. Electronic Properties of Random Polymers: Modelling Optical Spectra of Melanins

    Science.gov (United States)

    Bochenek, Kinga; Gudowska-Nowak, Ewa

    2003-05-01

    Melanins are a group of complex pigments of biological origin, widely spread in all species from fungi to man. Among diverse types of melanins, the human melanins, eumelanins, are brown or black nitrogen-containing pigments, mostly known for their photoprotective properties in human skin. We have undertaken theoretical studies aimed to understand absorption spectra of eumelanins and their chemical precursors. The structure of the biopigment is poorly defined, although it is believed to be composed of cross-linked heteropolymers based on indolequinones. As a basic model of the eumelanin structure, we have chosen pentamers containing hydroquinones (HQ) and/or 5,6-indolequinones (IQ) and/or semiquinones (SQ) often listed as structural melanin monomers. The eumelanin oligomers have been constructed as random compositions of basic monomers and optimized for the energy of bonding. Absorption spectra of model assemblies have been calculated within the semiempirical intermediate neglect of differential overlap (INDO) approximation. Model spectrum of eumelanin has been further obtained by sum of independent spectra of singular polymers. By comparison with experimental data it is shown that the INDO/CI method manages to reproduce well characteristic properties of experimental spectrum of synthetic eumelanins.

  8. Magnetic resonance sounding measurements for modeling of water flow transport in variably saturated porous media

    Science.gov (United States)

    Legchenko, Anatoly; Legout, Cédric; Descloitres, Marc

    2017-04-01

    Numerical modeling of water flow in partly saturated porous media requires knowledge of hydraulic properties of the media. The straightforward approach consists of directly measuring K(teta) and h(teta), which is challenging in many practically important applications. In-situ non-invasive measurements of K(teta) and h(teta) are even more difficult and probably impossible. Additionally, K(teta) and h(teta) are both scale dependent parameters. Under favorable conditions, surface geophysical methods may allow non-invasive identification of different geological formations and estimate of the porosity. A few papers report hydrogeological modeling considering water-saturated formations with integrated geophysical data (aquifer geometry, K and teta at saturation). However, modeling of water transport in partly saturated subsurface is more difficult task because it requires more extensive knowledge of soil hydraulic properties. We use Magnetic Resonance Sounding (MRS) method for non-invasive time-lapse measurements of the water content as an input into numerical modeling tool for hydrogeological modeling. However, MRS is not able to provide h(teta), which rest inaccessible. We propose an approach, which consists of performing infiltration tests (or observation of natural infiltration and monitoring rain water) and measuring corresponding variation of the water content in the subsurface. Then, we use a data base of soils with accurately known hydraulic properties. We try different soils for modeling water transport under our conditions (reproducing our experiment) and select one, which allows fitting experimentally observed variations in the water content. When such a soil is found we obtain K(teta) and h(teta). Thus, instead of looking for true hydraulic characteristics of the subsurface we obtain some equivalent media that allows reproducing our observations. We demonstrate the feasibility of our approach using simple 1-D models and commercially available software

  9. Effects of mass media action on the Axelrod model with social influence.

    Science.gov (United States)

    Rodríguez, Arezky H; Moreno, Y

    2010-07-01

    The use of dyadic interaction between agents, in combination with homophily (the principle that "likes attract") in the Axelrod model for the study of cultural dissemination, has two important problems: the prediction of monoculture in large societies and an extremely narrow window of noise levels in which diversity with local convergence is obtained. Recently, the inclusion of social influence has proven to overcome them [A. Flache and M. W. Macy, e-print arXiv:0808.2710]. Here, we extend the Axelrod model with social influence interaction for the study of mass media effects through the inclusion of a superagent which acts over the whole system and has non-null overlap with each agent of the society. The dependence with different parameters as the initial social diversity, size effects, mass media strength, and noise is outlined. Our results might be relevant in several socioeconomic contexts and for the study of the emergence of collective behavior in complex social systems.

  10. Social media monitoring model to guide decision making of destination management organization

    Directory of Open Access Journals (Sweden)

    Guilherme Mendes Thomaz

    2015-08-01

    Full Text Available The widespread adoption of social media by users and organizations has generated an exponential increase in data and content that offer opportunities to be processed into information and knowledge. However, dealing with such data is considered a challenge and requires the use of adequate resources. Considering this scenario, the aim of this study was to present a social media monitoring model to support decision making by DMOs. The model proposed has been tested before and during the 2014 FIFA World Cup, using Curitiba and Foz do Iguaçu (Paraná State as destinations, having a structured of seven stages. The results of the period were composed of about 50,000 messages, tours and associated ontology application. A large part of the frequency relations, between attractions or between host cities, have been com-patible with their reality in the tourist trade.

  11. DYNAMICS OF METAPHORIC MODELLING OF THE CONCEPT OF TERRORISM IN AMERICAN MASS MEDIA DISCOURSE

    Directory of Open Access Journals (Sweden)

    Rykova, O.V.

    2017-09-01

    Full Text Available The topicality of the research in modern linguistics is defined by the importance of studying the problem of the dynamic nature of the concept content, the need to define the connection type between the concept and discourse as well as to reveal the dependence of the concept content and verbalization means from the type of discourse. The subject of the research is dynamic properties of the verbalization of a socially marked concept in American mass media discourse. The aim is to define the dynamics of structuring and explicating the knowledge about terrorism in mass media discourse. To reach the aim the following tasks are set: to determine the corpus of linguistic units which serve as verbalizers of the concept of terrorism in American mass media discourse; to define the dynamics of the verbal representation of the concept of terrorism in American mass media discourse as exemplified by metaphoric modelling. The practical applicability of the research consists in the possibility of using its main points and results in such academic courses as general linguistics, stylistics, cultural linguistics, special courses in cognitive linguistics, theory of conceptual metaphor, discourse study and in lexicographic practice.

  12. Geometric and Hydrodynamic Characteristics of Three-dimensional Saturated Prefractal Porous Media Determined with Lattice Boltzmann Modeling

    Science.gov (United States)

    Fractal and prefractal geometric models have substantial potential of contributing to the analysis of flow and transport in porous media such as soils and reservoir rocks. In this study, geometric and hydrodynamic parameters of saturated 3D mass and pore-solid prefractal porous media were characteri...

  13. On the connection between morphological and stochastic permeability models of porous media

    Science.gov (United States)

    Hristopulos, D. T.

    2003-04-01

    We present a theoretical framework that connects morphological and stochastic models of the fluid permeability in porous media. Morphological models relate fluid permeability to properties of the pore space geometry, such as the porosity and specific interfacial area. On the other hand, stochastic theories of flow and transport are based on statistical representations of the fluid permeability obtained from the analysis of permeability data, which do not make a direct connection with the pore morphology. Using the local porosity theory, we develop a link between the morphological and stochastic permeability models, and we show how statistical properties follow from the small-scale variability of the morphology.

  14. Mass media and polarisation processes in the bounded confidence model of opinion dynamics

    OpenAIRE

    McKeown, Gary; Sheehy, Noel

    2006-01-01

    This paper presents a social simulation in which we add an additional layer of mass media communication to the social network 'bounded confidence' model of Deffuant et al (2000). A population of agents on a lattice with continuous opinions and bounded confidence adjust their opinions on the basis of binary social network interactions between neighbours or communication with a fixed opinion. There are two mechanisms for interaction. 'Social interaction' occurs between neighbours on a lattice a...

  15. Chaotic convective behavior and stability analysis of a fractional viscoelastic fluids model in porous media

    KAUST Repository

    N'Doye, Ibrahima

    2015-05-25

    In this paper, a dynamical fractional viscoelastic fluids convection model in porous media is proposed and its chaotic behavior is studied. A preformed equilibrium points analysis indicates the conditions where chaotic dynamics can be observed, and show the existence of chaos. The behavior and stability analysis of the integer-order and the fractional commensurate and non-commensurate orders of a fractional viscoelastic fluids system, which exhibits chaos, are presented as well.

  16. An agent-based model for emotion contagion and competition in online social media

    OpenAIRE

    Fan, Rui; Xu, Ke; Zhao, Jichang

    2017-01-01

    Recent studies suggest that human emotions diffuse in not only real-world communities but also online social media. More and more mechanisms beyond emotion contagion are revealed, including emotion correlations which indicate their influence and the coupling of emotion diffusion and network structure such as tie strength. Besides, different emotions might even compete in shaping the public opinion. However, a comprehensive model that considers up-to-date findings to replicate the patterns of ...

  17. Utilizing neural networks in magnetic media modeling and field computation: A review

    OpenAIRE

    Amr A. Adly; Abd-El-Hafiz, Salwa K.

    2013-01-01

    Magnetic materials are considered as crucial components for a wide range of products and devices. Usually, complexity of such materials is defined by their permeability classification and coupling extent to non-magnetic properties. Hence, development of models that could accurately simulate the complex nature of these materials becomes crucial to the multi-dimensional field-media interactions and computations. In the past few decades, artificial neural networks (ANNs) have been utilized in ma...

  18. A Unified Approach to Power Calculation and Sample Size Determination for Random Regression Models

    Science.gov (United States)

    Shieh, Gwowen

    2007-01-01

    The underlying statistical models for multiple regression analysis are typically attributed to two types of modeling: fixed and random. The procedures for calculating power and sample size under the fixed regression models are well known. However, the literature on random regression models is limited and has been confined to the case of all…

  19. A random effect multiplicative heteroscedastic model for bacterial growth

    Directory of Open Access Journals (Sweden)

    Quinto Emiliano J

    2010-02-01

    Full Text Available Abstract Background Predictive microbiology develops mathematical models that can predict the growth rate of a microorganism population under a set of environmental conditions. Many primary growth models have been proposed. However, when primary models are applied to bacterial growth curves, the biological variability is reduced to a single curve defined by some kinetic parameters (lag time and growth rate, and sometimes the models give poor fits in some regions of the curve. The development of a prediction band (from a set of bacterial growth curves using non-parametric and bootstrap methods permits to overcome that problem and include the biological variability of the microorganism into the modelling process. Results Absorbance data from Listeria monocytogenes cultured at 22, 26, 38, and 42°C were selected under different environmental conditions of pH (4.5, 5.5, 6.5, and 7.4 and percentage of NaCl (2.5, 3.5, 4.5, and 5.5. Transformation of absorbance data to viable count data was carried out. A random effect multiplicative heteroscedastic model was considered to explain the dynamics of bacterial growth. The concept of a prediction band for microbial growth is proposed. The bootstrap method was used to obtain resamples from this model. An iterative procedure is proposed to overcome the computer intensive task of calculating simultaneous prediction intervals, along time, for bacterial growth. The bands were narrower below the inflection point (0-8 h at 22°C, and 0-5.5 h at 42°C, and wider to the right of it (from 9 h onwards at 22°C, and from 7 h onwards at 42°C. A wider band was observed at 42°C than at 22°C when the curves reach their upper asymptote. Similar bands have been obtained for 26 and 38°C. Conclusions The combination of nonparametric models and bootstrap techniques results in a good procedure to obtain reliable prediction bands in this context. Moreover, the new iterative algorithm proposed in this paper allows one to

  20. Using Rich Social Media Information for Music Recommendation via Hypergraph Model

    Science.gov (United States)

    Tan, Shulong; Bu, Jiajun; Chen, Chun; He, Xiaofei

    There are various kinds of social media information, including different types of objects and relations among these objects, in music social communities such as Last.fm and Pandora. This information is valuable for music recommendation. However, there are two main challenges to exploit this rich social media information: (a) There are many different types of objects and relations in music social communities, which makes it difficult to develop a unified framework taking into account all objects and relations. (b) In these communities, some relations are much more sophisticated than pairwise relation, and thus cannot be simply modeled by a graph. We propose a novel music recommendation algorithm by using both multiple kinds of social media information and music acoustic-based content. Instead of graph, we use hypergraph to model the various objects and relations, and consider music recommendation as a ranking problem on this hypergraph. While an edge of an ordinary graph connects only two objects, a hyperedge represents a set of objects. In this way, hypergraph can be naturally used to model high-order relations.