WorldWideScience

Sample records for heterogeneous media problemas

  1. Percolation in Heterogeneous Media

    International Nuclear Information System (INIS)

    Vocka, Radim

    1999-01-01

    This work is a theoretical reflection on the problematic of the modeling of heterogeneous media, that is on the way of their simple representation conserving their characteristic features. Two particular problems are addressed in this thesis. Firstly, we study the transport in porous media, that is in a heterogeneous media which structure is quenched. A pore space is represented in a simple way - a pore is symbolized as a tube of a given length and a given diameter. The fact that the correlations in the distribution of pore sizes are taken into account by a construction of a hierarchical network makes possible the modeling of porous media with a porosity distributed over several length scales. The transport in the hierarchical network shows qualitatively different phenomena from those observed in simpler models. A comparison of numerical results with experimental data shows that the hierarchical network gives a good qualitative representation of the structure of real porous media. Secondly, we study a problem of the transport in a heterogeneous media which structure is evolving during the time. The models where the evolution of the structure is not influenced by the transport are studied in detail. These models present a phase transition of the same nature as that observed on the percolation networks. We propose a new theoretical description of this transition, and we express critical exponents describing the evolution of the conductivity as a function of fundamental exponents of percolation theory. (author) [fr

  2. Waves spontaneously generated by heterogeneity in oscillatory media

    Science.gov (United States)

    Cui, Xiaohua; Huang, Xiaodong; Hu, Gang

    2016-05-01

    Wave propagation is an important characteristic for pattern formation and pattern dynamics. To date, various waves in homogeneous media have been investigated extensively and have been understood to a great extent. However, the wave behaviors in heterogeneous media have been studied and understood much less. In this work, we investigate waves that are spontaneously generated in one-dimensional heterogeneous oscillatory media governed by complex Ginzburg-Landau equations; the heterogeneity is modeled by multiple interacting homogeneous media with different system control parameters. Rich behaviors can be observed by varying the control parameters of the systems, whereas the behavior is incomparably simple in the homogeneous cases. These diverse behaviors can be fully understood and physically explained well based on three aspects: dispersion relation curves, driving-response relations, and wave competition rules in homogeneous systems. Possible applications of heterogeneity-generated waves are anticipated.

  3. Scaling properties of conduction velocity in heterogeneous excitable media

    Science.gov (United States)

    Shajahan, T. K.; Borek, Bartłomiej; Shrier, Alvin; Glass, Leon

    2011-10-01

    Waves of excitation through excitable media, such as cardiac tissue, can propagate as plane waves or break up to form reentrant spiral waves. In diseased hearts reentrant waves can be associated with fatal cardiac arrhythmias. In this paper we investigate the conditions that lead to wave break, reentry, and propagation failure in mathematical models of heterogeneous excitable media. Two types of heterogeneities are considered: sinks are regions in space in which the voltage is fixed at its rest value, and breaks are nonconducting regions with no-flux boundary conditions. We find that randomly distributed heterogeneities in the medium have a decremental effect on the velocity, and above a critical density of such heterogeneities the conduction fails. Using numerical and analytical methods we derive the general relationship among the conduction velocity, density of heterogeneities, diffusion coefficient, and the rise time of the excitation in both two and three dimensions. This work helps us understand the factors leading to reduced propagation velocity and the formation of spiral waves in heterogeneous excitable media.

  4. Heterogeneous self-assembled media for biopolymerization

    DEFF Research Database (Denmark)

    Monnard, Pierre-Alain

    2011-01-01

    Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... polymerization, the initial elongation rates clearly depended on the complementarity of the monomers with the templating nucleobases3. However, metal-ion catalyzed reactions deliver RNA analogs with heterogeneous linkages. Moreover, the usefulness of this medium in the form of quasi-compartmentalization extends...... beyond metal-ion catalysis reactions, as we have recently demonstrated the catalytic power of a dipeptide, SerHis, for the regioselective formation of phosphodiester bonds. These results in conjonction with the synthesis of nucleobases at -78˚C, the demonstration of ribozyme activity (RNA ligase ribozyme...

  5. Modeling heterogeneous unsaturated porous media flow at Yucca Mountain

    International Nuclear Information System (INIS)

    Robey, T.H.

    1994-01-01

    Geologic systems are inherently heterogeneous and this heterogeneity can have a significant impact on unsaturated flow through porous media. Most previous efforts to model groundwater flow through Yucca Mountain have used stratigraphic units with homogeneous properties. However, modeling heterogeneous porous and fractured tuff in a more realistic manner requires numerical methods for generating heterogeneous simulations of the media, scaling of material properties from core scale to computational scale, and flow modeling that allows channeling. The Yucca Mountain test case of the INTRAVAL project is used to test the numerical approaches. Geostatistics is used to generate more realistic representations of the stratigraphic units and heterogeneity within units is generated using sampling from property distributions. Scaling problems are reduced using an adaptive grid that minimizes heterogeneity within each flow element. A flow code based on the dual mixed-finite-element method that allows for heterogeneity and channeling is employed. In the Yucca Mountain test case, the simulated volumetric water contents matched the measured values at drill hole USW UZ-16 except in the nonwelded portion of Prow Pass

  6. Non-Enzymatic biopolymerization reactions supported by heterogeneous media

    DEFF Research Database (Denmark)

    Monnard, Pierre-Alain

    2011-01-01

    Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... compartments and lipid-bilayer lattices. Another kind of media is represented by co-existing, self-assembled phases in the reaction medium, e.g., in water-ice matrices. These media have the capacity to assemble chemical molecules or complex catalytic assemblies into unique configurations that are unstable...

  7. Uranium (VI) transport in saturated heterogeneous media: Influence of kaolinite and humic acid.

    Science.gov (United States)

    Chen, Chong; Zhao, Kang; Shang, Jianying; Liu, Chongxuan; Wang, Jin; Yan, Zhifeng; Liu, Kesi; Wu, Wenliang

    2018-05-07

    Natural aquifers typically exhibit a variety of structural heterogeneities. However, the effect of mineral colloids and natural organic matter on the transport behavior of uranium (U) in saturated heterogeneous media are not totally understood. In this study, heterogeneous column experiments were conducted, and the constructed columns contained a fast-flow domain (FFD) and a slow-flow domain (SFD). The effect of kaolinite, humic acid (HA), and kaolinite/HA mixture on U(VI) retention and release in saturated heterogeneous media was examined. Media heterogeneity significantly influenced U fate and transport behavior in saturated subsurface environment. The presence of kaolinite, HA, and kaolinite/HA enhanced the mobility of U in heterogeneous media, and the mobility of U was the highest in the presence of kaolinite/HA and the lowest in the presence of kaolinite. In the presence of kaolinite, there was no difference in the amount of U released from the FFD and SFD. However, in the presence of HA and kaolinite/HA, a higher amount of U was released from the FFD. The findings in this study showed that medium structure and mineral colloids, as well as natural organic matter in the aqueous phase had significant effects on U transport and fate in subsurface environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. A numerical homogenization method for heterogeneous, anisotropic elastic media based on multiscale theory

    KAUST Repository

    Gao, Kai

    2015-06-05

    The development of reliable methods for upscaling fine-scale models of elastic media has long been an important topic for rock physics and applied seismology. Several effective medium theories have been developed to provide elastic parameters for materials such as finely layered media or randomly oriented or aligned fractures. In such cases, the analytic solutions for upscaled properties can be used for accurate prediction of wave propagation. However, such theories cannot be applied directly to homogenize elastic media with more complex, arbitrary spatial heterogeneity. Therefore, we have proposed a numerical homogenization algorithm based on multiscale finite-element methods for simulating elastic wave propagation in heterogeneous, anisotropic elastic media. Specifically, our method used multiscale basis functions obtained from a local linear elasticity problem with appropriately defined boundary conditions. Homogenized, effective medium parameters were then computed using these basis functions, and the approach applied a numerical discretization that was similar to the rotated staggered-grid finite-difference scheme. Comparisons of the results from our method and from conventional, analytical approaches for finely layered media showed that the homogenization reliably estimated elastic parameters for this simple geometry. Additional tests examined anisotropic models with arbitrary spatial heterogeneity in which the average size of the heterogeneities ranged from several centimeters to several meters, and the ratio between the dominant wavelength and the average size of the arbitrary heterogeneities ranged from 10 to 100. Comparisons to finite-difference simulations proved that the numerical homogenization was equally accurate for these complex cases.

  9. Heterogeneity of smooth muscle cells in tunica media of aorta in ...

    African Journals Online (AJOL)

    ... of the tunica media of goat aorta are phenotypically heterogeneous and run in multiple directions. These characteristics probably confer mechanical strength and functional plasticity to the aortic wall. Designers of aortic substitutes should bear this in mind. Keywords: Vascular, Smooth Muscle Cells, Heterogeneity, Aorta ...

  10. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, J.H.; Madilyn Fletcher

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

  11. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, J.H.

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media.

  12. Complexity Reduction of Multiphase Flows in Heterogeneous Porous Media

    KAUST Repository

    Ghommem, Mehdi; Gildin, Eduardo; Ghasemi, Mohammadreza

    2015-01-01

    In this paper, we apply mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in heterogeneous porous media. We propose intrusive and nonintrusive model-reduction approaches that enable a significant

  13. Dynamic characteristics of heterogeneous media in vibrational and wave processes

    International Nuclear Information System (INIS)

    Fedotovskij, V.S.; Sinyavskij, V.F.; Terenik, L.V.; Spirov, V.S.; Kokorev, B.V.

    1986-01-01

    The complex mechanic systems involving a great quantity of the same type elements, in particular, the rod systems flowed around by the one- or two-phase flow are considered as the two- or three-phase heterogeneous media with certain effective properties. Some recommendations for calculating effective properties and determining those on a base of the dynamic characteristics of various heterogeneous systems are given. (author)

  14. Upscaling of Constitutive Relations In Unsaturated Heterogeneous Porous Media

    International Nuclear Information System (INIS)

    Liu, H. H.; Bodvarsson, G. S.

    2001-01-01

    When numerical model are used for modeling field scale flow and transport processes in the subsurface, the problem of ''upscaling'' arises. Typical scales, corresponding to spatial resolutions of subsurface heterogeneity in numerical models, are generally much larger than the measurement scale of the parameters and physical processes involved. The upscaling problems is, then, one of assigning parameters to gridblock scale based on parameter values measured on small scales. The focus of this study is to develop an approach to determine large-scale (upscaled) constitutive relations (relationships among relative permeability, capillary pressure and saturation) from small-scale measurements for porous media for a range of air entry values that are typical for the tuff matrix in the unsaturated zone of Yucca Mountain. For porous media with large air entry values, capillary forces play a key role in determining spatial water distribution at large-scales. Therefore, a relatively uniform capillary pressure approximately exists even for a large gridblock scale under steady state flow conditions. Based on these reasoning, we developed formulations that relate upscaled constitutive relations to ones measured at core-scale. Numerical experiments with stochastically generated heterogeneous porous media were used to evaluate the upscaling formulations

  15. Nonlinear lattice waves in heterogeneous media

    International Nuclear Information System (INIS)

    Laptyeva, T V; Ivanchenko, M V; Flach, S

    2014-01-01

    We discuss recent advances in the understanding of the dynamics of nonlinear lattice waves in heterogeneous media, which enforce complete wave localization in the linear wave equation limit, especially Anderson localization for random potentials, and Aubry–André localization for quasiperiodic potentials. Additional nonlinear terms in the wave equations can either preserve the phase-coherent localization of waves, or destroy it through nonintegrability and deterministic chaos. Spreading wave packets are observed to show universal features in their dynamics which are related to properties of nonlinear diffusion equations. (topical review)

  16. Rupture Dynamics and Ground Motion from Earthquakes on Rough Faults in Heterogeneous Media

    Science.gov (United States)

    Bydlon, S. A.; Kozdon, J. E.; Duru, K.; Dunham, E. M.

    2013-12-01

    Heterogeneities in the material properties of Earth's crust scatter propagating seismic waves. The effects of scattered waves are reflected in the seismic coda and depend on the amplitude of the heterogeneities, spatial arrangement, and distance from source to receiver. In the vicinity of the fault, scattered waves influence the rupture process by introducing fluctuations in the stresses driving propagating ruptures. Further variability in the rupture process is introduced by naturally occurring geometric complexity of fault surfaces, and the stress changes that accompany slip on rough surfaces. Our goal is to better understand the origin of complexity in the earthquake source process, and to quantify the relative importance of source complexity and scattering along the propagation path in causing incoherence of high frequency ground motion. Using a 2D high order finite difference rupture dynamics code, we nucleate ruptures on either flat or rough faults that obey strongly rate-weakening friction laws. These faults are embedded in domains with spatially varying material properties characterized by Von Karman autocorrelation functions and their associated power spectral density functions, with variations in wave speed of approximately 5 to 10%. Flat fault simulations demonstrate that off-fault material heterogeneity, at least with this particular form and amplitude, has only a minor influence on the rupture process (i.e., fluctuations in slip and rupture velocity). In contrast, ruptures histories on rough faults in both homogeneous and heterogeneous media include much larger short-wavelength fluctuations in slip and rupture velocity. We therefore conclude that source complexity is dominantly influenced by fault geometric complexity. To examine contributions of scattering versus fault geometry on ground motions, we compute spatially averaged root-mean-square (RMS) acceleration values as a function of fault perpendicular distance for a homogeneous medium and several

  17. Mathematical modeling in mechanics of heterogeneous media

    International Nuclear Information System (INIS)

    Fedorov, A.V.; Fomin, V.M.

    1991-01-01

    The paper reviews the work carried out at the Department of Multi-Phase Media Mechanics of the Institute of Theoretical and Applied Mechanics of the Siberian Division of the USSR Academy of Sciences. It deals with mathematical models for the flow of gas mixtures and solid particles that account for phase transitions and chemical reactions. This work is concerned with the problems of construction of laws of conservation, determination of the type of equations of heterogeneous media mechanics, structure of shock waves, and combined discontinuities in mixtures. The theory of ideal and nonideal detonation in suspension of matter in gases is discussed. Self-similar flows of gas mixtures and responding particles, as well as the problem of breakup of discontinuity for suspension of matter in gases, is studied. 42 refs

  18. The kinetics of nonequilibrium chain plasma-chemical oxidation in heterogeneous media

    International Nuclear Information System (INIS)

    Deminskii, M.A.; Potapkin, B.V.; Rusanov, V.D.

    1994-01-01

    The kinetics of oxidation of low-impurity components in air mixtures under heterogeneous conditions was studied. The principal kinetic features of the process were determined on the basis of theoretical analysis of plasma-chemical oxidation in heterogeneous media. The analysis also showed that low concentrations of impurities in liquid aerosol particles can be efficiently oxidized via a chain process induced by reactive species formed in the gas

  19. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component. Final report

    International Nuclear Information System (INIS)

    Cushman, J.H.

    2000-01-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

  20. Transverse mixing in three-dimensional nonstationary anisotropic heterogeneous porous media

    DEFF Research Database (Denmark)

    Cirpka, Olaf; Chiogna, Gabriele; Rolle, Massimo

    2015-01-01

    -dimensional domains, more complex flow patterns are possible because streamlines can twist. In particular, spatially varying orientation of anisotropy can cause steady-state groundwater whirls. We analyze steady-state solute transport in three-dimensional locally isotropic heterogeneous porous media with blockwise...

  1. Numerical simulation of inertial two-phase flow in heterogenous media

    International Nuclear Information System (INIS)

    Ali Akbar ABBASIAN ARANI; Didier LASSEUX; Azita AHMADI

    2005-01-01

    In this work, we present the development of a 3 D numerical tool for simulation of non-Darcy two-phase flow in heterogeneous porous media. The physical model selected is the generalized Darcy-Forchheimer model. A validation is performed first by comparing numerical results with a semi-analytical solution of the Buckley-Leverett type. Secondly, numerical results obtained on 1 D and 2 D heterogeneous configurations are presented and we highlight the importance of the inertial terms according to a Reynolds number of the flow. (authors)

  2. Self-transparency effects in heterogeneous nonlinear scattering media and their possible use in lasers

    International Nuclear Information System (INIS)

    Al'tshuler, G.B.; Ermolaev, V.S.; Krylov, K.I.; Manenkov, A.A.; Prokhorov, A.M.

    1986-01-01

    Transmission of intense laser beams through heterogeneous scattering media is considered. Effects of intensity limitation, self-recovery of the wave front of a transmitted beam, and bistable reflection associated with the laser-induced self-transparency (suppression of scattering) of such media are predicted because of the compensation of the linear refractive-index difference Δn/sub L/ of the heterocomponents of a medium by nonlinear change Δn/sub N//sub L/ for different mechanisms of nonlinearity. Applications of these effects in lasers for Q switching and mode locking are discussed. The observation of self-transparency effects in several heterogeneous media (glass particles in toluene and nitrobenzene, and lead molybdenite powder) for cw Ar- and pulsed Nd- and CO 2 -laser radiation is reported. Q switching and mode locking have also been demonstrated with a YAG:Nd laser using nonlinear scattering in a heterogeneous cell as a control element in a laser resonator

  3. Sorption of strontium and fractal scaling of the heterogeneous media in a candidate VLLW disposal site

    International Nuclear Information System (INIS)

    Jinsheng Wang; Rui Zuo; Yanguo Teng; Zongjian Sun; Qinhong Hu

    2010-01-01

    Because of the deposit and accumulation from the debris flow, the heterogeneous geological characteristics is obvious for a candidate very low level waste (VLLW) disposal site, with the grain size ranging from tens of microns to 75 cm. Therefore, it is challenging to directly measure the sorption capacity of the media and the distribution coefficient of some radionuclides, such as strontium. We have studies the correlation of the particle mass content with different grade size and the sorption capacity, which is important in the modeling of radionuclide migration in the heterogeneous disposal site. A total of three deep pits and five shallow trenches were excavated, and 21 solid samples were collected for laboratory experiments. The grade and percentage of the different-sized particles were obtained, and the fractal dimension (D) of the media was calculated from the results of sieved experiments. Steady state sorption time and sorption isotherm of strontium was determined in the heterogeneous media, and sorption and distribution of strontium in the heterogeneous media were evaluated by the relationship between the mass percentage and distribution coefficient (K d ) of the fine-particle media, which was comprised of selected particles with a diameter less than 1 mm, and the correlation on the K d and D was regressed fit. The results indicated that fractal dimension bounded from 2.39 to 2.62 in the media, and K d values of strontium ranged between 119 and 126 in the fine-particle media, and corresponding value was 11 and 43 in the original media. The correlation between K d and D was approximately linear. (author)

  4. A note on variational multiscale methods for high-contrast heterogeneous porous media flows with rough source terms

    KAUST Repository

    Calo, Victor M.

    2011-09-01

    In this short note, we discuss variational multiscale methods for solving porous media flows in high-contrast heterogeneous media with rough source terms. Our objective is to separate, as much as possible, subgrid effects induced by the media properties from those due to heterogeneous source terms. For this reason, enriched coarse spaces designed for high-contrast multiscale problems are used to represent the effects of heterogeneities of the media. Furthermore, rough source terms are captured via auxiliary correction equations that appear in the formulation of variational multiscale methods [23]. These auxiliary equations are localized and one can use additive or multiplicative constructions for the subgrid corrections as discussed in the current paper. Our preliminary numerical results show that one can capture the effects due to both spatial heterogeneities in the coefficients (such as permeability field) and source terms (e.g., due to singular well terms) in one iteration. We test the cases for both smooth source terms and rough source terms and show that with the multiplicative correction, the numerical approximations are more accurate compared to the additive correction. © 2010 Elsevier Ltd.

  5. Modelling solute dispersion in periodic heterogeneous porous media: Model benchmarking against intermediate scale experiments

    Science.gov (United States)

    Majdalani, Samer; Guinot, Vincent; Delenne, Carole; Gebran, Hicham

    2018-06-01

    This paper is devoted to theoretical and experimental investigations of solute dispersion in heterogeneous porous media. Dispersion in heterogenous porous media has been reported to be scale-dependent, a likely indication that the proposed dispersion models are incompletely formulated. A high quality experimental data set of breakthrough curves in periodic model heterogeneous porous media is presented. In contrast with most previously published experiments, the present experiments involve numerous replicates. This allows the statistical variability of experimental data to be accounted for. Several models are benchmarked against the data set: the Fickian-based advection-dispersion, mobile-immobile, multirate, multiple region advection dispersion models, and a newly proposed transport model based on pure advection. A salient property of the latter model is that its solutions exhibit a ballistic behaviour for small times, while tending to the Fickian behaviour for large time scales. Model performance is assessed using a novel objective function accounting for the statistical variability of the experimental data set, while putting equal emphasis on both small and large time scale behaviours. Besides being as accurate as the other models, the new purely advective model has the advantages that (i) it does not exhibit the undesirable effects associated with the usual Fickian operator (namely the infinite solute front propagation speed), and (ii) it allows dispersive transport to be simulated on every heterogeneity scale using scale-independent parameters.

  6. 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

  7. On the validity of a Fickian diffusion model for the spreading of liquid infiltration plumes in partially saturated heterogeneous media

    International Nuclear Information System (INIS)

    Pruess, K.

    1994-01-01

    Localized infiltration of aqueous and -non-aqueous phase liquids (NAPLs) occurs in many circumstances. Examples include leaky underground pipelines and storage tanks, landfill and disposal sites, and surface spills. Because of ever-present heterogeneities on different scales such infiltration plumes are expected to disperse transversally and longitudinally. This paper examines recent suggestions that liquid plumes are being dispersed from medium heterogeneities in a manner that is analogous to Fickian diffusion. Numerical simulation experiments on liquid infiltration in heterogeneous media are performed to study the dispersive effects of small-scale heterogeneity. It is found that plume spreading indeed tends to be diffusive. Our results suggest that, as far as infiltration of liquids is concerned, broad classes of heterogeneous media behave as dispersive media with locally homogeneous (albeit anisotropic) permeability

  8. Multiscale analysis and computation for flows in heterogeneous media

    Energy Technology Data Exchange (ETDEWEB)

    Efendiev, Yalchin [Texas A & M Univ., College Station, TX (United States); Hou, T. Y. [California Inst. of Technology (CalTech), Pasadena, CA (United States); Durlofsky, L. J. [Stanford Univ., CA (United States); Tchelepi, H. [Stanford Univ., CA (United States)

    2016-08-04

    Our work in this project is aimed at making fundamental advances in multiscale methods for flow and transport in highly heterogeneous porous media. The main thrust of this research is to develop a systematic multiscale analysis and efficient coarse-scale models that can capture global effects and extend existing multiscale approaches to problems with additional physics and uncertainties. A key emphasis is on problems without an apparent scale separation. Multiscale solution methods are currently under active investigation for the simulation of subsurface flow in heterogeneous formations. These procedures capture the effects of fine-scale permeability variations through the calculation of specialized coarse-scale basis functions. Most of the multiscale techniques presented to date employ localization approximations in the calculation of these basis functions. For some highly correlated (e.g., channelized) formations, however, global effects are important and these may need to be incorporated into the multiscale basis functions. Other challenging issues facing multiscale simulations are the extension of existing multiscale techniques to problems with additional physics, such as compressibility, capillary effects, etc. In our project, we explore the improvement of multiscale methods through the incorporation of additional (single-phase flow) information and the development of a general multiscale framework for flows in the presence of uncertainties, compressible flow and heterogeneous transport, and geomechanics. We have considered (1) adaptive local-global multiscale methods, (2) multiscale methods for the transport equation, (3) operator-based multiscale methods and solvers, (4) multiscale methods in the presence of uncertainties and applications, (5) multiscale finite element methods for high contrast porous media and their generalizations, and (6) multiscale methods for geomechanics. Below, we present a brief overview of each of these contributions.

  9. Concept on groundwater flow and mass transport through heterogeneous porous media and application to in-situ test analysis

    International Nuclear Information System (INIS)

    Hatanaka, Koichiro; Umeki, Hiroyuki.

    1995-01-01

    Generally, geological media is modelled as porous or fractured media depending on their characteristics. Since the channels of groundwater flow and the transport paths are determined by the heterogeneity of the geological media, quantitative understanding of the heterogeneity is an important issue for modelling flow and transport processes through them. Therefore, it becomes popular way to develop statistical identification approaches of the heterogeneous field by using data from in-situ test and conduct validation studies of flow and transport models through the field by comparing with observed data. In this report, the theories of the identification approach and the concept on groundwater flow and mass transport are explained briefly and the application to tracer tests conducted at Grimsel test site, Switzerland, are described. (author)

  10. Bacterial transport in heterogeneous porous media: Observations from laboratory experiments

    Science.gov (United States)

    Silliman, S. E.; Dunlap, R.; Fletcher, M.; Schneegurt, M. A.

    2001-11-01

    Transport of bacteria through heterogeneous porous media was investigated in small-scale columns packed with sand and in a tank designed to allow the hydraulic conductivity to vary as a two-dimensional, lognormally distributed, second-order stationary, exponentially correlated random field. The bacteria were Pseudomonas ftuorescens R8, a strain demonstrating appreciable attachment to surfaces, and strain Ml, a transposon mutant of strain R8 with reduced attachment ability. In bench top, sand-filled columns, transport was determined by measuring intensity of fluorescence of stained cells in the effluent or by measuring radiolabeled cells that were retained in the sand columns. Results demonstrated that strain Ml was transported more efficiently than strain R8 through columns packed with either a homogeneous silica sand or a more heterogeneous sand with iron oxide coatings. Two experiments conducted in the tank involved monitoring transport of bacteria to wells via sampling from wells and sample ports in the tank. Bacterial numbers were determined by direct plate count. At the end of the first experiment, the distribution of the bacteria in the sediment was determined by destructive sampling and plating. The two experiments produced bacterial breakthrough curves that were quite similar even though the similarity between the two porous media was limited to first- and second-order statistical moments. This result appears consistent with the concept of large-scale, average behavior such as has been observed for the transport of conservative chemical tracers. The transported bacteria arrived simultaneously with a conservative chemical tracer (although at significantly lower normalized concentration than the tracer). However, the bacterial breakthrough curves showed significant late time tailing. The concentrations of bacteria attached to the sediment surfaces showed considerably more spatial variation than did the concentrations of bacteria in the fluid phase. This

  11. Mechanism of spiral formation in heterogeneous discretized excitable media.

    Science.gov (United States)

    Kinoshita, Shu-ichi; Iwamoto, Mayuko; Tateishi, Keita; Suematsu, Nobuhiko J; Ueyama, Daishin

    2013-06-01

    Spiral waves on excitable media strongly influence the functions of living systems in both a positive and negative way. The spiral formation mechanism has thus been one of the major themes in the field of reaction-diffusion systems. Although the widely believed origin of spiral waves is the interaction of traveling waves, the heterogeneity of an excitable medium has recently been suggested as a probable cause. We suggest one possible origin of spiral waves using a Belousov-Zhabotinsky reaction and a discretized FitzHugh-Nagumo model. The heterogeneity of the reaction field is shown to stochastically generate unidirectional sites, which can induce spiral waves. Furthermore, we found that the spiral wave vanished with only a small reduction in the excitability of the reaction field. These results reveal a gentle approach for controlling the appearance of a spiral wave on an excitable medium.

  12. in Heterogeneous Media

    Directory of Open Access Journals (Sweden)

    Saeed Balouchi

    2013-01-01

    Full Text Available Fractured reservoirs contain about 85 and 90 percent of oil and gas resources respectively in Iran. A comprehensive study and investigation of fractures as the main factor affecting fluid flow or perhaps barrier seems necessary for reservoir development studies. High degrees of heterogeneity and sparseness of data have incapacitated conventional deterministic methods in fracture network modeling. Recently, simulated annealing (SA has been applied to generate stochastic realizations of spatially correlated fracture networks by assuming that the elastic energy of fractures follows Boltzmann distribution. Although SA honors local variability, the objective function of geometrical fracture modeling is defined for homogeneous conditions. In this study, after the introduction of SA and the derivation of the energy function, a novel technique is presented to adjust the model with highly heterogeneous data for a fractured field from the southwest of Iran. To this end, the regular object-based model is combined with a grid-based technique to cover the heterogeneity of reservoir properties. The original SA algorithm is also modified by being constrained in different directions and weighting the energy function to make it appropriate for heterogeneous conditions. The simulation results of the presented approach are in good agreement with the observed field data.

  13. Convergence of Discontinuous Galerkin Methods for Incompressible Two-Phase Flow in Heterogeneous Media

    KAUST Repository

    Kou, Jisheng; Sun, Shuyu

    2013-01-01

    A class of discontinuous Galerkin methods with interior penalties is presented for incompressible two-phase flow in heterogeneous porous media with capillary pressures. The semidiscrete approximate schemes for fully coupled system of two-phase flow are formulated. In highly heterogeneous permeable media, the saturation is discontinuous due to different capillary pressures, and therefore, the proposed methods incorporate the capillary pressures in the pressure equation instead of saturation equation. By introducing a coupling approach for stability and error estimates instead of the conventional separate analysis for pressure and saturation, the stability of the schemes in space and time and a priori hp error estimates are presented in the L2(H 1) for pressure and in the L∞(L2) and L2(H1) for saturation. Two time discretization schemes are introduced for effectively computing the discrete solutions. © 2013 Societ y for Industrial and Applied Mathematics.

  14. Rupture Dynamics and Ground Motion from Earthquakes in Heterogeneous Media

    Science.gov (United States)

    Bydlon, S.; Dunham, E. M.; Kozdon, J. E.

    2012-12-01

    Heterogeneities in the material properties of Earth's crust scatter propagating seismic waves. The effects of scattered waves are reflected in the seismic coda and depend on the relative strength of the heterogeneities, spatial arrangement, and distance from source to receiver. In the vicinity of the fault, scattered waves influence the rupture process by introducing fluctuations in the stresses driving propagating ruptures. Further variability in the rupture process is introduced by naturally occurring geometric complexity of fault surfaces, and the stress changes that accompany slip on rough surfaces. We have begun a modeling effort to better understand the origin of complexity in the earthquake source process, and to quantify the relative importance of source complexity and scattering along the propagation path in causing incoherence of high frequency ground motion. To do this we extended our two-dimensional high order finite difference rupture dynamics code to accommodate material heterogeneities. We generate synthetic heterogeneous media using Von Karman correlation functions and their associated power spectral density functions. We then nucleate ruptures on either flat or rough faults, which obey strongly rate-weakening friction laws. Preliminary results for flat faults with uniform frictional properties and initial stresses indicate that off-fault material heterogeneity alone can lead to a complex rupture process. Our simulations reveal the excitation of high frequency bursts of waves, which radiate energy away from the propagating rupture. The average rupture velocity is thus reduced relative to its value in simulations employing homogeneous material properties. In the coming months, we aim to more fully explore parameter space by varying the correlation length, Hurst exponent, and amplitude of medium heterogeneities, as well as the statistical properties characterizing fault roughness.

  15. Space-fractional model for the spreading of matter in heterogeneous porous media

    International Nuclear Information System (INIS)

    Krepysheva, N.; Neel, M.Ch.

    2005-01-01

    In very heterogeneous porous media (like the soil, or an aquifer, for instance), experimental results showed that mass transport sometimes does not obey Fourier's law. Continuous Time Random Walks in the form of L y Flights provide a small scale model for super diffusive spreading of a tracer plume, dissolved in a fluid, itself enclosed in a porous medium. In an infinite medium, the corresponding behavior of the concentration of solute is known to obey a variant of Fourier's law, with a Riesz-Feller operator in place of the Laplacian. Here we show that with some modifications the result extends to semi infinite media. A numerical method allowing for the simulation of fractional derivatives is adapted to semi infinite media, with special attention to convective terms, associated to a possibly non zero global trough flow. (authors)

  16. Space-fractional model for the spreading of matter in heterogeneous porous media

    Energy Technology Data Exchange (ETDEWEB)

    Krepysheva, N. [Institut National de Recherches Agronomiques (INRA), UMRA Climat-Sol-Environnement, 84 - Avignon (France); Neel, M.Ch. [Universite d' Avignon, Faculte des Sciences, UMRA Climat-Sol-Environnement, 84 - Avignon (France)

    2005-07-01

    In very heterogeneous porous media (like the soil, or an aquifer, for instance), experimental results showed that mass transport sometimes does not obey Fourier's law. Continuous Time Random Walks in the form of L y Flights provide a small scale model for super diffusive spreading of a tracer plume, dissolved in a fluid, itself enclosed in a porous medium. In an infinite medium, the corresponding behavior of the concentration of solute is known to obey a variant of Fourier's law, with a Riesz-Feller operator in place of the Laplacian. Here we show that with some modifications the result extends to semi infinite media. A numerical method allowing for the simulation of fractional derivatives is adapted to semi infinite media, with special attention to convective terms, associated to a possibly non zero global trough flow. (authors)

  17. Reconstruction of absorption and scattering coefficients in two dimensional heterogeneous participating media

    International Nuclear Information System (INIS)

    Montero, Raul F. Carita; Roberty, Nilson C.; Silva Neto, Antonio J.; Universidade Federal, Rio de Janeiro, RJ

    2002-01-01

    In the present work it is presented the solution of the two dimensional inverse radiative transfer problem of scattering and absorption coefficients estimation, in heterogeneous media, using the source-detector methodology and a discrete ordinates method consistent with the source-detector system. The mathematical formulation of the direct and inverse problems is presented as well as test case results. (author)

  18. Impact of spatially correlated pore-scale heterogeneity on drying porous media

    Science.gov (United States)

    Borgman, Oshri; Fantinel, Paolo; Lühder, Wieland; Goehring, Lucas; Holtzman, Ran

    2017-07-01

    We study the effect of spatially-correlated heterogeneity on isothermal drying of porous media. We combine a minimal pore-scale model with microfluidic experiments with the same pore geometry. Our simulated drying behavior compares favorably with experiments, considering the large sensitivity of the emergent behavior to the uncertainty associated with even small manufacturing errors. We show that increasing the correlation length in particle sizes promotes preferential drying of clusters of large pores, prolonging liquid connectivity and surface wetness and thus higher drying rates for longer periods. Our findings improve our quantitative understanding of how pore-scale heterogeneity impacts drying, which plays a role in a wide range of processes ranging from fuel cells to curing of paints and cements to global budgets of energy, water and solutes in soils.

  19. A Context-Aware Adaptive Streaming Media Distribution System in a Heterogeneous Network with Multiple Terminals

    Directory of Open Access Journals (Sweden)

    Yepeng Ni

    2016-01-01

    Full Text Available We consider the problem of streaming media transmission in a heterogeneous network from a multisource server to home multiple terminals. In wired network, the transmission performance is limited by network state (e.g., the bandwidth variation, jitter, and packet loss. In wireless network, the multiple user terminals can cause bandwidth competition. Thus, the streaming media distribution in a heterogeneous network becomes a severe challenge which is critical for QoS guarantee. In this paper, we propose a context-aware adaptive streaming media distribution system (CAASS, which implements the context-aware module to perceive the environment parameters and use the strategy analysis (SA module to deduce the most suitable service level. This approach is able to improve the video quality for guarantying streaming QoS. We formulate the optimization problem of QoS relationship with the environment parameters based on the QoS testing algorithm for IPTV in ITU-T G.1070. We evaluate the performance of the proposed CAASS through 12 types of experimental environments using a prototype system. Experimental results show that CAASS can dynamically adjust the service level according to the environment variation (e.g., network state and terminal performances and outperforms the existing streaming approaches in adaptive streaming media distribution according to peak signal-to-noise ratio (PSNR.

  20. Large-scale model of flow in heterogeneous and hierarchical porous media

    Science.gov (United States)

    Chabanon, Morgan; Valdés-Parada, Francisco J.; Ochoa-Tapia, J. Alberto; Goyeau, Benoît

    2017-11-01

    Heterogeneous porous structures are very often encountered in natural environments, bioremediation processes among many others. Reliable models for momentum transport are crucial whenever mass transport or convective heat occurs in these systems. In this work, we derive a large-scale average model for incompressible single-phase flow in heterogeneous and hierarchical soil porous media composed of two distinct porous regions embedding a solid impermeable structure. The model, based on the local mechanical equilibrium assumption between the porous regions, results in a unique momentum transport equation where the global effective permeability naturally depends on the permeabilities at the intermediate mesoscopic scales and therefore includes the complex hierarchical structure of the soil. The associated closure problem is numerically solved for various configurations and properties of the heterogeneous medium. The results clearly show that the effective permeability increases with the volume fraction of the most permeable porous region. It is also shown that the effective permeability is sensitive to the dimensionality spatial arrangement of the porous regions and in particular depends on the contact between the impermeable solid and the two porous regions.

  1. Predicting Upscaled Behavior of Aqueous Reactants in Heterogeneous Porous Media

    Science.gov (United States)

    Wright, E. E.; Hansen, S. K.; Bolster, D.; Richter, D. H.; Vesselinov, V. V.

    2017-12-01

    When modeling reactive transport, reaction rates are often overestimated due to the improper assumption of perfect mixing at the support scale of the transport model. In reality, fronts tend to form between participants in thermodynamically favorable reactions, leading to segregation of reactants into islands or fingers. When such a configuration arises, reactions are limited to the interface between the reactive solutes. Closure methods for estimating control-volume-effective reaction rates in terms of quantities defined at the control volume scale do not presently exist, but their development is crucial for effective field-scale modeling. We attack this problem through a combination of analytical and numerical means. Specifically, we numerically study reactive transport through an ensemble of realizations of two-dimensional heterogeneous porous media. We then employ regression analysis to calibrate an analytically-derived relationship between reaction rate and various dimensionless quantities representing conductivity-field heterogeneity and the respective strengths of diffusion, reaction and advection.

  2. Rupture dynamics and ground motions from earthquakes in 2-D heterogeneous media

    KAUST Repository

    Bydlon, Samuel A.

    2015-03-21

    ©2015. American Geophysical Union. All Rights Reserved. We perform 2-D simulations of earthquakes on rough faults in media with random heterogeneities (with von Karman distribution) to study the effects of geometric and material heterogeneity on the rupture process and resulting high-frequency ground motions in the near-fault region (out to ∼20km). Variations in slip and rupture velocity can arise from material heterogeneity alone but are dominantly controlled by fault roughness. Scattering effects become appreciable beyond ∼3km from the fault. Near-fault scattering extends the duration of incoherent, high-frequency ground motions and, at least in our 2-D simulations, elevates root-mean-square accelerations (i.e., Arias intensity) with negligible reduction in peak velocities. We also demonstrate that near-fault scattering typically occurs in the power law tail of the power spectral density function, quantified by the Hurst exponent and another parameter combining standard deviation and correlation length. Key Points Fault roughness, not material heterogeneity, dominates rupture process Introduce parameter that can be used to quantify near-fault scattering Scattering affects the duration and amplitude of high-frequency ground motions

  3. Study on Two-Phase Flow in Heterogeneous Porous Media by Light Transmission Method

    Science.gov (United States)

    Qiao, W.

    2015-12-01

    The non-aqueous phase liquid (NAPL) released to the subsurface can form residual ganglia and globules occupying pores and also accumulate and form pools, in which multiphase system forms. Determining transient fluid saturations in a multiphase system is essential to understand the flow characteristics of systems and to perform effective remediation strategies. As a non-destructive and non-invasive laboratory technique utilized for the measurement of liquid saturation in porous media, light transmission is of the lowest cost and safe. Utilization of Coupled Charge Device camera in light transmission systems provides a nearly instantaneous high-density array of spatial measurements over a very large dynamic range. The migration of NAPL and air spariging technique applied to remove NAPL in aquifer systems are typically two-phase flow problem. Because of the natural aquifer normally being heterogeneous, two 2-D sandboxes (Length55cm×width1.3cm×hight45cm) are set up to study the migration of gas and DNAPL in heterogeneous porous media based on light transmission method and its application in two-phase flow. Model D for water/gas system developed by Niemet and Selker (2001) and Model NW-A for water/NAPL system developed by Zhang et al. (2014) are applied for the calculation of fluid saturation in the two experiments, respectively. The gas injection experiments show that the gas moves upward in the irregular channels, piling up beneath the low permeability lenses and starting lateral movement. Bypassing the lenses, the gas moves upward and forms continuous distribution in the top of the sandbox. The faster of gas injects, the wider of gas migration will be. The DNAPL infiltration experiment shows that TCE mainly moves downward as the influence of gravity, stopping vertical infiltration when reaching the low permeability lenses because of its failure to overcome the capillary pressure. Then, TCE accumulates on the surface and starts transverse movement. Bypassing the

  4. Simulation of density-driven flow in heterogeneous and fractured porous media

    Energy Technology Data Exchange (ETDEWEB)

    Grillo, A. [Politecnico di Torino (Italy). DISMA; Logashenko, D. [Steinbeis Research Center, Oelbronn (Germany); Stichel, S.; Wittum, G. [Frankfurt Univ., Frankfurt am Main (Germany). G-CSC

    2015-07-01

    The study of fractured porous media is an important and challenging problem in hydrogeology. One of the difficulties is that mathematical models have to account for heterogeneity introduced by fractures in hydrogeological media. Heterogeneity may strongly influence the physical processes taking place in these media. Moreover, the thickness of the fractures, which is usually negligible in comparison with the size of the whole domain, and the complicated geometry of fracture networks reduce essentially the efficiency of numerical methods. In order to overcome these difficulties, fractures are sometimes considered as objects of reduced dimensionality (surfaces in three dimensions), and the field equations are averaged along the fracture width. Fractures are assumed to be thin regions of space filled with a porous material whose properties differ from those of the porous medium enclosing them. The interfaces separating the fractures from the embedding medium are assumed to be ideal. We consider two approaches: (i) the fractures have the same dimension, d, as the embedding medium and are said to be d-dimensional; (ii) the fractures are considered as (d-1)-dimensional manifolds, and the equations of density-driven flow are found by averaging the d-dimensional laws over the fracture width. We show that the second approach is a valid alternative to the first one. For this purpose, we perform numerical experiments using a finite-volume discretization for both approaches. The results obtained by the two methods are in good agreement with each other. We derive a criterion for the validity of the simplified representation. The criterion characterizes the transition of a mainly parallel flow to a rotational flow, which cannot be reasonably approximated using a d-1 dimensional representation. We further present a numerical algorithm using adaptive dimensional representation.

  5. Generic evolution of mixing in heterogeneous media

    Science.gov (United States)

    De Dreuzy, J.; Carrera, J.; Dentz, M.; Le Borgne, T.

    2011-12-01

    Mixing in heterogeneous media results from the competition bewteen flow fluctuations and local scale diffusion. Flow fluctuations quickly create concentration contrasts and thus heterogeneity of the concentration field, which is slowly homogenized by local scale diffusion. Mixing first deviates from Gaussian mixing, which represents the potential mixing induced by spreading before approaching it. This deviation fundamentally expresses the evolution of the interaction between spreading and local scale diffusion. We characterize it by the ratio γ of the non-Gaussian to the Gaussian mixing states. We define the Gaussian mixing state as the integrated squared concentration of the Gaussian plume that has the same longitudinal dispersion as the real plume. The non-Gaussian mixing state is the difference between the overall mixing state defined as the integrated squared concentration and the Gaussian mixing state. The main advantage of this definition is to use the full knowledge previously acquired on dispersion for characterizing mixing even when the solute concentration field is highly non Gaussian. Using high precision numerical simulations, we show that γ quickly increases, peaks and slowly decreases. γ can be derived from two scales characterizing spreading and local mixing, at least for large flux-weighted solute injection conditions into classically log-normal Gaussian correlated permeability fields. The spreading scale is directly related to the longitudinal dispersion. The local mixing scale is the largest scale over which solute concentrations can be considered locally uniform. More generally, beyond the characteristics of its maximum, γ turns out to have a highly generic scaling form. Its fast increase and slow decrease depend neither on the heterogeneity level, nor on the ratio of diffusion to advection, nor on the injection conditions. They might even not depend on the particularities of the flow fields as the same generic features also prevail for

  6. Multi-level adaptive simulation of transient two-phase flow in heterogeneous porous media

    KAUST Repository

    Chueh, C.C.

    2010-10-01

    An implicit pressure and explicit saturation (IMPES) finite element method (FEM) incorporating a multi-level shock-type adaptive refinement technique is presented and applied to investigate transient two-phase flow in porous media. Local adaptive mesh refinement is implemented seamlessly with state-of-the-art artificial diffusion stabilization allowing simulations that achieve both high resolution and high accuracy. Two benchmark problems, modelling a single crack and a random porous medium, are used to demonstrate the robustness of the method and illustrate the capabilities of the adaptive refinement technique in resolving the saturation field and the complex interaction (transport phenomena) between two fluids in heterogeneous media. © 2010 Elsevier Ltd.

  7. Anomalous behaviors during infiltration into heterogeneous porous media

    Science.gov (United States)

    Aarão Reis, F. D. A.; Bolster, D.; Voller, V. R.

    2018-03-01

    Flow and transport in heterogeneous porous media often exhibit anomalous behavior. A physical analog example is the uni-directional infiltration of a viscous liquid into a horizontal oriented Hele-Shaw cell containing through thickness flow obstacles; a system designed to mimic a gravel/sand medium with impervious inclusions. When there are no obstacles present or the obstacles form a multi-repeating pattern, the change of the length of infiltration F with time t tends to follow a Fickian like scaling, F ∼t1/2 . In the presence of obstacle fields laid out as Sierpinski carpet fractals, infiltration is anomalous, i.e., F ∼ tn, n ≠ 1/2. Here, we study infiltration into such Hele-Shaw cells. First we investigate infiltration into a square cell containing one fractal carpet and make the observation that it is possible to generate both sub (n 1/2) diffusive behaviors within identical heterogeneity configurations. We show that this can be explained in terms of a scaling analysis developed from results of random-walk simulations in fractal obstacles; a result indicating that the nature of the domain boundary controls the exponent n of the resulting anomalous transport. Further, we investigate infiltration into a rectangular cell containing several repeats of a given Sierpinski carpet. At very early times, before the liquid encounters any obstacles, the infiltration is Fickian. When the liquid encounters the first (smallest scale) obstacle the infiltration sharply transitions to sub-diffusive. Subsequently, around the time where the liquid has sampled all of the heterogeneity length scales in the system, there is a rapid transition back to Fickian behavior. An explanation for this second transition is obtained by developing a simplified infiltration model based on the definition of a representative averaged hydraulic conductivity.

  8. Exact asymptotic relations for the effective response of linear viscoelastic heterogeneous media

    Science.gov (United States)

    Gallican, Valentin; Brenner, Renald; Suquet, Pierre

    2017-11-01

    This article addresses the asymptotic response of viscoelastic heterogeneous media in the frequency domain, at high and low frequencies, for different types of elementary linear viscoelastic constituents. By resorting to stationary principles for complex viscoelasticity and adopting a classification of the viscoelastic behaviours based on the nature of their asymptotic regimes, either elastic or viscous, four exact relations are obtained on the overall viscoelastic complex moduli in each case. Two relations are related to the asymptotic uncoupled heterogeneous problems, while the two remaining ones result from the viscoelastic coupling that manifests itself in the transient regime. These results also provide exact conditions on certain integrals in time of the effective relaxation spectrum. This general setting encompasses the results obtained in preceding studies on mixtures of Maxwell constituents [1,2]. xml:lang="fr"

  9. Probabilistic models for reactive behaviour in heterogeneous condensed phase media

    Science.gov (United States)

    Baer, M. R.; Gartling, D. K.; DesJardin, P. E.

    2012-02-01

    This work presents statistically-based models to describe reactive behaviour in heterogeneous energetic materials. Mesoscale effects are incorporated in continuum-level reactive flow descriptions using probability density functions (pdfs) that are associated with thermodynamic and mechanical states. A generalised approach is presented that includes multimaterial behaviour by treating the volume fraction as a random kinematic variable. Model simplifications are then sought to reduce the complexity of the description without compromising the statistical approach. Reactive behaviour is first considered for non-deformable media having a random temperature field as an initial state. A pdf transport relationship is derived and an approximate moment approach is incorporated in finite element analysis to model an example application whereby a heated fragment impacts a reactive heterogeneous material which leads to a delayed cook-off event. Modelling is then extended to include deformation effects associated with shock loading of a heterogeneous medium whereby random variables of strain, strain-rate and temperature are considered. A demonstrative mesoscale simulation of a non-ideal explosive is discussed that illustrates the joint statistical nature of the strain and temperature fields during shock loading to motivate the probabilistic approach. This modelling is derived in a Lagrangian framework that can be incorporated in continuum-level shock physics analysis. Future work will consider particle-based methods for a numerical implementation of this modelling approach.

  10. Geological entropy and solute transport in heterogeneous porous media

    Science.gov (United States)

    Bianchi, Marco; Pedretti, Daniele

    2017-06-01

    We propose a novel approach to link solute transport behavior to the physical heterogeneity of the aquifer, which we fully characterize with two measurable parameters: the variance of the log K values (σY2), and a new indicator (HR) that integrates multiple properties of the K field into a global measure of spatial disorder or geological entropy. From the results of a detailed numerical experiment considering solute transport in K fields representing realistic distributions of hydrofacies in alluvial aquifers, we identify empirical relationship between the two parameters and the first three central moments of the distributions of arrival times of solute particles at a selected control plane. The analysis of experimental data indicates that the mean and the variance of the solutes arrival times tend to increase with spatial disorder (i.e., HR increasing), while highly skewed distributions are observed in more orderly structures (i.e., HR decreasing) or at higher σY2. We found that simple closed-form empirical expressions of the bivariate dependency of skewness on HR and σY2 can be used to predict the emergence of non-Fickian transport in K fields considering a range of structures and heterogeneity levels, some of which based on documented real aquifers. The accuracy of these predictions and in general the results from this study indicate that a description of the global variability and structure of the K field in terms of variance and geological entropy offers a valid and broadly applicable approach for the interpretation and prediction of transport in heterogeneous porous media.

  11. Numerical simulation of the impact of water-air fronts on radionuclides plumes in heterogeneous media

    International Nuclear Information System (INIS)

    Aquino, J.; Francisco, A.S.; Pereira, F.; Amaral Souto, H.P.

    2004-01-01

    The goal of this paper is to investigate the interaction of water-air fronts with radionuclide plumes in unsaturated heterogeneous porous media. This problem is modeled by a system of equations that describes both the water-air flow and the radionuclide transport. The water-air problem is solved numerically by a mixed finite element combined with a non-oscillatory central difference scheme. For the radionuclide transport equation we use the Modified Method of Characteristics (MMOC). We present the results of numerical simulations for heterogeneous permeability fields taking into account sorption effects. (author)

  12. Inertial Effects on Flow and Transport in Heterogeneous Porous Media.

    Science.gov (United States)

    Nissan, Alon; Berkowitz, Brian

    2018-02-02

    We investigate the effects of high fluid velocities on flow and tracer transport in heterogeneous porous media. We simulate fluid flow and advective transport through two-dimensional pore-scale matrices with varying structural complexity. As the Reynolds number increases, the flow regime transitions from linear to nonlinear; this behavior is controlled by the medium structure, where higher complexity amplifies inertial effects. The result is, nonintuitively, increased homogenization of the flow field, which leads in the context of conservative chemical transport to less anomalous behavior. We quantify the transport patterns via a continuous time random walk, using the spatial distribution of the kinetic energy within the fluid as a characteristic measure.

  13. Three-phase flow in heterogeneous wettability porous media; Deplacements triphasiques en milieux poreux de mouillabilite heterogene

    Energy Technology Data Exchange (ETDEWEB)

    Jaffrennou-Laroche, C

    1998-11-26

    Better understanding and modelling of three-phase flow through porous media is of great interest, especially for improved oil recovery methods such as gas injection processes. Early theoretical and experimental studies have already demonstrated that the wettability characteristics of the solid surface and the spreading characteristics of the fluid system hold the key roles. This observation is confirmed by our theoretical results using DLP theory on the stability and the thickness of static oil films. In most of the works related to three-phase flow processes, homogeneous wettability is assumed. There exist only a few studies demonstrating the tremendous impact of the wettability heterogeneities on gas injection. The objective of the present work is twofold: to demonstrate the effect of small scale wettability heterogeneities on gas injection efficiency, and to develop a tool to predict this impact for various patterns and spatial distributions. To this end an experimental investigation in transparent glass micro-models is performed and a theoretical simulator is developed. Secondary and tertiary gas injections are performed for different heterogeneity patterns obtained by selective silane grafting. Displacement sequences are video-recorded and fluid saturations are determined by image analysis. Visualization of the displacement mechanisms provides the network model with the basic rules for water/oil and water/oil/gas motion. In water/oil displacement, drainage and imbibition occur according to the local wettability. Three-phase displacement is dominated by drainage mechanisms. The simulator allows the flow of oil through wetting films in the oil-wet regions and through spreading films on water in the water-wet regions. The effect of the wettability heterogeneities on: displacement mechanisms, sweep efficiency, and fluid distribution in three-phase gas injection is clearly demonstrated and successfully described by the network simulator. (author) 175 refs.

  14. Reactive solute transport in physically and chemically heterogeneous porous media with multimodal reactive mineral facies: the Lagrangian approach.

    Science.gov (United States)

    Soltanian, Mohamad Reza; Ritzi, Robert W; Dai, Zhenxue; Huang, Chao Cheng

    2015-03-01

    Physical and chemical heterogeneities have a large impact on reactive transport in porous media. Examples of heterogeneous attributes affecting reactive mass transport are the hydraulic conductivity (K), and the equilibrium sorption distribution coefficient (Kd). This paper uses the Deng et al. (2013) conceptual model for multimodal reactive mineral facies and a Lagrangian-based stochastic theory in order to analyze the reactive solute dispersion in three-dimensional anisotropic heterogeneous porous media with hierarchical organization of reactive minerals. An example based on real field data is used to illustrate the time evolution trends of reactive solute dispersion. The results show that the correlation between the hydraulic conductivity and the equilibrium sorption distribution coefficient does have a significant effect on reactive solute dispersion. The anisotropy ratio does not have a significant effect on reactive solute dispersion. Furthermore, through a sensitivity analysis we investigate the impact of changing the mean, variance, and integral scale of K and Kd on reactive solute dispersion. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Multiscale Adapted Time-Splitting Technique for Nonisothermal Two-Phase Flow and Nanoparticles Transport in Heterogenous Porous Media

    KAUST Repository

    El-Amin, Mohamed F.; Kou, Jisheng; Sun, Shuyu

    2017-01-01

    This paper is devoted to study the problem of nonisothermal two-phase flow with nanoparticles transport in heterogenous porous media, numerically. For this purpose, we introduce a multiscale adapted time-splitting technique to simulate the problem

  16. Geotrap: radionuclide migration in geologic, heterogeneous media. Summary of accomplishments

    International Nuclear Information System (INIS)

    2002-01-01

    GEOTRAP - the OECD/NEA Project on Radionuclide Migration in Geologic, Heterogeneous Media - was carried out in the context of site evaluation and safety assessment of deep repository systems for long-lived radioactive waste. The project was created in 1996 with the aim of developing an understanding of, and modelling capability for, potential radionuclide migration. This report provides an overview of the project's main findings and accomplishments over its five-year life. This summary should help make the valuable information collected and generated by the GEOTRAP project accessible to a wide readership both within and outside the radioactive waste community.It is a reflection of the careful attention paid by this community to the question of radionuclide transport. (authors)

  17. On the interpretation of double-packer tests in heterogeneous porous media: Numerical simulations using the stochastic continuum analogue

    International Nuclear Information System (INIS)

    Follin, S.

    1992-12-01

    Flow in fractured crystalline (hard) rocks is of interest in Sweden for assessing the postclosure radiological safety of a deep repository for high-level nuclear waste. For simulation of flow and mass transport in the far field different porous media concepts are often used, whereas discrete fracture/channel network concepts are often used for near-field simulations. Due to lack of data, it is generally necessary to have resort to single-hole double-packer test data for the far-field simulations, i.e., test data on a small scale are regularized in order to fit a comparatively coarser numerical discretization, which is governed by various computational constraints. In the present study the Monte Carlo method is used to investigate the relationship between the transmissivity value interpreted and the corresponding radius of influence in conjunction with single-hole double-packer tests in heterogeneous formations. The numerical flow domain is treated as a two-dimensional heterogeneous porous medium with a spatially varying diffusivity on 3 m scale. The Monte Carlo simulations demonstrate the sensitivity to the correlation range of a spatially varying diffusivity field. In contradiction to what is tacitly assumed in stochastic subsurface hydrology, the results show that the lateral support scale (e.g., the radius of influence) of transmissivity measurements in heterogeneous porous media is a random variable, which is affected by both the hydraulic and statistical characteristics. If these results are general, the traditional methods for scaling-up, assuming a constant lateral scale of support and a multi normal distribution, may lead to an underestimation of the persistence and connectivity of transmissive zones, particularly in highly heterogeneous porous media

  18. Inverse radiative transfer problems in two-dimensional heterogeneous media; Problemas inversos em transferencia radiativa em meios heterogeneos bidimensionais

    Energy Technology Data Exchange (ETDEWEB)

    Tito, Mariella Janette Berrocal

    2001-01-01

    The analysis of inverse problems in participating media where emission, absorption and scattering take place has several relevant applications in engineering and medicine. Some of the techniques developed for the solution of inverse problems have as a first step the solution of the direct problem. In this work the discrete ordinates method has been used for the solution of the linearized Boltzmann equation in two dimensional cartesian geometry. The Levenberg - Marquardt method has been used for the solution of the inverse problem of internal source and absorption and scattering coefficient estimation. (author)

  19. La obesidad en las personas mayores, un problema de salud pública

    OpenAIRE

    Abellán García, Antonio

    2016-01-01

    La obesidad es un serio problema de salud pública. Se suele medir utilizando el Índice de Masa Corporal. En España, un 23,6% de las personas mayores (65 y más años) tiene obesidad, y otro 45,0% sobrepeso, según la última Encuesta Europea de Salud (2014). Sólo un 30,0% está en un peso normal. En el resto de adultos también se observa esta circunstancia. Es decir, en España existe un problema de sobrepeso y obesidad, especialmente entre los mayores y estas cifras son peores que la media de la ...

  20. On the validity of effective formulations for transport through heterogeneous porous media

    Science.gov (United States)

    de Dreuzy, Jean-Raynald; Carrera, Jesus

    2016-04-01

    Geological heterogeneity enhances spreading of solutes and causes transport to be anomalous (i.e., non-Fickian), with much less mixing than suggested by dispersion. This implies that modeling transport requires adopting either stochastic approaches that model heterogeneity explicitly or effective transport formulations that acknowledge the effects of heterogeneity. A number of such formulations have been developed and tested as upscaled representations of enhanced spreading. However, their ability to represent mixing has not been formally tested, which is required for proper reproduction of chemical reactions and which motivates our work. We propose that, for an effective transport formulation to be considered a valid representation of transport through heterogeneous porous media (HPM), it should honor mean advection, mixing and spreading. It should also be flexible enough to be applicable to real problems. We test the capacity of the multi-rate mass transfer (MRMT) model to reproduce mixing observed in HPM, as represented by the classical multi-Gaussian log-permeability field with a Gaussian correlation pattern. Non-dispersive mixing comes from heterogeneity structures in the concentration fields that are not captured by macrodispersion. These fine structures limit mixing initially, but eventually enhance it. Numerical results show that, relative to HPM, MRMT models display a much stronger memory of initial conditions on mixing than on dispersion because of the sensitivity of the mixing state to the actual values of concentration. Because MRMT does not restitute the local concentration structures, it induces smaller non-dispersive mixing than HPM. However long-lived trapping in the immobile zones may sustain the deviation from dispersive mixing over much longer times. While spreading can be well captured by MRMT models, in general non-dispersive mixing cannot.

  1. Up scaling two-phase flow in heterogeneous porous media; Mise a l'echelle des ecoulements diphasiques dans les milieux poreux heterogenes

    Energy Technology Data Exchange (ETDEWEB)

    Artus, V.

    2003-11-01

    For two-phase flow in heterogeneous media, the emergence of different flow regimes at large-scale is driven by local interactions between the viscous coupling and the heterogeneity. In particular, when the viscosity ratio is favorable, viscous effects induce a transverse flow that stabilizes the front while flooding. However, most of recent stochastic models neglect the influence of the viscous coupling. We developed a stochastic model for the dynamics of the front, taking the viscous coupling into account. For stable cases, this model relates the statistical properties of the front to the statistical properties of the permeability field. For stable flow in stratified media, we show that the front is stationary by parts in the reservoir. These parts can be identified as large-scale hydrodynamic layers and separately coarsened in the large-scale simulation model. For flows with favorable viscosity ratios in isotropic reservoirs, we show that a stationary front occurs, in a statistical sense. For unfavorable viscosity ratios, the flow is driven by the development of viscous fingering. These different regimes lead to different large-scale saturation profiles that can be matched with a macro-dispersion equation, if the effective convective flux is modified to take into account stabilizing or destabilizing viscous effects. (author)

  2. Flexibilidad Cognitiva para Resolver Problemas entre Pares ¿Difiere esta Capacidad en Escolares de Contextos Urbanos y Urbanomarginales?

    Directory of Open Access Journals (Sweden)

    Silvina Laura Maddio

    2010-01-01

    Full Text Available La flexibilidad cognitiva para solucionar problemas interpersonales implica: generar respuestas con control inhibitorio funcional y considerar las consecuencias positivas en todas las personas. Se aplicó este concepto a los problemas entre pares, éstos conllevan emociones negativas, agresiones y rechazo (Bukowski, Hoza, & Boiven, 1993; Feldman, Rubenstein, & Rubin, 1988; Moreno, 2007. Objetivos: definir y comparar la flexibilidad cognitiva para solucionar problemas entre pares en niños de escuelas urbanas y urbanomarginales y describir sus características socioculturales. Estudio: empírico, transversal- descriptivo. Muestra: 120 escolares de 8 años de escuelas estatales de Argentina, n=60 (urbana y n=60 (urbanomarginal. Análisis de datos: Prueba t de diferencia entre medias (muestras independientes. Los resultados mostraron diferencias significativas en respuestas de flexibilidad cognitiva media e irrelevantes. Se aporta al diseño de programas para promover comportamientos socialmente competentes, bienestar y paz en niños/as.

  3. An ensemble heterogeneous classification methodology for discovering health-related knowledge in social media messages.

    Science.gov (United States)

    Tuarob, Suppawong; Tucker, Conrad S; Salathe, Marcel; Ram, Nilam

    2014-06-01

    The role of social media as a source of timely and massive information has become more apparent since the era of Web 2.0.Multiple studies illustrated the use of information in social media to discover biomedical and health-related knowledge.Most methods proposed in the literature employ traditional document classification techniques that represent a document as a bag of words.These techniques work well when documents are rich in text and conform to standard English; however, they are not optimal for social media data where sparsity and noise are norms.This paper aims to address the limitations posed by the traditional bag-of-word based methods and propose to use heterogeneous features in combination with ensemble machine learning techniques to discover health-related information, which could prove to be useful to multiple biomedical applications, especially those needing to discover health-related knowledge in large scale social media data.Furthermore, the proposed methodology could be generalized to discover different types of information in various kinds of textual data. Social media data is characterized by an abundance of short social-oriented messages that do not conform to standard languages, both grammatically and syntactically.The problem of discovering health-related knowledge in social media data streams is then transformed into a text classification problem, where a text is identified as positive if it is health-related and negative otherwise.We first identify the limitations of the traditional methods which train machines with N-gram word features, then propose to overcome such limitations by utilizing the collaboration of machine learning based classifiers, each of which is trained to learn a semantically different aspect of the data.The parameter analysis for tuning each classifier is also reported. Three data sets are used in this research.The first data set comprises of approximately 5000 hand-labeled tweets, and is used for cross validation of the

  4. Nonlinear Poisson equation for heterogeneous media.

    Science.gov (United States)

    Hu, Langhua; Wei, Guo-Wei

    2012-08-22

    The Poisson equation is a widely accepted model for electrostatic analysis. However, the Poisson equation is derived based on electric polarizations in a linear, isotropic, and homogeneous dielectric medium. This article introduces a nonlinear Poisson equation to take into consideration of hyperpolarization effects due to intensive charges and possible nonlinear, anisotropic, and heterogeneous media. Variational principle is utilized to derive the nonlinear Poisson model from an electrostatic energy functional. To apply the proposed nonlinear Poisson equation for the solvation analysis, we also construct a nonpolar solvation energy functional based on the nonlinear Poisson equation by using the geometric measure theory. At a fixed temperature, the proposed nonlinear Poisson theory is extensively validated by the electrostatic analysis of the Kirkwood model and a set of 20 proteins, and the solvation analysis of a set of 17 small molecules whose experimental measurements are also available for a comparison. Moreover, the nonlinear Poisson equation is further applied to the solvation analysis of 21 compounds at different temperatures. Numerical results are compared to theoretical prediction, experimental measurements, and those obtained from other theoretical methods in the literature. A good agreement between our results and experimental data as well as theoretical results suggests that the proposed nonlinear Poisson model is a potentially useful model for electrostatic analysis involving hyperpolarization effects. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  5. Global-local nonlinear model reduction for flows in heterogeneous porous media

    KAUST Repository

    AlOtaibi, Manal; Calo, Victor M.; Efendiev, Yalchin R.; Galvis, Juan; Ghommem, Mehdi

    2015-01-01

    In this paper, we combine discrete empirical interpolation techniques, global mode decomposition methods, and local multiscale methods, such as the Generalized Multiscale Finite Element Method (GMsFEM), to reduce the computational complexity associated with nonlinear flows in highly-heterogeneous porous media. To solve the nonlinear governing equations, we employ the GMsFEM to represent the solution on a coarse grid with multiscale basis functions and apply proper orthogonal decomposition on a coarse grid. Computing the GMsFEM solution involves calculating the residual and the Jacobian on a fine grid. As such, we use local and global empirical interpolation concepts to circumvent performing these computations on the fine grid. The resulting reduced-order approach significantly reduces the flow problem size while accurately capturing the behavior of fully-resolved solutions. We consider several numerical examples of nonlinear multiscale partial differential equations that are numerically integrated using fully-implicit time marching schemes to demonstrate the capability of the proposed model reduction approach to speed up simulations of nonlinear flows in high-contrast porous media.

  6. Global-local nonlinear model reduction for flows in heterogeneous porous media

    KAUST Repository

    AlOtaibi, Manal

    2015-08-01

    In this paper, we combine discrete empirical interpolation techniques, global mode decomposition methods, and local multiscale methods, such as the Generalized Multiscale Finite Element Method (GMsFEM), to reduce the computational complexity associated with nonlinear flows in highly-heterogeneous porous media. To solve the nonlinear governing equations, we employ the GMsFEM to represent the solution on a coarse grid with multiscale basis functions and apply proper orthogonal decomposition on a coarse grid. Computing the GMsFEM solution involves calculating the residual and the Jacobian on a fine grid. As such, we use local and global empirical interpolation concepts to circumvent performing these computations on the fine grid. The resulting reduced-order approach significantly reduces the flow problem size while accurately capturing the behavior of fully-resolved solutions. We consider several numerical examples of nonlinear multiscale partial differential equations that are numerically integrated using fully-implicit time marching schemes to demonstrate the capability of the proposed model reduction approach to speed up simulations of nonlinear flows in high-contrast porous media.

  7. Pore-scale simulations of concentration tails in heterogeneous porous media

    Science.gov (United States)

    Di Palma, Paolo Roberto; Parmigiani, Andrea; Huber, Christian; Guyennon, Nicolas; Viotti, Paolo

    2017-10-01

    The retention of contaminants in the finest and less-conductive regions of natural aquifer is known to strongly affect the decontamination of polluted aquifers. In fact, contaminant transfer from low to high mobility regions at the back end of a contaminant plume (i.e. back diffusion) is responsible for the long-term release of contaminants during remediation operation. In this paper, we perform pore-scale calculations for the transport of contaminant through heterogeneous porous media composed of low and high mobility regions with two objectives: (i) study the effect of permeability contrast and solute transport conditions on the exchange of solutes between mobile and immobile regions and (ii) estimate the mass of contaminants sequestered in low mobility regions based on concentration breakthrough curves.

  8. Determination of optical properties in heterogeneous turbid media using a cylindrical diffusing fiber

    International Nuclear Information System (INIS)

    Dimofte, Andreea; Finlay, Jarod C; Liang Xing; Zhu, Timothy C

    2012-01-01

    For interstitial photodynamic therapy (PDT), cylindrical diffusing fibers (CDFs) are often used to deliver light. This study examines the feasibility and accuracy of using CDFs to characterize the absorption (μ a ) and reduced scattering (μ′ s ) coefficients of heterogeneous turbid media. Measurements were performed in tissue-simulating phantoms with μ a between 0.1 and 1 cm −1 and μ′ s between 3 and 10 cm −1 with CDFs 2 to 4 cm in length. Optical properties were determined by fitting the measured light fluence rate profiles at a fixed distance from the CDF axis using a heterogeneous kernel model in which the cylindrical diffusing fiber is treated as a series of point sources. The resulting optical properties were compared with independent measurement using a point source method. In a homogenous medium, we are able to determine the absorption coefficient μ a using a value of μ′ s determined a priori (uniform fit) or μ′ s obtained by fitting (variable fit) with standard (maximum) deviations of 6% (18%) and 18% (44%), respectively. However, the CDF method is found to be insensitive to variations in μ′ s , thus requiring a complementary method such as using a point source for determination of μ′ s . The error for determining μ a decreases in very heterogeneous turbid media because of the local absorption extremes. The data acquisition time for obtaining the one-dimensional optical properties distribution is less than 8 s. This method can result in dramatically improved accuracy of light fluence rate calculation for CDFs for prostate PDT in vivo when the same model and geometry is used for forward calculations using the extrapolated tissue optical properties. (paper)

  9. Fluid-driven fracture propagation in heterogeneous media: Probability distributions of fracture trajectories.

    Science.gov (United States)

    Santillán, David; Mosquera, Juan-Carlos; Cueto-Felgueroso, Luis

    2017-11-01

    Hydraulic fracture trajectories in rocks and other materials are highly affected by spatial heterogeneity in their mechanical properties. Understanding the complexity and structure of fluid-driven fractures and their deviation from the predictions of homogenized theories is a practical problem in engineering and geoscience. We conduct a Monte Carlo simulation study to characterize the influence of heterogeneous mechanical properties on the trajectories of hydraulic fractures propagating in elastic media. We generate a large number of random fields of mechanical properties and simulate pressure-driven fracture propagation using a phase-field model. We model the mechanical response of the material as that of an elastic isotropic material with heterogeneous Young modulus and Griffith energy release rate, assuming that fractures propagate in the toughness-dominated regime. Our study shows that the variance and the spatial covariance of the mechanical properties are controlling factors in the tortuousness of the fracture paths. We characterize the deviation of fracture paths from the homogenous case statistically, and conclude that the maximum deviation grows linearly with the distance from the injection point. Additionally, fracture path deviations seem to be normally distributed, suggesting that fracture propagation in the toughness-dominated regime may be described as a random walk.

  10. Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Kai, E-mail: kaigao87@gmail.com [Department of Geology and Geophysics, Texas A& M University, College Station, TX 77843 (United States); Fu, Shubin, E-mail: shubinfu89@gmail.com [Department of Mathematics, Texas A& M University, College Station, TX 77843 (United States); Gibson, Richard L., E-mail: gibson@tamu.edu [Department of Geology and Geophysics, Texas A& M University, College Station, TX 77843 (United States); Chung, Eric T., E-mail: tschung@math.cuhk.edu.hk [Department of Mathematics, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Efendiev, Yalchin, E-mail: efendiev@math.tamu.edu [Department of Mathematics, Texas A& M University, College Station, TX 77843 (United States); Numerical Porous Media SRI Center (NumPor), King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)

    2015-08-15

    It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as finite-difference method and finite-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional finite-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the elastic wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.

  11. Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media

    International Nuclear Information System (INIS)

    Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin

    2015-01-01

    It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as finite-difference method and finite-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional finite-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the elastic wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system

  12. Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media

    KAUST Repository

    Gao, Kai

    2015-04-14

    It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as finite-difference method and finite-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both boundaries and the interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional finite-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the elastic wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.

  13. Discontinuous finite elements applied to solution of problems about heat transfer in heterogeneous media

    International Nuclear Information System (INIS)

    Ferreira, Monica Barcellos Jansen; Carmo, Eduardo Gomes Dutra do

    2000-01-01

    Heat transfer problems in heterogenous media with large variation of thermal conductivity are notorious for the difficulties in obtaining good numerical results. In this work it is proposed an application of a new mixed discontinuous finite element formulation to this class of problems, which produces good results without the need of high mesh refinement. Stability and consistency aspects are considered and numerical results are presented to show the efficacy of the method. (author)

  14. Lattice Boltzmann simulation of immiscible fluid displacement in porous media: Homogeneous versus heterogeneous pore network

    International Nuclear Information System (INIS)

    Liu, Haihu; Zhang, Yonghao; Valocchi, Albert J.

    2015-01-01

    Injection of anthropogenic carbon dioxide (CO 2 ) into geological formations is a promising approach to reduce greenhouse gas emissions into the atmosphere. Predicting the amount of CO 2 that can be captured and its long-term storage stability in subsurface requires a fundamental understanding of multiphase displacement phenomena at the pore scale. In this paper, the lattice Boltzmann method is employed to simulate the immiscible displacement of a wetting fluid by a non-wetting one in two microfluidic flow cells, one with a homogeneous pore network and the other with a randomly heterogeneous pore network. We have identified three different displacement patterns, namely, stable displacement, capillary fingering, and viscous fingering, all of which are strongly dependent upon the capillary number (Ca), viscosity ratio (M), and the media heterogeneity. The non-wetting fluid saturation (S nw ) is found to increase nearly linearly with logCa for each constant M. Increasing M (viscosity ratio of non-wetting fluid to wetting fluid) or decreasing the media heterogeneity can enhance the stability of the displacement process, resulting in an increase in S nw . In either pore networks, the specific interfacial length is linearly proportional to S nw during drainage with equal proportionality constant for all cases excluding those revealing considerable viscous fingering. Our numerical results confirm the previous experimental finding that the steady state specific interfacial length exhibits a linear dependence on S nw for either favorable (M ≥ 1) or unfavorable (M < 1) displacement, and the slope is slightly higher for the unfavorable displacement

  15. Lattice Boltzmann simulation of immiscible fluid displacement in porous media: Homogeneous versus heterogeneous pore network

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haihu, E-mail: haihu.liu@mail.xjtu.edu.cn [School of Energy and Power Engineering, Xi’an Jiaotong University, 28 West Xianning Road, Xi’an 710049 (China); James Weir Fluids Laboratory, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Zhang, Yonghao [James Weir Fluids Laboratory, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Valocchi, Albert J. [Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2015-05-15

    Injection of anthropogenic carbon dioxide (CO{sub 2}) into geological formations is a promising approach to reduce greenhouse gas emissions into the atmosphere. Predicting the amount of CO{sub 2} that can be captured and its long-term storage stability in subsurface requires a fundamental understanding of multiphase displacement phenomena at the pore scale. In this paper, the lattice Boltzmann method is employed to simulate the immiscible displacement of a wetting fluid by a non-wetting one in two microfluidic flow cells, one with a homogeneous pore network and the other with a randomly heterogeneous pore network. We have identified three different displacement patterns, namely, stable displacement, capillary fingering, and viscous fingering, all of which are strongly dependent upon the capillary number (Ca), viscosity ratio (M), and the media heterogeneity. The non-wetting fluid saturation (S{sub nw}) is found to increase nearly linearly with logCa for each constant M. Increasing M (viscosity ratio of non-wetting fluid to wetting fluid) or decreasing the media heterogeneity can enhance the stability of the displacement process, resulting in an increase in S{sub nw}. In either pore networks, the specific interfacial length is linearly proportional to S{sub nw} during drainage with equal proportionality constant for all cases excluding those revealing considerable viscous fingering. Our numerical results confirm the previous experimental finding that the steady state specific interfacial length exhibits a linear dependence on S{sub nw} for either favorable (M ≥ 1) or unfavorable (M < 1) displacement, and the slope is slightly higher for the unfavorable displacement.

  16. 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.

  17. Problemas de matemáticas

    OpenAIRE

    Usunáriz Balanzategui, Ubaldo; Usunáriz Sala, Ignacio

    2012-01-01

    Este libro, Problemas de Matemáticas, junto con otros dos, Problemas de Geometría y Problemas de Geometría Analítica y Diferencial, están dedicados a la presentación y resolución de problemas que se planteaban hace unas décadas, en la preparación para ingreso en las carreras de ingeniería técnica superior. Incluye 1578 problemas, de los que 848 se refieren al Álgebra (operaciones algebraicas, divisibilidad, combinatoria, determinantes, ecuaciones e inecuaciones, fracciones continuas, números ...

  18. The analytical solution to the 1D diffusion equation in heterogeneous media

    International Nuclear Information System (INIS)

    Ganapol, B.D.; Nigg, D.W.

    2011-01-01

    The analytical solution to the time-independent multigroup diffusion equation in heterogeneous plane cylindrical and spherical media is presented. The solution features the simplicity of the one-group formulation while addressing the complication of multigroup diffusion in a fully heterogeneous medium. Beginning with the vector form of the diffusion equation, the approach, based on straightforward mathematics, resolves a set of coupled second order ODEs. The analytical form is facilitated through matrix diagonalization of the neutron interaction matrix rendering the multigroup solution as a series of one-group solutions which, when re-assembled, gives the analytical solution. Customized Eigenmode solutions of the one-group diffusion operator then represent the homogeneous solution in a uniform spatial domain. Once the homogeneous solution is known, the particular solution naturally emerges through variation of parameters. The analytical expression is then numerically implemented through recurrence. Finally, we apply the theory to assess the accuracy of a second order finite difference scheme and to a 1D slab BWR reactor in the four-group approximation. (author)

  19. A discrete model for compressible flows in heterogeneous media

    International Nuclear Information System (INIS)

    Le Metayer, O.; Massol, A.; Favrie, N.; Hank, S.

    2011-01-01

    This work deals with the building of a discrete model able to describe and to predict the evolution of complex gas flows in heterogeneous media. In many physical applications, large scales numerical simulation is no longer possible because of a lack of computing resources. Indeed the medium topology may be complex due to the presence of many obstacles (walls, pipes, equipments, geometric singularities etc.). Aircraft powerplant compartments are examples where topology is complex due to the presence of pipes, ducts, coolers and other equipment. Other important examples are gas explosions and large scale dispersion of hazardous materials in urban places, cities or underground involving obstacles such as buildings and various infrastructures. In all cases efficient safety responses are required. Then a new discrete model is built and solved in reasonable execution times for large cells volumes including such obstacles. Quantitative comparisons between experimental and numerical results are shown for different significant test cases, showing excellent agreement.

  20. Transport of Cryptosporidium parvum Oocysts in Charge Heterogeneous Porous Media: Microfluidics Experiment and Numerical Simulation

    Science.gov (United States)

    Liu, Y.; Meng, X.; Guo, Z.; Zhang, C.; Nguyen, T. H.; Hu, D.; Ji, J.; Yang, X.

    2017-12-01

    Colloidal attachment on charge heterogeneous grains has significant environmental implications for transport of hazardous colloids, such as pathogens, in the aquifer, where iron, manganese, and aluminium oxide minerals are the major source of surface charge heterogeneity of the aquifer grains. A patchwise surface charge model is often used to describe the surface charge heterogeneity of the grains. In the patchwise model, the colloidal attachment efficiency is linearly correlated with the fraction of the favorable patches (θ=λ(θf - θu)+θu). However, our previous microfluidic study showed that the attachment efficiency of oocysts of Cryptosporidium parvum, a waterborne protozoan parasite, was not linear correlated with the fraction of the favorable patches (λ). In this study, we developed a pore scale model to simulate colloidal transport and attachment on charge heterogeneous grains. The flow field was simulated using the LBM method and colloidal transport and attachment were simulated using the Lagrange particle tracking method. The pore scale model was calibrated with experimental results of colloidal and oocyst transport in microfluidic devices and was then used to simulate oocyst transport in charge heterogeneous porous media under a variety of environmental relative conditions, i.e. the fraction of favorable patchwise, ionic strength, and pH. The results of the pore scale simulations were used to evaluate the effect of surface charge heterogeneity on upscaling of oocyst transport from pore to continuum scale and to develop an applicable correlation between colloidal attachment efficiency and the fraction of the favorable patches.

  1. Spectral-element simulation of two-dimensional elastic wave propagation in fully heterogeneous media on a GPU cluster

    Science.gov (United States)

    Rudianto, Indra; Sudarmaji

    2018-04-01

    We present an implementation of the spectral-element method for simulation of two-dimensional elastic wave propagation in fully heterogeneous media. We have incorporated most of realistic geological features in the model, including surface topography, curved layer interfaces, and 2-D wave-speed heterogeneity. To accommodate such complexity, we use an unstructured quadrilateral meshing technique. Simulation was performed on a GPU cluster, which consists of 24 core processors Intel Xeon CPU and 4 NVIDIA Quadro graphics cards using CUDA and MPI implementation. We speed up the computation by a factor of about 5 compared to MPI only, and by a factor of about 40 compared to Serial implementation.

  2. Algoritmos para problemas de empacotamento

    OpenAIRE

    Eduardo Candido Xavier

    2006-01-01

    Resumo: Neste trabalho estudamos diversos problemas de empacotamento considerados NP-difíceis. Assumindo a hipótese de que P ? NP, sabemos que não existem algoritmos eficientes (complexidade de tempo polinomial) exatos para resolver tais problemas. Uma das abordagens consideradas para tratar tais problemas é a de algoritmos de aproximação, que são algoritmos eficientes e que geram soluções com garantia de qualidade. Neste trabalho apresentamos alguns algoritmos aproximados para problemas de e...

  3. Flow of miscible and immiscible hydrocarbons in heterogeneous porous media

    Energy Technology Data Exchange (ETDEWEB)

    Butts, M.B.

    1996-12-31

    A series of large-scale two-dimensional physical model studies has been carried out in order to better understand and predict the multiphase flow of hydrocarbon contaminants and the release of the water-soluble fraction of such contaminants into the groundwater stream. The detailed measurements of the fluid saturations within the bulk hydrocarbon plume as well as the aqueous concentrations recorded downstream should provide a useful data set for testing and improving numerical models of both multiphase flow and transport. Predictions of a numerical model of immiscible multiphase flow developed in the petroleum industry were found to compare favourably with the observed oil plume for the case of an immiscible oil spill. Nevertheless, subtle layering within the experimental flume altered the long-term development of the oil plume in a manner not predicted by the numerical model. A stochastic model for three-dimensional, two-phase incompressible flow in heterogeneous soil and rock formations is developed. Analytical solutions for the resulting stochastic differential equations are derived for asymptotic flows using a perturbation approach. These solutions were used to derive general expressions for the large-scale (effective) properties for large-scale two-phase flow in porous media. An important observation from this analysis is that general large-scale flow in heterogeneous soils cannot be predicted on the basis of simple averages of the soil hydraulic properties alone. The large-scale capillary pressure saturation relation is evaluated for imbibition into a wet soil or rock formation. (EG) 194 refs.

  4. Flow of miscible and immiscible hydrocarbons in heterogeneous porous media

    Energy Technology Data Exchange (ETDEWEB)

    Butts, M B

    1997-12-31

    A series of large-scale two-dimensional physical model studies has been carried out in order to better understand and predict the multiphase flow of hydrocarbon contaminants and the release of the water-soluble fraction of such contaminants into the groundwater stream. The detailed measurements of the fluid saturations within the bulk hydrocarbon plume as well as the aqueous concentrations recorded downstream should provide a useful data set for testing and improving numerical models of both multiphase flow and transport. Predictions of a numerical model of immiscible multiphase flow developed in the petroleum industry were found to compare favourably with the observed oil plume for the case of an immiscible oil spill. Nevertheless, subtle layering within the experimental flume altered the long-term development of the oil plume in a manner not predicted by the numerical model. A stochastic model for three-dimensional, two-phase incompressible flow in heterogeneous soil and rock formations is developed. Analytical solutions for the resulting stochastic differential equations are derived for asymptotic flows using a perturbation approach. These solutions were used to derive general expressions for the large-scale (effective) properties for large-scale two-phase flow in porous media. An important observation from this analysis is that general large-scale flow in heterogeneous soils cannot be predicted on the basis of simple averages of the soil hydraulic properties alone. The large-scale capillary pressure saturation relation is evaluated for imbibition into a wet soil or rock formation. (EG) 194 refs.

  5. Multiscale Lattice Boltzmann method for flow simulations in highly heterogenous porous media

    KAUST Repository

    Li, Jun

    2013-01-01

    A lattice Boltzmann method (LBM) for flow simulations in highly heterogeneous porous media at both pore and Darcy scales is proposed in the paper. In the pore scale simulations, flow of two phases (e.g., oil and gas) or two immiscible fluids (e.g., water and oil) are modeled using cohesive or repulsive forces, respectively. The relative permeability can be computed using pore-scale simulations and seamlessly applied for intermediate and Darcy-scale simulations. A multiscale LBM that can reduce the computational complexity of existing LBM and transfer the information between different scales is implemented. The results of coarse-grid, reduced-order, simulations agree very well with the averaged results obtained using fine grid.

  6. Simulation of DNAPL migration in heterogeneous translucent porous media based on estimation of representative elementary volume

    Science.gov (United States)

    Wu, Ming; Wu, Jianfeng; Wu, Jichun

    2017-10-01

    When the dense nonaqueous phase liquid (DNAPL) comes into the subsurface environment, its migration behavior is crucially affected by the permeability and entry pressure of subsurface porous media. A prerequisite for accurately simulating DNAPL migration in aquifers is then the determination of the permeability, entry pressure and corresponding representative elementary volumes (REV) of porous media. However, the permeability, entry pressure and corresponding representative elementary volumes (REV) are hard to determine clearly. This study utilizes the light transmission micro-tomography (LTM) method to determine the permeability and entry pressure of two dimensional (2D) translucent porous media and integrates the LTM with a criterion of relative gradient error to quantify the corresponding REV of porous media. As a result, the DNAPL migration in porous media might be accurately simulated by discretizing the model at the REV dimension. To validate the quantification methods, an experiment of perchloroethylene (PCE) migration is conducted in a two-dimensional heterogeneous bench-scale aquifer cell. Based on the quantifications of permeability, entry pressure and REV scales of 2D porous media determined by the LTM and relative gradient error, different models with different sizes of discretization grid are used to simulate the PCE migration. It is shown that the model based on REV size agrees well with the experimental results over the entire migration period including calibration, verification and validation processes. This helps to better understand the microstructures of porous media and achieve accurately simulating DNAPL migration in aquifers based on the REV estimation.

  7. A perfectly matched layer for the time-dependent wave equation in heterogeneous and layered media

    KAUST Repository

    Duru, Kenneth

    2014-01-01

    A mathematical analysis of the perfectly matched layer (PML) for the time-dependent wave equation in heterogeneous and layered media is presented. We prove the stability of the PML for discontinuous media with piecewise constant coefficients, and derive energy estimates for discontinuous media with piecewise smooth coefficients. We consider a computational setup consisting of smaller structured subdomains that are discretized using high order accurate finite difference operators for approximating spatial derivatives. The subdomains are then patched together into a global domain by a weak enforcement of interface conditions using penalties. In order to ensure the stability of the discrete PML, it is necessary to transform the interface conditions to include the auxiliary variables. In the discrete setting, the transformed interface conditions are crucial in deriving discrete energy estimates analogous to the continuous energy estimates, thus proving stability and convergence of the numerical method. Finally, we present numerical experiments demonstrating the stability of the PML in a layered medium and high order accuracy of the proposed interface conditions. © 2013 Elsevier Inc.

  8. An accurate discontinuous Galerkin method for solving point-source Eikonal equation in 2-D heterogeneous anisotropic media

    Science.gov (United States)

    Le Bouteiller, P.; Benjemaa, M.; Métivier, L.; Virieux, J.

    2018-03-01

    Accurate numerical computation of wave traveltimes in heterogeneous media is of major interest for a large range of applications in seismics, such as phase identification, data windowing, traveltime tomography and seismic imaging. A high level of precision is needed for traveltimes and their derivatives in applications which require quantities such as amplitude or take-off angle. Even more challenging is the anisotropic case, where the general Eikonal equation is a quartic in the derivatives of traveltimes. Despite their efficiency on Cartesian meshes, finite-difference solvers are inappropriate when dealing with unstructured meshes and irregular topographies. Moreover, reaching high orders of accuracy generally requires wide stencils and high additional computational load. To go beyond these limitations, we propose a discontinuous-finite-element-based strategy which has the following advantages: (1) the Hamiltonian formalism is general enough for handling the full anisotropic Eikonal equations; (2) the scheme is suitable for any desired high-order formulation or mixing of orders (p-adaptivity); (3) the solver is explicit whatever Hamiltonian is used (no need to find the roots of the quartic); (4) the use of unstructured meshes provides the flexibility for handling complex boundary geometries such as topographies (h-adaptivity) and radiation boundary conditions for mimicking an infinite medium. The point-source factorization principles are extended to this discontinuous Galerkin formulation. Extensive tests in smooth analytical media demonstrate the high accuracy of the method. Simulations in strongly heterogeneous media illustrate the solver robustness to realistic Earth-sciences-oriented applications.

  9. Solving radiative transfer problems in highly heterogeneous media via domain decomposition and convergence acceleration techniques

    International Nuclear Information System (INIS)

    Previti, Alberto; Furfaro, Roberto; Picca, Paolo; Ganapol, Barry D.; Mostacci, Domiziano

    2011-01-01

    This paper deals with finding accurate solutions for photon transport problems in highly heterogeneous media fastly, efficiently and with modest memory resources. We propose an extended version of the analytical discrete ordinates method, coupled with domain decomposition-derived algorithms and non-linear convergence acceleration techniques. Numerical performances are evaluated using a challenging case study available in the literature. A study of accuracy versus computational time and memory requirements is reported for transport calculations that are relevant for remote sensing applications.

  10. Study of gas-liquid flow in model porous media for heterogeneous catalysis

    Science.gov (United States)

    Francois, Marie; Bodiguel, Hugues; Guillot, Pierre; Laboratory of the Future Team

    2015-11-01

    Heterogeneous catalysis of chemical reactions involving a gas and a liquid phase is usually achieved in fixed bed reactors. Four hydrodynamic regimes have been observed. They depend on the total flow rate and the ratio between liquid and gas flow rate. Flow properties in these regimes influence transfer rates. Rather few attempts to access local characterization have been proposed yet, though these seem to be necessary to better describe the physical mechanisms involved. In this work, we propose to mimic slices of reactor by using two-dimensional porous media. We have developed a two-dimensional system that is transparent to allow the direct observation of the flow and the phase distribution. While varying the total flow rate and the gas/liquid flow rate ratio, we observe two hydrodynamic regimes: at low flow rate, the gaseous phase is continuous (trickle flow), while it is discontinuous at higher flow rate (pulsed flow). Thanks to some image analysis techniques, we are able to quantify the local apparent liquid saturation in the system. Its fluctuations in time are characteristic of the transition between the two regimes: at low liquid flow rates, they are negligible since the liquid/gas interface is fixed, whereas at higher flow rates we observe an alternation between liquid and gas. This transition between trickle to pulsed flow is in relative good agreement with the existing state of art. However, we report in the pulsed regime important flow heterogeneities at the scale of a few pores. These heterogeneities are likely to have a strong influence on mass transfers. We acknowledge the support of Solvay.

  11. Generalized nonequilibrium capillary relations for two-phase flow through heterogeneous media.

    Science.gov (United States)

    Amaziane, Brahim; Milišić, Josipa Pina; Panfilov, Mikhail; Pankratov, Leonid

    2012-01-01

    For two-phase flow in porous media, the natural medium heterogeneity necessarily gives rise to capillary nonequilibrium effects. The relaxation to the equilibrium is a slow process which should be introduced in macroscopic flow models. Many nonequilibrium models are based on a phenomenological approach. At the same time there exists a rigorous mathematical way to develop the nonequilibrium equations. Its formalism, developed by Bourgeat and Panfilov [Computational Geosciences 2, 191 (1998)], is based on the homogenization of the microscale flow equations over medium heterogeneities. In contrast with the mentioned paper, in which the case of a sufficiently fast relaxation was analyzed, we consider the case of long relaxation, which leads to the appearance of long-term memory on the macroscale. Due to coupling between the nonlinearity and nonlocality in time, the macroscopic model remains, however, incompletely homogenized, in the general case. At the same time, frequently only the relationship for the nonequilibrium capillary pressure is of interest for applications. In the present paper, we obtain such an exact relationship in two different independent forms for the case of long-term memory. This relationship is more general than that obtained by Bourgeat and Panfilov. In addition, we prove the comparison theorem which determines the upper and lower bounds for the macroscopic model. These bounds represent linear flow models, which are completely homogenized. The results obtained are illustrated by numerical simulations.

  12. Viscous fingering with permeability heterogeneity

    International Nuclear Information System (INIS)

    Tan, C.; Homsy, G.M.

    1992-01-01

    Viscous fingering in miscible displacements in the presence of permeability heterogeneities is studied using two-dimensional simulations. The heterogeneities are modeled as stationary random functions of space with finite correlation scale. Both the variance and scale of the heterogeneities are varied over modest ranges. It is found that the fingered zone grows linearly in time in a fashion analogous to that found in homogeneous media by Tan and Homsy [Phys. Fluids 31, 1330 (1988)], indicating a close coupling between viscous fingering on the one hand and flow through preferentially more permeable paths on the other. The growth rate of the mixing zone increases monotonically with the variance of the heterogeneity, as expected, but shows a maximum as the correlation scale is varied. The latter is explained as a ''resonance'' between the natural scale of fingers in homogeneous media and the correlation scale

  13. Development of models for fast fluid pathways through unsaturated heterogeneous porous media

    International Nuclear Information System (INIS)

    Robey, T.H.

    1994-11-01

    The pre-waste-emplacement ground water travel time requirement is a regulatory criterion that specifies ground water travel time to the accessible environment shall be greater than 1,000 years. Satisfying the ground water travel time criterion for the potential repository at Yucca Mountain requires the study of fast travel path formation in the unsaturated zone and development of models that simulate the formation of fast paths. Conceptual models for unsaturated flow that have been used for total-systems performance assessment generally fall into the categories of composite-porosity or fracture models. The actual hydrologic conditions at Yucca Mountain are thought to lie somewhere between the extremes of these two types of models. The current study considers the effects of heterogeneities on composite-porosity models and seeks to develop numerical methods (and models) that can produce locally saturated zones where fracture flow can occur. The credibility of the model and numerical methods is investigated by using test data from the INTRAVAL project (Swedish Nuclear Inspectorate, 1992) to attempt to predict in-situ volumetric water content at specific locations in Yucca Mountain. Work based on the numerical methods presented in this study is eventually intended to allow the calculation of ground water travel times in heterogeneous media. 60 refs

  14. The implications of heterogeneity for repository performance assessments

    International Nuclear Information System (INIS)

    Jackson, C.P.; Porter, J.D.; Morris, S.T.; Herbert, A.W.

    1991-01-01

    We outline the current views of the Nirex Disposal Safety Assessment Team on heterogeneity, we describe the pragmatic approach to modelling the consequences of heterogeneity that is being currently used, we present work that is being undertaken in the Nirex Safety Assessment Research Programme to develop improved models and we discuss the implications of heterogeneity for site investigation. We point out the need to develop simple models for use in probabilistic analyses. Heterogeneity leads to dispersion, which is currently modelled using a simple diffusion-like model. We discuss the differences between structured heterogeneity, such as fracture zones, and random heterogeneity. We consider that the geostatistical approach to modelling random heterogeneity is probably that most suitable for the needs of Nirex. More measurements are needed in order to characterize heterogeneous media than to characterize homogeneous media. 18 refs., 4 figs

  15. Complexity Reduction of Multiphase Flows in Heterogeneous Porous Media

    KAUST Repository

    Ghommem, Mehdi

    2015-04-22

    In this paper, we apply mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in heterogeneous porous media. We propose intrusive and nonintrusive model-reduction approaches that enable a significant reduction in the size of the subsurface flow problem while capturing the behavior of the fully resolved solutions. In one approach, we use the dynamic mode decomposition. This approach does not require any modification of the reservoir simulation code but rather post-processes a set of global snapshots to identify the dynamically relevant structures associated with the flow behavior. In the second approach, we project the governing equations of the velocity and the pressure fields on the subspace spanned by their proper-orthogonal-decomposition modes. Furthermore, we use the discrete empirical interpolation method to approximate the mobility-related term in the global-system assembly and then reduce the online computational cost and make it independent of the fine grid. To show the effectiveness and usefulness of the aforementioned approaches, we consider the SPE-10 benchmark permeability field, and present a numerical example in two-phase flow. One can efficiently use the proposed model-reduction methods in the context of uncertainty quantification and production optimization.

  16. A stochastic multiscale framework for modeling flow through random heterogeneous porous media

    International Nuclear Information System (INIS)

    Ganapathysubramanian, B.; Zabaras, N.

    2009-01-01

    Flow through porous media is ubiquitous, occurring from large geological scales down to the microscopic scales. Several critical engineering phenomena like contaminant spread, nuclear waste disposal and oil recovery rely on accurate analysis and prediction of these multiscale phenomena. Such analysis is complicated by inherent uncertainties as well as the limited information available to characterize the system. Any realistic modeling of these transport phenomena has to resolve two key issues: (i) the multi-length scale variations in permeability that these systems exhibit, and (ii) the inherently limited information available to quantify these property variations that necessitates posing these phenomena as stochastic processes. A stochastic variational multiscale formulation is developed to incorporate uncertain multiscale features. A stochastic analogue to a mixed multiscale finite element framework is used to formulate the physical stochastic multiscale process. Recent developments in linear and non-linear model reduction techniques are used to convert the limited information available about the permeability variation into a viable stochastic input model. An adaptive sparse grid collocation strategy is used to efficiently solve the resulting stochastic partial differential equations (SPDEs). The framework is applied to analyze flow through random heterogeneous media when only limited statistics about the permeability variation are given

  17. Aprendizaje activo basado en problemas

    OpenAIRE

    Álvarez Martínez, Carlos; Fernández Jiménez, Agustín; Llosa Espuny, José Francisco; Sánchez Carracedo, Fermín

    2013-01-01

    Durante años, los autores del presente trabajo hemos practicado diversos métodos para fomentar el aprendizaje activo de los estudiantes a partir de la resolución de problemas, tanto en clase como fuera de ella. Los últimos cuatro cursos hemos utilizado en clase de problemas de la asignatura una metodología que consiste en encargar a los estudiantes cada semana que resuelvan un pequeño conjunto de problemas que trabajarán en clase la semana siguiente. En clase, los j...

  18. Experimental validation of the DPM Monte Carlo code using minimally scattered electron beams in heterogeneous media

    International Nuclear Information System (INIS)

    Chetty, Indrin J.; Moran, Jean M.; Nurushev, Teamor S.; McShan, Daniel L.; Fraass, Benedick A.; Wilderman, Scott J.; Bielajew, Alex F.

    2002-01-01

    A comprehensive set of measurements and calculations has been conducted to investigate the accuracy of the Dose Planning Method (DPM) Monte Carlo code for electron beam dose calculations in heterogeneous media. Measurements were made using 10 MeV and 50 MeV minimally scattered, uncollimated electron beams from a racetrack microtron. Source distributions for the Monte Carlo calculations were reconstructed from in-air ion chamber scans and then benchmarked against measurements in a homogeneous water phantom. The in-air spatial distributions were found to have FWHM of 4.7 cm and 1.3 cm, at 100 cm from the source, for the 10 MeV and 50 MeV beams respectively. Energy spectra for the electron beams were determined by simulating the components of the microtron treatment head using the code MCNP4B. Profile measurements were made using an ion chamber in a water phantom with slabs of lung or bone-equivalent materials submerged at various depths. DPM calculations are, on average, within 2% agreement with measurement for all geometries except for the 50 MeV incident on a 6 cm lung-equivalent slab. Measurements using approximately monoenergetic, 50 MeV, 'pencil-beam'-type electrons in heterogeneous media provide conditions for maximum electronic disequilibrium and hence present a stringent test of the code's electron transport physics; the agreement noted between calculation and measurement illustrates that the DPM code is capable of accurate dose calculation even under such conditions. (author)

  19. The Effect of Wettability Heterogeneity on Relative Permeability of Two-Phase Flow in Porous Media: A Lattice Boltzmann Study

    Science.gov (United States)

    Zhao, Jianlin; Kang, Qinjun; Yao, Jun; Viswanathan, Hari; Pawar, Rajesh; Zhang, Lei; Sun, Hai

    2018-02-01

    Relative permeability is a critical parameter characterizing multiphase flow in porous media and it is strongly dependent on the wettability. In many situations, the porous media are nonuniformly wet. To investigate the effect of wettability heterogeneity on relative permeability of two-phase flow in porous media, a multi-relaxation-time color-gradient lattice Boltzmann model is adopted to simulate oil/water two-phase flow in porous media with different oil-wet solid fractions. For the water phase, when the water saturation is high, the relative permeability of water increases with the increase of oil-wet solid fraction under a constant water saturation. However, as the water saturation decreases to an intermediate value (about 0.4-0.7), the relative permeability of water in fractionally wet porous media could be lower than that in purely water-wet porous media, meaning additional flow resistance exists in the fractionally wet porous media. For the oil phase, similar phenomenon is observed. This phenomenon is mainly caused by the wettability-related microscale fluid distribution. According to both our simulation results and theoretical analysis, it is found that the relative permeability of two-phase flow in porous media is strongly related to three parameters: the fluid saturation, the specific interfacial length of fluid, and the fluid tortuosity in the flow direction. The relationship between the relative permeability and these parameters under different capillary numbers is explored in this paper.

  20. Multiscale Adapted Time-Splitting Technique for Nonisothermal Two-Phase Flow and Nanoparticles Transport in Heterogenous Porous Media

    KAUST Repository

    El-Amin, Mohamed F.

    2017-05-05

    This paper is devoted to study the problem of nonisothermal two-phase flow with nanoparticles transport in heterogenous porous media, numerically. For this purpose, we introduce a multiscale adapted time-splitting technique to simulate the problem under consideration. The mathematical model consists of equations of pressure, saturation, heat, nanoparticles concentration in the water–phase, deposited nanoparticles concentration on the pore–walls, and entrapped nanoparticles concentration in the pore–throats. We propose a multiscale time splitting IMplicit Pressure Explicit Saturation–IMplicit Temperature Concentration (IMPES-IMTC) scheme to solve the system of governing equations. The time step-size adaptation is achieved by satisfying the stability Courant–Friedrichs–Lewy (CFL<1) condition. Moreover, numerical test of a highly heterogeneous porous medium is provided and the water saturation, the temperature, the nanoparticles concentration, the deposited nanoparticles concentration, and the permeability are presented in graphs.

  1. Educabilidad y problemas de aprendizaje

    Directory of Open Access Journals (Sweden)

    Jorge Capella Riera

    1993-12-01

    Full Text Available En el presente artículo voy a intentar responder al pedido de algunos colegas de desarrollar esas ideas a fin de contribuir al estudio de un problema que, por su magnitud y proyección, está causando preocupación entre educadores y psicólogos. Y al hacerlo parto de la idea de que los problemas, no importa de qué índole sean, no pueden resolverse aisladamente. Su interconexión e interdependencia respecto a otros problemas reclaman una visión deconjunto y una gran apertura a la contrastación teórica.

  2. XAMPP: Problemas

    OpenAIRE

    Luján Mora, Sergio

    2013-01-01

    Dos problemas muy comunes, y sus soluciones, que pueden ocurrir con XAMPP, la plataforma de desarrollo para los sistemas operativos Linux, Windows, MacOS X y Solaris que incluye Apache, MySQL, PHP y Perl.

  3. Synthetic seismograms in laterrally heterogeneous anelastic media: Modal summation for the case of offshore seismic sources (deep-sea trough)

    International Nuclear Information System (INIS)

    Alvarez, Leonardo; Romanelli, Fabio; Panza, Giuliano F.

    2001-12-01

    While waiting for the increment of strong motion data, especially for earthquake prone areas outside the United States and Japan, a very useful approach to perform immediate site specific seismic hazard assessment is the development and use of modelling tools. They are based, on one hand, on the theoretical knowledge of the physics of the seismic source and of wave propagation and, on the other hand, on the exploitation of the relatively rich database, already available, that can be used for the definition of the source and structural models. With these input data we model the ground motion using the mode-coupling approach for sharply varying laterally heterogeneous anelastic media, i.e. computing the coupling coefficients for the modes transmitted and reflected at the vertical interface, between two quarter spaces in welded contact. The formalism can be readily applied to any laterally heterogeneous structure by using a custom series of layered anelastic structures in welded contact at vertical interfaces. The case of seismic wave propagation in smooth varying laterally heterogeneous layered media, is solved with an approximation, equivalent to WKBJ method. The theoretical formulation that combines both WKBJ and the coupling coefficients approaches, is implemented in a computer program package. The computer code we have developed allows us to calculate synthetic seismograms for a wide range of laterally inhomogeneous layered anelastic media. As a case study we use an earthquake which occurred on December 16, 1999 (m b =4.8) beneath the Bartlett sea trough, south of Santiago de Cuba city, that was recorded by an accelerometer (SMA-100) placed in Rio Carpintero (RCC) station, at an epicentral distance of about 30 Km. The path travelled by the waves corresponds to a complex structure from undersea source to inland seismic station. A good fit between the observed transverse component (SH-waves) of acceleration and the corresponding synthetic signal is obtained for a

  4. Up-scaling of a two-phase flow model including gravity effect in geological heterogeneous media: application to CO2 sequestration

    International Nuclear Information System (INIS)

    Ngo, Tri-Dat

    2016-01-01

    This work deals with the mathematical modeling and the numerical simulation of the migration under gravity and capillarity effects of the supercritical CO 2 injected into a geological heterogeneous sequestration site. The simulations are performed with the code DuMux. Particularly, we consider the up-scaling, from the cell scale to the reservoir scale, of a two-phase (CO 2 -brine) flow model within a periodic stratified medium made up of horizontal low permeability barriers, continuous or discontinuous. The up-scaling is done by the two-scale asymptotic method. First, we consider perfectly layered media. An homogenized model is developed and validated by numerical simulation for different values of capillary number and the incident flux of CO 2 . The homogenization method is then applied to the case of a two-dimensional medium made up of discontinuous layers. Due to the gravity effect, the CO 2 accumulates under the low permeability layers, which leads to a non-standard local mathematical problem. This stratification is modeled using the gravity current approach. This approach is then extended to the case of semi-permeable strata taking into account the capillarity. The up-scaled model is compared with numerical simulations for different types of layers, with or without capillary pressure, and its limit of validity is discussed in each of these cases. The final part of this thesis is devoted to the study of the parallel computing performances of the code DuMux to simulate the injection and migration of CO 2 in three-dimensional heterogeneous media (layered periodic media, fluvial media and reservoir model SPE 10). (author) [fr

  5. Solución al Problema de Secuenciación de Trabajos mediante el Problema del Agente Viajero

    Directory of Open Access Journals (Sweden)

    G.E. Anaya Fuentes

    2016-10-01

    Full Text Available Resumen: En este trabajo se estudia el Problema de Secuenciación de Trabajos codificado como un Problema de Agente Viajero y resuelto mediante Algoritmos Genéticos. Se propone un Algoritmo Genético en donde se comparan dos tipos de selección: por torneo y por ruleta. Se realizan diferentes pruebas para la solución del Problema del Agente Viajero con los dos tipos de selección bajo diferentes parámetros: número de individuos, número de iteraciones, probabilidad de cruce y probabilidad de mutación; a partir de estos se seleccionan los parámetros y el tipo de selección. Posteriormente se codifica al Problema de Secuenciación como un Problema del Agente Viajero. La propuesta se presenta mediante la aplicación a diferentes ejemplos del Problema de Secuenciación de Trabajos y la comparación con los resultados obtenidos en la literatura. Abstract: In this paper we proposed a solution to the Job-Shop Scheduling Problem using the Traveling Salesman Problem solved by Genetic Algorithms. We proposed a genetic algorithm where we compare two types of selection: tournament and roulette. Different tests are performed to solve the Traveling Salesman Problem with the two types of selection under different parameters: number of individuals, number of iterations, crossover probability and mutation probability. Then the best type of selection and the best parameters are used to solve the Job-Shop Scheduling Problem with Genetic Algorithms for the Traveling Salesman Problem. The proposal is presented solving different examples of Job Sequencing Problem and compare them with the results obtained in the literature. Palabras clave: algoritmos eficientes, sistemas industriales de producción, problemas de optimización, problema de agente viajero, Keywords: Efficient algorithms, industrial production systems, optimization problem, traveling salesman problem

  6. New heavy scintillating materials for precise heterogeneous EM-calorimeters

    International Nuclear Information System (INIS)

    Britvich, G.I.; Britvich, I.G.; Vasil'chenko, V.G.; Lishin, V.A.; Obraztsov, V.F.; Polyakov, V.A.; Solovjev, A.S.; Ryzhikov, V.D.

    2001-01-01

    This investigation shows some optical and scintillation properties of new scintillating media, based on heavy composite materials and an inorganic crystal CsI:Br, intended for the creation of precise heterogeneous EM-calorimeters with the energy resolution σ/E congruent with 4-5% E-radical. The possibility to use cheap heavy scintillating plates based on optical ceramics as active media in heterogeneous EM-calorimeters is considered

  7. Upscaled Lattice Boltzmann Method for Simulations of Flows in Heterogeneous Porous Media

    Directory of Open Access Journals (Sweden)

    Jun Li

    2017-01-01

    Full Text Available An upscaled Lattice Boltzmann Method (LBM for flow simulations in heterogeneous porous media at the Darcy scale is proposed in this paper. In the Darcy-scale simulations, the Shan-Chen force model is used to simplify the algorithm. The proposed upscaled LBM uses coarser grids to represent the average effects of the fine-grid simulations. In the upscaled LBM, each coarse grid represents a subdomain of the fine-grid discretization and the effective permeability with the reduced-order models is proposed as we coarsen the grid. The effective permeability is computed using solutions of local problems (e.g., by performing local LBM simulations on the fine grids using the original permeability distribution and used on the coarse grids in the upscaled simulations. The upscaled LBM that can reduce the computational cost of existing LBM and transfer the information between different scales is implemented. The results of coarse-grid, reduced-order, simulations agree very well with averaged results obtained using a fine grid.

  8. Upscaled Lattice Boltzmann Method for Simulations of Flows in Heterogeneous Porous Media

    KAUST Repository

    Li, Jun

    2017-02-16

    An upscaled Lattice Boltzmann Method (LBM) for flow simulations in heterogeneous porous media at the Darcy scale is proposed in this paper. In the Darcy-scale simulations, the Shan-Chen force model is used to simplify the algorithm. The proposed upscaled LBM uses coarser grids to represent the average effects of the fine-grid simulations. In the upscaled LBM, each coarse grid represents a subdomain of the fine-grid discretization and the effective permeability with the reduced-order models is proposed as we coarsen the grid. The effective permeability is computed using solutions of local problems (e.g., by performing local LBM simulations on the fine grids using the original permeability distribution) and used on the coarse grids in the upscaled simulations. The upscaled LBM that can reduce the computational cost of existing LBM and transfer the information between different scales is implemented. The results of coarse-grid, reduced-order, simulations agree very well with averaged results obtained using a fine grid.

  9. Finite-fault source inversion using adjoint methods in 3D heterogeneous media

    Science.gov (United States)

    Somala, Surendra Nadh; Ampuero, Jean-Paul; Lapusta, Nadia

    2018-04-01

    , homogeneous velocity model. We find that, for velocity uncertainties that have standard deviation and correlation length typical of available 3D crustal models, the inverted sources can be severely contaminated by spurious features even if the station density is high. When data from thousand or more receivers is used in source inversions in 3D heterogeneous media, the computational cost of the method proposed in this work is at least two orders of magnitude lower than source inversion based on pre-computed Green's functions.

  10. Optimization of an algorithm for 3D calculation of radiation dose distribution in heterogeneous media for use in radiotherapy planning

    International Nuclear Information System (INIS)

    Perles, L.A.; Chinellato, C.D.; Rocha, J.R.O.

    2001-01-01

    In this paper has been presented a modification of a algorithm for three-dimensional (3D) radiation dose distribution in heterogeneous media by convolutions. This modification has maintained good accordance between calculated and simulated data in EGS4 code. The results of algorithm have been compared with commercial program PLATO, where have been noticed inconsistency for equivalent density regions in a muscle-lung-muscle interface system

  11. Dispersivity in heterogeneous permeable media

    International Nuclear Information System (INIS)

    Chesnut, D.A.

    1994-01-01

    When one fluid displaces another through a one-dimensional porous medium, the composition changes from pure displacing fluid at the inlet to pure displaced fluid some distance downstream. The distance over which an arbitrary percentage of this change occurs is defined as the mixing zone length, which increases with increasing average distance traveled by the displacement front. For continuous injection, the mixing zone size can be determined from a breakthrough curve as the time required for the effluent displacing fluid concentration to change from, say, 10% to 90%. In classical dispersion theory, the mixing zone grows in proportion to the square root of the mean distance traveled, or, equivalently, to the square root of the mean breakthrough time. In a multi-dimensional heterogeneous medium, especially at field scales, the size of the mixing zone grows almost linearly with mean distance or travel time. If an observed breakthrough curve is forced to fit the, clinical theory, the resulting effective dispersivity, instead of being constant, also increases almost linearly with the spatial or temporal scale of the problem. This occurs because the heterogeneity in flow properties creates a corresponding velocity distribution along the different flow pathways from the inlet to the outlet of the system. Mixing occurs mostly at the outlet, or wherever the fluid is sampled, rather than within the medium. In this paper, we consider the effects. of this behavior on radionuclide or other contaminant migration

  12. Dispersivity in heterogeneous permeable media

    International Nuclear Information System (INIS)

    Chesnut, D.A.

    1994-01-01

    When one fluid displaces another through a one-dimensional porous medium, the composition changes from pure displacing fluid at the inlet to pure displaced fluid some distance downstream. The distance over which an arbitrary percentage (typically 80%) of this change occurs is defined as the mixing zone length, which increases with increasing average distance traveled by the displacement front. Alternatively, for continuous injection, the mixing zone size can be determined from a breakthrough curve as the time required for the effluent displacing fluid concentration to change from, say, 10% to 90%. In classical dispersion theory, the mixing zone grows in proportion to the square root of the mean distance traveled, or, equivalently, to the square root of the mean breakthrough time. In a multi-dimensional heterogeneous medium, especially at field scales, the size of the mixing zone grows almost linearly with mean distance or travel time. If an observed breakthrough curve is forced to fit the classical theory, the resulting effective dispersivity, instead of being constant, also increases almost linearly with the spatial or temporal scale of the problem. This occurs because the heterogeneity in flow properties creates a corresponding velocity distribution along the different flow pathways from the inlet to the outlet of the system. Mixing occurs mostly at the outlet, or wherever the fluid is sampled, rather than within the medium. In this paper, we consider the effects of this behavior on radionuclide or other contaminant migration

  13. Complexity reduction of multi-phase flows in heterogeneous porous media

    KAUST Repository

    Ghommem, Mehdi

    2013-01-01

    In this paper, we apply mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in highly heterogeneous porous media. We propose intrusive and non-intrusive model reduction approaches that enable a significant reduction in the dimension of the flow problem size while capturing the behavior of the fully-resolved solutions. In one approach, we employ the dynamic mode decomposition (DMD) and the discrete empirical interpolation method (DEIM). This approach does not require any modification of the reservoir simulation code but rather postprocesses a set of global snapshots to identify the dynamically-relevant structures associated with the flow behavior. In a second approach, we project the governing equations of the velocity and the pressure fields on the subspace spanned by their proper orthogonal decomposition (POD) modes. Furthermore, we use DEIM to approximate the mobility related term in the global system assembly and then reduce the online computational cost and make it independent of the fine grid. To show the effectiveness and usefulness of the aforementioned approaches, we consider the SPE 10 benchmark permeability field and present a variety of numerical examples of two-phase flow and transport. The proposed model reduction methods can be efficiently used when performing uncertainty quantification or optimization studies and history matching.

  14. Micro-macro model for prediction of local temperature distribution in heterogeneous and two-phase media

    Directory of Open Access Journals (Sweden)

    Furmański Piotr

    2014-09-01

    Full Text Available Heat flow in heterogeneous media with complex microstructure follows tortuous path and therefore determination of temperature distribution in them is a challenging task. Two-scales, micro-macro model of heat conduction with phase change in such media was considered in the paper. A relation between temperature distribution on the microscopic level, i.e., on the level of details of microstructure, and the temperature distribution on the macroscopic level, i.e., on the level where the properties were homogenized and treated as effective, was derived. The expansion applied to this relation allowed to obtain its more simplified, approximate form corresponding to separation of micro- and macro-scales. Then the validity of this model was checked by performing calculations for 2D microstructure of a composite made of two constituents. The range of application of the proposed micro-macro model was considered in transient states of heat conduction both for the case when the phase change in the material is present and when it is absent. Variation of the effective thermal conductivity with time was considered and a criterion was found for which application of the considered model is justified.

  15. Relación entre Problemas de Conducta en Adolescentes y Conflicto Interparental en Familias Intactas y Monoparentales

    Directory of Open Access Journals (Sweden)

    Cecilia Mayorga Muñoz

    2016-01-01

    Full Text Available El propósito del estudio fue analizar la influencia del conflicto interparental en la aparición de problemas de conducta en adolescentes de familias intactas y monoparentales. Se utilizó un diseño explicativo que consideró prueba de medias y análisis multivariado de varianza. La muestra estuvo compuesta de 466 adolescentes de 12 a 16 años. Para la medición de las variables se utilizaron las escalas Children’s Perception of Interparental Conflict ( cpic y Youth Self Report ( ysr . Los resultados confirman la asociación entre conflicto interparental y problemas de conducta en los hijos, y muestran que, cuando hay conflicto en las familias intactas, se produce una mayor frecuencia de conductas externalizantes que en familias monoparentales.

  16. Heterogeneous continuous-time random walks

    Science.gov (United States)

    Grebenkov, Denis S.; Tupikina, Liubov

    2018-01-01

    We introduce a heterogeneous continuous-time random walk (HCTRW) model as a versatile analytical formalism for studying and modeling diffusion processes in heterogeneous structures, such as porous or disordered media, multiscale or crowded environments, weighted graphs or networks. We derive the exact form of the propagator and investigate the effects of spatiotemporal heterogeneities onto the diffusive dynamics via the spectral properties of the generalized transition matrix. In particular, we show how the distribution of first-passage times changes due to local and global heterogeneities of the medium. The HCTRW formalism offers a unified mathematical language to address various diffusion-reaction problems, with numerous applications in material sciences, physics, chemistry, biology, and social sciences.

  17. Aprendizaje colaborativo a través de problemas

    Directory of Open Access Journals (Sweden)

    María José Labrador Piquer

    2011-01-01

    Full Text Available El objetivo de este taller ha sido acercar a los asistentes al aprendizaje colaborativo a través de problemas en la enseñanza de ELE, para ello, partimos de unas nociones básicas de aprendizaje cooperativo/colaborativo y del análisis de problemas, continuamos con el estudio de problemas y finalizamos con una serie de reflexiones sobre la evaluación. Durante la sesión los asistentes han realizado dos funciones: una, como alumnos analizando y resolviendo los problemas y otra, como profesores reflexionando sobre las destrezas practicadas y sobre la evaluación.

  18. Aprendizaje colaborativo a través de problemas

    Directory of Open Access Journals (Sweden)

    María José Labrador Piquer

    2012-08-01

    Full Text Available El objetivo de este taller ha sido acercar a los asistentes al aprendizaje colaborativo a través de problemas en la enseñanza de ELE, para ello, partimos de unas nociones básicas de aprendizaje cooperativo/colaborativo y del análisis de problemas, continuamos con el estudio de problemas y finalizamos con una serie de reflexiones sobre la evaluación. Durante la sesión los asistentes han realizado dos funciones: una, como alumnos analizando y resolviendo los problemas y otra, como profesores reflexionando sobre las destrezas practicadas y sobre la evaluación.

  19. Estudo dos problemas do carteiro chines e do caixeiro viajante

    OpenAIRE

    Denise Helena Lombardo

    1986-01-01

    Resumo: Esta dissertação envolve o estudo de dois problemas de otimização combinatória: O Problema do Caixeiro Viajante (PCV) e o Problema do Carteiro Chinês (PCC). Dada uma rede (ou grafo), primeiro problema consiste em determinar uma rota circular mínima que passa em cada nó e o segundo em determinar uma rota circular mínima que passa em cada linha da rede. Embora ambos problemas sejam da classe NP-"árduo" (NP- hard ), o problema do Carteiro Chinês é apresentado na literatura como um proble...

  20. Reconstructing random media

    International Nuclear Information System (INIS)

    Yeong, C.L.; Torquato, S.

    1998-01-01

    We formulate a procedure to reconstruct the structure of general random heterogeneous media from limited morphological information by extending the methodology of Rintoul and Torquato [J. Colloid Interface Sci. 186, 467 (1997)] developed for dispersions. The procedure has the advantages that it is simple to implement and generally applicable to multidimensional, multiphase, and anisotropic structures. Furthermore, an extremely useful feature is that it can incorporate any type and number of correlation functions in order to provide as much morphological information as is necessary for accurate reconstruction. We consider a variety of one- and two-dimensional reconstructions, including periodic and random arrays of rods, various distribution of disks, Debye random media, and a Fontainebleau sandstone sample. We also use our algorithm to construct heterogeneous media from specified hypothetical correlation functions, including an exponentially damped, oscillating function as well as physically unrealizable ones. copyright 1998 The American Physical Society

  1. Stability of Miscible Displacements Across Stratified Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Shariati, Maryam; Yortsos, Yanis C.

    2000-09-11

    This report studied macro-scale heterogeneity effects. Reflecting on their importance, current simulation practices of flow and displacement in porous media were invariably based on heterogeneous permeability fields. Here, it was focused on a specific aspect of such problems, namely the stability of miscible displacements in stratified porous media, where the displacement is perpendicular to the direction of stratification.

  2. A Structural Finite Element Model for Lamellar Unit of Aortic Media Indicates Heterogeneous Stress Field After Collagen Recruitment

    Science.gov (United States)

    Thunes, James R.; Pal, Siladitya; Fortunato, Ronald N.; Phillippi, Julie A.; Gleason, Thomas G.; Vorp, David A.; Maiti, Spandan

    2016-01-01

    Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue. Motivated by this need, we developed a finite element based three-dimensional structural model of the lamellar units of the ATA media that directly incorporates the collagen fiber microarchitecture. The fiber architecture was computer generated utilizing network features, namely fiber orientation distribution, intersection density and areal concentration, obtained from image analysis of multiphoton microscopy images taken from human aneurysmal ascending thoracic aortic media specimens with bicuspid aortic valve (BAV) phenotype. Our model reproduces the typical J-shaped constitutive response of the aortic wall tissue. We found that the stress state in the non-fibrous matrix was homogeneous until the collagen fibers were recruited, but became highly heterogeneous after that event. The degree of heterogeneity was dependent upon local network architecture with high stresses observed near disrupted fibers. The magnitude of non-fibrous matrix stress at higher stretch levels was negatively correlated with local fiber density. The localized stress concentrations, elucidated by this model, may be a factor in the degenerative changes in aneurysmal ATA tissue. PMID:27113538

  3. Whole-body voxel-based personalized dosimetry: Multiple voxel S-value approach for heterogeneous media with non-uniform activity distributions.

    Science.gov (United States)

    Lee, Min Sun; Kim, Joong Hyun; Paeng, Jin Chul; Kang, Keon Wook; Jeong, Jae Min; Lee, Dong Soo; Lee, Jae Sung

    2017-12-14

    Personalized dosimetry with high accuracy is becoming more important because of the growing interests in personalized medicine and targeted radionuclide therapy. Voxel-based dosimetry using dose point kernel or voxel S-value (VSV) convolution is available. However, these approaches do not consider medium heterogeneity. Here, we propose a new method for whole-body voxel-based personalized dosimetry for heterogeneous media with non-uniform activity distributions, which is referred to as the multiple VSV approach. Methods: The multiple numbers (N) of VSVs for media with different densities covering the whole-body density ranges were used instead of using only a single VSV for water. The VSVs were pre-calculated using GATE Monte Carlo simulation; those were convoluted with the time-integrated activity to generate density-specific dose maps. Computed tomography-based segmentation was conducted to generate binary maps for each density region. The final dose map was acquired by the summation of N segmented density-specific dose maps. We tested several sets of VSVs with different densities: N = 1 (single water VSV), 4, 6, 8, 10, and 20. To validate the proposed method, phantom and patient studies were conducted and compared with direct Monte Carlo, which was considered the ground truth. Finally, patient dosimetry (10 subjects) was conducted using the multiple VSV approach and compared with the single VSV and organ-based dosimetry approaches. Errors at the voxel- and organ-levels were reported for eight organs. Results: In the phantom and patient studies, the multiple VSV approach showed significant improvements regarding voxel-level errors, especially for the lung and bone regions. As N increased, voxel-level errors decreased, although some overestimations were observed at lung boundaries. In the case of multiple VSVs ( N = 8), we achieved voxel-level errors of 2.06%. In the dosimetry study, our proposed method showed much improved results compared to the single VSV and

  4. Simulating propagation of decomposed elastic waves using low-rank approximate mixed-domain integral operators for heterogeneous transversely isotropic media

    KAUST Repository

    Cheng, Jiubing

    2014-08-05

    In elastic imaging, the extrapolated vector fields are decomposed into pure wave modes, such that the imaging condition produces interpretable images, which characterize reflectivity of different reflection types. Conventionally, wavefield decomposition in anisotropic media is costly as the operators involved is dependent on the velocity, and thus not stationary. In this abstract, we propose an efficient approach to directly extrapolate the decomposed elastic waves using lowrank approximate mixed space/wavenumber domain integral operators for heterogeneous transverse isotropic (TI) media. The low-rank approximation is, thus, applied to the pseudospectral extrapolation and decomposition at the same time. The pseudo-spectral implementation also allows for relatively large time steps in which the low-rank approximation is applied. Synthetic examples show that it can yield dispersionfree extrapolation of the decomposed quasi-P (qP) and quasi- SV (qSV) modes, which can be used for imaging, as well as the total elastic wavefields.

  5. The Green's function method for critical heterogeneous slabs

    International Nuclear Information System (INIS)

    Kornreich, D.E.

    1996-01-01

    Recently, the Green's Function Method (GFM) has been employed to obtain benchmark-quality results for nuclear engineering and radiative transfer calculations. This was possible because of fast and accurate calculations of the Green's function and the associated Fourier and Laplace transform inversions. Calculations have been provided in one-dimensional slab geometries for both homogeneous and heterogeneous media. A heterogeneous medium is analyzed as a series of homogeneous slabs, and Placzek's lemma is used to extend each slab to infinity. This allows use of the infinite medium Green's function (the anisotropic plane source in an infinite homogeneous medium) in the solution. To this point, a drawback of the GFM has been the limitation to media with c 1; however, mathematical solutions exist which result in oscillating Green's functions. Such calculations are briefly discussing. The limitation to media with c < 1 has been relaxed so that the Green's function may also be calculated for media with c ≥ 1. Thus, materials that contain fissionable isotopes may be modeled

  6. Algoritmos para problemas de corte e empacotamento

    OpenAIRE

    Thiago Alves de Queiroz

    2010-01-01

    Resumo: Problemas de Corte e Empacotamento são, em sua maioria, NP-difíceis e não existem algoritmos exatos de tempo polinomial para tais se for considerado P ¿ NP. Aplicações práticas envolvendo estes problemas incluem a alocação de recursos para computadores; o corte de chapas de ferro, de madeira, de vidro, de alumínio, peças em couro, etc.; a estocagem de objetos; e, o carregamento de objetos dentro de contêineres ou caminhões-baú. Nesta tese investigamos problemas de Corte e Empacotament...

  7. Anomaly detection in heterogeneous media via saliency analysis of propagating wavefields

    Science.gov (United States)

    Druce, Jeffrey M.; Haupt, Jarvis D.; Gonella, Stefano

    2014-03-01

    This work investigates the problem of anomaly detection by means of an agnostic inference strategy based on the concepts of spatial saliency and data sparsity. Specifically, it addresses the implementation and experimental validation aspects of a salient feature extraction methodology that was recently proposed for laser-based diagnostics and leverages the wavefield spatial reconstruction capability offered by scanning laser vibrometers. The methodology consists of two steps. The first is a spatiotemporal windowing strategy designed to partition the structural domain in small sub-domains and replicate impinging wave conditions at each location. The second is the construction of a low-rank-plus-outlier model of the regional data set using principal component analysis. Regions are labeled salient when their behavior does not belong to a common low-dimensional subspace that successfully describes the typical behavior of the anomaly-free portion of the surrounding medium. The most at­ tractive feature of this method is that it requires virtually no knowledge of the structural and material properties of the medium. This property makes it a powerful diagnostic tool for the inspection of media with pronounced heterogeneity or with unknown or unreliable material property distributions, e.g., as a result of severe material degradation over large portions of their domain.

  8. Diseño de escenarios virtuales para problemas de optimización a través de geometría dinámica.

    OpenAIRE

    Freddy Yesid Villamizar Araque; Olga Lucy Rincón Leal; Mawency Vergel Ortega

    2018-01-01

    El presente artículo tiene el objetivo de analizar la influencia del uso de tecnologías digitales, particularmente, de software de geometría dinámica, acompañado de una didáctica en la concepción y solución de problemas aplicados, en un enfoque de enseñanza activa, en temas de optimización. La metodología siguió un enfoque cualitativo, se desarrolló a partir de taller con profesores, en el cual se resolvieron problemas en el contexto de máximos y mínimos de forma analítica y dinámica media...

  9. The Effect of Velocity Correlation on the Spatial Evolution of Breakthrough Curves in Heterogeneous Media

    Science.gov (United States)

    Massoudieh, A.; Dentz, M.; Le Borgne, T.

    2017-12-01

    In heterogeneous media, the velocity distribution and the spatial correlation structure of velocity for solute particles determine the breakthrough curves and how they evolve as one moves away from the solute source. The ability to predict such evolution can help relating the spatio-statistical hydraulic properties of the media to the transport behavior and travel time distributions. While commonly used non-local transport models such as anomalous dispersion and classical continuous time random walk (CTRW) can reproduce breakthrough curve successfully by adjusting the model parameter values, they lack the ability to relate model parameters to the spatio-statistical properties of the media. This in turns limits the transferability of these models. In the research to be presented, we express concentration or flux of solutes as a distribution over their velocity. We then derive an integrodifferential equation that governs the evolution of the particle distribution over velocity at given times and locations for a particle ensemble, based on a presumed velocity correlation structure and an ergodic cross-sectional velocity distribution. This way, the spatial evolution of breakthrough curves away from the source is predicted based on cross-sectional velocity distribution and the connectivity, which is expressed by the velocity transition probability density. The transition probability is specified via a copula function that can help construct a joint distribution with a given correlation and given marginal velocities. Using this approach, we analyze the breakthrough curves depending on the velocity distribution and correlation properties. The model shows how the solute transport behavior evolves from ballistic transport at small spatial scales to Fickian dispersion at large length scales relative to the velocity correlation length.

  10. Entrenamiento en la solución de problemas de matemática discreta. Impacto social

    OpenAIRE

    Carranza Carpio, Gustavo

    2016-01-01

    La matemática discreta no es bien comprendida por los implicados en la Educación Media. Aquí se brinda una panorámica de la importancia de la matemática discreta en el desarrollo actual de la sociedad y se aborda la necesidad del entrenamiento en la resolución de problemas. Se analizan las interrelaciones existentes entre las características psicopedagógicas y de la personalidad de los estudiantes implicados; los métodos y procedimientos para el desarrollo de la actividad tratada, las formas ...

  11. Mecánica de suelos : problemas resueltos

    OpenAIRE

    Olivella Pastallé, Sebastià

    2001-01-01

    Esta publicación contiene una colección de problemas resueltos de mecánica de suelos que ha sido preparada para los estudios de ingeniería técnica de obras públicas que se imparten en la UPC. Se trata de una titulación de primer ciclo, por lo que el enfoque que se da a los problemas se centra en aspectos de concepto y no requiere la realización de desarrollos matemáticos. Incluye problemas relativos a propiedades básicas de los suelos, aspectos básicos de la mecánica de medios porosos indefor...

  12. La Media Literacy nella prospettiva finlandese, nordica ed europea

    Directory of Open Access Journals (Sweden)

    Sol-Britt Arnolds-Granlund

    2013-03-01

    Full Text Available Nel secolo scorso, e in special modo negli ultimi dieci anni, la questione dei media e, in particolare, il tema della media literacy ha attratto l’interesse delle autorità, degli studiosi e di altri responsabili nel settore educativo. Nel tempo sono entrati in uso molti concetti, ma sfortunatamente senza che ne venisse fornita una definizione, nella maggior parte dei casi. Questo articolo si focalizza sulla media literacy, su come può essere definita e sul significato di concetti affini utilizzati nel contesto finlandese. Inoltre viene discussa la relazione tra i concetti di media literacy e digital literacy e la collocazione della media literacy nei curricula scolastici in Finlandia. Il contributo affronta anche il problema della valutazione della media literacy nelle politiche istituzionali e chiude con un accenno alle prospettive future di ricerca nel campo dell’educazione ai media. Trattandosi di un lavoro di ampio respiro sulla media literacy, si riferisce sia a iniziative politiche che ai risultati della ricerca e alle pratiche educative.

  13. Social media and the transformation of activist communication: exploring the social media ecology of the 2010 Toronto G20 protests

    NARCIS (Netherlands)

    Poell, T.

    2014-01-01

    How does the massive use of social media in contemporary protests affect the character of activist communication? Moving away from the conceptualization of social media as tools, this research explores how activist social media communication is entangled with and shaped by heterogeneous

  14. Finite volume approximation of the three-dimensional flow equation in axisymmetric, heterogeneous porous media based on local analytical solution

    KAUST Repository

    Salama, Amgad

    2013-09-01

    In this work the problem of flow in three-dimensional, axisymmetric, heterogeneous porous medium domain is investigated numerically. For this system, it is natural to use cylindrical coordinate system, which is useful in describing phenomena that have some rotational symmetry about the longitudinal axis. This can happen in porous media, for example, in the vicinity of production/injection wells. The basic feature of this system is the fact that the flux component (volume flow rate per unit area) in the radial direction is changing because of the continuous change of the area. In this case, variables change rapidly closer to the axis of symmetry and this requires the mesh to be denser. In this work, we generalize a methodology that allows coarser mesh to be used and yet yields accurate results. This method is based on constructing local analytical solution in each cell in the radial direction and moves the derivatives in the other directions to the source term. A new expression for the harmonic mean of the hydraulic conductivity in the radial direction is developed. Apparently, this approach conforms to the analytical solution for uni-directional flows in radial direction in homogeneous porous media. For the case when the porous medium is heterogeneous or the boundary conditions is more complex, comparing with the mesh-independent solution, this approach requires only coarser mesh to arrive at this solution while the traditional methods require more denser mesh. Comparisons for different hydraulic conductivity scenarios and boundary conditions have also been introduced. © 2013 Elsevier B.V.

  15. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    Science.gov (United States)

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Problemas de investigación en contabilidad y problemas de la investigación en contabilidad

    Directory of Open Access Journals (Sweden)

    Henry Antonio Romero León

    2015-01-01

    Full Text Available En este escrito se plantean dos problemáticas que padece el mundo contable en su concepción de la investigación y en la ejecución de la misma como proceso dinamizador de la disciplina. Se precisan problemas de investigación y problemas de la investigación contable, que derivan en el diagnóstico y descripción de aspectos generadores de trabas en la investigación. A manera de ejemplo se presentan investigaciones en orden de las grandes temáticas de investigación a través de las revistas académicas más representativas con la intención de evidenciar la investigación contable mundial. La problemática que guía la argumentación es la necesidad de distinguir dos ejes problemáticos en la investigación contable que hacen de este ejercicio una actividad que históricamente marcha a pasos lentos, buscando así comprender que con las aclaraciones conceptuales y analíticas en las concepciones que gobiernan el conocimiento contable, se pueda contribuir al desempantanamiento de este asunto. Se logra establecer que no es lo mismo los problemas como motivadores de la investigación, que los problemas que giran alrededor de la investigación como actividad humana.Palabras Clave: problemas de investigación en contabilidad; problemas de la investigación en contabilidad epistemología contable; ontología contable; investigación; problema; giro epistemológico.Research problems in accounting and problems in accounting research.AbstractThere are two questions being raised here regarding the accounting research and foundational research problems in accounting as a dynamizing agent of the discipline progress. Research problems in accounting and problems in accounting research derived therein have been discussed, through a diagnostic process, including a description of the main issues in these problematic research areas. By way of example, research topics published in the main accounting journals will be presented, with the intent to overview the

  17. O Problema da mochila compartimentada e aplicações

    Directory of Open Access Journals (Sweden)

    Marques Fabiano do Prado

    2002-01-01

    Full Text Available O Problema da Mochila Compartimentada é uma variação do clássico problema da mochila e pode ser enunciado considerando-se a seguinte situação hipotética: um alpinista deve carregar sua mochila compossíveis itens de seu interesse. A cada item atribui-se o seu peso e um valor de utilidade (até aqui, o problema coincide com o clássico Problema da Mochila. Entretanto, os itens são de agrupamentos distintos (alimentos, medicamentos, utensílios, etc. e devem estar em compartimentos separados na mochila. Os compartimentos da mochila são flexíveis e têm capacidades limitadas. A inclusão de um compartimento tem um custo fixo que depende do agrupamento com que foi preenchido, além de introduzir uma perda da capacidade da mochila. O problema consiste em determinar as capacidades adequadas de cada compartimento e como esses devem ser carregados, maximizando o valor de utilidade total, descontado o custo de incluir compartimentos. Neste trabalho propomos um modelo de otimização não linear inteiro para o problema e algumas heurísticas para sua resolução. Uma aplicação prática de relevância deste problema aparece no corte de bobinas de aço, sujeito à laminação, detalhado em apêndice.

  18. Discontinuous Galerkin Subgrid Finite Element Method for Heterogeneous Brinkman’s Equations

    KAUST Repository

    Iliev, Oleg P.; Lazarov, Raytcho D.; Willems, Joerg

    2010-01-01

    We present a two-scale finite element method for solving Brinkman's equations with piece-wise constant coefficients. This system of equations model fluid flows in highly porous, heterogeneous media with complex topology of the heterogeneities. We

  19. Robust Multiscale Iterative Solvers for Nonlinear Flows in Highly Heterogeneous Media

    KAUST Repository

    Efendiev, Y.

    2012-08-01

    In this paper, we study robust iterative solvers for finite element systems resulting in approximation of steady-state Richards\\' equation in porous media with highly heterogeneous conductivity fields. It is known that in such cases the contrast, ratio between the highest and lowest values of the conductivity, can adversely affect the performance of the preconditioners and, consequently, a design of robust preconditioners is important for many practical applications. The proposed iterative solvers consist of two kinds of iterations, outer and inner iterations. Outer iterations are designed to handle nonlinearities by linearizing the equation around the previous solution state. As a result of the linearization, a large-scale linear system needs to be solved. This linear system is solved iteratively (called inner iterations), and since it can have large variations in the coefficients, a robust preconditioner is needed. First, we show that under some assumptions the number of outer iterations is independent of the contrast. Second, based on the recently developed iterative methods, we construct a class of preconditioners that yields convergence rate that is independent of the contrast. Thus, the proposed iterative solvers are optimal with respect to the large variation in the physical parameters. Since the same preconditioner can be reused in every outer iteration, this provides an additional computational savings in the overall solution process. Numerical tests are presented to confirm the theoretical results. © 2012 Global-Science Press.

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

    Science.gov (United States)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yurkin, Maxim A.; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R. Lee; Travis, Larry D.; Yang, Ping; Zakharova, Nadezhda T.

    2018-01-01

    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

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

    International Nuclear Information System (INIS)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yurkin, Maxim A.; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R. Lee; Travis, Larry D.; Yang, Ping; Zakharova, Nadezhda T.

    2016-01-01

    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

  2. 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

  3. First-Principles Modeling Of Electromagnetic Scattering By Discrete and Discretely Heterogeneous Random Media

    Science.gov (United States)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yurkin, Maxim A.; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R. Lee; Travis, Larry D.; Yang, Ping; Zakharova, Nadezhda T.

    2016-01-01

    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 of

  4. Emergent dynamics of spatio-temporal chaos in a heterogeneous excitable medium.

    Science.gov (United States)

    Bittihn, Philip; Berg, Sebastian; Parlitz, Ulrich; Luther, Stefan

    2017-09-01

    Self-organized activation patterns in excitable media such as spiral waves and spatio-temporal chaos underlie dangerous cardiac arrhythmias. While the interaction of single spiral waves with different types of heterogeneity has been studied extensively, the effect of heterogeneity on fully developed spatio-temporal chaos remains poorly understood. We investigate how the complexity and stability properties of spatio-temporal chaos in the Bär-Eiswirth model of excitable media depend on the heterogeneity of the underlying medium. We employ different measures characterizing the chaoticity of the system and find that the spatial arrangement of multiple discrete lower excitability regions has a strong impact on the complexity of the dynamics. Varying the number, shape, and spatial arrangement of the heterogeneities, we observe strong emergent effects ranging from increases in chaoticity to the complete cessation of chaos, contrasting the expectation from the homogeneous behavior. The implications of our findings for the development and treatment of arrhythmias in the heterogeneous cardiac muscle are discussed.

  5. Educational Potential of New Media

    Directory of Open Access Journals (Sweden)

    Maria Yu. Kazak

    2017-11-01

    Full Text Available Digitalization of the mass media, which has radically changed the information environment, creates new opportunities for self-education and upgrowth of the audience. The paper defines the communicative and cultural status of new media, characterizes the socio-cultural and technological aspects of their dynamics; substantiates the necessity of elaborating mechanisms for systematization of heterogeneous information flows and elaborating criteria for their evaluation in the era of globalization of the media sphere, what implies a qualitatively different level of media competence of the audience, provided with such factors as media education, media coverage, media criticism. The definition of concepts "media competence", "media enlightenment", "media education", "media criticism" is given and their functional areas are delineated. Social networks are considered as an important tool for media enlightenment which provides significant opportunities for promoting cultural achievements in the new media environment.

  6. Sobre o problema da demarcação

    Directory of Open Access Journals (Sweden)

    Marcos Barbosa de Oliveira

    1982-12-01

    Full Text Available Desde sua publicação, não têm faltado ataques ao critério da refutabilidade - a solução proposta por Popper para seu problema da demarcação. A crítica do presente artigo é mais fundamental: seu alvo é o próprio problema da demarcação. Como preliminar, mostra-se haver na obra de Popper não apenas um, mas dois problemas da demarcação, distintos e incompatíveis. Uma análise do antiessencialismo de Popper é o ponto de partida para a demonstração da tese central do artigo, a saber, a tese de que o problema da demarcação deve ser abandonado, por ser parte de uma abordagem cientificista da questão do valor das ciências.

  7. Algoritmos multirecombinativos aplicados al problema de ruteo de vehículos

    Directory of Open Access Journals (Sweden)

    Renzo Ramon Miño

    2014-06-01

    Full Text Available El diseño de algoritmos eficientes para resolver problemas complejos ha sido tradicionalmente uno de los aspectos más importantes en la investigación en el campo de la informática. El objetivo perseguido en este campo es fundamentalmente el desarrollo de nuevos métodos capaces de resolver problemas complejos con el menor esfuerzo computacional posible, mejorando así a los algoritmos existentes. En consecuencia, esto no sólo permite afrontar los problemas de forma más eficiente, sino afrontar tareas vedadas en el pasado debido a su alto costo computacional. Las metaheurísticas son métodos que integran procedimientos de mejora local y estrategias de alto nivel para realizar una búsqueda robusta en el espacio-problema. El problema de ruteo de vehículos es un problema de optimización combinatoria de gran importancia en diferentes entornos logísticos debido a su dificultad (NP-duros y a sus múltiples aplicaciones industriales. Se han propuestos varias soluciones a este problema haciendo uso de heurísticas y metaheurísticas. En este trabajo proponemos dos algoritmos para resolver el problema de ruteo de vehículos con capacidad limitada, utilizando como base un Algoritmo Evolutivo conocido como MCMP-SRI (Stud and Random Inmigrants combinados con Hill- Climbing. Detalles de los algoritmos y los resultados de los experimentos muestran un promisorio comportamiento para resolver el problema.

  8. A obesidade infantil: um problema emergente

    OpenAIRE

    Sousa, Joana; Loureiro, Isabel; Carmo, Isabel do

    2008-01-01

    A obesidade é um dos problemas de saúde mais graves que afecta crianças e adolescentes a nível mundial. As evidências sugerem que o problema está a agravar-se rapidamente. O aumento da prevalência de obesidade infantil pode fazer com que a próxima geração apresente indicadores de obesidade no adulto superiores aos indicadores actuais. Pelo facto de a obesidade estar intimamente associada a diferentes patologias crónicas faz com que estejamos perante um enorme desafio para o sistema de cuidado...

  9. Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media

    Science.gov (United States)

    Ellefsen, K.J.; Croize, D.; Mazzella, A.T.; McKenna, J.R.

    2009-01-01

    Green's functions for radar waves propagating in heterogeneous 2.5D media might be calculated in the frequency domain using a hybrid method. The model is defined in the Cartesian coordinate system, and its electromagnetic properties might vary in the x- and z-directions, but not in the y-direction. Wave propagation in the x- and z-directions is simulated with the finite-difference method, and wave propagation in the y-direction is simulated with an analytic function. The absorbing boundaries on the finite-difference grid are perfectly matched layers that have been modified to make them compatible with the hybrid method. The accuracy of these numerical Greens functions is assessed by comparing them with independently calculated Green's functions. For a homogeneous model, the magnitude errors range from -4.16% through 0.44%, and the phase errors range from -0.06% through 4.86%. For a layered model, the magnitude errors range from -2.60% through 2.06%, and the phase errors range from -0.49% through 2.73%. These numerical Green's functions might be used for forward modeling and full waveform inversion. ?? 2009 Society of Exploration Geophysicists. All rights reserved.

  10. A generalized multiscale finite element method for elastic wave propagation in fractured media

    KAUST Repository

    Chung, Eric T.

    2016-02-26

    In this paper, we consider elastic wave propagation in fractured media applying a linear-slip model to represent the effects of fractures on the wavefield. Fractured media, typically, are highly heterogeneous due to multiple length scales. Direct numerical simulations for wave propagation in highly heterogeneous fractured media can be computationally expensive and require some type of model reduction. We develop a multiscale model reduction technique that captures the complex nature of the media (heterogeneities and fractures) in the coarse scale system. The proposed method is based on the generalized multiscale finite element method, where the multiscale basis functions are constructed to capture the fine-scale information of the heterogeneous, fractured media and effectively reduce the degrees of freedom. These multiscale basis functions are coupled via the interior penalty discontinuous Galerkin method, which provides a block-diagonal mass matrix. The latter is needed for fast computation in an explicit time discretization, which is used in our simulations. Numerical results are presented to show the performance of the presented multiscale method for fractured media. We consider several cases where fractured media contain fractures of multiple lengths. Our numerical results show that the proposed reduced-order models can provide accurate approximations for the fine-scale solution.

  11. A generalized multiscale finite element method for elastic wave propagation in fractured media

    KAUST Repository

    Chung, Eric T.; Efendiev, Yalchin R.; Gibson, Richard L.; Vasilyeva, Maria

    2016-01-01

    In this paper, we consider elastic wave propagation in fractured media applying a linear-slip model to represent the effects of fractures on the wavefield. Fractured media, typically, are highly heterogeneous due to multiple length scales. Direct numerical simulations for wave propagation in highly heterogeneous fractured media can be computationally expensive and require some type of model reduction. We develop a multiscale model reduction technique that captures the complex nature of the media (heterogeneities and fractures) in the coarse scale system. The proposed method is based on the generalized multiscale finite element method, where the multiscale basis functions are constructed to capture the fine-scale information of the heterogeneous, fractured media and effectively reduce the degrees of freedom. These multiscale basis functions are coupled via the interior penalty discontinuous Galerkin method, which provides a block-diagonal mass matrix. The latter is needed for fast computation in an explicit time discretization, which is used in our simulations. Numerical results are presented to show the performance of the presented multiscale method for fractured media. We consider several cases where fractured media contain fractures of multiple lengths. Our numerical results show that the proposed reduced-order models can provide accurate approximations for the fine-scale solution.

  12. Stochastic description of heterogeneities of permeability within groundwater flow models

    International Nuclear Information System (INIS)

    Cacas, M.C.; Lachassagne, P.; Ledoux, E.; Marsily, G. de

    1991-01-01

    In order to model radionuclide migration in the geosphere realistically at the field scale, the hydrogeologist needs to be able to simulate groundwater flow in heterogeneous media. Heterogeneity of the medium can be described using a stochastic approach, that affects the way in which a flow model is formulated. In this paper, we discuss the problems that we have encountered in modelling both continuous and fractured media. The stochastic approach leads to a methodology that enables local measurements of permeability to be integrated into a model which gives a good prediction of groundwater flow on a regional scale. 5 Figs.; 8 Refs

  13. Approximations for transport parameters and self-averaging properties for point-like injections in heterogeneous media

    International Nuclear Information System (INIS)

    Eberhard, Jens

    2004-01-01

    We focus on transport parameters in heterogeneous media with a flow modelled by an ensemble of periodic and Gaussian random fields. The parameters are determined by ensemble averages. We study to what extent these averages represent the behaviour in a single realization. We calculate the centre-of-mass velocity and the dispersion coefficient using approximations based on a perturbative expansion for the transport equation, and on the iterative solution of the Langevin equation. Compared with simulations, the perturbation theory reproduces the numerical results only poorly, whereas the iterative solution yields good results. Using these approximations, we investigate the self-averaging properties. The ensemble average of the velocity characterizes the behaviour of a realization for large times in both ensembles. The dispersion coefficient is not self-averaging in the ensemble of periodic fields. For the Gaussian ensemble the asymptotic dispersion coefficient is self-averaging. For finite times, however, the fluctuations are so large that the average does not represent the behaviour in a single realization

  14. Effective properties of linear viscoelastic heterogeneous media: Internal variables formulation and extension to ageing behaviours

    International Nuclear Information System (INIS)

    Ricaud, J.M.; Masson, R.; Masson, R.

    2009-01-01

    The Laplace-Carson transform classically used for homogenization of linear viscoelastic heterogeneous media yields integral formulations of effective behaviours. These are far less convenient than internal variables formulations with respect to computational aspects as well as to theoretical extensions to closely related problems such as ageing viscoelasticity. Noticing that the collocation method is usually adopted to invert the Laplace-Carson transforms, we first remark that this approximation is equivalent to an internal variables formulation which is exact in some specific situations. This result is illustrated for a two-phase composite with phases obeying a compressible Maxwellian behaviour. Next, an incremental formulation allows to extend at each time step the previous general framework to ageing viscoelasticity. Finally, with the help of a creep test of a porous viscoelastic matrix reinforced with elastic inclusions, it is shown that the method yields accurate predictions (comparing to reference results provided by periodic cell finite element computations). (authors)

  15. Symmetric wetting heterogeneity suppresses fluid displacement hysteresis in granular piles

    Science.gov (United States)

    Moosavi, R.; Schröter, M.; Herminghaus, S.

    2018-02-01

    We investigate experimentally the impact of heterogeneity on the capillary pressure hysteresis in fluid invasion of model porous media. We focus on symmetric heterogeneity, where the contact angles the fluid interface makes with the oil-wet (θ1) and the water-wet (θ2) beads add up to π . While enhanced heterogeneity is usually known to increase hysteresis phenomena, we find that hysteresis is greatly reduced when heterogeneities in wettability are introduced. On the contrary, geometric heterogeneity (like bidisperse particle size) does not lead to such an effect. We provide a qualitative explanation of this surprising result, resting on rather general geometric arguments.

  16. Thermal non-equilibrium in heterogeneous media

    CERN Document Server

    de Lemos, Marcelo J S

    2016-01-01

    This book presents, in a self-contained fashion, a series of studies on flow and heat transfer in porous media, in which distinct energy balances are considered for the porous matrix and for the permeating fluid. Detailed mathematical modeling is presented considering both volume and time averaging operators simultaneously applied to the governing equations. System involving combustion in the gaseous phase, moving bed and double-diffusion mechanism are analyzed. Numerical results are presented for each case. In the end, this book contains the description of a tool that might benefit engineers in developing and designing more efficient thermal equipment.

  17. Heterogeneous porous media permeability field characterization from fluid displacement data; Integration de donnees de deplacements de fluides dans la caracterisation de milieux poreux heterogenes

    Energy Technology Data Exchange (ETDEWEB)

    Kretz, V.

    2002-11-01

    The prediction of oil recovery or pollutant dispersion requires an accurate knowledge of the permeability field distribution. Available data are usually measurements in well bores, and, since a few years, 4D-seismic data (seismic mappings repeated in time). Such measurements allow to evaluate fluids displacements fronts evolution. The purpose of the thesis is to evaluate the possibility to determinate permeability fields from fluid displacement measurements in heterogeneous porous media. At the laboratory scale, experimental studies are made on a model and on numerical simulations. The system uses blocks of granular materials whose individual geometries and permeabilities are controlled. The fluids displacements are detected with an acoustical. The key parameters of the study are the size and spatial correlation of the permeability heterogeneity distribution, and the influence of viscosity and gravity contrasts between the injected ant displaced fluid. Then the inverse problem - evaluating the permeability field from concentration fronts evolution - is approached. At the reservoir scale, the work will mainly be focused on the integration of 4D-seismic data into inversion programs on a 3D synthetic case. A particular importance will be given to the calculation of gradients, in order to obtain a complementary information about the sensitivity of data. The information provided by 4D-seismic data consists in maps showing the vertical average of oil saturation or the presence of gas. The purpose is to integrate this qualitative information in the inversion process and to evaluate the impact on the reservoir characterization. Comparative studies - with or without 4D-seismic data - will be realized on a synthetic case. (author)

  18. Resolución algebraica de problemas estequiométricos

    OpenAIRE

    Reza García, J.

    2009-01-01

    La resolución de problemas, entendida como la metodología para enfrentar situaciones nuevas que impliquen un reto personal, es una estrategia didáctica eficaz que permite generar, consolidar e integrar conocimientos. La resolución de un problema típico en ciencias parte de la comprensión de su enunciado, constituido por un texto corto escrito en lenguaje natural; la traducción de dicha situación al lenguaje matemático constituye un obstáculo en el proceso de resolución de problemas con estruc...

  19. Problemas de teoria dos números

    OpenAIRE

    Pontes, Dúnia Lisandra Serra Lêdo

    2013-01-01

    Tese de mestrado em Matemática para Professores, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013 A tese em questão, como o título sugere – Problemas de teoria dos números – propõe-se a estudar problemas relativos a uma das áreas mais antigas e mais ricas da matemática, considerada uma forte influência na evolução de grandes matemáticos. Este trabalho conjuga dois temas deveras importantes para o desenvolvimento da criatividade e do conhecimento matemático: reso...

  20. Simulation of Tracer Transport in Porous Media: Application to Bentonites

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.

    2001-01-01

    We present a formal framework to describe tracer transport in heterogeneous media, such as porous media like bentonites. In these media, mean field approximation is not valid because there exist some geometrical constraints and the transport is anomalous. (Author)

  1. Monte Carlo simulation of the Leksell Gamma KnifeTM: II. Effects of heterogeneous versus homogeneous media for stereotactic radiosurgery

    International Nuclear Information System (INIS)

    Moskvin, Vadim; Timmerman, Robert; DesRosiers, Colleen; Randall, Marcus; DesRosiers, Paul; Dittmer, Phil; Papiez, Lech

    2004-01-01

    The absence of electronic equilibrium in the vicinity of bone-tissue or air-tissue heterogeneity in the head can misrepresent deposited dose with treatment planning algorithms that assume all treatment volume as homogeneous media. In this paper, Monte Carlo simulation (PENELOPE) and measurements with a specially designed heterogeneous phantom were applied to investigate the effect of air-tissue and bone-tissue heterogeneity on dose perturbation with the Leksell Gamma Knife TM . The dose fall-off near the air-tissue interface caused by secondary electron disequilibrium leads to overestimation of dose by the vendor supplied treatment planning software (GammaPlan TM ) at up to 4 mm from an interface. The dose delivered to the target area away from an air-tissue interface may be underestimated by up to 7% by GammaPlan TM due to overestimation of attenuation of photon beams passing through air cavities. While the underdosing near the air-tissue interface cannot be eliminated with any plug pattern, the overdosage due to under-attenuation of the photon beams in air cavities can be eliminated by plugging the sources whose beams intersect the air cavity. Little perturbation was observed next to bone-tissue interfaces. Monte Carlo results were confirmed by measurements. This study shows that the employed Monte Carlo treatment planning is more accurate for precise dosimetry of stereotactic radiosurgery with the Leksell Gamma Knife TM for targets in the vicinity of air-filled cavities

  2. Levantamento de problemas comportamentais/emocionais em um ambulatório para adolescentes

    Directory of Open Access Journals (Sweden)

    Benedita Salete Costa Lima Valverde

    2012-12-01

    Full Text Available Este estudo teve como objetivo identificar os principais problemas comportamentais e emocionais percebidos por adolescentes que frequentam um ambulatório de saúde. Participaram 320 adolescentes que não estavam em atendimento psicoterápico e que responderam, na sala de espera de um ambulatório, o Youth Self Report. O principal problema relatado foi Ansiedade/Depressão. Os meninos obtiveram escores mais altos em Problemas Sociais e mais baixos em Comportamento Delinquente; as meninas apresentaram-se com menos problemas no agrupamento Problemas Somáticos e com mais problemas em Ansiedade/Depressão. Quanto à faixa etária, observou-se que Problemas Sociais esteve associado ao início da adolescência. Quanto à incidência, menos de um quarto dos adolescentes apresentaram-se com problemas, sugerindo que a adolescência não é um período de turbulência. Observou-se que alguns adolescentes necessitam de uma avaliação mais detalhada, pois relataram comportamentos indicativos de transtornos mentais. Conclui-se a necessidade de profissionais de saúde mental integrarem a equipe de saúde que atende adolescentes.

  3. Algunas relaciones entre algoritmos y resolución de problemas

    Directory of Open Access Journals (Sweden)

    Jaime Fonseca González

    2012-04-01

    Full Text Available Como parte del estudio realizado en la tesis de maestría “Uso de algoritmos en la resolución de problemas sobre isometrías del plano. Un estudio de caso”, se han identificado diversas formas en que se relacionan los algoritmos con la resolución de problemas, no sólo como procesos mecánicos, sino como fuente de información en el planteamiento de estrategias al resolver un problema, de modo que surgen algunas maneras en que se da esta relación, ejemplificando cada una de ellas con problemas cuyo objeto matemático central son las isometrías del plano.

  4. Coupled enzyme reactions performed in heterogeneous reaction media: experiments and modeling for glucose oxidase and horseradish peroxidase in a PEG/citrate aqueous two-phase system.

    Science.gov (United States)

    Aumiller, William M; Davis, Bradley W; Hashemian, Negar; Maranas, Costas; Armaou, Antonios; Keating, Christine D

    2014-03-06

    The intracellular environment in which biological reactions occur is crowded with macromolecules and subdivided into microenvironments that differ in both physical properties and chemical composition. The work described here combines experimental and computational model systems to help understand the consequences of this heterogeneous reaction media on the outcome of coupled enzyme reactions. Our experimental model system for solution heterogeneity is a biphasic polyethylene glycol (PEG)/sodium citrate aqueous mixture that provides coexisting PEG-rich and citrate-rich phases. Reaction kinetics for the coupled enzyme reaction between glucose oxidase (GOX) and horseradish peroxidase (HRP) were measured in the PEG/citrate aqueous two-phase system (ATPS). Enzyme kinetics differed between the two phases, particularly for the HRP. Both enzymes, as well as the substrates glucose and H2O2, partitioned to the citrate-rich phase; however, the Amplex Red substrate necessary to complete the sequential reaction partitioned strongly to the PEG-rich phase. Reactions in ATPS were quantitatively described by a mathematical model that incorporated measured partitioning and kinetic parameters. The model was then extended to new reaction conditions, i.e., higher enzyme concentration. Both experimental and computational results suggest mass transfer across the interface is vital to maintain the observed rate of product formation, which may be a means of metabolic regulation in vivo. Although outcomes for a specific system will depend on the particulars of the enzyme reactions and the microenvironments, this work demonstrates how coupled enzymatic reactions in complex, heterogeneous media can be understood in terms of a mathematical model.

  5. Relación entre Problemas de Conducta en Adolescentes y Conflicto Interparental en Familias Intactas y Monoparentales/Relationship between Teen Behavior Problems and Interparental Conflict in Intact and Single-Parent Families/Relação entre Problemas de Comportamento em Adolescentes e Conflito Interparental em Famílias Intactas e Monoparentais

    Directory of Open Access Journals (Sweden)

    Cecilia Mayorga Muñoz

    2016-03-01

    Full Text Available El propósito del estudio fue analizar la influencia del conflicto interparentalen la aparición de problemas de conducta en adolescentes de familias intactas y monoparentales. Se utilizó un diseño explicativo que consideró prueba de medias y análisis multivariado de varianza. La muestra estuvo compuesta de 466 adolescentes de 12 a 16 años. Para la medición de las variables se utilizaron las escalas Children’s Perception of Interparental Conflict (cpic y Youth Self Report (ysr. Los resultados confirman la asociación entre conflicto interparental y problemas de conducta en los hijos, y muestran que, cuando hay conflicto en las familias intactas, se produce una mayor frecuencia de conductas externalizantes que en familias monoparentales.

  6. Estimating the effect of treatment rate changes when treatment benefits are heterogeneous: antibiotics and otitis media.

    Science.gov (United States)

    Park, Tae-Ryong; Brooks, John M; Chrischilles, Elizabeth A; Bergus, George

    2008-01-01

    Contrast methods to assess the health effects of a treatment rate change when treatment benefits are heterogeneous across patients. Antibiotic prescribing for children with otitis media (OM) in Iowa Medicaid is the empirical example. Instrumental variable (IV) and linear probability model (LPM) are used to estimate the effect of antibiotic treatments on cure probabilities for children with OM in Iowa Medicaid. Local area physician supply per capita is the instrument in the IV models. Estimates are contrasted in terms of their ability to make inferences for patients whose treatment choices may be affected by a change in population treatment rates. The instrument was positively related to the probability of being prescribed an antibiotic. LPM estimates showed a positive effect of antibiotics on OM patient cure probability while IV estimates showed no relationship between antibiotics and patient cure probability. Linear probability model estimation yields the average effects of the treatment on patients that were treated. IV estimation yields the average effects for patients whose treatment choices were affected by the instrument. As antibiotic treatment effects are heterogeneous across OM patients, our estimates from these approaches are aligned with clinical evidence and theory. The average estimate for treated patients (higher severity) from the LPM model is greater than estimates for patients whose treatment choices are affected by the instrument (lower severity) from the IV models. Based on our IV estimates it appears that lowering antibiotic use in OM patients in Iowa Medicaid did not result in lost cures.

  7. Media life of the young

    DEFF Research Database (Denmark)

    Westlund, Oscar; Bjur, Jakob

    2014-01-01

    This is a thorough investigation into contemporary young people and their media life. The article conceptualizes a typology of media life, drawing on a theoretical body involving the sociology of generations, life course research, media life and individualization. This empirically derived typology...... makes a strong instrument for an understanding of the media life of the young, furnishing insights into how they have constructed their use of media. The investigation is based on a robust national survey with Swedes born 1994–2001, conducted in 2010, and focusing on four media: television, gaming......, the Internet and mobile devices. Two of the findings are particularly surprising. Firstly, the results reveal that the young generally lead heterogeneous media lives, varying with age and sex. Secondly, although some young people literarily live their life in media, there are also de facto young who live...

  8. Travelling wave phenomena in non-heterogeneous tissues

    DEFF Research Database (Denmark)

    Pedersen, Michael

    2006-01-01

    Disturbances (or information) propagating in heterogeneous biological tissues (or other media) are often modeled by a partial differential equation of the form $$ u''(t,x) +D(x)u'(t,x) +A(x)u(t,x)=f(t,x), $$ for $ 0...

  9. La escuela media : el punto crítico de los sistemas escolares

    Directory of Open Access Journals (Sweden)

    Ricardo Bruera

    2000-01-01

    Full Text Available El concepto de la Escuela Media ha sido objeto de múltiples discusiones durante la última década. Todavía no se ha llegado a un acuerdo sobre la defmición precisa de este concepto. Tras diversos estudios exhaustivos se ha comprobado que el principal problema de la Escuela Media es que es utilizada, bien para completar, o bien para introducir otras formaciones. Son dos las hipótesis que argumentan esta problemática: a la Escuela Media no obtiene buenos resultados y b la Escuela Media origina fracasos escolares. El origen de este problema radica en las nuevas políticas de ampliación de la escolarización global en las poblaciones y en la falta de un conocimiento propio que la distinga. La Escuela Media representa, por tanto, un conflicto dentro del sistema educativo. Una posible solución es mejorar el rendimiento cualitativo y cuantitativo. El articulo realiza un análisis de las reformas educativas de la última década en diferentes países (España, Argentina, Francia, Canadá, Gran Bretaña e Italia. Sin embargo, estas reformas no parecen adecuadas para subsanar tan compleja problemática, ya que su origen es más didáctico que político. Es necesario, además, tener en cuenta las necesidades propias de crecimiento del alumno y realizar acciones más concretas para asegurar el éxito de la Escuela Media, y no sólo limitarnos a bajar los niveles globales de formación para mejorar el rendimiento. 

  10. Effect of the image resolution on the statistical descriptors of heterogeneous media

    Science.gov (United States)

    Ledesma-Alonso, René; Barbosa, Romeli; Ortegón, Jaime

    2018-02-01

    The characterization and reconstruction of heterogeneous materials, such as porous media and electrode materials, involve the application of image processing methods to data acquired by scanning electron microscopy or other microscopy techniques. Among them, binarization and decimation are critical in order to compute the correlation functions that characterize the microstructure of the above-mentioned materials. In this study, we present a theoretical analysis of the effects of the image-size reduction, due to the progressive and sequential decimation of the original image. Three different decimation procedures (random, bilinear, and bicubic) were implemented and their consequences on the discrete correlation functions (two-point, line-path, and pore-size distribution) and the coarseness (derived from the local volume fraction) are reported and analyzed. The chosen statistical descriptors (correlation functions and coarseness) are typically employed to characterize and reconstruct heterogeneous materials. A normalization for each of the correlation functions has been performed. When the loss of statistical information has not been significant for a decimated image, its normalized correlation function is forecast by the trend of the original image (reference function). In contrast, when the decimated image does not hold statistical evidence of the original one, the normalized correlation function diverts from the reference function. Moreover, the equally weighted sum of the average of the squared difference, between the discrete correlation functions of the decimated images and the reference functions, leads to a definition of an overall error. During the first stages of the gradual decimation, the error remains relatively small and independent of the decimation procedure. Above a threshold defined by the correlation length of the reference function, the error becomes a function of the number of decimation steps. At this stage, some statistical information is lost

  11. Educational Potential of New Media

    OpenAIRE

    Maria Yu. Kazak; Irina I. Karpenko; Aleksandr P. Korochenskiy; Andrey V. Polonskiy; Yan I. Tiazhlov; Svetlana V. Ushakova

    2017-01-01

    Digitalization of the mass media, which has radically changed the information environment, creates new opportunities for self-education and upgrowth of the audience. The paper defines the communicative and cultural status of new media, characterizes the socio-cultural and technological aspects of their dynamics; substantiates the necessity of elaborating mechanisms for systematization of heterogeneous information flows and elaborating criteria for their evaluation in the era of globalization ...

  12. Upscaling of Large-Scale Transport in Spatially Heterogeneous Porous Media Using Wavelet Transformation

    Science.gov (United States)

    Moslehi, M.; de Barros, F.; Ebrahimi, F.; Sahimi, M.

    2015-12-01

    Modeling flow and solute transport in large-scale heterogeneous porous media involves substantial computational burdens. A common approach to alleviate this complexity is to utilize upscaling methods. These processes generate upscaled models with less complexity while attempting to preserve the hydrogeological properties comparable to the original fine-scale model. We use Wavelet Transformations (WT) of the spatial distribution of aquifer's property to upscale the hydrogeological models and consequently transport processes. In particular, we apply the technique to a porous formation with broadly distributed and correlated transmissivity to verify the performance of the WT. First, transmissivity fields are coarsened using WT in such a way that the high transmissivity zones, in which more important information is embedded, mostly remain the same, while the low transmissivity zones are averaged out since they contain less information about the hydrogeological formation. Next, flow and non-reactive transport are simulated in both fine-scale and upscaled models to predict both the concentration breakthrough curves at a control location and the large-scale spreading of the plume around its centroid. The results reveal that the WT of the fields generates non-uniform grids with an average of 2.1% of the number of grid blocks in the original fine-scale models, which eventually leads to a significant reduction in the computational costs. We show that the upscaled model obtained through the WT reconstructs the concentration breakthrough curves and the spreading of the plume at different times accurately. Furthermore, the impacts of the Hurst coefficient, size of the flow domain and the orders of magnitude difference in transmissivity values on the results have been investigated. It is observed that as the heterogeneity and the size of the domain increase, better agreement between the results of fine-scale and upscaled models can be achieved. Having this framework at hand aids

  13. Micromechanics of heterogeneous materials

    CERN Document Server

    Buryachenko, Valeriy

    2007-01-01

    Here is an accurate and timely account of micromechanics, which spans materials science, mechanical engineering, applied mathematics, technical physics, geophysics, and biology. The book features rigorous and unified theoretical methods of applied mathematics and statistical physics in the material science of microheterogeneous media. Uniquely, it offers a useful demonstration of the systematic and fundamental research of the microstructure of the wide class of heterogeneous materials of natural and synthetic nature.

  14. Los nuevos problemas de la infancia, propuestas de solución

    Directory of Open Access Journals (Sweden)

    María Eugenia Mansilla

    1992-12-01

    Full Text Available En este trabajo se analizan los problemas que viven los niños de los sectores populares del Perú, haciendo algunos alcances con la realidad de otros países latinoamericanos. El enfoque del análisis es que el origen de tales problemas se encuentra en la forma que hemos organizado la sociedad, de ahí que se plantee que corresponden a una sociedad del horno sapiens y que "la mayoría de los problemas no son nuevos, (sino que lo nuevo es la forma en que se expresan y la manera en la que los vernos". La revisión de los problemas se inicia con el concepto niño discutiendo el enfoque tradicional con una propuesta alternativa que considera al niño un ser humano en desarrollo; se revisan algunos problemas que son productos de la urbanización y del actual modelo económico y la vigencia de algunos problemas viejos corno la discriminación y el trabajo infantil; se analizan brevemente las políticas sociales y se plantean algunas alternativas dirigidas a superarlos y avanzar en la construcción de una sociedad humana.

  15. 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.

  16. 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.

  17. Monte Carlo simulation of the Leksell Gamma Knife{sup TM}: II. Effects of heterogeneous versus homogeneous media for stereotactic radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Moskvin, Vadim; Timmerman, Robert; DesRosiers, Colleen; Randall, Marcus; DesRosiers, Paul; Dittmer, Phil; Papiez, Lech [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, 535 Barnhill Dr, RT041, IN 46202-5289 (United States)

    2004-11-07

    The absence of electronic equilibrium in the vicinity of bone-tissue or air-tissue heterogeneity in the head can misrepresent deposited dose with treatment planning algorithms that assume all treatment volume as homogeneous media. In this paper, Monte Carlo simulation (PENELOPE) and measurements with a specially designed heterogeneous phantom were applied to investigate the effect of air-tissue and bone-tissue heterogeneity on dose perturbation with the Leksell Gamma Knife{sup TM}. The dose fall-off near the air-tissue interface caused by secondary electron disequilibrium leads to overestimation of dose by the vendor supplied treatment planning software (GammaPlan{sup TM}) at up to 4 mm from an interface. The dose delivered to the target area away from an air-tissue interface may be underestimated by up to 7% by GammaPlan{sup TM} due to overestimation of attenuation of photon beams passing through air cavities. While the underdosing near the air-tissue interface cannot be eliminated with any plug pattern, the overdosage due to under-attenuation of the photon beams in air cavities can be eliminated by plugging the sources whose beams intersect the air cavity. Little perturbation was observed next to bone-tissue interfaces. Monte Carlo results were confirmed by measurements. This study shows that the employed Monte Carlo treatment planning is more accurate for precise dosimetry of stereotactic radiosurgery with the Leksell Gamma Knife{sup TM} for targets in the vicinity of air-filled cavities.

  18. Numerical study of compositional compressible degenerate two-phase flow in saturated–unsaturated heterogeneous porous media

    KAUST Repository

    Saad, Ali S.; Saad, Bilal Mohammed; Saad, Mazen

    2016-01-01

    We study the convergence of a combined finite volume-nonconforming finite element scheme on general meshes for a partially miscible two-phase flow model in anisotropic porous media. This model includes capillary effects and exchange between the phases. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh. The relative permeability of each phase is decentered according to the sign of the velocity at the dual interface. The convergence of the scheme is proved thanks to an estimate on the two pressures which allows to show estimates on the discrete time and compactness results in the case of degenerate relative permeabilities. A key point in the scheme is to use particular averaging formula for the dissolution function arising in the diffusion term. We show also a simulation of hydrogen production in nuclear waste management. Numerical results are obtained by in-house numerical code. © 2015 Elsevier Ltd.

  19. Numerical study of compositional compressible degenerate two-phase flow in saturated–unsaturated heterogeneous porous media

    KAUST Repository

    Saad, Ali S.

    2016-01-02

    We study the convergence of a combined finite volume-nonconforming finite element scheme on general meshes for a partially miscible two-phase flow model in anisotropic porous media. This model includes capillary effects and exchange between the phases. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh. The relative permeability of each phase is decentered according to the sign of the velocity at the dual interface. The convergence of the scheme is proved thanks to an estimate on the two pressures which allows to show estimates on the discrete time and compactness results in the case of degenerate relative permeabilities. A key point in the scheme is to use particular averaging formula for the dissolution function arising in the diffusion term. We show also a simulation of hydrogen production in nuclear waste management. Numerical results are obtained by in-house numerical code. © 2015 Elsevier Ltd.

  20. Estructura orbital en el Problema Restringido Rectilíneo Isósceles

    Science.gov (United States)

    Orellana, R. B.

    Para definir problemas en Mecánica Celeste se utilizan diferentes parámetros. El conocimiento de la dinámica del problema para valores particulares de estos parámetros nos permite entender el comportamiento en casos más generales. El Problema Restringido Rectilíneo Isósceles puede ser considerado como el caso límite del Problema de Sitnikov cuando la excentricidad tiende a uno o como el Problema Isósceles cuando la masa central tiende a cero. Se ha compactificado el espacio de fases y analizado la dinámica en el límite. Esto ha permitido separar el espacio de fases en diferentes regiones dependiendo de las clases de órbitas.

  1. Quantifying seismic anisotropy induced by small-scale chemical heterogeneities

    Science.gov (United States)

    Alder, C.; Bodin, T.; Ricard, Y.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

    2017-12-01

    Observations of seismic anisotropy are usually used as a proxy for lattice-preferred orientation (LPO) of anisotropic minerals in the Earth's mantle. In this way, seismic anisotropy observed in tomographic models provides important constraints on the geometry of mantle deformation associated with thermal convection and plate tectonics. However, in addition to LPO, small-scale heterogeneities that cannot be resolved by long-period seismic waves may also produce anisotropy. The observed (i.e. apparent) anisotropy is then a combination of an intrinsic and an extrinsic component. Assuming the Earth's mantle exhibits petrological inhomogeneities at all scales, tomographic models built from long-period seismic waves may thus display extrinsic anisotropy. In this paper, we investigate the relation between the amplitude of seismic heterogeneities and the level of induced S-wave radial anisotropy as seen by long-period seismic waves. We generate some simple 1-D and 2-D isotropic models that exhibit a power spectrum of heterogeneities as what is expected for the Earth's mantle, that is, varying as 1/k, with k the wavenumber of these heterogeneities. The 1-D toy models correspond to simple layered media. In the 2-D case, our models depict marble-cake patterns in which an anomaly in shear wave velocity has been advected within convective cells. The long-wavelength equivalents of these models are computed using upscaling relations that link properties of a rapidly varying elastic medium to properties of the effective, that is, apparent, medium as seen by long-period waves. The resulting homogenized media exhibit extrinsic anisotropy and represent what would be observed in tomography. In the 1-D case, we analytically show that the level of anisotropy increases with the square of the amplitude of heterogeneities. This relation is numerically verified for both 1-D and 2-D media. In addition, we predict that 10 per cent of chemical heterogeneities in 2-D marble-cake models can

  2. Light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities based on hybrid simplified spherical harmonics with radiosity model.

    Science.gov (United States)

    Yang, Defu; Chen, Xueli; Peng, Zhen; Wang, Xiaorui; Ripoll, Jorge; Wang, Jing; Liang, Jimin

    2013-01-01

    Modeling light propagation in the whole body is essential and necessary for optical imaging. However, non-scattering, low-scattering and high absorption regions commonly exist in biological tissues, which lead to inaccuracy of the existing light transport models. In this paper, a novel hybrid light transport model that couples the simplified spherical harmonics approximation (SPN) with the radiosity theory (HSRM) was presented, to accurately describe light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities. In the model, the radiosity theory was used to characterize the light transport in non-scattering regions and the SPN was employed to handle the scattering problems, including subsets of low-scattering and high absorption. A Neumann source constructed by the light transport in the non-scattering region and formed at the interface between the non-scattering and scattering regions was superposed into the original light source, to couple the SPN with the radiosity theory. The accuracy and effectiveness of the HSRM was first verified with both regular and digital mouse model based simulations and a physical phantom based experiment. The feasibility and applicability of the HSRM was then investigated by a broad range of optical properties. Lastly, the influence of depth of the light source on the model was also discussed. Primary results showed that the proposed model provided high performance for light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities.

  3. Algoritmos y complejidad para algunos problemas de dominación

    OpenAIRE

    Mizrahi, Michel Jonathan

    2014-01-01

    Los problemas de dominación forman un área de investigación en crecimiento, debido a la cantidad de aplicaciones que pueden modelar, entre las cuales podemos nombrar redes sociales, sistemas distribuidos, redes biológicas, problemas de localización de instalaciones, etc. En esta tesis estudiamos los siguientes problemas de dominación (i) el conjunto dominante mínimo, (ii) dominación romana, (iii) dominación eficiente por vértices, (iv) dominación eficiente por aristas (también conocida como m...

  4. Contribution to gamma ray transport calculation in heterogeneous media

    International Nuclear Information System (INIS)

    Bourdet, L.

    1985-04-01

    This thesis presents the development of gamma transport calculation codes in three dimension heterogeneous geometries. These codes allow us to define the protection against gamma-rays or verify their efficiency. The laws that govern the interactions of gamma-rays with matters are briefly revised. A library with the all necessary constants for these codes is created. TRIPOLI-2, a code that treats in exact way the neutron transport in matters using Monte-Carlo method, has been adapted to deal with the transport of gamma-rays in matters as well. TRINISHI, a code which considers only one collision, has been realized to treat heterogeneous geometries containing voids. Elaborating a formula that calculates the albedo for gamma-ray reflection (the code ALBANE) allows us to solve the problem of gamma-ray reflection on plane surfaces. NARCISSE-2 deals with gamma-rays that suffer only one reflection on the inner walls of any closed volume (rooms, halls...) [fr

  5. Heterogeneity and Scaling in Geologic Media: Applications to Transport in the Vadose and Saturated Zones

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Stephen R.

    2003-06-01

    Heterogeneity and Scaling in Geologic Media: Applications to Transport in the Vadose and Saturated Zones Stephen Brown, Gregory Boitnott, and Martin Smith New England Research In rocks and soils, the bulk geophysical and transport properties of the matrix and of fracture systems are determined by the juxtaposition of geometric features at many length scales. For sedimentary materials the length scales are: the pore scale (irregularities in grain surface roughness and cementation), the scale of grain packing faults (and the resulting correlated porosity structures), the scale dominated by sorting or winnowing due to depositional processes, and the scale of geomorphology at the time of deposition. We are studying the heterogeneity and anisotropy in geometry, permeability, and geophysical response from the pore (microscopic), laboratory (mesoscopic), and backyard field (macroscopic) scales. In turn these data are being described and synthesized for development of mathematical models. Eventually, we will perform parameter studies to explore these models in the context of transport in the vadose and saturated zones. We have developed a multi-probe physical properties scanner which allows for the mapping of geophysical properties on a slabbed sample or core. This device allows for detailed study of heterogeneity at those length scales most difficult to quantify using standard field and laboratory practices. The measurement head consists of a variety of probes designed to make local measurements of various properties, including: gas permeability, acoustic velocities (compressional and shear), complex electrical impedance (4 electrode, wide frequency coverage), and ultrasonic reflection (ultrasonic impedance and permeability). We can thus routinely generate detailed geophysical maps of a particular sample. With the exception of the acoustic velocity, we are testing and modifying these probes as necessary for use on soil samples. As a baseline study we have been

  6. Generalized Multiscale Finite Element Methods for Wave Propagation in Heterogeneous Media

    KAUST Repository

    Chung, Eric T.

    2014-11-13

    Numerical modeling of wave propagation in heterogeneous media is important in many applications. Due to their complex nature, direct numerical simulations on the fine grid are prohibitively expensive. It is therefore important to develop efficient and accurate methods that allow the use of coarse grids. In this paper, we present a multiscale finite element method for wave propagation on a coarse grid. The proposed method is based on the generalized multiscale finite element method (GMsFEM) (see [Y. Efendiev, J. Galvis, and T. Hou, J. Comput. Phys., 251 (2012), pp. 116--135]). To construct multiscale basis functions, we start with two snapshot spaces in each coarse-grid block, where one represents the degrees of freedom on the boundary and the other represents the degrees of freedom in the interior. We use local spectral problems to identify important modes in each snapshot space. These local spectral problems are different from each other and their formulations are based on the analysis. To the best of knowledge, this is the first time that multiple snapshot spaces and multiple spectral problems are used and necessary for efficient computations. Using the dominant modes from local spectral problems, multiscale basis functions are constructed to represent the solution space locally within each coarse block. These multiscale basis functions are coupled via the symmetric interior penalty discontinuous Galerkin method which provides a block diagonal mass matrix and, consequently, results in fast computations in an explicit time discretization. Our methods\\' stability and spectral convergence are rigorously analyzed. Numerical examples are presented to show our methods\\' performance. We also test oversampling strategies. In particular, we discuss how the modes from different snapshot spaces can affect the proposed methods\\' accuracy.

  7. Um sistema multiagente de apoio à aprendizagem baseada em problema

    Directory of Open Access Journals (Sweden)

    Laysa Mabel Oliveira Fontes

    2011-12-01

    Full Text Available A aprendizagem baseada em problema (Problem-Based Learning - PBL é uma teoria de aprendizagem que enfatiza a colaboração e o trabalho em grupo para resolução de um problema. No entanto, um problema que ocorre com freqüência no processo de aplicação da PBL é a presença de conversações fora do contexto, que é uma situação onde os estudantes perdem o foco das discussões do problema e passam a discutir outros assuntos. Outro aspecto importante é com relação ao processo de formação de grupos na PBL. Pode ser difícil para o facilitador alocar estudantes aos grupos a distância, uma vez que a ausência de um contato presencial dificulta o conhecimento de certas características importantes do perfil dos estudantes envolvidos no processo. Outro aspecto a ser considerado é a ausência de padronização dos conceitos relacionados à PBL, pois isto dificulta a compreensão comum e compartilhada sobre este domínio. Desta forma, este trabalho apresenta um sistema multiagente de apoio à PBL, com o objetivo de detectar e corrigir problemas inerentes à implantação desta teoria de aprendizagem. Para solucionar o problema de padronização dos conceitos relacionados à PBL, é proposta uma ontologia que preenche requisitos de abstração e significação dos conceitos relacionados ao domínio.

  8. Estudios sobre "clase media" en la antropología social: una agenda para la Argentina

    OpenAIRE

    Visacovsky, Sergio

    2008-01-01

    El objetivo de este trabajo es exponer un panorama de los estudios antropológicos sobre clase media. Primero, ofrezco una respuesta para explicar por qué la antropología social sólo recientemente se interesó en estudiar poblaciones definidas como "de clase media". Segundo, analizo cómo la sociología en la Argentina hizo de la clase media uno de sus objetos de investigación centrales en los años 1950 (en relación con los problemas del desarrollo y la modernización), y desde los 1990 (en relaci...

  9. Estudio poliedral y algoritmo branch-and-cut para el problema de coloreo equitativo en grafos

    OpenAIRE

    Severin, Daniel E.

    2012-01-01

    Los problemas de coloreo de grafos constituyen una familia de problemas de una gran relevancia tanto teórica como práctica. Todos ellos son variaciones del problema del coloreo clásico, cuyo estudio se inició en el Siglo XIX. El origen de estas variaciones radica en las restricciones adicionales que imponen las aplicaciones a problemas de la vida real. En esta tesis abordamos en particular el Problema de Coloreo Equitativo en Grafos. Como muchos problemas de Optimización Combinatoria, el Prob...

  10. The energy deposition of slowing down particles in heterogeneous media

    International Nuclear Information System (INIS)

    Prinja, A.K.; Williams, M.M.R.

    1980-01-01

    Energy deposition by atomic particles in adjacent semi-infinite, amorphous media is described using the forward form of the Boltzmann transport equation. A transport approximation to the scattering kernel, developed elsewhere, incorporating realistic energy transfer is employed to assess the validity of the commonly used isotropic-scattering and straight-ahead approximations. Results are presented for integral energy deposition rates due to a plane, isotropic and monoenergetic source in one half-space for a range of mass ratios between 0.1 and 5.0. Integral profiles for infinite and semi-infinite media are considered and the influence of reflection for different mass ratios is evaluated. The dissimilar scattering properties of the two media induce a discontinuity at the interface in the energy deposition rate the magnitude of which is sensitive to the source position relative to the interface. A comprehensive evaluation of the total energy deposited in the source free medium is presented for a range of mass ratios and source positions. An interesting minimum occurs for off-interface source locations as a function of the source-medium mass ratio, the position of which varies with the source position but is insensitive to the other mass ratio. As a special case, energy reflection and escape coefficients for semi-infinite media are obtained which demonstrates that the effect of a vacuum interface is insignificant for deep source locations except for large mass ratios when reflection becomes dominant. (author)

  11. Magnetism in heterogeneous thin film systems: Resonant X-ray scattering studies

    International Nuclear Information System (INIS)

    Kortright, J.B.; Jiang, J.S.; Bader, S.D.; Hellwig, O.; Marguiles, D.T.; Fullerton, E.E.

    2002-01-01

    Magnetic and chemical heterogeneity are common in a broad range of magnetic thin film systems. Emerging resonant soft x-ray scattering techniques are well suited to resolve such heterogeneity at relevant length scales. Resonant x-ray magneto-optical Kerr effect measurements laterally average over heterogeneity but can provide depth resolution in different ways, as illustrated in measurements resolving reversible and irreversible changes in different layers of exchange-spring heterostructures. Resonant small-angle scattering measures in-plane heterogeneity and can resolve magnetic and chemical scattering sources in different ways, as illustrated in measurements of granular alloy recording media

  12. Porting Social Media Contributions with SIOC

    Science.gov (United States)

    Bojars, Uldis; Breslin, John G.; Decker, Stefan

    Social media sites, including social networking sites, have captured the attention of millions of users as well as billions of dollars in investment and acquisition. To better enable a user's access to multiple sites, portability between social media sites is required in terms of both (1) the personal profiles and friend networks and (2) a user's content objects expressed on each site. This requires representation mechanisms to interconnect both people and objects on the Web in an interoperable, extensible way. The Semantic Web provides the required representation mechanisms for portability between social media sites: it links people and objects to record and represent the heterogeneous ties that bind each to the other. The FOAF (Friend-of-a-Friend) initiative provides a solution to the first requirement, and this paper discusses how the SIOC (Semantically-Interlinked Online Communities) project can address the latter. By using agreed-upon Semantic Web formats like FOAF and SIOC to describe people, content objects, and the connections that bind them together, social media sites can interoperate and provide portable data by appealing to some common semantics. In this paper, we will discuss the application of Semantic Web technology to enhance current social media sites with semantics and to address issues with portability between social media sites. It has been shown that social media sites can serve as rich data sources for SIOC-based applications such as the SIOC Browser, but in the other direction, we will now show how SIOC data can be used to represent and port the diverse social media contributions (SMCs) made by users on heterogeneous sites.

  13. Quantification and Control of Wall Effects in Porous Media Experiments

    Science.gov (United States)

    Roth, E. J.; Mays, D. C.; Neupauer, R.; Crimaldi, J. P.

    2017-12-01

    Fluid flow dynamics in porous media are dominated by media heterogeneity. This heterogeneity can create preferential pathways in which local seepage velocities dwarf system seepage velocities, further complicating an already incomplete understanding of dispersive processes. In physical models of porous media flows, apparatus walls introduce preferential flow paths (i.e., wall effects) that may overwhelm other naturally occurring preferential pathways within the apparatus, leading to deceptive results. We used planar laser-induced fluorescence (PLIF) in conjunction with refractive index matched (RIM) porous media and pore fluid to observe fluid dynamics in the porous media, with particular attention to the region near the apparatus walls in a 17 cm x 8 cm x 7 cm uniform flow cell. Hexagonal close packed spheres were used to create an isotropic, homogenous porous media field in the interior of the apparatus. Visualization of the movement of a fluorescent dye revealed the influence of the wall in creating higher permeability preferential flow paths in an otherwise homogenous media packing. These preferential flow paths extended approximately one half of one sphere diameter from the wall for homogenously packed regions, with a quickly diminishing effect on flow dynamics for homogenous media adjacent to the preferential pathway, but with major influence on flow dynamics for adjoining heterogeneous regions. Multiple approaches to mitigate wall effects were investigated, and a modified wall was created such that the fluid dynamics near the wall mimics the fluid dynamics within the homogenous porous media. This research supports the design of a two-dimensional experimental apparatus that will simulate engineered pumping schemes for use in contaminant remediation. However, this research could benefit the design of fixed bed reactors or other engineering challenges in which vessel walls contribute to unwanted preferential flow.

  14. Contribution to analytical solution of neutron slowing down problem in homogeneous and heterogeneous media; Prilog analitickom resavanju problema usporavanja neutrona u homogenim i heterogenim sredinama

    Energy Technology Data Exchange (ETDEWEB)

    Stefanovic, D B [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1970-07-01

    The objective of this work is to describe the new analytical solution of the neutron slowing down equation for infinite monoatomic media with arbitrary energy dependence of cross section. The solution is obtained by introducing Green slowing down functions instead of starting from slowing down equations directly. The previously used methods for calculation of fission neutron spectra in the reactor cell were numerical. The proposed analytical method was used for calculating the space-energy distribution of fast neutrons and number of neutron reactions in a thermal reactor cell. The role of analytical method in solving the neutron slowing down in reactor physics is to enable understating of the slowing down process and neutron transport. The obtained results could be used as standards for testing the accuracy od approximative and practical methods.

  15. Orden de no reanimar, consideraciones sobre este problema

    Directory of Open Access Journals (Sweden)

    Dr. G. Luis Cereceda

    2011-05-01

    Se analizan los principales problemas, comenzando por las dificultades según los diferentes escenarios (servicio de urgencia, pabellón de maternidad, sala de hospitalizados, unidad de intensivo, pabellones quirúrgicos; se analiza la incertidumbre sobre el pronóstico de cada pacientes y sobre quién(es deben tomar las decisiones sobre el fin de la vida. Idealmente debe ser el paciente autónomo quien tome la decisión, pero en otros casos se requieren alternativas, una de ellas es la Orden Unilateral. Otros problemas son la Validez de las órdenes de no-RCP en los diferentes tiempos evolutivos, el problema de la Futilidad y la Validez de las “Directivas Anticipadas”, en este grupo resalta el enfoque POLST (Physician’s Order for Life Sustaining Treatment como más comprehensivo; como complemento ha surgido también el concepto AND (Allow Natural Death, que podría estar destinado a remplazar la orden de no-RCP (DNR.

  16. The effect of heterogeneity on the character of density-driven natural convection of CO{sub 2} overlying a brine layer

    Energy Technology Data Exchange (ETDEWEB)

    Farajzadeh, R. [Shell International Exploration and Production, Houston, TX (United States); Ranganathan, P.; Zitha, P.L.J.; Bruining, J. [Delft Univ. of Technology, Delft (Netherlands)

    2010-07-01

    This paper investigated the effect of heterogeneity on the character of natural-convection flow of carbon dioxide (CO{sub 2}) in aquifers and on the dissolution rate of CO{sub 2} in brine, contributing to a better understanding of the effect of heterogeneity on CO{sub 2} mass transfer in aquifers, which is necessary for efficient storage of CO{sub 2} in aquifers. The aquifer permeability, which is in practice heterogeneous, largely governs the efficiency of mixing in density-driven natural convection. The aquifer's degree of permeability variance and the correlation length informs the character of flow-driven mixing processes. Numerical simulation was used to identify different flow regimes of a density-driven natural flow regime. Heterogeneous fields were generated using a spectral method that allows the use of power-law variograms. From the simulations it was observed that the rate of mass transfer of carbon dioxide (CO{sub 2}) into water is higher for heterogeneous media. The formulation of the physical model and related equations and the method for generating the permeability fields were described. The simulation results indicated that gravity-induced fingering is the dominant pattern in low heterogeneity, but fingering will not occur in realistic porous media. The results also showed that the permeability field structure dominates at moderate heterogeneity, and that the flow is dispersive at high heterogeneity when the correlation length of the field is small. Heterogeneous media facilitate a larger rate of CO{sub 2} dissolution than homogenous media, which means that the former can store larger volumes of CO{sub 2}. 49 refs., 3 tabs., 13 figs.

  17. User recommendation in healthcare social media by assessing user similarity in heterogeneous network.

    Science.gov (United States)

    Jiang, Ling; Yang, Christopher C

    2017-09-01

    The rapid growth of online health social websites has captured a vast amount of healthcare information and made the information easy to access for health consumers. E-patients often use these social websites for informational and emotional support. However, health consumers could be easily overwhelmed by the overloaded information. Healthcare information searching can be very difficult for consumers, not to mention most of them are not skilled information searcher. In this work, we investigate the approaches for measuring user similarity in online health social websites. By recommending similar users to consumers, we can help them to seek informational and emotional support in a more efficient way. We propose to represent the healthcare social media data as a heterogeneous healthcare information network and introduce the local and global structural approaches for measuring user similarity in a heterogeneous network. We compare the proposed structural approaches with the content-based approach. Experiments were conducted on a dataset collected from a popular online health social website, and the results showed that content-based approach performed better for inactive users, while structural approaches performed better for active users. Moreover, global structural approach outperformed local structural approach for all user groups. In addition, we conducted experiments on local and global structural approaches using different weight schemas for the edges in the network. Leverage performed the best for both local and global approaches. Finally, we integrated different approaches and demonstrated that hybrid method yielded better performance than the individual approach. The results indicate that content-based methods can effectively capture the similarity of inactive users who usually have focused interests, while structural methods can achieve better performance when rich structural information is available. Local structural approach only considers direct connections

  18. Bayesian uncertainty quantification for flows in heterogeneous porous media using reversible jump Markov chain Monte Carlo methods

    KAUST Repository

    Mondal, A.

    2010-03-01

    In this paper, we study the uncertainty quantification in inverse problems for flows in heterogeneous porous media. Reversible jump Markov chain Monte Carlo algorithms (MCMC) are used for hierarchical modeling of channelized permeability fields. Within each channel, the permeability is assumed to have a lognormal distribution. Uncertainty quantification in history matching is carried out hierarchically by constructing geologic facies boundaries as well as permeability fields within each facies using dynamic data such as production data. The search with Metropolis-Hastings algorithm results in very low acceptance rate, and consequently, the computations are CPU demanding. To speed-up the computations, we use a two-stage MCMC that utilizes upscaled models to screen the proposals. In our numerical results, we assume that the channels intersect the wells and the intersection locations are known. Our results show that the proposed algorithms are capable of capturing the channel boundaries and describe the permeability variations within the channels using dynamic production history at the wells. © 2009 Elsevier Ltd. All rights reserved.

  19. Nuestro único problema

    Directory of Open Access Journals (Sweden)

    Héctor Rojas Herazo

    1967-12-01

    Full Text Available Toda vida humana por ser, en profundidad y superficie, una batalla contra la muerte, es un fenómeno epopéyico. Más admirable cuanto más secreta y personal sea esa batalla. Pues no nos enfrentamos a este o aquel obstáculo ni somos atraídos por este o aquel señuelo. Nuestra íntima preocupación, nuestro único problema, nuestro máximo terror es sabernos materia de disolución, míseras astillas para alimentar el insaciable fuego de la muerte.

  20. Flows and chemical reactions in heterogeneous mixtures

    CERN Document Server

    Prud'homme, Roger

    2014-01-01

    This book - a sequel of previous publications 'Flows and Chemical Reactions' and 'Chemical Reactions in Flows and Homogeneous Mixtures' - is devoted to flows with chemical reactions in heterogeneous environments.  Heterogeneous media in this volume include interfaces and lines. They may be the site of radiation. Each type of flow is the subject of a chapter in this volume. We consider first, in Chapter 1, the question of the generation of environments biphasic individuals: dusty gas, mist, bubble flow.  Chapter 2 is devoted to the study at the mesoscopic scale: particle-fluid exchange of mom

  1. Heterogenization of Homogeneous Catalysts: the Effect of the Support

    Energy Technology Data Exchange (ETDEWEB)

    Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

    1999-06-29

    We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

  2. Contabilidad de Costos I. - Problemas sobre contabilización de las actividades relacionadas con los materiales

    OpenAIRE

    Morillo Moreno, Marysela C.

    2008-01-01

    ÍNDICE Introducción Problemas sobre terminología básica Problemas básicos sobre el Ciclo de la Contabilidad de Costos Problemas sobre contabilización de las actividades relacionadas con los materiales Problemas sobre la contabilización de las actividades relacionadas con la mano de obra Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación Problemas sobre el Ciclo de la Contabilida...

  3. Principales problemas de traducción en el doblaje italiano-español

    OpenAIRE

    Ortega Paredes, Laura

    2015-01-01

    La traducción para doblaje resulta especialmente complicada debido a las restricciones causadas por la cohesión entre el texto y la imagen. En el presente trabajo trataremos ciertos problemas generales de traducción cuya dificultad se ve acentuada en el caso del doblaje y también otros problemas propios de este tipo de traducción. Trabajaremos con la combinación italiano-español, por lo que algunos de los problemas a tratar serán problemas específicos de esta lengua La traducció pel doblat...

  4. EL PROBLEMA DEL CUMPLEAÑOS, UNA GENERALIZACIÓN

    OpenAIRE

    Aranda, Moisés; Departamento de Matemáticas, Pontificia Universidad Javeriana y Universidad Sergio Arboleda; Molina, Fabio; Departamento de Matemáticas, Pontificia Universidad Javeriana y Universidad Sergio Arboleda; Moreno, Vladimir; Departamento de Matemáticas, Facultad de Ciencias, Pontificia Universidad Javeriana Cra. 7 No 43-82. Bogotá,

    2008-01-01

    El problema del cumpleaños, en el contexto clásico, se resuelve asumiendo una distribución de probabilidades uniforme discreta de los nacimientos. El propósito de este artículo es resolver el mismo problema bajo una distribución de probabilidades discreta arbitraria, y demostrar que bajo la distribución uniforme discreta, la probabilidad de que dos o más personas cumplan años en el mismo día es subestimada. Palabras clave: combinatoria, probabilidad, distribuciones discretas, muestra aleator...

  5. Bacterial Transport in Heterogeneous Porous Media: Laboratory and Field Experiments

    Science.gov (United States)

    Fuller, M. E.

    2001-12-01

    A fully instrumented research site for examining field-scale bacterial transport has been established on the eastern shore of Virginia. Studies employing intact sediment cores from the South Oyster site have been performed to examine the effects of physical and chemical heterogeneity, to derive transport parameters, and to aid in the selection of bacterial strains for use in field experiments. A variety of innovative methods for tracking bacteria were developed and evaluated under both laboratory and field conditions, providing the tools to detect target cell concentrations in groundwater down to effects of physical and chemical heterogeneity on field-scale bacterial transport. The results of this research not only contribute to the development of more effective bioremediation strategies, but also have implications for a better understanding of bacterial movement in the subsurface as it relates to public health microbiology and general microbial ecology.

  6. Finite-Difference Modeling of Seismic Wave Scattering in 3D Heterogeneous Media: Generation of Tangential Motion from an Explosion Source

    Science.gov (United States)

    Hirakawa, E. T.; Pitarka, A.; Mellors, R. J.

    2015-12-01

    Evan Hirakawa, Arben Pitarka, and Robert Mellors One challenging task in explosion seismology is development of physical models for explaining the generation of S-waves during underground explosions. Pitarka et al. (2015) used finite difference simulations of SPE-3 (part of Source Physics Experiment, SPE, an ongoing series of underground chemical explosions at the Nevada National Security Site) and found that while a large component of shear motion was generated directly at the source, additional scattering from heterogeneous velocity structure and topography are necessary to better match the data. Large-scale features in the velocity model used in the SPE simulations are well constrained, however, small-scale heterogeneity is poorly constrained. In our study we used a stochastic representation of small-scale variability in order to produce additional high-frequency scattering. Two methods for generating the distributions of random scatterers are tested. The first is done in the spatial domain by essentially smoothing a set of random numbers over an ellipsoidal volume using a Gaussian weighting function. The second method consists of filtering a set of random numbers in the wavenumber domain to obtain a set of heterogeneities with a desired statistical distribution (Frankel and Clayton, 1986). This method is capable of generating distributions with either Gaussian or von Karman autocorrelation functions. The key parameters that affect scattering are the correlation length, the standard deviation of velocity for the heterogeneities, and the Hurst exponent, which is only present in the von Karman media. Overall, we find that shorter correlation lengths as well as higher standard deviations result in increased tangential motion in the frequency band of interest (0 - 10 Hz). This occurs partially through S-wave refraction, but mostly by P-S and Rg-S waves conversions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore

  7. Resolvendo o problema de Bernstein

    Directory of Open Access Journals (Sweden)

    2006-11-01

    Full Text Available O grande problema no controle do movimento diz respeito à redução da redundância do sistema motor, convertendo-o a um sistema controlável. A aprendizagem cerebelar pela realimentação do erro propõe, de forma simples e engenhosa, uma solução biologicamente plausível para este problema, com uma importante característica: é um processo que deve ser aprendido. Importantes aspectos relativos a estas questões são discutidos neste artigo. PALAVRAS-CHAVE: controle motor – aprendizagem motora – aprendizagem cerebelar The great problem about controlling the movement is the reduction of the motor system redundance, converting it into a controlable system. The cerebellar feedback errar learning praposes, by simple and ingenius way, one biologic plausible solution to this problem, with an important feature: it is a process that has to be learnt. Some important aspects about these questions are being discussed in this paper. KEY WORDS: Motor contrai – Motor learning – Cerebellar learning

  8. Secure Media Independent Handover Message Transport in Heterogeneous Networks

    Directory of Open Access Journals (Sweden)

    Cho Choong-Ho

    2009-01-01

    Full Text Available The IEEE 802.21 framework for Media Independent Handover (MIH provides seamless vertical handover support for multimode mobile terminals. MIH messages are exchanged over various wireless media between mobile terminals and access networks to facilitate seamless handover. This calls for the need to secure MIH messages against network security threats in the wireless medium. In this paper, we first analyze IPSec/IKEv2 and DTLS security solution for secure MIH message transport. We show that handover latency can be an impediment to the use of IPSec and DTLS solutions. To overcome the handover overhead and hence minimize authentication time, a new secure MIH message transport solution, referred as MIHSec in this paper, is proposed. Experimental results are obtained for MIH between WLAN and Ethernet networks and the impacts of MIH message security on the handover latency are evaluated for IPSec, DTLS, and MIHSec security solutions. The effectiveness of MIHSec is demonstrated.

  9. Pore-network model of evaporation-induced salt precipitation in porous media: The effect of correlations and heterogeneity

    Science.gov (United States)

    Dashtian, Hassan; Shokri, Nima; Sahimi, Muhammad

    2018-02-01

    Salt transport and precipitation in porous media constitute a set of complex and fascinating phenomena that are of considerable interest to several important problems, ranging from storage of CO2 in geological formations, to soil fertility, and protection of pavements and roads, as well as historical monuments. The phenomena occur at the pore scale and are greatly influenced by the heterogeneity of the pore space morphology. We present a pore-network (PN) model to study the phenomena. Vapor diffusion, capillary effect at the brine-vapor interface, flow of brine, and transport of salt and its precipitation in the pores that plug the pores partially or completely are all accounted for. The drying process is modeled by the invasion percolation, while transport of salt in brine is accounted for by the convective-diffusion equation. We demonstrate that the drying patterns, the clustering and connectivity of the pore throats in which salt precipitation occurs, the saturation distribution, and the drying rate are all strongly dependent upon the pore-size distribution, the correlations among the pore sizes, and the anisotropy of the pore space caused by stratification that most natural porous media contain. In particular, if the strata are more or less parallel to the direction of injection of the gas that dries out the pore space (air, for example) and/or causes salt precipitation (CO2, for example), the drying rate increases significantly. Moreover, salt tends to precipitate in clusters of neighboring pores that are parallel to the open surface of the porous medium.

  10. Risk factors for infant developmental problems Factores de riesgo para problemas de desarrollo infantil Fatores de risco para problemas de desenvolvimento infantil

    Directory of Open Access Journals (Sweden)

    Margaret Rose Santa Maria-Mengel

    2007-10-01

    Full Text Available This descriptive-correlational study aimed to detect risks for child developmental problems in the first four years of age, to identify the protective resources in the familiar environment, and to verify the best predictive variables of the development at risk. The non-clinical sample was composed by 120 children registered in a Family Health Program. The assessment instruments for global development, expressive language and familiar environment were used. The logistic regression analysis indicated that the lower the father's educational level, the higher the risk for developmental problems. Both the history of low nutritional state at six months of age and the psychosocial risk in the family environment increased the chances of having expressive language problems. It is concluded that screening tests of risk for developmental problems and the analysis of the psychosocial factors in the familiar context should be considered as preventive intervention procedure in the Family Health Programs.El estudio descriptivo-correlacional objetiva detectar riesgos para problemas del desarrollo del niño en los cuatro primeros años, identificar recursos protectores en el ambiente familiar, verificar las mejores variables antedichas del desarrollo en riesgo, en una muestra no-clínica de 120 niños registrados en un Programa de Salud de la Familia. Fueron utilizados instrumentos de evaluación del desarrollo global, lenguaje expresivo del niño y ambiente familiar. El análisis de regresión logística indicó que cuanto menor escolaridad del padre, mayor chance de riesgo para problemas de desarrollo. El histórico del estado nutricional debajo de lo normal a los seis meses de edad y el riesgo psicosocial en el ambiente familiar aumentaba la probabilidad de problemas de lenguaje expresivo. Concluyendo, la selección de riesgos para problemas de desarrollo del niño y el análisis de factores psicosociales del contexto familiar deben incluirse como

  11. Lizard locomotion in heterogeneous granular media

    Science.gov (United States)

    Schiebel, Perrin; Goldman, Daniel

    2014-03-01

    Locomotion strategies in heterogeneous granular environments (common substrates in deserts), are relatively unexplored. The zebra-tailed lizard (C. draconoides) is a useful model organism for such studies owing to its exceptional ability to navigate a variety of desert habitats at impressive speed (up to 50 body-lengths per second) using both quadrapedal and bidepal gaits. In laboratory experiments, we challenge the lizards to run across a field of boulders (2.54 cm diameter glass spheres or 3.8 cm 3D printed spheres) placed in a lattice pattern and embedded in a loosely packed granular medium of 0.3 mm diameter glass particles. Locomotion kinematics of the lizard are recorded using high speed cameras, with and without the scatterers. The data reveals that unlike the lizard's typical quadrupedal locomotion using a diagonal gait, when scatterers are present the lizard is most successful when using a bipedal gait, with a raised center of mass (CoM). We propose that the kinematics of bipedal running in conjunction with the lizard's long toes and compliant hind foot are the keys to this lizard's successful locomotion in the presence of such obstacles. NSF PoLS

  12. Compositional multiphase flow and transport in heterogeneous porous media

    Energy Technology Data Exchange (ETDEWEB)

    Huber, R U

    2000-07-01

    This work first treats the conceptual models for the description of multiphase flow processes in porous media. The thermodynamic laws are explained and the description and quantification of multi-fluid equilibria are discussed in order to account for fluid composition. The fully and weakly coupled approaches for the mathematical description of such flow processes with respect to systems consisting of two and three fluid phases as well as with respect to compositional single and multiphase systems are assessed. For the discretization of the two-phase flow equations node- and cell-centered finite volume methods and mixed and mixed-hybrid finite element approaches are applied. Based upon these methods five solution algorithms are developed. Four of these algorithms are based on the simultaneous solution of the discretized equations in combination with the Newton-Raphson technique. Methods 1 and 2 treat two- three-phase flow processes, Method 3 applies to the solution of partially miscible three-component systems while Method 4 is created for three-phase three-component systems. The latter method uses a variable substitution dependent on the local presence of the fluid phases. Method 5 is based on the IMPES/IMPESC concept. The time-implicit pressure equation is discretized with the mixed-hybrid finite element method. The saturation and concentration equations, respectively, are solved with a cell-centered finite volume scheme. The developed algorithms are applied to the two- and three-phase Buckley-Leverett problems. A partitioning interwell tracer test is simulated. The propagation behavior of nonaqueous phase liquids (NAPLs) in the saturated and unsaturated ground zone under the influence of heterogeneities are examined. In addition, a larger-scale experiment is simulated, which involves an injection of trichloroethylene into the subsurface and the subsequent distribution. Here, the development of a dissolved contaminant plume as well as the behavior of organic

  13. PERCEPCIÓN DEL MUNDO: MAPAS MENTALES Y PROBLEMAS SOCIOAMBIENTALES

    Directory of Open Access Journals (Sweden)

    Antonio José Morales Hernández

    Full Text Available Resumen:Las personas construyen su imagen del mundo en relación con relatos que oyen de familiares y amigos, de noticias que observan en los medios de comunicación de masas... También es relevante la influencia del medio escolar, en especial desde materias como la Geografía, que les presenta no sólo hechos y datos del mundo, sino también una representación del planeta en un mapa. En este artículo queremos ofrecer una experiencia empírica sobre la construcción mental del mapamundi por parte de alumnos de Magisterio de Valencia. Con ello queremos mostrar la necesidad de trabajar este contenido de habilidades cartográficas para evitar la deformación de la explicación del planeta Tierra y sus problemas. Palabras ClaveMapas mentales, percepción de los problemas sociambientales, educación en valores. AbstractPeople build their own image of the world in relation to stories they hear from family and friends, news that they observed in the mass media... It is also relevant the influence of school environment, especially from the subject of Geography, which not only presents facts of the world, it is also a representation of the planet on a map.In this paper we want to provide of an empirical experience of the mental construction of the world map made by students that will be primary teachers in Valencia. With all we explained, we want to show the need of working this contents of cartographic skills to prevent deformation of the explanation of planet Earth and its problems.Key WordsMind mapping, perception of socio-environmental issues, education in valuesRésuméLes personnes construissent leur image du monde en rapport avec les récits qu’ils écoutent à d’autres membres de la famille et les amis, les nouvelles qu’ils observent aux mass media... Il est aussi remarquable l’influence du moyen scolaire, spécialement depuis des matières comme la Géographie, qui ne présente que des faits et des renseignements sur le monde, mais

  14. El maltrato infantil: un problema mundial

    Directory of Open Access Journals (Sweden)

    SANTANA-TAVIRA ROSALINDA

    1998-01-01

    Full Text Available Al abordar el maltrato infantil se presentan diversos problemas: desconocimiento de la verdadera proporción de dicha problemática; raíces culturales e históricas profundas; diversidad de opiniones en cuanto a su definición y clasificación; dificultades en la investigación y, finalmente, una diversidad de consideraciones sobre sus repercusiones y su manejo terapéutico. En el presente artículo se estudia el maltrato infantil desde sus antecedentes históricos, así como sus clasificaciones, sus definiciones y su epidemiología. Asimismo, se revisan las repercusiones y se plantean las alternativas de tratamiento que en la bibliografía existente se han manejado como fundamentales para enfrentar este fenómeno cada vez más alarmante. Queda subrayada la necesidad de unificar criterios en cuanto a la definición y clasificación de información científica en torno a datos demográficos que, finalmente, hablarán de la realidad del problema, de los avances relacionados con sus causas, su diagnóstico, sus medidas preventivas y su tratamiento. Es fundamental utilizar medidas tendientes a prevenir el maltrato, pues una gran parte de los problemas en el niño se ven reflejados en la vida adulta. Se comparan las distintas clasificaciones en torno al tema, así como las características tanto del agredido como del agresor en los distintos tipos de maltrato.

  15. Annotation of Heterogeneous Multimedia Content Using Automatic Speech Recognition

    NARCIS (Netherlands)

    Huijbregts, M.A.H.; Ordelman, Roeland J.F.; de Jong, Franciska M.G.

    2007-01-01

    This paper reports on the setup and evaluation of robust speech recognition system parts, geared towards transcript generation for heterogeneous, real-life media collections. The system is deployed for generating speech transcripts for the NIST/TRECVID-2007 test collection, part of a Dutch real-life

  16. Crack deflection in brittle media with heterogeneous interfaces and its application in shale fracking

    Science.gov (United States)

    Zeng, Xiaguang; Wei, Yujie

    Driven by the rapid progress in exploiting unconventional energy resources such as shale gas, there is growing interest in hydraulic fracture of brittle yet heterogeneous shales. In particular, how hydraulic cracks interact with natural weak zones in sedimentary rocks to form permeable cracking networks is of significance in engineering practice. Such a process is typically influenced by crack deflection, material anisotropy, crack-surface friction, crustal stresses, and so on. In this work, we extend the He-Hutchinson theory (He and Hutchinson, 1989) to give the closed-form formulae of the strain energy release rate of a hydraulic crack with arbitrary angles with respect to the crustal stress. The critical conditions in which the hydraulic crack deflects into weak interfaces and exhibits a dependence on crack-surface friction and crustal stress anisotropy are given in explicit formulae. We reveal analytically that, with increasing pressure, hydraulic fracture in shales may sequentially undergo friction locking, mode II fracture, and mixed mode fracture. Mode II fracture dominates the hydraulic fracturing process and the impinging angle between the hydraulic crack and the weak interface is the determining factor that accounts for crack deflection; the lower friction coefficient between cracked planes and the greater crustal stress difference favor hydraulic fracturing. In addition to shale fracking, the analytical solution of crack deflection could be used in failure analysis of other brittle media.

  17. Problemas en la interpretación de la FFT

    OpenAIRE

    Acocella, Emilio Carlos; Tierra, Carlos J.

    1995-01-01

    La Transformada Rápida de Fourier (FFT) es una herramienta muy útil para diversas aplicaciones. Sin embargo, algunos aspectos relativos a la Transformada Discreta de Fourier (DFT) son ignorados, pudiendo en muchas ocasiones llevar a interpretaciones erróneas. El presente estudio trata de los problemas que pueden resultar del hecho que al DFT corresponde al muestreo de la Transformada de Fourier. Se presentan casos típicos en los que ocurre este problema y son propuestas soluciones para evitar...

  18. Producer-centric vs. Participation-centric: On the Shaping of Mobile Media

    DEFF Research Database (Denmark)

    Westlund, Oscar

    2012-01-01

    the challenges coupled with mobile media. It shows how heterogeneous sensemaking processes emerge among media workers from editorial, business and IT departments. Most importantly, it shows two polarized constellations within the newspaper organization when it comes to the shaping of its mobile application...

  19. Reacciones adversas y problemas relacionados con medicamentos en un servicio de urgencia

    Directory of Open Access Journals (Sweden)

    Güemes Artiles Martín

    1999-01-01

    Full Text Available FUNDAMENTO: Las Reacciones Adversas a Medicamentos y los Problemas Relacionados con Medicamentos (PRM, son una causa frecuente de asistencia en los servicios de urgencias y requieren una mejor evaluación. MÉTODO: Se analizaron 1.097 admisiones consecutivas en el servicio de urgencias de "Nuestra Señora de los Volcanes" (actualmente "Hospital General de Lanzarote" en Arrecife de Lanzarote (Islas Canarias durante un período de tres meses, para determinar la existencia de Reacciones Adversas a Medicamentos o de otros problemas relacionados con fármacos. RESULTADOS: Diecinueve de las 1.097 admisiones se debieron a reacciones adversas a medicamentos (1.73%; 95 % CI: 0.96 % - 2.5%. Entre los otros "Problemas Relacionados con los Medicamentos", destacaron la intoxicación por medicamentos, que se diagnosticó en 5 de los pacientes (0.45%; el agravamiento del cuadro clínico por supresión del medicamento apareció en 8 (0.72% y los tratamientos inadecuados que precisaron atención médica en el servicio de urgencia fueron 11 (1.0%. El número total de problemas relacionados con medicamentos en la muestra fue de 43 (3.9%. Los problemas relacionados con medicamentos causaron hospitalización en el 1.9% de los pacientes atendidos en urgencias y resultó ser la causa de hospitalización en el 9.6% del total de ingresos urgentes en el hospital durante el periodo de estudio. En cuanto a las reacciones adversas a medicamentos causaron 4.1% del total de ingresos en el hospital. CONCLUSIONES: Los problemas relacionados con los medicamentos son un problema frecuente, importante y no bien estudiado en los servicios de urgencias. Además, los servicios de urgencias pueden actuar como el primer sitio de reconocimiento para las reacciones adversas a medicamentos en la población ambulatoria.

  20. Aprendizaje basado en problemas

    OpenAIRE

    Morral, A.; Bou, T.; Cabot, A.; Capitán, A.; Díaz, J.; Fatjó, J.; Macaya, J.L.; Montmany, A.; Romero, D.

    2002-01-01

    Desde el Área de fundamentos de Fisioterapia y con el objetivo de mejorar nuestra calidad docente, iniciamos durante el curso 1999-2000 un conjunto de actividades alrededor de una metodología docente conocida internacionalmente como "problem-based learning". En este articulo explicaremos brevemente en qué consiste el aprendizaje a partir de problemas y cuáles podrían ser las ventajas, desventajas y las posibilidades de implementar este métodos dentro de la Diplomatura de Fisioterapia. T...

  1. Physics of DNAPL Migration and Remediation in the Presence of Heterogeneities; TOPICAL

    International Nuclear Information System (INIS)

    CONRAD, STEPHEN H.; GLASS, ROBERT J.

    1999-01-01

    The goal of our research is to develop a fundamental quantitative understanding of the role of physical heterogeneities on DNAPL migration and remediation in aquifers. Such understanding is critical to cost effectively identify the location of the subsurface zone of contamination and design remediation schemes focused on removing the source of the contamination, the DNAPL itself. To reach this goal, the following objectives for the proposed research are defined: Objective 1: Develop fundamental understanding of the physics of DNAPL migration processes within heterogeneous porous media: (a) Conduct a suite of two-dimensional physical experiments within controlled and systematically varied heterogeneous porous media at scales up to one meter. Vary system parameters to consider a range of capillary and bond numbers within these heterogeneous porous structures. (b) Develop a new DNAPL migration model based on an up-scaling of invasion percolation (UP) to model the migration process. Compare the model predictions to experimental results. Accomplishing objective 1 provides a series of experiments against which we will be able to evaluate the validity of existing multi-phase flow theory as formulated in both percolation codes and in continuum flow codes. These experimental results will also provide new insights into DNAPL migration behavior. Development of the UIP model will provide an exciting alternative to continuum multi-phase flow codes since UIP offers several advantages for modeling DNAPL migration. The UIP model is fast, allowing for: (1) modeling in three dimensions; (2) the incorporation of much more geologic detail; and (3) its use in probabilistic modeling by way of Monte Carlo techniques. Objective 2: Develop fundamental understanding of the physics of DNAPL remediation processes within heterogeneous porous media: Conduct a suite of physical experiments within controlled and systematically varied heterogeneous porous media at scales up to one meter that

  2. Transport in Stochastic Media

    International Nuclear Information System (INIS)

    Haran, O.; Shvarts, D.; Thieberger, R.

    1998-01-01

    Classical transport of neutral particles in a binary, scattering, stochastic media is discussed. It is assumed that the cross-sections of the constituent materials and their volume fractions are known. The inner structure of the media is stochastic, but there exist a statistical knowledge about the lump sizes, shapes and arrangement. The transmission through the composite media depends on the specific heterogeneous realization of the media. The current research focuses on the averaged transmission through an ensemble of realizations, frm which an effective cross-section for the media can be derived. The problem of one dimensional transport in stochastic media has been studied extensively [1]. In the one dimensional description of the problem, particles are transported along a line populated with alternating material segments of random lengths. The current work discusses transport in two-dimensional stochastic media. The phenomenon that is unique to the multi-dimensional description of the problem is obstacle bypassing. Obstacle bypassing tends to reduce the opacity of the media, thereby reducing its effective cross-section. The importance of this phenomenon depends on the manner in which the obstacles are arranged in the media. Results of transport simulations in multi-dimensional stochastic media are presented. Effective cross-sections derived from the simulations are compared against those obtained for the one-dimensional problem, and against those obtained from effective multi-dimensional models, which are partially based on a Markovian assumption

  3. Voice over IP in Wireless Heterogeneous Networks

    DEFF Research Database (Denmark)

    Fathi, Hanane; Chakraborty, Shyam; Prasad, Ramjee

    with the deployment of wireless heterogeneous systems, both speech and data traffic are carrried over wireless links by the same IP-based packet-switched infrastructure. However, this combination faces some challenges due to the inherent properties of the wireless network. The requirements for good quality VoIP...... communications are difficult to achieve in a time-varying environment due to channel errors and traffic congestion and across different systems. The provision of VoIP in wireless heterogeneous networks requires a set of time-efficient control mechanisms to support a VoIP session with acceptable quality....... The focus of Voice over IP in Wierless Heterogeneous Networks is on mechanisms that affect the VoIP user satisfaction  while not explicitly involved in the media session. This relates to the extra delays introduced by the security and the signaling protocols used to set up an authorized VoIP session...

  4. Simulation results for a multirate mass transfer modell for immiscible displacement of two fluids in highly heterogeneous porous media

    Science.gov (United States)

    Tecklenburg, Jan; Neuweiler, Insa; Dentz, Marco; Carrera, Jesus; Geiger, Sebastian

    2013-04-01

    Flow processes in geotechnical applications do often take place in highly heterogeneous porous media, such as fractured rock. Since, in this type of media, classical modelling approaches are problematic, flow and transport is often modelled using multi-continua approaches. From such approaches, multirate mass transfer models (mrmt) can be derived to describe the flow and transport in the "fast" or mobile zone of the medium. The porous media is then modeled with one mobile zone and multiple immobile zones, where the immobile zones are connected to the mobile zone by single rate mass transfer. We proceed from a mrmt model for immiscible displacement of two fluids, where the Buckley-Leverett equation is expanded by a sink-source-term which is nonlocal in time. This sink-source-term models exchange with an immobile zone with mass transfer driven by capillary diffusion. This nonlinear diffusive mass transfer can be approximated for particular imbibition or drainage cases by a linear process. We present a numerical scheme for this model together with simulation results for a single fracture test case. We solve the mrmt model with the finite volume method and explicit time integration. The sink-source-term is transformed to multiple single rate mass transfer processes, as shown by Carrera et. al. (1998), to make it local in time. With numerical simulations we studied immiscible displacement in a single fracture test case. To do this we calculated the flow parameters using information about the geometry and the integral solution for two phase flow by McWorther and Sunnada (1990). Comparision to the results of the full two dimensional two phase flow model by Flemisch et. al. (2011) show good similarities of the saturation breakthrough curves. Carrera, J., Sanchez-Vila, X., Benet, I., Medina, A., Galarza, G., and Guimera, J.: On matrix diffusion: formulations, solution methods and qualitative effects, Hydrogeology Journal, 6, 178-190, 1998. Flemisch, B., Darcis, M

  5. La preeclampsia un problema de salud pública mundial

    OpenAIRE

    Vargas H,Víctor Manuel; Acosta A,Gustavo; Moreno E,Mario Adán

    2012-01-01

    La preeclampsia es un problema de salud pública y una de las principales causas de muerte materna. La prevalencia oscila entre 1,8-16,7%. La causa sigue desconocida y se asocia a problemas de salud importantes, existiendo muchos retos para la predicción, prevención y tratamiento. Las medidas profilácticas como dosis baja de aspirina y suplementos de calcio, requieren mayor evidencia para uso rutinario. El control prenatal, diagnóstico oportuno, manejo adecuado, y parto son las medidas más efi...

  6. Gremialismo y política en los profesionales universitarios argentinos : el problema de la identidad de clase durante la primera mitad del siglo XX.

    OpenAIRE

    Adamovsky, Ezequiel

    2011-01-01

    Adamovsky, E. (2011) Gremialismo y política en los profesionales universitarios argentinos: el problema de la identidad de clase durante la primera mitad del siglo XX. Redes, 17(33), 35-61. Este trabajo se propone contribuir al conocimiento sobre la formación de la clase media en Argentina, a partir del estudio empírico del gremialismo de uno de los sectores que la componen: el de los profesionales universitarios. Indagaremos en las prácticas reivindicativas de este grupo y en las identida...

  7. Online Adaptive Local-Global Model Reduction for Flows in Heterogeneous Porous Media

    KAUST Repository

    Efendiev, Yalchin R.; Gildin, Eduardo; Yang, Yanfang

    2016-01-01

    We propose an online adaptive local-global POD-DEIM model reduction method for flows in heterogeneous porous media. The main idea of the proposed method is to use local online indicators to decide on the global update, which is performed via reduced cost local multiscale basis functions. This unique local-global online combination allows (1) developing local indicators that are used for both local and global updates (2) computing global online modes via local multiscale basis functions. The multiscale basis functions consist of offline and some online local basis functions. The approach used for constructing a global reduced system is based on Proper Orthogonal Decomposition (POD) Galerkin projection. The nonlinearities are approximated by the Discrete Empirical Interpolation Method (DEIM). The online adaption is performed by incorporating new data, which become available at the online stage. Once the criterion for updates is satisfied, we adapt the reduced system online by changing the POD subspace and the DEIM approximation of the nonlinear functions. The main contribution of the paper is that the criterion for adaption and the construction of the global online modes are based on local error indicators and local multiscale basis function which can be cheaply computed. Since the adaption is performed infrequently, the new methodology does not add significant computational overhead associated with when and how to adapt the reduced basis. Our approach is particularly useful for situations where it is desired to solve the reduced system for inputs or controls that result in a solution outside the span of the snapshots generated in the offline stage. Our method also offers an alternative of constructing a robust reduced system even if a potential initial poor choice of snapshots is used. Applications to single-phase and two-phase flow problems demonstrate the efficiency of our method.

  8. Online Adaptive Local-Global Model Reduction for Flows in Heterogeneous Porous Media

    KAUST Repository

    Efendiev, Yalchin R.

    2016-06-07

    We propose an online adaptive local-global POD-DEIM model reduction method for flows in heterogeneous porous media. The main idea of the proposed method is to use local online indicators to decide on the global update, which is performed via reduced cost local multiscale basis functions. This unique local-global online combination allows (1) developing local indicators that are used for both local and global updates (2) computing global online modes via local multiscale basis functions. The multiscale basis functions consist of offline and some online local basis functions. The approach used for constructing a global reduced system is based on Proper Orthogonal Decomposition (POD) Galerkin projection. The nonlinearities are approximated by the Discrete Empirical Interpolation Method (DEIM). The online adaption is performed by incorporating new data, which become available at the online stage. Once the criterion for updates is satisfied, we adapt the reduced system online by changing the POD subspace and the DEIM approximation of the nonlinear functions. The main contribution of the paper is that the criterion for adaption and the construction of the global online modes are based on local error indicators and local multiscale basis function which can be cheaply computed. Since the adaption is performed infrequently, the new methodology does not add significant computational overhead associated with when and how to adapt the reduced basis. Our approach is particularly useful for situations where it is desired to solve the reduced system for inputs or controls that result in a solution outside the span of the snapshots generated in the offline stage. Our method also offers an alternative of constructing a robust reduced system even if a potential initial poor choice of snapshots is used. Applications to single-phase and two-phase flow problems demonstrate the efficiency of our method.

  9. Numerical Simulation of Natural Convection in Heterogeneous Porous media for CO2 Geological Storage

    NARCIS (Netherlands)

    Ranganathan, P.; Farajzadeh, R.; Bruining, J.; Zitha, P.L.J.

    2012-01-01

    We report a modeling and numerical simulation study of density-driven natural convection during geological CO2 storage in heterogeneous formations. We consider an aquifer or depleted oilfield overlain by gaseous CO2, where the water density increases due to CO2 dissolution. The heterogeneity of the

  10. Paradigm shift in LUNG SBRT dose calculation associated with Heterogeneity correction

    International Nuclear Information System (INIS)

    Zucca Aparicio, D.; Perez Moreno, J. M.; Fernandez Leton, P.; Garcia Ruiz-Zorrilla, J.; Pinto Monedero, M.; Marti Asensjo, J.; Alonso Iracheta, L.

    2015-01-01

    Treatment of lung injury SBRT requires great dosimetric accuracy, the increasing clinical importance of dose calculation heterogeneities introducing algorithms that adequately model the transport of particles narrow beams in media of low density, as with Monte Carlo calculation. (Author)

  11. Dispersion analysis for waves propagated in fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Lesniak, A; Niitsuma, H [Tohoku University, Sendai (Japan). Faculty of Engineering

    1996-05-01

    Dispersion of velocity is defined as a variation of the phase velocity with frequency. This paper describes the dispersion analysis of compressional body waves propagated in the heterogeneous fractured media. The new method proposed and discussed here permitted the evaluation of the variation in P wave arrival with frequency. For this processing method, any information about the attenuation of the medium are not required, and only an assumption of weak heterogeneity is important. It was shown that different mechanisms of dispersion can be distinguished and its value can be quantitatively estimated. Although the frequency used in this study was lower than those in most previous experiments reported in literature, the evaluated dispersion was large. It was suggested that such a large dispersion may be caused by the velocity structure of the media studied and by frequency dependent processes in a highly fractured zone. It was demonstrated that the present method can be used in the evaluation of subsurface fracture systems or characterization of any kind of heterogeneities. 10 refs., 6 figs.

  12. Teoría de juegos aplicada a problemas de bancarrota.

    Directory of Open Access Journals (Sweden)

    Hinojosa Ramos, Miguel Ángel

    2003-01-01

    Full Text Available En una situación de bancarrota adquiere gran relevancia la cuestión de cómo dividir el valor neto de la empresa entre sus acreedores. En este trabajo se da respuesta a este problema económico usando reglas de reparto para problemas de bancarrota. Se usará como instrumento la Teoría de Juegos, en particular nos centraremos en los Juegos Cooperativos, y definiremos el Juego de Bancarrota asociado con los Problemas de Bancarrota a través de la definición de Juego de Bancarrota, indicando conceptos de solución en dicho juego. Se ha realizado una aplicación al Plan de Ayudas a la Investigación en Andalucía para el año 2001, en el que se calcularán el valor de Shapley, el nucleolo y el τ-valor.

  13. Estratégia Educacional Baseada em Problemas para Grandes Grupos: Relato de Experiência

    Directory of Open Access Journals (Sweden)

    Sonia Leite da Silva

    Full Text Available RESUMO Nos últimos anos, o olhar sobre a formação dos profissionais de saúde tem se intensificado, particularmente sobre aquela que possa impactar a resolução dos problemas de saúde da população. Um dos aspectos para o alcance desta demanda refere-se a uma formação que incorpore metodologias ativas no processo ensino-aprendizagem de estudantes da saúde. Neste entendimento, tomando como referência metodologias de aprendizagem baseada em problemas, as quais utilizam certos passos para a resolução de problemas, e diante dos desafios de trabalhar com grandes grupos, desenvolveu-se a estratégia educacional denominada Ciclo de Discussão de Problemas (CDP. Este artigo tem por objetivo descrever o CDP como uma estratégia educacional utilizada em grandes grupos no ensino da graduação em saúde. Esta estratégia ancora-se nos princípios de metodologia ativa, pois utiliza problemas com temáticas comuns aos cursos da área da saúde, para desenvolver nos alunos o aprendizado autodirigido, a habilidade de solucionar problemas, o pensamento crítico e o estudo colaborativo, além da visão integrada das ciências básicas. Esta estratégia envolve dois momentos em sala de aula para cada problema: análise e resolução, englobando 12 passos.

  14. From Ivory Tower to Cross-Media Personas

    DEFF Research Database (Denmark)

    Kristensen, Nete Nørgaard; From, Unni

    2015-01-01

    This article introduces a theoretical typology of four rivalling yet converging ideal types of cultural critics in contemporary media culture and in cultural journalism, more specifically, encapsulated by the term the heterogeneous cultural critic and characterized by different kinds of authority...

  15. Application of X-ray CT investigation of CO{sub 2}-brine flow in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Lanlan; Liu, Yu; Song, Yongchen; Yang, Mingjun; Zhao, Yuechao; Zhao, Jiafei; Zhang, Yi; Shen, Zijian [Dalian University of Technology, Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian (China); Xue, Ziqiu [Research Institute of Innovative Technology for the Earth, Kizugawa City, Kyoto (Japan); Suekane, Tetsuya [Tokyo Institute Technology, Department of Energy Sciences, Nagatsuta, Yokohama (Japan)

    2015-05-15

    A clear understanding of two-phase flows in porous media is important for investigating CO{sub 2} geological storage. In this study, we conducted an experiment of CO{sub 2}/brine flow process in porous media under sequestration conditions using X-ray CT technique. The flow properties of relative permeability, porosity heterogeneity, and CO{sub 2} saturation were observed in this experiment. The porous media was packed with glass beads having a diameter of 0.2 mm. The porosity distribution along the flow direction is heterogeneous owing to the diameter and shape of glass beads along the flow direction. There is a relationship between CO{sub 2} saturation and porosity distribution, which changes with different flow rates and fractional flows. The heterogeneity of the porous media influences the distribution of CO{sub 2}; moreover, gravity, fractional flows, and flow rates influence CO{sub 2} distribution and saturation. The relative permeability curve was constructed using the steady-state method. The results agreed well with the relative permeability curve simulated using pore-network model. (orig.)

  16. Niveles de verbalización y resolución colaborativa de problemas poco estructurados

    Directory of Open Access Journals (Sweden)

    José D. Chávez

    2015-01-01

    Full Text Available Se describieron las verbalizaciones de seis estudian - tes universitarios que resolvieron colaborativamen - te un problema poco estructurado. Partiendo de que aportaban información sobre la regulación metacog - nitiva y la solución de problemas, las verbalizacio - nes fueron categorizadas en niveles. Se utilizaron matrices espacio estado para interpretar los niveles de verbalización y los procesos de resolución de problemas poco estructurados. Se evidenció el predo - minio de verbalizaciones no reguladas, la ausencia de verbalizaciones relacionadas a la elaboración de justificaciones y la superficialidad del monitoreo y la evaluación. La evidencia apoya la idea de que la interacción entre pares no mejora por sí misma la solución de problemas. Los resultados invitan al diseño de situaciones de resolución de problemas que efectivamente promuevan la regulación meta - cognitiva entre pares.

  17. Boécio e o problema dos futuros contingentes

    Directory of Open Access Journals (Sweden)

    William de Siqueira Piauí

    2010-09-01

    Full Text Available Esse artigo representa nossa crença de que é possível introduzir o pensamento de Boécio a partir de um dos problemas mais recorrentes da filosofia, o problema dos futuros contingentes, explicitando, a partir daquela problemática é claro, quais as ligações mais fundamentais entre três de suas obras, seus dois comentários ao De Interpretatione de Aristóteles e sua Consolaçáo da Filosofia, e, de forma bastante resumida evidentemente, como o alcance do pensamento contido nessas obras chega até pelo menos a filosofia kantiana.

  18. Tipo de agresión resultado de un problema y conflicto en la población adolescente de siete instituciones públicas de educación media de San Juan de Pasto

    Directory of Open Access Journals (Sweden)

    Claudia Amanda Chaves

    2015-06-01

    Full Text Available Objetivo: determinar el tipo de agresión que resulta de un problema o conflicto en adolescentes de siete instituciones públicas de educación media de San Juan de Pasto, Nariño, periodo 2013 - 2014. Materiales y Métodos: estudio cuantitativo con diseño descriptivo. La información se obtuvo a través de un cuestionario diseñado y modificado por las investigadoras y autoadministrado por los estudiantes de siete instituciones públicas de educación media jornada de la mañana. La población estuvo conformada por 5537 adolescentes entre las edades de 10 a 17 años, se realizó un muestreo probabilístico aleatorio simple y a través de la afijación proporcional se tomó una muestra de 774 estudiantes. Resultados: se encontró que los lugares con mayor prevalencia donde se presenta el tipo de agresión entre estudiantes son: cerca al colegio, al salir de clase, al interior del aula cuando no está el profesor y por último en pasillos y baños. El tipo de agresión más frecuente es la verbal, que por lo general se origina cuando se habla mal de la persona o por decir palabras ofensivas; las patadas, golpes y peleas entre grupos como tipo de agresión física no reportaron una frecuencia alta entre los adolescentes. Conclusión: el matoneo continúa presente en las instituciones de educación media convirtiéndose en una problemática social que ha sido tratada por diferentes sectores con el fin de encontrar una solución, pero los esfuerzos no están dando resultados; por ello, se debe continuar fortaleciendo el diseño de estrategias e implementación de modelos de convivencia sana orientadas a padres, educadores y estudiantes para la solución de conflictos y comprensión de consecuencias.

  19. El método de las ponderaciones en el problema fraccional lineal multiobjetivo

    Directory of Open Access Journals (Sweden)

    Hernández Huelin, Mónica.

    2003-01-01

    Full Text Available Dentro de la programación matemática no lineal, el problema que se ha abordado más en términos teóricos y algorítmicos es el problema convexo. Cuando estamos ante una función fraccional, no tenemos convexidad, pero sí otras buenas propiedades que pueden hacer más o menos fácil la elaboración de algoritmos propios de resolución del problema. En este trabajo nos centramos en adaptar el Método de las Ponderaciones, uno de los métodos clásicos de resolución a priori del problema multiobjetivo convexo, al caso no convexo de objetivos fraccionales lineales. Dado que no tenemos convexidad ni concavidad de las funciones objetivo, y esta condición es básica para la aplicación de dicho método, estudiaremos este inconveniente con profundidad, estableciendo condiciones bajo las cuales resulta válido este método como generador de los conjuntos eficiente y débilmente eficiente de nuestro problema. Para ello se plantea la necesidad de un estudio detallado de los conceptos de pseudoconvexidad, cuasiconvexidad, invexidad, pseudoinvexidad, etc.. Ofreceremos además un contraejemplo que nos muestra que, si no se dan las condiciones que previamente estableceremos, el Método de las Ponderaciones no es válido para generar todo el conjunto débilmente eficiente de nuestro problema

  20. Cálculo : problemas y soluciones

    OpenAIRE

    Estela Carbonell, M. Rosa; Cuello Nebot, Eva; Carmona Mejías, Ángeles

    2000-01-01

    Los problemas contenidos en el libro que se presenta son el resultado de cuatro años de docencia en la asignatura Cálcul I de la ETSECCPB. En ellos se desarrolla el cálculo diferencial e integral de una y varias variables, así como una introducción a las sucesiones y series funcionales, con lo que se pretende cubrir cualquier programa de un primer curso de cálculo.

  1. Influence of food matrix on outgrowth heterogeneity of heat damaged Bacillus cereus spores.

    Science.gov (United States)

    Warda, Alicja K; den Besten, Heidy M W; Sha, Na; Abee, Tjakko; Nierop Groot, Masja N

    2015-05-18

    Spoilage of heat treated foods can be caused by the presence of surviving spore-formers. It is virtually impossible to prevent contamination at the primary production level as spores are ubiquitous present in the environment and can contaminate raw products. As a result spore inactivation treatments are widely used by food producing industries to reduce the microbial spore loads. However consumers prefer mildly processed products that have less impact on its quality and this trend steers industry towards milder preservation treatments. Such treatments may result in damaged instead of inactivated spores, and these spores may germinate, repair, and grow out, possibly leading to quality and safety issues. The ability to repair and grow out is influenced by the properties of the food matrix. In the current communication we studied the outgrowth from heat damaged Bacillus cereus ATCC 14579 spores on Anopore membrane, which allowed following outgrowth heterogeneity of individual spores on broccoli and rice-based media as well as standard and mildly acidified (pH 5.5) meat-based BHI. Rice, broccoli and BHI pH 5.5 media resulted in delayed outgrowth from untreated spores, and increased heterogeneity compared to BHI pH 7.4, with the most pronounced effect in rice media. Exposure to wet heat for 1 min at 95 °C caused 2 log inactivation and approximately 95% of the spores in the surviving fraction were damaged resulting in substantial delay in outgrowth based on the time required to reach a maximum microcolony size of 256 cells. The delay was most pronounced for heat-treated spores on broccoli medium followed by spores on rice media (both untreated and treated). Interestingly, the increase in outgrowth heterogeneity of heat treated spores on BHI pH 7.4 was more pronounced than on rice, broccoli and BHI pH 5.5 conceivably reflecting that conditions in BHI pH 7.4 better support spore damage repair. This study compares the effects of three main factors, namely heat treatment, p

  2. Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li [Pennsylvania State Univ., State College, PA (United States); Li, Li [Pennsylvania State Univ., State College, PA (United States)

    2015-10-22

    The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in natural systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport

  3. Effects of ionization chamber construction on dose measurements in a heterogeneity

    International Nuclear Information System (INIS)

    Mauceri, T.; Kase, K.

    1987-01-01

    Traditionally, measurements have been made in heterogeneous phantoms to determine the factors which should be applied to dose calculations, when calculating a dose to a heterogeneous medium. Almost all measurements have relied on relatively thin-walled ion chambers, with no attempt to match ion chamber wall material to the measuring medium. The recent AAPM dosimetry protocol has established that a mismatch between ion chamber wall and phantom material can have an effect on dose measurement. To investigate the affect of this mismatch of ion chamber wall material to phantom material, two parallel-plate ion chambers were constructed. One ion chamber from solid water, for measurements in a solid water phantom and the other from plastic lung material, for measurements in a plastic lung material phantom. Correction factors measured by matching ion chamber to media were compared to correction factors measured by using a thin-walled cavity ion chamber with no regard for matching wall and media for cobalt-60, 6-, 10- and 20-MV photon beams. The results demonstrated that the matching of ion chamber to measuring media can be ignored, provided that a small, approximately tissue-equivalent, thin-walled ion chamber is used for measuring the correction factors

  4. Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

    DEFF Research Database (Denmark)

    Plampin, Michael R.; Lassen, Rune Nørbæk; Sakaki, Toshihiro

    2014-01-01

    sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2......, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been...... quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test...

  5. Contabilidad de Costos I. - Problemas sobre la contabilización de las actividades relacionadas con la mano de obra

    OpenAIRE

    Morillo Moreno, Marysela C.

    2008-01-01

    ÍNDICE Introducción Problemas sobre terminología básica Problemas básicos sobre el Ciclo de la Contabilidad de Costos Problemas sobre contabilización de las actividades relacionadas con los materiales Problemas sobre la contabilización de las actividades relacionadas con la mano de obra Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación Problemas sobre el Ciclo de la Contabilida...

  6. Unscrewing social media networks, twice

    DEFF Research Database (Denmark)

    Birkbak, Andreas

    2017-01-01

    Social media are often claimed to be an important new force in politics. One way to investigate such a claim is to follow an early call made in actor-network theory (ANT) to “unscrew” those entities that are assumed to be important and show how they are made up of heterogeneous networks of many...... different actors (Callon and Latour 1981). In this article I take steps towards unscrewing seven Facebook pages that were used to mobilize citizens for and against road pricing in Copenhagen in 2011-2012. But I encounter the difficulty that social media are already explicitly understood in Internet Studies...... that it can be combined with liberal notions of a singular public sphere (Somers 1995b; 1995a). In order to unscrew social media as a political force, I suggest that we need to work through both the assembling of social media networks and attend to corresponding reconstructions of liberal political narratives...

  7. An effective anisotropic poroelastic model for elastic wave propagation in finely layered media

    NARCIS (Netherlands)

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

    2016-01-01

    Mesoscopic-scale heterogeneities in porous media cause attenuation and dispersion at seismic frequencies. Effective models are often used to account for this. We have developed a new effective poroelastic model for finely layered media, and we evaluated its impact focusing on the angledependent

  8. O efeito da terapia comportamental para enurese sobre outros problemas de comportamento

    Directory of Open Access Journals (Sweden)

    Rodrigo Fernando Pereira

    Full Text Available O objetivo do estudo foi investigar o efeito do tratamento para enurese sobre os escores de outros problemas de comportamento. Foram coletadas as informações de 97 prontuários de crianças e adolescentes atendidos no período de 2002 a 2006 em uma clínica-escola de psicologia, em programa específico para enurese com uso do alarme de urina. Os dados sobre problemas de comportamento foram avaliados por meio do Child Behavior Checklist, respondido pelas mães antes e depois do tratamento. Foi encontrada uma redução significativa nos escores de problemas de comportamento, independentemente do sucesso ou não no tratamento para enurese.

  9. Off-fault heterogeneities promote supershear transition of dynamic mode II cracks

    Science.gov (United States)

    Albertini, Gabriele; Kammer, David S.

    2017-08-01

    The transition from sub-Rayleigh to supershear propagation of mode II cracks is a fundamental problem of fracture mechanics. It has extensively been studied in homogeneous uniform setups. When the applied shear load exceeds a critical value, transition occurs through the Burridge-Andrews mechanism at a well-defined crack length. However, velocity structures in geophysical conditions can be complex and affect the transition. Damage induced by previous earthquakes causes low-velocity zones surrounding mature faults and inclusions with contrasting material properties can be present at seismogenic depth. We relax the assumption of homogeneous media and investigate dynamic shear fracture in heterogeneous media using two-dimensional finite element simulations and a linear slip-weakening law. We analyze the role of heterogeneities in the elastic media, while keeping the frictional interface properties uniform. We show that supershear transition is possible due to the sole presence of favorable off-fault heterogeneities. Subcritical shear loads, for which propagation would remain permanently sub-Rayleigh in an equivalent homogeneous setup, will transition to supershear as a result of reflected waves. P wave reflected as S waves, followed by further reflections, affect the amplitude of the shear stress peak in front of the propagating crack, leading to supershear transition. A wave reflection model allows to uniquely describe the effect of off-fault inclusions on the shear stress peak. A competing mechanism of modified released potential energy affects transition and becomes predominant with decreasing distance between fault and inclusions. For inclusions at far distances, the wave reflection is the predominant mechanism.

  10. EL ÁLGEBRA LINEAL Y EL PROBLEMA DE MÁXIMOS Y MÍNIMOS

    Directory of Open Access Journals (Sweden)

    Santiago Relos Paco

    2004-01-01

    Full Text Available En este artículo se presenta una aplicación del álgebra lineal al problema de máximos y mínimos de funciones a varias variables. Se considera una función , U abierto y f dos veces diferenciable, se toma un punto tal que , se plantea el problema de determinar si en este punto existe un máximo, mínimo o ninguna de estas situaciones. Se calcula , como se sabe esta segunda derivada es una matriz simétrica en , dependiendo de la signatura de se dará una respuesta al problema planteado.

  11. Problemas médicos habituales relacionados con la paciente embarazada

    Directory of Open Access Journals (Sweden)

    V. Lorena Quiroz, DRA.

    2014-11-01

    Full Text Available Problemas médicos como enfermedades del tiroides, deficiencia de vitamina D, anemia, infecciones del tracto urinario e insulino resistencia entre otros, pueden complicar el embarazo. Dado las molestias propias de la gestación, muchas de estas patologías no son diagnosticadas ni tratadas, aumentando la morbilidad materna y fetal. Algunas de estas enfermedades tienen diferentes criterios diagnósticos comparados con la mujer no embarazada. Se revisan los criterios diagnósticos y tratamientos de los problemas médicos más frecuentes en el embarazo.

  12. Máquinas hidráulicas: teoría y problemas

    OpenAIRE

    Zamora Parra, Blas; Viedma Robles, Antonio

    2016-01-01

    Máquinas Hidráulicas (Teoría y Problemas), es un texto orientado a la docencia de las Máquinas Hidráulicas en titulaciones relacionadas con las Ingenierías Industrial y Energética. El enfoque del libro es fundamentalmente académico para un nivel de posgrado, por lo que presenta una colección completa de problemas propuestos, y otros resueltos, que pueden ayudar a conseguir un conocimiento firmemente asentado en sus principios físicos sobre las Máquinas Hidráulicas y sus instalaciones. Se ha p...

  13. Heterogeneous Face Attribute Estimation: A Deep Multi-Task Learning Approach.

    Science.gov (United States)

    Han, Hu; K Jain, Anil; Shan, Shiguang; Chen, Xilin

    2017-08-10

    Face attribute estimation has many potential applications in video surveillance, face retrieval, and social media. While a number of methods have been proposed for face attribute estimation, most of them did not explicitly consider the attribute correlation and heterogeneity (e.g., ordinal vs. nominal and holistic vs. local) during feature representation learning. In this paper, we present a Deep Multi-Task Learning (DMTL) approach to jointly estimate multiple heterogeneous attributes from a single face image. In DMTL, we tackle attribute correlation and heterogeneity with convolutional neural networks (CNNs) consisting of shared feature learning for all the attributes, and category-specific feature learning for heterogeneous attributes. We also introduce an unconstrained face database (LFW+), an extension of public-domain LFW, with heterogeneous demographic attributes (age, gender, and race) obtained via crowdsourcing. Experimental results on benchmarks with multiple face attributes (MORPH II, LFW+, CelebA, LFWA, and FotW) show that the proposed approach has superior performance compared to state of the art. Finally, evaluations on a public-domain face database (LAP) with a single attribute show that the proposed approach has excellent generalization ability.

  14. Un modelo de programación binaria mixta para el problema generalizado de la p-centdiana

    Directory of Open Access Journals (Sweden)

    Marisa Martinez

    2002-01-01

    Full Text Available Los problemas de localización tratan de averiguar la ubicación de las instalaciones de una empresa de modo que se minimicen los costes o se maximicen los beneficios. Dos de los modelos más utilizados en localización en redes son el problema de la p-mediana y el problema del p-centro. El primero consiste en minimizar la suma total de las distancias ponderadas, mientras que el segundo trata de minimizar la máxima distancia ponderada desde un centro de servicio hasta sus usuarios asignados. El objetivo del problema de la p-mediana hace que sea eficiente pero no equitativo, mientras que la cota implícita en el problema del p-centro lo convierte en equitativo pero no eficiente. Para combinar ambos aspectos, aparece en la década de los 70 un nuevo problema, el de la p-centdiana, cuya función objetivo es una mezcla de las dos anteriores. En este trabajo presentamos un modelo de programación binaria mixta para el problema generalizado de la p-centdiana sobre una red en el que los pesos asociados al p-centro y a la p-mediana no son necesariamente iguales. El primer paso para resolver el problema es identificar su conjunto dominante finito. En consecuencia, previamente a la descripción del modelo, proponemos un algoritmo que nos permitirá calcular este conjunto.

  15. Problemas actuales del automóvil y el futuro del mismo

    OpenAIRE

    Gómez San Martín, María Begoña

    2011-01-01

    315 p. El automóvil es un elemento indispensable en la sociedad actual a nivel mundial. Pero presenta serios problemas no resueltos al día de hoy, ocasionados principalmente por el combustible universalmente utilizado: el petróleo. Estos problemas plantean serias preocupaciones cara al futuro. En esta Tesis realizamos una investigación y una prospección sobre los posibles elementos energéticos sustitutivos del petróleo.

  16. Resolución estructurada de problemas a través del método Kobetsu Kaizen

    OpenAIRE

    Torre Llera, Francisco

    2017-01-01

    En este Trabajo Fin de Grado nos centraremos en explicar la importancia de la resolución de problemas dentro de una empresa. Definiremos los métodos seguidos por una empresa para conseguir la resolución de problemas. En este caso, nos centraremos en la resolución estructurada de problemas. Más concretamente, nos centraremos en resolver el problema de control visual de los discos en busca de defectos de fundición. El método a aplicar será el Kobetsu Kaizen, relacionado con la...

  17. Algunas consideraciones sobre el problema de la prostitución en colombia

    OpenAIRE

    Piñeros Piñeros, Víctor J.

    2011-01-01

    El problema de la prostitución es en todas partes y más entre nosotros, un problema muy complejo, que importa desentrañar y estudiar en sus principales aspectos: así, hay que considerar la prostitución en sí, y luégo en sus relaciones con la sociedad y sobre todo en su aspecto sanitario.

  18. A multi-scale computational scheme for anisotropic hydro-mechanical couplings in saturated heterogeneous porous media

    NARCIS (Netherlands)

    Mercatoris, B.C.N.; Massart, T.J.; Sluys, L.J.

    2013-01-01

    This contribution discusses a coupled two-scale framework for hydro-mechanical problems in saturated heterogeneous porous geomaterials. The heterogeneous nature of such materials can lead to an anisotropy of the hydro-mechanical couplings and non-linear effects. Based on an assumed model of the

  19. Evidence for a Significant Level of Extrinsic Anisotropy Due to Heterogeneities in the Mantle.

    Science.gov (United States)

    Alder, C.; Bodin, T.; Ricard, Y. R.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

    2017-12-01

    Observations of seismic anisotropy are used as a proxy for lattice-preferred orientation (LPO) of anisotropic minerals in the Earth's mantle. In this way, it provides important constraints on the geometry of mantle deformation. However, in addition to LPO, small-scale heterogeneities that cannot be resolved by long-period seismic waves may also produce anisotropy. The observed (i.e. apparent) anisotropy is then a combination of an intrinsic and an extrinsic component. Assuming the Earth's mantle exhibits petrological inhomogeneities at all scales, tomographic models built from long-period seismic waves may thus display extrinsic anisotropy. Here, we investigate the relation between the amplitude of seismic heterogeneities and the level of induced S-wave radial anisotropy as seen by long-period seismic waves. We generate some simple 1D and 2D isotropic models that exhibit a power spectrum of heterogeneities as what is expected for the Earth's mantle, i.e. varying as 1/k, with k the wavenumber of these heterogeneities. The 1D toy models correspond to simple layered media. In the 2D case, our models depict marble-cake patterns in which an anomaly in S-wave velocity has been advected within convective cells. The long-wavelength equivalents of these models are computed using upscaling relations that link properties of a rapidly varying elastic medium to properties of the effective, i.e. apparent, medium as seen by long-period waves. The resulting homogenized media exhibit extrinsic anisotropy and represent what would be observed in tomography. In the 1D case, we analytically show that the level of anisotropy increases with the square of the amplitude of heterogeneities. This relation is numerically verified for both 1D and 2D media. In addition, we predict that 10 % of chemical heterogeneities in 2D marble-cake models can induce more than 3.9 % of extrinsic radial S-wave anisotropy. We thus predict that a non-negligible part of the observed anisotropy in tomographic

  20. Massively Parallel Geostatistical Inversion of Coupled Processes in Heterogeneous Porous Media

    Science.gov (United States)

    Ngo, A.; Schwede, R. L.; Li, W.; Bastian, P.; Ippisch, O.; Cirpka, O. A.

    2012-04-01

    The quasi-linear geostatistical approach is an inversion scheme that can be used to estimate the spatial distribution of a heterogeneous hydraulic conductivity field. The estimated parameter field is considered to be a random variable that varies continuously in space, meets the measurements of dependent quantities (such as the hydraulic head, the concentration of a transported solute or its arrival time) and shows the required spatial correlation (described by certain variogram models). This is a method of conditioning a parameter field to observations. Upon discretization, this results in as many parameters as elements of the computational grid. For a full three dimensional representation of the heterogeneous subsurface it is hardly sufficient to work with resolutions (up to one million parameters) of the model domain that can be achieved on a serial computer. The forward problems to be solved within the inversion procedure consists of the elliptic steady-state groundwater flow equation and the formally elliptic but nearly hyperbolic steady-state advection-dominated solute transport equation in a heterogeneous porous medium. Both equations are discretized by Finite Element Methods (FEM) using fully scalable domain decomposition techniques. Whereas standard conforming FEM is sufficient for the flow equation, for the advection dominated transport equation, which rises well known numerical difficulties at sharp fronts or boundary layers, we use the streamline diffusion approach. The arising linear systems are solved using efficient iterative solvers with an AMG (algebraic multigrid) pre-conditioner. During each iteration step of the inversion scheme one needs to solve a multitude of forward and adjoint problems in order to calculate the sensitivities of each measurement and the related cross-covariance matrix of the unknown parameters and the observations. In order to reduce interprocess communications and to improve the scalability of the code on larger clusters

  1. 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.

  2. Inverse radiative transfer problems in two-dimensional heterogeneous media

    International Nuclear Information System (INIS)

    Tito, Mariella Janette Berrocal

    2001-01-01

    The analysis of inverse problems in participating media where emission, absorption and scattering take place has several relevant applications in engineering and medicine. Some of the techniques developed for the solution of inverse problems have as a first step the solution of the direct problem. In this work the discrete ordinates method has been used for the solution of the linearized Boltzmann equation in two dimensional cartesian geometry. The Levenberg - Marquardt method has been used for the solution of the inverse problem of internal source and absorption and scattering coefficient estimation. (author)

  3. Los problemas de las fronteras humanitarias

    Directory of Open Access Journals (Sweden)

    Ticktin, Miriam

    2015-12-01

    Full Text Available This text engages a critical analysis of humanitarian discourses and practices regarding our understanding of migration and the public policies developed in relation to the population movementsacross international borders. It is based on the premise that humanitarianism, even if well intentioned, can have pernicious effects if, eventually, it ends up replacing justice and migrants’ rights. To explore this paradox, the paper sequentially analyzes various problems associated with humanitarian aid: the problem of innocence —the understanding of refugees as victims calls for humanitarian compassion—; the problem with emergency —«rapid response» operations inhibit the contextualized and historical understanding of the root causes of the problems—; and, finally, the problem of compassion —humanitarianism privilegessentiments over rights. The study of these three key features of humanitarianism in Europe and the USA fosters a healthy skepticism of the emerging forms of the legitimation of exclusion. The article also explores alternative political and discursive strategies which allow for new imaginaries to confront migratory processes beyond borders and humanitarianism, breaking up their dynamic of reproduction of social inequalities and placing justice in the horizon of action.Este texto plantea un análisis crítico del papel de los discursos y prácticas humanitaristas en nuestra concepción de la migración y en las políticas públicas desarrolladas en relación a la movilidad poblacional a través de las fronteras internacionales. Se parte de la premisa de que el humanitarismo, aunque fuera bien intencionado, puede tener efectos perniciosos sobre la situación que se vive en las fronteras, especialmente si acaba por sustituir a la justicia y a los derechos que tienen los emigrantes. Para estudiar esta paradoja, el texto analiza, sucesivamente, varios problemas asociados a la acción humanitaria: el problema con la inocencia

  4. Los museos: un instrumento para el Aprendizaje Basado en Problemas (ABP

    Directory of Open Access Journals (Sweden)

    Yosajandi Pérez Campillo

    2011-01-01

    Full Text Available Diversos estudios han demostrado que el Aprendizaje Basado en Problemas (ABP es una propuesta educativa innovadora, que se caracteriza porque promueve que el aprendizaje sea significativo y contribuye a desarrollar una serie de habilidades y competencias indispensables para el crecimiento intelectual de cualquier persona. Sin embargo, esta estretegia implica repensar los problemas como problemas para aprender partiendo de preguntas que sean relevantes para los alumnos en el contexto del aprendizaje de ciencias. Y es justamente, el planteamiento de estas preguntas lo que hace complejo al ABP, pues platear "buenas preguntas" no es fácil, se requiere no sólo de habilidad y práctica sino también un conocimiento mínimo del tema y motivación para iniciar una investigación. Por lo anterior, una de las preocupaciones es encontrar los mecanismos que permitan introducir y motivar al estudiante para que sea capaz de plantear preguntas (problemas. En el presente trabajo se describen la propuesta de una serie de actividades que tienen como propósito preparar a un grupo de estudiantes de bachillerato para que planteen "buenas preguntas" de investigación sobre el tema de minerales. Para lograrlo, se considera el uso de varios recursos como: la visita a los museos, la lectura y análisis de textos y la actividad experimental.

  5. Problemas en la investigación procesal-penal del feminicidio en el Perú.

    OpenAIRE

    Tuesta, Diego; Mujica, Jaris

    2015-01-01

    La tipificación del feminicidio en el Perú conlleva diversos problemas para la investigación preparatoria en el campo judicial. Basado en el registro cualitativo de la experiencia de fiscales especializados y el cuerpo de forense de los cuatro distritos judiciales de Lima, este artículo describe los problemas centrales en el uso del tipo penal. El problema central identificado por los fiscales es la poca traductibilidad de la categoría “discriminación de género” a términos operativos en mater...

  6. Algunas consideraciones sobre el problema de la prostitución en Colombia

    Directory of Open Access Journals (Sweden)

    Víctor J. Piñeros Piñeros

    1935-01-01

    Full Text Available El problema de la prostitución es en todas partes y más entre nosotros, un problema muy complejo, que importa desentrañar y estudiar en sus principales aspectos: así, hay que considerar la prostitución en sí, y luégo en sus relaciones con la sociedad y sobre todo en su aspecto sanitario.

  7. A model for the ultrasonic field radiated by an immersed transducer into an anisotropic and heterogeneous medium; Modelisation du champ ultrasonore rayonne dans un solide anisotrope et heterogene par un traducteur immerge

    Energy Technology Data Exchange (ETDEWEB)

    Gengembre, N

    2000-07-01

    A model for the field radiated by an ultrasonic transducer into anisotropic and heterogeneous media is developed in this thesis. This work aims at improving the settings and interpretations of non destructive tests in welded structures. Since the shape of the transducer is assumed arbitrary, its emitting surface is divided into small elementary sources. The overall field at an observation point in the medium is derived by a summation of the elementary contributions of these point sources. An accurate and numerically efficient model is developed using the Geometrical Optics approximation to evaluate these elementary contributions. Two different forms of this approximation are used: The stationary phase method and the pencil method. The first one is based on an exact formulation of the field and is used for fields into anisotropic and homogeneous media. It allows to emphasize specific configurations for which additional developments are required; this need arises for calculation points in the vicinity of caustics (zones of high intensity). This problem is solved for both harmonic and transient fields, for points laying on caustics or in their neighborhood. The pencil method is used for the calculation of fields in heterogeneous media, although it does not permit to overcome the problem of caustics. It is also advantageous for the implementation of the model. A comparison of both above-mentioned methods is drawn, and their equivalence is proved for some cases. The calculation of fields in anisotropic and heterogeneous media is performed using both methods together, and then the problem of caustics is also treated. Calculated fields into welded components are shown and compared with experiments or with a numerical model, in order to validate the developments. (author)

  8. Fluid flow and heat transfer in rotating porous media

    CERN Document Server

    Vadasz, Peter

    2016-01-01

    This Book concentrates the available knowledge on rotating fluid flow and heat transfer in porous media in one single reference. Dr. Vadasz develops the fundamental theory of rotating flow and heat transfer in porous media and introduces systematic classification and identification of the relevant problems. An initial distinction between rotating flows in isothermal heterogeneous porous systems and natural convection in homogeneous non-­‐isothermal porous systems provides the two major classes of problems to be considered. A few examples of solutions to selected problems are presented, highlighting the significant impact of rotation on the flow in porous media.

  9. Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

    Science.gov (United States)

    Plampin, Michael R.; Lassen, Rune N.; Sakaki, Toshihiro; Porter, Mark L.; Pawar, Rajesh J.; Jensen, Karsten H.; Illangasekare, Tissa H.

    2014-12-01

    A primary concern for geologic carbon storage is the potential for leakage of stored carbon dioxide (CO2) into the shallow subsurface where it could degrade the quality of groundwater and surface water. In order to predict and mitigate the potentially negative impacts of CO2 leakage, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2 concentration in the flowing water, the distance between the heterogeneity and the leakage location, and some fundamental properties of the porous media. Results also show that interfaces where a less permeable material overlies a more permeable material affect gas phase evolution more significantly than interfaces with the opposite layering.

  10. Computer simulation of the interplay between fractal structures and surrounding heterogeneous multifractal distributions. Applications

    OpenAIRE

    Martin Martin, Miguel Angel; Reyes Castro, Miguel E.; Taguas Coejo, Fco. Javier

    2014-01-01

    In a large number of physical, biological and environmental processes interfaces with high irregular geometry appear separating media (phases) in which the heterogeneity of constituents is present. In this work the quantification of the interplay between irregular structures and surrounding heterogeneous distributions in the plane is made For a geometric set image and a mass distribution (measure) image supported in image, being image, the mass image gives account of the interplay between th...

  11. Variantes del problema del cartero mixto que se pueden resolver usando programación lineal

    Directory of Open Access Journals (Sweden)

    Francisco Javier Zaragoza Martínez

    2012-07-01

    Full Text Available Dada una gráfica mixta y conexa con costos en sus aristas y arcos, el problema del cartero mixto consiste en encontrar un circuito cerrado de la gráfica mixta que recorra sus aristas y arcos a costo mínimo. Se sabe que este problema es NP-duro. Sin embargo, bajo ciertas condiciones adicionales, el problema se puede resolver en tiempo polinomial usando programación lineal, en otras palabras, los poliedros correspondientes son enteros. Algunas de estas condiciones son: la gráfica mixta es serie paralelo o la gráfica mixta tiene grado total par en todos sus vértices. Además, mostramos que si agregamos la restricción adicional de que cada arista se recorra exactamente una vez entonces el problema se puede resolver en tiempo polinomial si el conjunto de arcos forma un bosque. Palabras clave: Gráfica mixta, problema de cartero, programación lineal. Mathematics Subject Classification: 05C45, 90C35.

  12. Overview of medium heterogeneity and transport processes

    International Nuclear Information System (INIS)

    Tsang, Y.; Tsang, C.F.

    1993-11-01

    Medium heterogeneity can have significant impact on the behavior of solute transport. Tracer breakthrough curves from transport in a heterogeneous medium are distinctly different from that in a homogeneous porous medium. Usually the shape of the breakthrough curves are highly non-symmetrical with a fast rise at early times and very long tail at late times, and often, they consist of multiple peaks. Moreover, unlike transport in a homogeneous medium where the same transport parameters describe the entire medium, transport through heterogeneous media gives rise to breakthrough curves which have strong spatial dependence. These inherent characteristics of transport in heterogeneous medium present special challenge to the performance assessment of a potential high level nuclear waste repository with respect to the possible release of radio nuclides to the accessible environment. Since an inherently desirable site characteristic for a waste repository is that flow and transport should be slow, then transport measurements in site characterization efforts will necessarily be spatially small and temporally short compare to the scales which are of relevance to performance assessment predictions. In this paper we discuss the role of medium heterogeneity in site characterization and performance assessment. Our discussion will be based on a specific example of a 3D heterogeneous stochastic model of a site generally similar to, the Aespoe Island, the site of the Hard Rock Laboratory in Southern Sweden. For our study, alternative 3D stochastic fields of hydraulic conductivities conditioned on ''point'' measurements shall be generated. Results of stochastic flow and transport simulations would be used to address the issues of (1) the relationship of tracer breakthrough with the structure of heterogeneity, and (2) the inference from small scale testing results to large scale and long term predictions

  13. Numerical analysis for Darcy-Forchheimer flow in presence of homogeneous-heterogeneous reactions

    Directory of Open Access Journals (Sweden)

    Muhammad Ijaz Khan

    Full Text Available A mathematical study is presented to investigate the influences of homogeneous and heterogeneous reactions in local similar flow caused by stretching sheet with a non-linear velocity and variable thickness. Porous medium effects are characterized by using Darcy-Forchheimer porous-media. A simple isothermal model of homogeneous-heterogeneous reactions is used. The multiphysical boundary value problem is dictated by ten thermophysical parameters: ratio of mass diffusion coefficients, Prandtl number, local inertia coefficient parameter, inverse Darcy number, shape parameter, surface thickness parameter, Hartman number, Homogeneous heat reaction, strength of homogeneous-heterogeneous reactions and Schmidt number. Resulting systems are computed by Runge-Kutta-Fehlberg method. Different shapes of velocity are noticed for n > 1 and n < 1. Keywords: Homogeneous-heterogeneous reactions, Non Darcy porous medium, Variable sheet thickness, Homogeneous heat reaction with stoichiometric coefficient, Runge-Kutta-Fehlberg method

  14. A programação por restrições aplicada à um problema de corte unidimensional

    OpenAIRE

    Preissler Junior, Sigmundo

    2009-01-01

    Esta dissertação apresenta um estudo sobre o problema de corte unidimensional. Como resultado deste estudo, é proposta e desenvolvida uma aplicação da programação por restrições na solução do problema em uma aplicação industrial. O problema consiste em encontrar uma solução do factível para o problema de corte unidimensional de bobinas de aço, em uma situação real, considerando o tempo de preparação. O algoritmo gera planos de corte para um determinado período. Além da abordagem PSR (Programa...

  15. Uporaba algoritmov inteligence rojev za rešitev problema dostavnih vozil

    OpenAIRE

    Hlastec, Urban

    2018-01-01

    V magistrski nalogi smo obravnavali in implementirali algoritem umetne kolonije čebel za reševanje problema dostavnih vozil z več skladišči. Zanimalo nas je, kako so algoritmi s področja inteligence rojev ustrezni in uporabni za reševanje optimizacijskih problemov. V nalogi smo združili algoritem umetne kolonije čebel ter algoritem za reševanje problema dostavnih vozil. Primerjali smo tudi rezultate pred optimizacijo različnih spremenljivk in po in tako ugotovili, kaj najbolj vpliva na hitros...

  16. Problemas de bancarrota multi-escenario.

    Directory of Open Access Journals (Sweden)

    Francisca J. Sánchez

    2004-01-01

    Full Text Available Los problemas de bancarrota representan situaciones donde un número de individuos o entidades acreedoras realizan reclamaciones sobre un cierto bien (estado y el estado total disponible es insuficiente para satisfacer la demanda de todos los acreedores. En este trabajo consideramos el caso en que las reclamaciones de los acreedores dependen de distintos escenarios o que son diferentes bajo distintos estados de la naturaleza. Para obtener repartos del estado disponible en estas situaciones proponemos distintas reglas de división que pueden considerarse racionales independientemente del escenario considerado.

  17. Algoritmos relax-and-cut para problemas de programação inteira 0-1

    OpenAIRE

    Victor Fernandes Cavalcante

    2008-01-01

    Resumo: Uma das principais motivações para o estudo de Otimização Discreta reside no elevado número de problemas do nosso cotidiano representáveis através de modelos de Otimização Inteira e Combinatória. Em particular, muitos destes problemas podem ser formulados com Programação Inteira 0-1, o que desperta especial interesse em técnicas capazes de resolver tais modelos. Dentre as inúmeras formas de solução atualmente disponíveis para problemas desta natureza, os algoritmos baseados na técnica...

  18. Direct Breakthrough Curve Prediction From Statistics of Heterogeneous Conductivity Fields

    Science.gov (United States)

    Hansen, Scott K.; Haslauer, Claus P.; Cirpka, Olaf A.; Vesselinov, Velimir V.

    2018-01-01

    This paper presents a methodology to predict the shape of solute breakthrough curves in heterogeneous aquifers at early times and/or under high degrees of heterogeneity, both cases in which the classical macrodispersion theory may not be applicable. The methodology relies on the observation that breakthrough curves in heterogeneous media are generally well described by lognormal distributions, and mean breakthrough times can be predicted analytically. The log-variance of solute arrival is thus sufficient to completely specify the breakthrough curves, and this is calibrated as a function of aquifer heterogeneity and dimensionless distance from a source plane by means of Monte Carlo analysis and statistical regression. Using the ensemble of simulated groundwater flow and solute transport realizations employed to calibrate the predictive regression, reliability estimates for the prediction are also developed. Additional theoretical contributions include heuristics for the time until an effective macrodispersion coefficient becomes applicable, and also an expression for its magnitude that applies in highly heterogeneous systems. It is seen that the results here represent a way to derive continuous time random walk transition distributions from physical considerations rather than from empirical field calibration.

  19. Transport Visualization for Studying Mass Transfer and Solute Transport in Permeable Media

    International Nuclear Information System (INIS)

    Roy Haggerty

    2004-01-01

    Understanding and predicting mass transfer coupled with solute transport in permeable media is central to several energy-related programs at the US Department of Energy (e.g., CO 2 sequestration, nuclear waste disposal, hydrocarbon extraction, and groundwater remediation). Mass transfer is the set of processes that control movement of a chemical between mobile (advection-dominated) domains and immobile (diffusion- or sorption-dominated) domains within a permeable medium. Consequences of mass transfer on solute transport are numerous and may include (1) increased sequestration time within geologic formations; (2) reduction in average solute transport velocity by as much as several orders of magnitude; (3) long ''tails'' in concentration histories during removal of a solute from a permeable medium; (4) poor predictions of solute behavior over long time scales; and (5) changes in reaction rates due to mass transfer influences on pore-scale mixing of solutes. Our work produced four principle contributions: (1) the first comprehensive visualization of solute transport and mass transfer in heterogeneous porous media; (2) the beginnings of a theoretical framework that encompasses both macrodispersion and mass transfer within a single set of equations; (3) experimental and analytical tools necessary for understanding mixing and aqueous reaction in heterogeneous, granular porous media; (4) a clear experimental demonstration that reactive transport is often not accurately described by a simple coupling of the convection-dispersion equation with chemical reaction equations. The work shows that solute transport in heterogeneous media can be divided into 3 regimes--macrodispersion, advective mass transfer, and diffusive mass transfer--and that these regimes can be predicted quantitatively in binary media. We successfully predicted mass transfer in each of these regimes and verified the prediction by completing quantitative visualization experiments in each of the regimes, the

  20. Analisi matematica del problema dello spazio

    CERN Document Server

    Weyl, Hermann

    1990-01-01

    Al fine di rendere concettualmente evidente il privilegio posseduto dalla metrica pitagorico-riemanniana, e dalle varie metriche riemanniane "indefinite", rispetto alle altre metriche possibili, nel 1921 Weyl, stimolato dagli sviluppi della relatività einsteiniana (sulla quale aveva scritto il mirabile "Raum-Zeit-Materie"), intraprese un profondo studio del problema giovandosi dei metodi della teoria dei gruppi di Lie, studio che egli portò a conclusione con la monografia del 1923 intitolata "Mathematische Analyse des Raumproblems".

  1. Problemas epistemológicos al historiar

    Directory of Open Access Journals (Sweden)

    Alvar Ezquerra, Alfredo

    1998-09-01

    Full Text Available Not available.Se sintetiza los grandes problemas de la historiografía del XVI y deja al lector la reflexión abierta sobre la situación historiográfica actual. Las similitudes y divergencias entre las angustias y apuestas de aquellos historiadores y los de hoy, esto es, la percepción de la realidad y del pasado por medio de la Historia, ¿son aún iguales?

  2. Optimización multi-objetivo : Aplicaciones a problemas del mundo real

    OpenAIRE

    López, Javier

    2013-01-01

    Cuando hablamos de optimización en el ámbito de las ciencias de la computación hacemos referencia al mismo concepto coloquial asociado a esa palabra, la concreción de un objetivo utilizando la menor cantidad de recursos disponibles, o en una visión similar, la obtención del mejor objetivo posible utilizando todos los recursos con lo que se cuenta. Los métodos para encontrar la mejor solución (óptima) varían de acuerdo a la complejidad del problema enfrentado. Para problemas triviales, el c...

  3. Los estilos de aprendizaje en la resolución de problemas

    OpenAIRE

    Crespo, Beatriz del Pilar; Lentini, María Cristina; Matulovich, Miriam Isabel; Lentini, Marta Lucía

    2011-01-01

    p. 187-194 Numerosos estudios realizados en el ámbito de la investigación en educación superior muestran que la repitencia es uno de los problemas a resolver en el ámbito universitario. Desde ese espacio, para superar tal problema, se generan propuestas tales como los cursos de ingreso o de nivelación, entre otros, que todavía no se reflejan en los aprendizajes de los alumnos ingresantes. En la búsqueda de alguna estrategia de enseñanza y aprendizaje superadora, repensamos nuestra investig...

  4. Optimal implicit 2-D finite differences to model wave propagation in poroelastic media

    Science.gov (United States)

    Itzá, Reymundo; Iturrarán-Viveros, Ursula; Parra, Jorge O.

    2016-08-01

    Numerical modeling of seismic waves in heterogeneous porous reservoir rocks is an important tool for the interpretation of seismic surveys in reservoir engineering. We apply globally optimal implicit staggered-grid finite differences (FD) to model 2-D wave propagation in heterogeneous poroelastic media at a low-frequency range (differentiation involves solving tridiagonal linear systems of equations through Thomas' algorithm.

  5. Towards Media Intercloud Standardization Evaluating Impact of Cloud Storage Heterogeneity

    OpenAIRE

    Aazam, Mohammad; StHilaire, Marc; Huh, EuiNam

    2016-01-01

    Digital media has been increasing very rapidly, resulting in cloud computing's popularity gain. Cloud computing provides ease of management of large amount of data and resources. With a lot of devices communicating over the Internet and with the rapidly increasing user demands, solitary clouds have to communicate to other clouds to fulfill the demands and discover services elsewhere. This scenario is called intercloud computing or cloud federation. Intercloud computing still lacks standard ar...

  6. Digital Humanities and networked digital media

    DEFF Research Database (Denmark)

    Finnemann, Niels Ole

    2014-01-01

    This article discusses digital humanities and the growing diversity of digital media, digital materials and digital methods. The first section describes the humanities computing tradition formed around the interpretation of computation as a rule-based process connected to a concept of digital...... materials centred on the digitisation of non-digital, finite works, corpora and oeuvres. The second section discusses “the big tent” of contemporary digital humanities. It is argued that there can be no unifying interpretation of digital humanities above the level of studying digital materials with the help...... of software-supported methods. This is so, in part, because of the complexity of the world and, in part, because digital media remain open to the projection of new epistemologies onto the functional architecture of these media. The third section discusses the heterogeneous character of digital materials...

  7. Adaptive mixed-hybrid and penalty discontinuous Galerkin method for two-phase flow in heterogeneous media

    KAUST Repository

    Hou, Jiangyong

    2016-02-05

    In this paper, we present a hybrid method, which consists of a mixed-hybrid finite element method and a penalty discontinuous Galerkin method, for the approximation of a fractional flow formulation of a two-phase flow problem in heterogeneous media with discontinuous capillary pressure. The fractional flow formulation is comprised of a wetting phase pressure equation and a wetting phase saturation equation which are coupled through a total velocity and the saturation affected coefficients. For the wetting phase pressure equation, the continuous mixed-hybrid finite element method space can be utilized due to a fundamental property that the wetting phase pressure is continuous. While it can reduce the computational cost by using less degrees of freedom and avoiding the post-processing of velocity reconstruction, this method can also keep several good properties of the discontinuous Galerkin method, which are important to the fractional flow formulation, such as the local mass balance, continuous normal flux and capability of handling the discontinuous capillary pressure. For the wetting phase saturation equation, the penalty discontinuous Galerkin method is utilized due to its capability of handling the discontinuous jump of the wetting phase saturation. Furthermore, an adaptive algorithm for the hybrid method together with the centroidal Voronoi Delaunay triangulation technique is proposed. Five numerical examples are presented to illustrate the features of proposed numerical method, such as the optimal convergence order, the accurate and efficient velocity approximation, and the applicability to the simulation of water flooding in oil field and the oil-trapping or barrier effect phenomena.

  8. Adaptive mixed-hybrid and penalty discontinuous Galerkin method for two-phase flow in heterogeneous media

    KAUST Repository

    Hou, Jiangyong; Chen, Jie; Sun, Shuyu; Chen, Zhangxin

    2016-01-01

    In this paper, we present a hybrid method, which consists of a mixed-hybrid finite element method and a penalty discontinuous Galerkin method, for the approximation of a fractional flow formulation of a two-phase flow problem in heterogeneous media with discontinuous capillary pressure. The fractional flow formulation is comprised of a wetting phase pressure equation and a wetting phase saturation equation which are coupled through a total velocity and the saturation affected coefficients. For the wetting phase pressure equation, the continuous mixed-hybrid finite element method space can be utilized due to a fundamental property that the wetting phase pressure is continuous. While it can reduce the computational cost by using less degrees of freedom and avoiding the post-processing of velocity reconstruction, this method can also keep several good properties of the discontinuous Galerkin method, which are important to the fractional flow formulation, such as the local mass balance, continuous normal flux and capability of handling the discontinuous capillary pressure. For the wetting phase saturation equation, the penalty discontinuous Galerkin method is utilized due to its capability of handling the discontinuous jump of the wetting phase saturation. Furthermore, an adaptive algorithm for the hybrid method together with the centroidal Voronoi Delaunay triangulation technique is proposed. Five numerical examples are presented to illustrate the features of proposed numerical method, such as the optimal convergence order, the accurate and efficient velocity approximation, and the applicability to the simulation of water flooding in oil field and the oil-trapping or barrier effect phenomena.

  9. El Problema de Investigación: Algunos Aspectos Metodológicos e Históricos

    Directory of Open Access Journals (Sweden)

    Gustavo Jaimes Monroy

    2011-07-01

    Full Text Available El problema científico, es sin duda el motor de la ciencia, se puede escribir la historia de la ciencia con base en las preguntas resueltas y por resolver. En los programas de postgrado, la formulación del problema suele ser difícil de  delimitar y contextualizar para el estudiante. El presente escrito es una reflexión sobre lo que significa la obtención de un problema científico y como podría este conocimiento ser útil para plantearlo.

  10. Problemas escolares e o consumo de álcool e outras drogas entre adolescentes

    Directory of Open Access Journals (Sweden)

    Luciana Roberta Donola Cardoso

    Full Text Available A relação entre problemas escolares e o uso de álcool, tabaco e drogas ilícitas em 965 adolescentes dos municípios de Jacareí e Diadema (SP foi avaliada pelo instrumento de autopreenchimento Drug Use Screening Inventory. Este instrumento avalia o consumo de drogas e problemas a ele relacionados. O uso de substâncias foi associado a repetências, falta de concentração, notas baixas, desejo de abandonar a escola, sentir-se entediado no ambiente escolar, não fazer os deveres, faltar/chegar atrasado e prejuízos acadêmicos decorrentes do uso de drogas. A combinação do uso de álcool e tabaco foi associada a mais problemas escolares do que os encontrados em usuários exclusivos de álcool. Os problemas associados a esta combinação foram semelhantes aos observados em usuários de drogas ilícitas. Gostar da escola foi um fator protetor contra o uso de substâncias. Os resultados mostram a importância de se atentar para o relato de consumo das drogas lícitas combinadas.

  11. Problemas psicosociales en hostelería

    OpenAIRE

    Pérez Martínez, Alberto

    2015-01-01

    Las metas consistirán en: 1- Describir los distintos factores psicosociales que pueden dar lugar a generar estrés en función de las condiciones de trabajo en el que se encuentran la plantilla. 2- Determinar los principales responsables de la existencia de riesgo en los problemas psicosociales. 3- Definir los puntos positivos que permiten unas buenas condiciones de trabajo psicosociales. He trabajado las competencias relativas al estudio que pretende el TFG. Competencias de Psicolo...

  12. Identificación y analisis de los problemas presentes en los textos escolares sobre disoluciones y propiedades coligativas

    OpenAIRE

    Díaz, Edson

    2013-01-01

    En el presente trabajo se analizaron los problemas que se encuentran en los libros de texto de Química, utilizados por profesores y estudiantes, con la finalidad de poder hacer una clasificación en relación a la tipología de problemas presentes en ellos, sobre disoluciones y propiedades coligativas. Se trabajó con tres libros de secundaria. Se analizaron 142 problemas. A partir del análisis cualitativo- descriptivo se evidencia que hay mayor recurrencia de problemas de tipo artificial, ejerci...

  13. Los problemas de esbeltez en el diseño de columnas de concreto

    Directory of Open Access Journals (Sweden)

    Luis Guillermo Aycardi

    1981-07-01

    Full Text Available EI presente es el primero de una serie de artículos en los cuales se pretende estudiar los problemas de segundo orden en el diseño de columnas, la razón de las expresiones que proponen los reglamentos, y  de paso los problemas de inestabilidad estructural de pórticos y estructuras elementales.

  14. Contabilidad de Costos I. - Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación

    OpenAIRE

    Morillo Moreno, Marysela C.

    2008-01-01

    ÍNDICE Introducción Problemas sobre terminología básica Problemas básicos sobre el Ciclo de la Contabilidad de Costos Problemas sobre contabilización de las actividades relacionadas con los materiales Problemas sobre la contabilización de las actividades relacionadas con la mano de obra Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación Problemas sobre el Ciclo de la Contabilida...

  15. Personalidade e comportamentos problema: um estudo comparativo com adolescentes em contexto escolar

    Directory of Open Access Journals (Sweden)

    Renato G. Carvalho

    2014-03-01

    Full Text Available Neste estudo transversal analisámos a relação entre os comportamentos problema ao nível da indisciplina, desrespeito e conflituosidade dos adolescentes, em contexto escolar, e a personalidade e a psicopatologia, operacionalizadas nas dimensões PSY-5 do MMPI-A. Participaram no estudo 351 estudantes do 9º ao 12º ano, com idades compreendidas entre os 14 e os 18 anos, distribuídos em três grupos diferentes, de acordo com o reporte da frequência de comportamentos problema. Os instrumentos foram a versão experimental portuguesa do MMPI-A e um questionário sobre diferentes dimensões do percurso escolar, em que se incluem os comportamentos problema. Através de análise estatística multivariada, verificámos diferenças significativas entre os grupos nas dimensões PSY-5, num padrão em que o grupo de maior frequência de comportamentos problema apresenta resultados superiores no MMPI-A. Os resultados são interpretados numa perspetiva que sublinha a relevância da personalidade na adaptação à vida escolar, bem como a importância da existência de técnicas de avaliação psicológica de forma a detetar, em contexto de normalidade, estudantes em risco de desenvolvimento de trajetórias inadaptativas.

  16. Heterogeneity of Rapid Sand Filters and Its Effect on Contaminant Transport and Nitrification Performance

    DEFF Research Database (Denmark)

    Lopato, Laure Rose; Galaj, Zofia; Delpont, Sébastien

    2011-01-01

    Laboratory and full-scale experiments were conducted to investigate the development and effect of heterogeneity caused by filter media nonuniformity, biofilm, particles, precipitates, and gas bubbles in rapid sand filters used for drinking-water treatment. Salt tracer experiments were conducted...

  17. Heterogeneous counting on filter support media

    International Nuclear Information System (INIS)

    Long, E.; Kohler, V.; Kelly, M.J.

    1976-01-01

    Many investigators in the biomedical research area have used filter paper as the support for radioactive samples. This means that a heterogeneous counting of sample sometimes results. The count rate of a sample on a filter will be affected by positioning, degree of dryness, sample application procedure, the type of filter, and the type of cocktail used. Positioning of the filter (up or down) in the counting vial can cause a variation of 35% or more when counting tritiated samples on filter paper. Samples of varying degrees of dryness when added to the counting cocktail can cause nonreproducible counts if handled improperly. Count rates starting at 2400 CPM initially can become 10,000 CPM in 24 hours for 3 H-DNA (deoxyribonucleic acid) samples dried on standard cellulose acetate membrane filters. Data on cellulose nitrate filters show a similar trend. Sample application procedures in which the sample is applied to the filter in a small spot or on a large amount of the surface area can cause nonreproducible or very low counting rates. A tritiated DNA sample, when applied topically, gives a count rate of 4,000 CPM. When the sample is spread over the whole filter, 13,400 CPM are obtained with a much better coefficient of variation (5% versus 20%). Adding protein carrier (bovine serum albumin-BSA) to the sample to trap more of the tritiated DNA on the filter during the filtration process causes a serious beta absorption problem. Count rates which are one-fourth the count rate applied to the filter are obtained on calibrated runs. Many of the problems encountered can be alleviated by a proper choice of filter and the use of a liquid scintillation cocktail which dissolves the filter. Filter-Solv has been used to dissolve cellulose nitrate filters and filters which are a combination of cellulose nitrate and cellulose acetate. Count rates obtained for these dissolved samples are very reproducible and highly efficient

  18. Optimization of permanent breast seed implant dosimetry incorporating tissue heterogeneity

    Science.gov (United States)

    Mashouf, Shahram

    Seed brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose around brachytherapy sources is based on the AAPM TG43 formalism, which generates the dose in homogeneous water medium. Recently, AAPM task group no. 186 (TG186) emphasized the importance of accounting for heterogeneities. In this work we introduce an analytical dose calculation algorithm in heterogeneous media using CT images. The advantages over other methods are computational efficiency and the ease of integration into clinical use. An Inhomogeneity Correction Factor (ICF) is introduced as the ratio of absorbed dose in tissue to that in water medium. ICF is a function of tissue properties and independent of the source structure. The ICF is extracted using CT images and the absorbed dose in tissue can then be calculated by multiplying the dose as calculated by the TG43 formalism times ICF. To evaluate the methodology, we compared our results with Monte Carlo simulations as well as experiments in phantoms with known density and atomic compositions. The dose distributions obtained through applying ICF to TG43 protocol agreed very well with those of Monte Carlo simulations and experiments in all phantoms. In all cases, the mean relative error was reduced by at least a factor of two when ICF correction factor was applied to the TG43 protocol. In conclusion we have developed a new analytical dose calculation method, which enables personalized dose calculations in heterogeneous media using CT images. The methodology offers several advantages including the use of standard TG43 formalism, fast calculation time and extraction of the ICF parameters directly from Hounsfield Units. The methodology was implemented into our clinical treatment planning system where a cohort of 140 patients were processed to study the clinical benefits of a heterogeneity corrected dose.

  19. Algoritmos de aproximação para problemas de empacotamento em faixa com restrições de descarregamento

    OpenAIRE

    Jefferson Luiz Moisés da Silveira

    2011-01-01

    Resumo: Neste trabalho estudamos problemas de empacotamento com restrições de descarregamento considerados NP-difíceis. Estes problemas possuem aplicações nas áreas de logística e roteamento. Assumindo a hipótese de que P ? NP, sabemos que não existem algoritmos eficientes para resolver tais problemas. Uma das abordagens consideradas para tratar tais problemas é a de algoritmos de aproximação, que são algoritmos eficientes (complexidade de tempo polinomial) e que geram soluções com garantia d...

  20. Problemas de adaptación fisiológica en personas con angina

    OpenAIRE

    Nóbrega Fortes, Allyne; Martins da Silva, Viviane; Lopes, Marcos Venícios de Oliveira

    2006-01-01

    En este artículo fueron identificados los problemas comunes de adaptación fisiológica presentados por pacientes con angina inestable teniendo como base el Modelo de la Adaptación de Callista Roy. Estudio descriptivo desarrollado en un hospital de servicio especializado en enfermedades cardíacas. La muestra para el estudio fue de 20 pacientes. Para caracterización y discusión, utilizamos las definiciones presentadas por Roy para cada problema de adaptación fisiológic...

  1. Estudo transversal sobre problemas bucais em pacientes obesos mórbidos

    OpenAIRE

    Joselene Martinelli Yamashita

    2013-01-01

    A prevalência da obesidade tem aumentado em proporções alarmantes, tornando-se um problema de saúde pública. Há relatos de uma possível relação da obesidade com a condição bucal e o objetivo do presente estudo foi identificar os problemas bucais e seu impacto na qualidade de vida de indivíduos obesos mórbidos. A amostra foi composta por 100 pacientes obesos mórbidos (grupo obeso) e 50 indivíduos eutróficos (grupo controle), atendidos no Hospital das Clínicas da Faculdade de Medicina de Ribeir...

  2. Interações entre mães e adolescentes e os problemas de comportamento

    Directory of Open Access Journals (Sweden)

    Gabriela Mello Sabbag

    2015-01-01

    Full Text Available El estudio trata de describir y comparar los problemas de conducta, en grupos de riesgo y sin riesgo para diagnósticos de problemas, la competencia y las habilidades sociales y las interacciones sociales que se establecen entre las 24 madres y sus hijos adolescentes. El Inventario de Estilo Parental (IEP permitió la composición de los grupos, la Child Behavior Checklist (CBCL y el Guión de Entrevista de Habilidades Sociales para Educación de los Padres (RE-HSE-P se utilizaron para recopilar datos. Los diagnósticos de los problemas de comportamiento (Tablas de contingencia de prueba y las interacciones sociales (Mann-Whitney se compararon entre los grupos. Las interacciones se diferencian en que las madres del grupo sin riesgo cuando se comunican, expresan sentimientos y establecen límites, los niños responden con habilidades sociales. Al contrario, los grupos de riesgo, cuando las madres emiten estas conductas, los adolescentes responden con problemas de conducta. Se discuten las implicaciones de los hallazgos para esta población.

  3. Effect of capillary forces on immiscible two-phase flow in heterogeneous porous media

    Energy Technology Data Exchange (ETDEWEB)

    van Duijn, C.J.; Molenaar, J.; de Neef, M.J.

    1994-12-31

    We consider the one-dimensional two-phase flow including capillary effects through a heterogeneous porous medium. The heterogeneity is due to the spatial variation of the absolute permeability and the porosity. Both these quantities are assumed to be piecewise constant. At interfaces where the rock properties are discontinuous, we derive, by a regularization technique, conditions to match the values of the saturation on both sides. There are two conditions: a flux condition and an extended pressure condition. Applying these conditions we show that trapping of the wetting phase may occur near hetergeneities. To illustrate the behavior of the saturation we consider a time-dependent diffusion problem without convection, a stationary convection-diffusion problem, and the full time-dependent convection-diffusion problem (numerically). In particular the last two problems explicitly show the trapping behavior.

  4. Saúde mental e trabalho: os problemas que persistem

    Directory of Open Access Journals (Sweden)

    Leny Sato

    Full Text Available Este artigo toma por objeto a Saúde Mental e Trabalho como uma subárea do campo da Saúde do Trabalhador. Parte da constatação de que os problemas de saúde mental e trabalho, já identificados em meados da década de 1980, persistem. Após retomar a taxonomia de tais problemas, busca evidenciar algumas de suas expressões atuais a partir da assistência e da vigilância em saúde do trabalhador, bem como pela perspectiva de alguns sindicatos mais atentos à questão. Para tal, toma como ponto de partida o Centro de Referência em Saúde do Trabalhador (CRST de Campinas. Por fim, pontua algumas características do trabalho no contexto atual para compreender as motivações dessa persistência.

  5. Shock propagation in a heterogeneous medium

    International Nuclear Information System (INIS)

    Elbaz, D.

    2011-01-01

    In the frame of the inertial confinement fusion in direct drive, the use of foams as ablator allows the reduction of hydrodynamic instabilities created on the target by the direct laser irradiation. The foam is made up of carbon (CH) fibers impregnated of cryogenic deuterium-tritium (DT). In the past, studies have been carried out considering this foam to be a homogeneous medium. Yet, the foam presents heterogeneous features. We study the effects of this heterogeneity on the shock velocity when the laser irradiates the target. Thanks to experimental and numerical studies, we show that the shock propagates faster in the heterogeneous medium than in the homogeneous one with the same averaged density. This velocity gap depends on the presence rate of the CH fibers in the foam, the density ratio, the adiabatic coefficient and the foam geometry. We model the foam by different ways, more and more complex. The shock velocity modification is due to the baroclinicity which, during the interaction between the shock front and the interface, creates a vorticity deposition, responsible for the shock acceleration. Accordingly, an interface, which is plane and perpendicular to the front shock, maximizes the vorticity deposition and increases the velocity gaps between heterogeneous and homogeneous media. We found a correlation between the kinetic energy behind the shock front and the velocities relative difference. We compared our results with two analytical models. However, the system is not closed, so we can't for the moment develop a predictive model. (author) [fr

  6. Shock dynamics in layered periodic media

    KAUST Repository

    Ketcheson, David I.

    2012-01-01

    Solutions of constant-coeffcient nonlinear hyperbolic PDEs generically develop shocks, even if the initial data is smooth. Solutions of hyperbolic PDEs with variable coeffcients can behave very differently. We investigate formation and stability of shock waves in a one-dimensional periodic layered medium by a computational study of time-reversibility and entropy evolution. We find that periodic layered media tend to inhibit shock formation. For small initial conditions and large impedance variation, no shock formation is detected even after times much greater than the time of shock formation in a homogeneous medium. Furthermore, weak shocks are observed to be dynamically unstable in the sense that they do not lead to significant long-term entropy decay. We propose a characteristic condition for admissibility of shocks in heterogeneous media that generalizes the classical Lax entropy condition and accurately predicts the formation or absence of shocks in these media.

  7. Micro-scale displacement of NAPL by surfactant and microemulsion in heterogeneous porous media

    Science.gov (United States)

    Javanbakht, Gina; Arshadi, Maziar; Qin, Tianzhu; Goual, Lamia

    2017-07-01

    Industrial processes such as remediation of oil-contaminated aquifers and enhanced oil recovery (EOR) often utilize chemical additives to increase the removal of non-aqueous phase liquids (NAPLs) from subsurface formations. Although the majority of crude oils are classified as LNAPLs, they often contain heavy molecules (DNAPLs) such as asphaltenes that tend to adsorb on minerals and alter their wettability. Effective additives are therefore those that can reduce the threshold capillary pressure, thus mobilizing LNAPL inside pore spaces and solubilizing DNAPL from rock surfaces. Nonionic surfactants in brine have often been injected to oil or contaminated aquifer formations in order to enhance NAPL displacement through IFT reduction. Recent studies revealed that surfactant-based microemulsions have a higher tendency to alter the wettability of surfaces, compared to surfactants alone, leading to more effective NAPL removal. However, the impact of these additives on pore-scale displacement mechanisms and multi-phase fluid occupancy in porous media is, to date, still unclear. In this study, x-ray microtomography experiments were performed to investigate the impact of surfactants and microemulsions on the mobilization and solubilization of NAPL in heterogeneous rocks. Saturation profiles indicated that an incremental NAPL removal was attained by addition of microemulsion to brine, compared with surfactant. Residual cluster size distributions revealed that microemulsions could break up large clusters into smaller disconnected ones, improving their mobilization in the rock. In-situ contact angle measurements showed that microemulsions could reverse the wettability of rough contaminated surfaces to a higher extent than surfactants. Unlike surfactant alone, the surfactant-solvent blend in the carrier fluid of microemulsions was able to penetrate rough grain surfaces, particularly those of dolomite cement, and desorb asphaltenes in the form of small-emulsified NAPL droplets

  8. Algunos métodos para la solución de problemas de la física-matemática

    Directory of Open Access Journals (Sweden)

    R Quintero

    2016-03-01

    Full Text Available En este trabajo, se exponen algunos métodos para la solución de problemas de frontera, en regiones donde esta frontera es desconocida y se encuentra en movimiento (problema tipo Stefan. Como ejemplo se resuelve analíticamente el problema de congelamiento de un suelo húmedo. Brevemente se exponen algunos conceptos y resultados de la teoría de funciones generalizadas pertinentes a esta investigación, procediendo luego, al planteo del citado problema del congelamiento de un suelo húmedo como un problema generalizado de Cauchy y a su correspondiente solución. Se expone también un método  numérico de solución.

  9. Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media

    International Nuclear Information System (INIS)

    Corno, S.E.

    1965-01-01

    In this work we investigate the time and space dependence of the neutron flux within a highly heterogeneous assembly, in which pulsed or sinusoidally modulated neutrons are injected. We consider, for the sake of simplicity, a device consisting of a cylindrical block of heavy moderator, along the axis of which a line-shaped region of fissionable material is located. The driving neutron source is assumed to be located on one of the end faces of the cylinder. The extent of the fissionable region allows us to deal with it as with an absorbing and multiplying singularity of the neutron field. As our attention is mostly concentrated on space and time variation of the neutron flux, rather crude approximations are assumed as far as the energy dependence of the neutron population is concerned. Within the limits of the age-diffusion theory, the response of the device to any neutron excitation may be found in closed form. For a sinusoidally modulated source of given frequency, it may easily be shown that, if the axial singularity were a purely absorbing one, the neutron waves being propagated along the device would possess a phase shift; a wavelength and an attenuation constant depending on the absorbing properties of the singularity. This picture becomes more and more complicated when neutron multiplication occurs. For this general case the solution derived in our paper obviously turns out to be dependent on both absorption and multiplication properties of the singularity. This circumstance suggests, among others, the idea of using a device of the type described above for testing fuel elements of heterogeneous reactors. (author) [fr

  10. An analytical method for neutron thermalization calculations in heterogenous reactors

    Energy Technology Data Exchange (ETDEWEB)

    Pop-Jordanov, J [Boris Kidric Institute of Nuclear Sciences, Vinca, Belgrade (Yugoslavia)

    1965-07-01

    It is well known that the use of the diffusion approximation for stuheterogeneous reactors may result in considerable errors. On the other hand, more exact numerical methods are rather laborious and require the use of large digital computers. In this paper, the use of the diffusion approximation in absorbing media has been avoided, but the treatment remained analytical, thus simplifying practical calculations.

  11. An analytical method for neutron thermalization calculations in heterogenous reactors

    International Nuclear Information System (INIS)

    Pop-Jordanov, J.

    1965-01-01

    It is well known that the use of the diffusion approximation for studying neutron thermalization in heterogeneous reactors may result in considerable errors. On the other hand, more exact numerical methods are rather laborious and require the use of large digital computers. In this paper, the use of the diffusion approximation in absorbing media has been avoided, but the treatment remained analytical, thus simplifying practical calculations

  12. Aprender con problemas: un enfoque contextualizado y socializado del conocimiento

    Directory of Open Access Journals (Sweden)

    Lola GARCÍA OLALLA

    2008-01-01

    Full Text Available El estudio que presentamos se centra en la utilización del ABP (Aprendizaje Basado en Problemas, que articula dos asignaturas cuatrimestrales: Desarrollo Socioafectivo y Desarrollo Psicomotor. Concluimos que la metodología ABP favorece el aprendizaje significativo, aprender a trabajar en grupo, resolver problemas de forma cooperativa, y la conexión entre la formación teórica y los contextos de actuación profesional. El aprendizaje cooperativo favorece la dinámica de trabajo en equipo, la responsabilidad personal y el desarrollo de estrategias de colaboración, y de competencias sociales como aprender a escuchar, respetar las opiniones de otros, organizar el trabajo, debatir y llegar a consensos, saber expresarse y exponer opiniones, o empatizar.

  13. Arquitectura y construcción sostenibles: conceptos, problemas y estrategias

    Directory of Open Access Journals (Sweden)

    Domingo Acosta

    2009-07-01

    Full Text Available La necesidad de atender e intentar resolver los problemas que afectan la calidad de vida de los actuales habitantes del planeta, sin comprometer la posibilidad de que las futuras generaciones puedan disponer de recursos para enfrentar los suyos, es una referencia directa a la modificación del medio ambiente natural, actividad inherente a los arquitectos e ingenieros. Es un enfoque de carácter multifocal, que implica aspectos tecnológicos, políticos, sociales, económicos, ecológicos y éticos. En este artículo se desarrollan un conjunto de conceptos, problemas y estrategias que permiten definir las características que se aspira detenten las edificaciones para el logro de una mayor sostenibilidad o ecoeficiencia.

  14. Una metodología activa para la resolución de problemas

    Directory of Open Access Journals (Sweden)

    Miró-Julià, Margaret

    2006-01-01

    Full Text Available El objetivo de esta ponencia es presentar las conclusiones del proyecto de mejora de la calidad docente titulado “El uso de estrategias adecuadas para la resolución de problemas de Estadística” que se realizó en la Universidad de las Islas Baleares durante el curso 2005-2006. Debido a nuestra dilatada experiencia en la enseñanza de las asignaturas Estadística Económica y Métodos Matemáticos para la Economía I, II y III de los estudios que dependen de la Facultad de Economía, somos conscientes del desánimo y desinterés de nuestros alumnos. Es indiscutible que existen dificultades por parte de los profesores a la hora de enseñar, pero también existen obstáculos por parte de los alumnos para aprender. Esta problemática resulta evidente a la hora de resolver problemas. El proyecto, cuyas conclusiones presentamos, pretende ensayar nuevas formas de enseñanza/aprendizaje que responden a las recientes directrices del espacio Europeo. El proyecto está dirigido a potenciar la tarea del alumno a la hora de enfrentarse con un problema. Se basa fundamentalmente en la creación de guiones que ofrezcan al alumno las pautas a seguir a la hora de resolver problemas y que también le permitan realizar una auto-evaluación de los resultados obtenidos.

  15. Bias and Uncertainty in Regression-Calibrated Models of Groundwater Flow in Heterogeneous Media

    DEFF Research Database (Denmark)

    Cooley, R.L.; Christensen, Steen

    2006-01-01

    by a lumped or smoothed m-dimensional approximation γθ*, where γ is an interpolation matrix and θ* is a stochastic vector of parameters. Vector θ* has small enough dimension to allow its estimation with the available data. The consequence of the replacement is that model function f(γθ*) written in terms......Groundwater models need to account for detailed but generally unknown spatial variability (heterogeneity) of the hydrogeologic model inputs. To address this problem we replace the large, m-dimensional stochastic vector β that reflects both small and large scales of heterogeneity in the inputs...... small. Model error is accounted for in the weighted nonlinear regression methodology developed to estimate θ* and assess model uncertainties by incorporating the second-moment matrix of the model errors into the weight matrix. Techniques developed by statisticians to analyze classical nonlinear...

  16. Organizaciones y Problemas Sociales. Una aproximación sistémica

    Directory of Open Access Journals (Sweden)

    Juan Pablo Gonnet

    2011-09-01

    Full Text Available Este trabajo indaga teóricamente acerca de las relaciones entre organizaciones y problemas sociales (problemasde la sociedad. Una observación constante en los estudios sociológicos sobre la materia ha sido la distorsiónentre fines y acciones organizacionales. Es decir, las organizaciones en su actividad y operación dejande lado la finalidad (resolución de la problemática para la que habían sido constituidas bajo criterios deauto-reproducción. Dada la generalidad de estos resultados, nos interesamos por reflexionar teóricamentesobre los supuestos que se encuentran detrás de este modo de observar a las organizaciones (sus condicionesde posibilidad. Con este fin, presentamos tres estudios de caso de organizaciones dedicadas al tratamientode problemas sociales. A partir de estos procedemos a analizar los modos de observación que están vinculadosa la evaluación de la relación organización-problema social. Finalmente, desde la teoría de los sistemassociales (Luhmann, proponemos una forma diferente de analizar y conceptualizar la mencionada relación.

  17. Servicio militar un problema de identidades

    OpenAIRE

    Sánchez Navarro, Eulogio

    2005-01-01

    Las diferencias entre la vida civil y la militar han supuesto tradicionalmente lo que podríamos definir como un choque cultural entre aquellos que tuvieron que realizar el servicio militar obligatorio. este choque se vio incrementado en los últimos años de conscripción debido al creciente distanciamiento entre las visiones de mundo de militares y civiles. esta tesis analiza desde la perspectiva de la antropología social los problemas de identidad de los soldados de reemplazo, que habían de...

  18. Anorgasmia femenina como problema de salud

    OpenAIRE

    Farramola Bello, Luis Antonio; Erice Rivero, Teresa Sandra; Frías Alvarez, Yaumara

    2011-01-01

    OBJETIVO: Demostrar que la anorgasmia constituye un problema de salud. MÉTODOS: Se realizó un estudio transversal descriptivo de 227 mujeres que acudieron al Hospital General «Calixto García Iñiguez». Las variables seleccionadas fueron: edad, nivel de escolaridad, edad de inicio de las primeras relaciones sexuales, relación anorgasmia y masturbación femenina. Análisis con porcentajes. RESULTADOS: El mayor porcentaje de anorgasmia coital fue del 35 % y el 40 % eran anorgásmicas fortuitas, toda...

  19. 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

  20. Deposition of colloidal particles in porous media; Depot de particules minerales de taille colloidale en milieu poreux

    Energy Technology Data Exchange (ETDEWEB)

    Coste, J.P.

    1998-12-09

    The aim of this study was to determine the deposition rates of colloidal particles in porous media in relation with particle stability. It combines experimental results and theoretical analysis and gives an original approach which allows to improve the predictions of particle deposition. The colloidal particles studied are several times smaller than the pore restrictions. Experimental results shows that the porous media surface is heterogeneous, whatever the preparation mean and the history of the porous media. The degree of surface heterogeneity depends both on salinity and porous media cleaning process. Heterogeneity is responsible for initial collection efficiency values higher that the theoretical predictions. When deposition occurs mainly on the less repulsive zones, the velocity dependence of the effective grain collection efficiency is close to the -2/3 value expected for the diffusion limited deposition regime. On the other hand, when these zones have been covered and thus behave as strongly repulsive, we obtain a collection efficiency on the more repulsive zones, with a slope close to -1, which is the value expected for the reaction limited deposition regime. The fraction of surface favorable for deposition can be assessed from attachment efficiency values. The attachment efficiency can be estimated from the measurement of particles stability. (author)

  1. Um problema de corte com padrões compartimentados

    Directory of Open Access Journals (Sweden)

    Robinson Hoto

    2003-01-01

    Full Text Available Neste artigo apresentaremos a aplicação do Problema da Mochila Compartimentada (PMC no Problema de Corte de Bobinas de Aço (PCBA, que é um problema de corte em duas etapas com restrições especiais de agrupamento dos itens. O PMC consiste em construir compartimentos de capacidades desconhecidas em uma mochila de capacidade conhecida, tendo em vista que os itens de interesse estão agrupados em subconjuntos, de modo que, itens de um agrupamento não podem ser combinados com itens de outro. Para entender melhor o PMC admita que a mochila de um alpinista deve ser composta por um número ideal de compartimentos com itens de quatro categorias (remédios, alimentos, ferramentas, roupas, porém, itens de categorias distintas não podem ser combinados para formar um mesmo compartimento, além do mais, são desconhecidas as capacidades ideais de cada compartimento da mochila.In this paper we will present the application of the Compartmented Knapsack Problem (CKP in the Cut Problem of Steel Rolls (CPSR, that it is a problem of cut in two stages with restrictions special of grouping of items. The CKP consists of constructing compartments of unknown capacities in a knapsack of known capacity, in view of that items of interest is grouped in subgroups, in mode that, items of a grouping cannot be matched with items of another one. To understand the CKP more good it admits that the knapsack of a alpinist must be composite for an ideal number of compartments with items of four categories (remedies, foods, tools, clothes, however, items of distinct categories cannot be matched to form one same compartment, in addition, is unknown the ideal capacities of each compartment of the knapsack.

  2. Estudios sobre clase media en la antropología social: una agenda para la Argentina. En: Avá, nº 13

    OpenAIRE

    Visacovsky, Sergio

    2008-01-01

    El objetivo de este trabajo es exponer un panorama de los estudios antropológicos sobre clase media. Primero,ofrezco una respuesta para explicar porqué la antropología social sólo recientemente se interesó en estudiar poblaciones definidas como “de clase media”. Segundo, analizo cómo la sociología en la Argentina hizo de la clase media uno de sus objetos de investigación centrales en los años 1950 (en relación con los problemas del desarrollo y la modernización), y desde los 1990 (en relación...

  3. Simulation of Tracer Transport in Porous Media: Application to Bentonites; Simulacion del Transporte de Trazadores en Medios Porosos: Aplicacion al Caso de Arcillas

    Energy Technology Data Exchange (ETDEWEB)

    Bru, A; Casero, D [CIEMAT, Madrid (Spain)

    2001-07-01

    We present a formal framework to describe tracer transport in heterogeneous media, such as porous media like bentonites. In these media, mean field approximation is not valid because there exist some geometrical constraints and the transport is anomalous. (Author)

  4. Aprendizaje basado en problemas en ingeniería

    DEFF Research Database (Denmark)

    es una colección de artículos publicados, recogiendo las principales consideraciones para diseñar e implementar PBL. Los editores seleccionaron artículos originales en inglés para presentar una visión general de la teoría y la práctica del PBL. Se cubren tópicos como: Principios del trabajo en...... problemas y proyectos Modelos de PBL Trabajo en grupos y facilitación Desarrollo de competencias y habilidades Formulación de problemas en PBL Gestión de proyectos Implementación de cambio PBL en para aprendizaje en línea y tecnologías de la información El diseño de un modelo de PBL utiliza teorías de...... aprendizaje con diferentes necesidades sociales y culturales. Este libro será una lectura clave para los académicos e investigadores que diseñan, implementan y ponen en práctica el PBL en cualquier sistema educativo. Descargar libro electrónico aquí...

  5. Modelos matemáticos en un problema de epidemias

    Directory of Open Access Journals (Sweden)

    Anna Vidal

    2016-01-01

    Full Text Available La introducción de conceptos matemáticos a través del desarrollo y estudio de modelos ha sido tratado en numerosos trabajos. La introducción de los modelos suele hacerse básicamente desde el discurso del professor y el trabajo del alumno suele reducirse a la experimentación con el modelo dado. La aproximación a un problema mediante modelos IBM (Individual Based Model resulta más comprensible para el alumno, permite justificar y complementar otras aproximaciones a la solución (modelos diferenciales continuos y/o modelos discretos. En este trabajo se presenta una experiencia docente basada en afrontar un mismo problema mediante enfoques complementarios en base a modelos continuos, discretos e IBM. Finalmente se presenta una propuesta metodológica para ponerla en práctica utilizando el Aprendizaje Cooperativo y el Problem/Project Based Learning.

  6. Diseño de un sistema de soporte de decisiones para resolver el problema de ruteo en un servicio de courier

    OpenAIRE

    Tomalá Robles, James; Pincay Villa, Johnny

    2010-01-01

    El Problema de Ruteo de Vehículos (VRP), en el cual se debe determinar un conjunto de rutas a un mínimo costo, tiene numerosas aplicaciones en las operaciones logísticas. El VRP es bien conocido como un problema de programación entera el cual cae dentro de la categoría de problemas NP-Hard, significando que los esfuerzos computacionales requeridos para resolver este problema se incrementan exponencialmente con su tamaño. Visto el VRP como un Problema de Optimización Combinatoria (OC), existen...

  7. Aprendizaje basado en problemas: Metodología de aprendizaje centrada en el estudiante

    Directory of Open Access Journals (Sweden)

    V. Tórtora

    2013-11-01

    Full Text Available 8vas Jornadas de la Sociedad de Bioquímica y Biología Molecular. 12 y 13 de setiembre 2013. SIMPOSIO VI: “Educación en Ciencias” Coordinadores: María Noel Álvarez, Andrea MedeirosLa reforma del plan de estudios de la carrera de Doctor en Medicina implicó, entre outras modificaciones, la incorporación de nuevas metodologías de enseñanza y aprendizaje. Una de ellas es la de “aprendizaje basado en problemas” (ABP, que se caracteriza por colocar al estudiante en el centro del proceso de aprendizaje, promoviendo que este sea significativo, además de desarrollar habilidades y competencias indispensables en el ejercicio profesional. El ABP se realiza en grupos de aproximadamente 20 estudiantes, en dos instancias. El problema es diseñado por un equipo docente interdisciplinario, en función a los objetivos del curso. En la primera instancia se presenta el problema y los estudiantes discuten en función de sus conocimientos previos, identificando las áreas de saber y de no saber sobre el problema, e intentan plantear hipótesis explicativas sobre las dificultades identificadas. Lugo deben determinar qué competencias y nuevos conocimientos necesitan para comprobarlas. Este proceso es realizado de manera autónoma por los estudiantes, bajo la dirección de un docente tutor que actúa como facilitador del aprendizaje. Entre una instancia y otra buscan la información necesaria para lograr los objetivos de estudio definidos por el grupo, y regresan al problema en la segunda instancia. La información encontrada es compartida entre los integrantes del grupo, mediante discusión en foros en la plataforma de aprendizaje virtual (EVA y durante las clases presenciales, haciendo que el aprendizaje sea además cooperativo. En esta presentación se expondrá esta metodología de trabajo junto con un ejemplo de un problema específico con objetivos de bioquímica.En esta presentación se expondrá esta metodología de trabajo junto con un ejemplo

  8. Study of heterogeneous multiplying and non-multiplying media by the neutron pulsed source technique

    International Nuclear Information System (INIS)

    Deniz, V.

    1969-01-01

    The pulsed neutron technique consists essentially in sending in the medium to be studied a short neutron pulse and in determining the asymptotic decay constant of the generated population. The variation of the decay constant as a function of the size of the medium allows the medium characteristics to be defined. This technique has been largely developed these last years and has been applied as well to moderator as to multiplying media, in most cases homogeneous ones. We considered of interest of apply this technique to lattices, to see if useful informations could be collected for lattice calculations. We present here a general theoretical study of the problem, and results and interpretation of a series of experiments made on graphite lattices. There is a good agreement for non-multiplying media. In the case of multiplying media, it is shown that the age value used until now in graphite lattices calculations is over-estimated by about 10 per cent [fr

  9. Los problemas de la Educación Ambiental: ¿es posible una Educación Ambiental integradora?

    OpenAIRE

    García, J. Eduardo

    2002-01-01

    En este trabajo se presentan diferentes problemas y carencias de la Educación Ambiental. Para el tratamiento de estos problemas se plantea una perspectiva integradora que supere los reduccionismos actualmente existentes

  10. From medium heterogeneity to flow and transport: A time-domain random walk approach

    Science.gov (United States)

    Hakoun, V.; Comolli, A.; Dentz, M.

    2017-12-01

    The prediction of flow and transport processes in heterogeneous porous media is based on the qualitative and quantitative understanding of the interplay between 1) spatial variability of hydraulic conductivity, 2) groundwater flow and 3) solute transport. Using a stochastic modeling approach, we study this interplay through direct numerical simulations of Darcy flow and advective transport in heterogeneous media. First, we study flow in correlated hydraulic permeability fields and shed light on the relationship between the statistics of log-hydraulic conductivity, a medium attribute, and the flow statistics. Second, we determine relationships between Eulerian and Lagrangian velocity statistics, this means, between flow and transport attributes. We show how Lagrangian statistics and thus transport behaviors such as late particle arrival times are influenced by the medium heterogeneity on one hand and the initial particle velocities on the other. We find that equidistantly sampled Lagrangian velocities can be described by a Markov process that evolves on the characteristic heterogeneity length scale. We employ a stochastic relaxation model for the equidistantly sampled particle velocities, which is parametrized by the velocity correlation length. This description results in a time-domain random walk model for the particle motion, whose spatial transitions are characterized by the velocity correlation length and temporal transitions by the particle velocities. This approach relates the statistical medium and flow properties to large scale transport, and allows for conditioning on the initial particle velocities and thus to the medium properties in the injection region. The approach is tested against direct numerical simulations.

  11. RETOS DEL APRENDIZAJE BASADO EN PROBLEMAS

    OpenAIRE

    Carlos Antonio Poot-Delgado

    2013-01-01

    Se realiza una breve descripción de la viabilidad y retos de llevar a la práctica docente el aprendizaje basado en problemas, con una estructura organizada, donde se plasman ideas bien fundamentadas con claridad y precisión. Asimismo, se plantean reflexiones pertinentes, mediante ejercicios alusivos y ubicados en la práctica docente. Es decir, una forma de trabajo que puede ser usada por el edu- cador en una parte de su curso, combinado con otras técnicas didácticas y de- limitando los objeti...

  12. Problemas psiquiátricos em geriatria

    Directory of Open Access Journals (Sweden)

    Marcelo Blaya

    1960-06-01

    Full Text Available Foi apresentado um resumo das idéias comumente aceitas em psiquiatria dinâmica com relação aos problemas emocionais da velhice. A necessidade de uma solução eclética para esta questão de crescente importância na sociedade hodierna não impede que se utilize, com vantagem, uma orientação psicanalítica no tratamento dêsses indivíduos. No caso apresentado acham-se ilustrados alguns pontos de vista do autor.

  13. Modelagem Integrada do Problema de Programação de Tripulantes de Aeronaves

    Directory of Open Access Journals (Sweden)

    Wagner de Paula Gomes

    2011-09-01

    Full Text Available

    Este artigo trata o Problema de Programação de Tripulantes (PPT, de importância fundamental no planejamento operacional das empresas aéreas. O PPT é normalmente dividido na literatura em dois subproblemas, formulados e resolvidos sequencialmente: Problema de Determinação das Viagens (PDV e Problema de Atribuição de Escalas (PAE. Esta decomposição justifica-se pela sua natureza combinatória, porém deixa de proporcionar um tratamento global ao PPT, em termos de custo e qualidade da solução final. Portanto, o estado da arte envolve a solução integrada do PPT, em que ambos os subproblemas são resolvidos simultaneamente. O problema, no entanto, é NP-Difícil. Esta pesquisa apresenta uma metodologia para modelagem integrada do PPT, através de um Algoritmo Genético Híbrido (AGH associado a um procedimento de busca em profundidade, levando em conta as particularidades da legislação brasileira. A metodologia foi testada, com sucesso, para a solução de instâncias baseadas na malha real de uma empresa aérea brasileira.

  14. A model for the ultrasonic field radiated by an immersed transducer into an anisotropic and heterogeneous medium

    International Nuclear Information System (INIS)

    Gengembre, N.

    2000-01-01

    A model for the field radiated by an ultrasonic transducer into anisotropic and heterogeneous media is developed in this thesis. This work aims at improving the settings and interpretations of non destructive tests in welded structures. Since the shape of the transducer is assumed arbitrary, its emitting surface is divided into small elementary sources. The overall field at an observation point in the medium is derived by a summation of the elementary contributions of these point sources. An accurate and numerically efficient model is developed using the Geometrical Optics approximation to evaluate these elementary contributions. Two different forms of this approximation are used: The stationary phase method and the pencil method. The first one is based on an exact formulation of the field and is used for fields into anisotropic and homogeneous media. It allows to emphasize specific configurations for which additional developments are required; this need arises for calculation points in the vicinity of caustics (zones of high intensity). This problem is solved for both harmonic and transient fields, for points laying on caustics or in their neighborhood. The pencil method is used for the calculation of fields in heterogeneous media, although it does not permit to overcome the problem of caustics. It is also advantageous for the implementation of the model. A comparison of both above-mentioned methods is drawn, and their equivalence is proved for some cases. The calculation of fields in anisotropic and heterogeneous media is performed using both methods together, and then the problem of caustics is also treated. Calculated fields into welded components are shown and compared with experiments or with a numerical model, in order to validate the developments. (author)

  15. Problemas Familiares Contemporâneos o Situaciones Familiares Actuales: Invariancia y Novedad

    OpenAIRE

    Berenstein,Isidoro

    2002-01-01

    O autor inicia por perguntar-se sobre a relevância da família na atualidade. Para responder esta questão, examina os vínculos de casal e de relação entre pais e filhos, situando-os historicamente. Sugere que os "problemas familiares" instauram-se a partir do momento em que se institui uma forma de família como oficial, sendo "problemas" as que não seguem esse modelo. Por isto, prefere referir-se a diferentes "situações familiares", que passam a ser pensadas a partir da crítica de dois critéri...

  16. Apoio comportamental positivo: estratégias educacionais aplicadas a comportamentos-problema de alunos

    Directory of Open Access Journals (Sweden)

    Karyne de Souza Augusto Rios

    Full Text Available Baseado no modelo de Apoio Comportamental Positivo o estudo objetivou identificar como 40 diretores de escolas de educação infantil descreviam o processo de elaboração, aplicação e avaliação de estratégias educativas para comportamentos-problema de alunos. Resultados do questionário apontaram que 77,5% dos diretores indicaram comportamentos-problema em seus alunos. As estratégias educativas mais utilizadas foram conversar com a criança (13,3% e conversar com pais (13,3%. A ação mais utilizada para a avaliação foi a observação da criança (27,6%. De forma geral, verificou-se que as estratégias utilizadas foram realizadas informal e assistematicamente. Aponta-se a necessidade de pesquisas sobre a inclusão de crianças com comportamentos-problema e o desafio de repensar a formação dos educadores.

  17. La solución de problemas cognitivos. Una reflexión cognitiva sociocultural

    Directory of Open Access Journals (Sweden)

    Rosalía Montealegre

    2007-06-01

    Full Text Available Este artículo, que se basa en la psicología histórico-cultural, enfatiza la solución de problemas como función psicológica superior ligada con otras funciones psíquicas: lenguaje, pensamiento, razonamiento, etc. Presenta una reflexión sociocultural sobre la solución de problemas cognitivos al abordar: 1. El pensamiento productivo (creativo: los métodos de investigación y los instrumentos (artefactos de mediación; 2. La ciencia cognitiva: el sistema de procesamiento de información, la cognición distribuida y la formación de acciones mentales; 3. El conflicto sociocognitivo: las interacciones sociales, el conflicto estructurante, la regulación sociocognitiva y la zona de desarrollo próximo. Concluye en la necesidad de formar la solución de problemas desarrollando: el pensamiento productivo, las estrategias cognitivas y el análisis de conceptos y hechos sociales

  18. Resolución e invención de problemas en la Educación Matemática

    OpenAIRE

    Espinoza, Johan

    2013-01-01

    Los programas de estudio de Matemática en Costa Rica, proponen la Resolución de Problemas en contextos reales como estrategia metodológica principal y el Planteamiento de Problemas como uno de los cinco procesos matemáticos. Así, este estudio analiza algunos elementos que intervienen en el proceso de enseñanza y aprendizaje de contenidos matemáticos empleando dicha estrategia y el papel del planteamiento de problemas como actividad complementaria en dicho proceso. Los resultados muestran la i...

  19. PROBLEMAS LOCOMOTORES EM FRANGOS DE CORTE - REVISÃO. / LOCOMOTOR PROBLEMS IN BROILER CHICKENS - A REVIEW.

    Directory of Open Access Journals (Sweden)

    IBIARA CORREIA DE LIMA ALMEIDA PAZ

    2008-12-01

    Full Text Available O bem estar animal é, sem dúvida, um dos pontos em que os produtores de aves devem se atentar para conseguir melhor rentabilidade e colocação no mercado externo. No entanto, é necessário ter uma ampla idéia de que alguns pontos impostos por mercados importadores, muitas vezes não tem fundamento científico e tratam-se mais de barreiras não tarifárias que de problemas de produção propriamente ditos. Dentre os vários fatores que afetam o bem estar animal pode-se destacar a incidência de problemas locomotores, principalmente em animais confinados. Estes distúrbios podem acarretar em perdas de até 6% em lotes comercias de frangos de corte, além de outras perdas não mensuráveis em linhas de abate, por fraturas e hematomas. Existem diversas metodologias para diagnosticar problemas locomotores, entretanto, a mais difundida na indústria avícola é o Gait Score, por sua facilidade de aplicação e por englobar os diferentes tipos de problemas locomotores. Sabe-se, contudo que esta metodologia é bastante subjetiva e pode inferir  em  diferentes  níveis  de  avaliação  dependendo  do método  utilizado. Os  problemas locomotores devem ser prevenidos já que depois de estabelecidos as perdas são inevitáveis.

  20. Social movement heterogeneity in public policy framing: A multi-stakeholder analysis of the Keystone XL pipeline

    Science.gov (United States)

    Wesley, David T. A.

    In 2011, stakeholders with differing objectives formed an alliance to oppose the Keystone XL heavy oil pipeline. The alliance, which came to be known as "Tar Sands Action," implemented various strategies, some of which were more successful than others. Tar Sands Action was a largely heterogeneous alliance that included indigenous tribes, environmentalists, ranchers, landowners, and trade unions, making it one of the more diverse social movement organizations in history. Each of these stakeholder categories had distinct demographic structures, representing an array of racial, ethnic, educational, occupational, and political backgrounds. Participants also had differing policy objectives that included combating climate change and protecting jobs, agricultural interests, water resources, wildlife, and human health. The current dissertation examines the Tar Sands Action movement to understand how heterogeneous social movement organizations mobilize supporters, maintain alliances, and create effective frames to achieve policy objectives. A multi-stakeholder analysis of the development, evolution and communication of frames concerning the Keystone XL controversy provides insight into the role of alliances, direct action, and the news media in challenging hegemonic frames. Previous research has ignored the potential value that SMO heterogeneity provides by treating social movements as culturally homogenous. However, diversity has been shown to affect performance in business organizations. The current study demonstrates that under some circumstances, diversity can also improve policy outcomes. Moreover, policy frames are shown to be more effective in sustaining news media and public interest through a process the author calls dynamic frame sequencing (DFS). DFS refers to a process implementing different stakeholder frames at strategically opportune moments. Finally, Tar Sands Action was one of the first SMOs to rely heavily on social media to build alliances, disseminate

  1. Climate Change, a Case Study of Media Construction of Environmental Problems; El Cambio Climatico como Casuistica de la Construccion Mediatica de los Problemas Medioambientales

    Energy Technology Data Exchange (ETDEWEB)

    Lopera, E.

    2009-07-21

    Nowadays climate change is one of the environmental problems in the global policy agenda. However, in countries like United States and United Kingdom the media started to report regularly on this issue in 1988. Since then many researches have been carrying out focused on how the media influence, along with other factors, public understanding of climate change through the media construction of the problem in several countries. Given the implications of social acceptance for design and implementation of public policies on mitigation and adaptation to climate change, the overall aim of this report is to review the status of the issue from a qualitative and quantitative approach. Qualitatively, media construction of climate change is described as the result of different processes taking place at macro and micro scales. Interactions among scientists, politicians, industry, the media themselves and the social context are considered macro-scale influences, while journalistic values and norms shape the media coverage of this environmental problem at micro-scale when media professionals report on climate change. From a quantitative point of view this paper also includes the evolution of newspaper coverage on climate change in Spain from 1996 to 2006 and these figures are compared to the results obtained in the United States and United Kingdom during the same period. (Author) 23 refs.

  2. Aproximación de los problemas de optimización por redes neuronales artificiales

    Directory of Open Access Journals (Sweden)

    Caballero Fernandez, Rafael

    2001-01-01

    Full Text Available En el presente artículo, pretendemos aportar un conocimiento de cómo puede aproximarse un problema de optimización mediante la dinámica de las redes neuronales artificiales, específicamente mediante las redes de tipo Hopfield. La elección de este tipo de redes radica en el objetivo que nos hemos propuesto en el presente trabajo, la resolución on-line de los problemas de optimización lineal, cuadrática, no lineal y combinatoria. Construimos, desarrollamos y justificamos formalmente una metodología integral que permite recoger los distintos tipos de problemas de optimización y construir una red neuronal de tipo Hopfield que los resuelva de una manera computacionalmente adecuada y formalmente correcta, comparando los resultados obtenidos con los publicados más recientemente.

  3. Effect of heterogeneities on evaluating earthquake triggering of volcanic eruptions

    Directory of Open Access Journals (Sweden)

    J. Takekawa

    2013-02-01

    Full Text Available Recent researches have indicated coupling between volcanic eruptions and earthquakes. Some of them calculated static stress transfer in subsurface induced by the occurrences of earthquakes. Most of their analyses ignored the spatial heterogeneity in subsurface, or only took into account the rigidity layering in the crust. On the other hand, a smaller scale heterogeneity of around hundreds of meters has been suggested by geophysical investigations. It is difficult to reflect that kind of heterogeneity in analysis models because accurate distributions of fluctuation are not well understood in many cases. Thus, the effect of the ignorance of the smaller scale heterogeneity on evaluating the earthquake triggering of volcanic eruptions is also not well understood. In the present study, we investigate the influence of the assumption of homogeneity on evaluating earthquake triggering of volcanic eruptions using finite element simulations. The crust is treated as a stochastic media with different heterogeneous parameters (correlation length and magnitude of velocity perturbation in our simulations. We adopt exponential and von Karman functions as spatial auto-correlation functions (ACF. In all our simulation results, the ignorance of the smaller scale heterogeneity leads to underestimation of the failure pressure around a chamber wall, which relates to dyke initiation. The magnitude of the velocity perturbation has a larger effect on the tensile failure at the chamber wall than the difference of the ACF and the correlation length. The maximum effect on the failure pressure in all our simulations is about twice larger than that in the homogeneous case. This indicates that the estimation of the earthquake triggering due to static stress transfer should take account of the heterogeneity of around hundreds of meters.

  4. Problemas de saúde mental e tabagismo em adolescentes do sul do Brasil

    Directory of Open Access Journals (Sweden)

    Ana M B Menezes

    2011-08-01

    Full Text Available OBJETIVO: Analisar a associação entre problemas de saúde mental e uso de tabaco em adolescentes. MÉTODOS: Foram analisados 4.325 adolescentes de 15 anos da coorte de nascimentos de 1993 da cidade de Pelotas, RS. Tabagismo foi definido como fumar um ou mais cigarros nos últimos 30 dias. Saúde mental foi avaliada de acordo com o escore total do questionário Strengths and Difficulties Questionnaire e escore maior ou igual a 20 pontos foi considerado como positivo. Os dados foram analisados por regressão de Poisson, com ajuste robusto para variância. RESULTADOS: A prevalência de tabagismo foi 6,0% e cerca de 30% dos adolescentes apresentaram algum tipo de problema de saúde mental. Na análise bruta, a razão de prevalências para tabagismo foi de 3,3 (IC95% 2,5; 4,2. Após ajuste (para sexo, idade, cor da pele, renda familiar, escolaridade da mãe, grupo de amigos fumantes, trabalho no último ano, repetência escolar, atividade física de lazer e uso experimental de bebida alcoólica, diminuiu para 1,7 (IC95% 1,2; 2,3 entre aqueles com problemas de saúde mental. CONCLUSÕES: Problemas de saúde mental na adolescência podem ter relação com o consumo de tabaco.

  5. An effective dead oil model for two-phase flow in inhomogeneous porous media

    International Nuclear Information System (INIS)

    Bourgeat, A.

    1988-01-01

    The authors are investigating displacement process of incompressible two phase flow miscible or immiscible in heterogeneous porous media, including capillary and gravity effects. The authors' aim is to derive rigorously a Global or Effective Model which then allow, in Numerical Simulations, to disconnect the numerical mesh size from the heterogeneities size inside the reservoir itself. The reservoir is assumed to be made of uniformly (or non uniformly) periodically repeated cells. Each cell being made with different types of porous media. Then, calling ε the ratio of the cell size to the Reservoir size, we get equations depending on the parameter ε because the Porosity and Permeabilities, say Phi/sup ε/ and Κ/sup ε/ are themselves rapidly oscillating. From these ε-parametrized equations the authors derive simpler ''Effective Equations'' no more dependant on ε, called ''Homongenized Equations by the mathematical technique of Homogenization. In these new equations, which are describing Global Displacement process throughout a Globally Equivallent homogenous media where now //Phi and Κ are no more depending on the space variable or ε

  6. An improved intermediate resonance method for heterogeneous media

    International Nuclear Information System (INIS)

    Chiovato, O.; Corno, S.; Pasquantonio, F.Di.

    1977-01-01

    A new formulation is described of the Intermediate Resonance method which incorporates the previous developments suitably modified and improved, together with some new contributions. The 'intermediate' character is directly introduced in the integral operator K, allowing a more rigorous deduction of the equations for evaluating the intermediate parameters related to the nuclides involved in the system. There is no limit to the number of internal (admixed in the fuel) and external moderators. The capability to take into account the interference scattering has been extended to heterogeneous systems. The Doppler broadening is described by means of new accurate rational approximations to the broadened line shape psi. Finally the use of energy mean values suitably defined refines the values of the resonance integrals and resonance absorption cross sections. The Intermediate Resonance method so extended and improved, has been coded in a group of FORTRAN routines, which have been inserted as a calculation option in the fast section of the GGC code for the evaluation of multigroup cross sections. A series of calculations has been carried out, using these routines, and comparisons have been made with Monte Carlo and Nordheim's methods. The results obtained show that the Intermediate Resonance method developed in the present work offers considerable advantages over Nordheim's method: better accuracy in evaluating resonance absorption cross sections, and much smaller computing times. (author)

  7. Tamanho ao nascer e problemas de saúde mental aos 11 anos em uma coorte brasileira de nascimentos

    Directory of Open Access Journals (Sweden)

    Erika Alejandra Giraldo Gallo

    2011-08-01

    Full Text Available O objetivo foi avaliar a associação entre tamanho ao nascer e problemas de saúde mental aos 11 anos na Coorte de Nascimentos de Pelotas, Rio Grande do Sul, Brasil, de 1993. Foram pesados e medidos ao nascer 4.358 recém-nascidos. Avaliou-se problemas de saúde mental com o questionário de capacidades e dificuldades (Strengths and Difficulties Questionnaire - SDQ. A prevalência de problemas de saúde mental foi de 32% (IC95%: 31-33. Na análise ajustada, os 291 (6,7% recém-nascidos com escorez de peso/idade e os 268 (6,2% com índice de massa corporal (IMC/idade +2 DP tiveram, respectivamente, 34% (IC95%: 6-71 e 19% (IC95%: 1-40 maior risco de apresentar esses problemas se comparados com aqueles com escore normal. Os resultados sugerem que fatores ocorridos na gestação e refletidos nas medidas de tamanho ao nascer podem ocasionar problemas de saúde mental em etapas tardias.

  8. Acting on Media: Influencing, Shaping and (ReConfiguring the Fabric of Everyday Life

    Directory of Open Access Journals (Sweden)

    Sigrid Kannengießer

    2017-09-01

    Full Text Available Computerization, digitalization and datafication are by far no neutral or self-dependent occurrences. They are, to a large degree, co-determined by heterogeneous actors who reflect about, construct, configure, manipulate or even control media. The contributors to this issue put the spotlight on these actors and investigate how they influence, shape and (reconfigure broader social constellations. Instead of exploring what people do with media, the articles focus on the many ways individuals, civil society initiatives, corporations and social movements act on media. The notion of acting on media denotes the efforts of a wide range of actors to take an active part in the molding of media organizations, infrastructures and technologies that are part of the fabric of everyday life. Therefore, by conceptualizing acting on media as a form of political action, the issue aims to contribute to ongoing discussions on the media practice paradigm.

  9. APLICACIÓN DEL APRENDIZAJE BASADO EN PROBLEMAS EN INGENIERÍA APLICAÇÃO DA APRENDIZAGEM BASEADA EM PROBLEMAS EM ENGENHARIA PROBLEM-BASED LEARNING APPLICATION IN ENGINEERING

    Directory of Open Access Journals (Sweden)

    Maria Victoria Echavarria

    2010-12-01

    Full Text Available El aprendizaje basado en problemas es una estrategia pedagógica ampliamente utilizada en el mundo con el propósito de mejorar el aprendizaje de los estudiantes, quienes se convierten en el centro del proceso. Este artículo presenta el reporte de un caso que ilustra la aplicación, el proceso y sus resultados de aprendizaje basado en problemas (ABP durante cinco semestres consecutivos en el curso de Gestión y Control de Procesos perteneciente a las carreras de Ingeniería Industrial e Ingeniería Administrativa en Colombia. El papel del profesor y los resultados de los alumnos son elementos críticos en la evaluación del proceso de implementación de ABP.A aprendizagem baseada em problemas é uma estratégia pedagógica amplamente utilizada no mundo, com o objetivo de melhorar a aprendizagem dos alunos, que se tornam o centro do processo. Este artigo apresenta um relatório de um caso que ilustra a aplicação, o processo e os resultados da aprendizagem baseada em problemas (ABP durante cinco semestres consecutivos no curso de Gestão e Controle de Processos pertencente às carreiras de Engenharia Industrial e Engenharia Administrativa na Colômbia. O papel do professor e os resultados dos alunos são elementos críticos na avaliação do processo de implementação da PBL.Problem-based learning is a pedagogical strategy widely applied in many universities worldwide with the purpose of improving the learning out come of the students who become the center of the process. This paper presents a case report illustrating an experience, its evolving process and subsequent results of a problem-based learning (PBL application during five semesters in a Process Management and Control course for under graduate programs of Industrial Engineering and Management Engineering in Colombia. The teacher's role and student assessments are critical elements for the evaluation of the PBL implementation process.

  10. UNA HERRAMIENTA MATRICIAL PARA EL MODELADO EN 2-D DE ALGUNOS PROBLEMAS DE CONTACTO ELÁSTICO

    Directory of Open Access Journals (Sweden)

    FABIO ALEXANDER SUÁREZ

    2008-01-01

    Full Text Available En los contactos localizados, la búsqueda de las relaciones entre la carga, la geometría de los cuerpos, sus propiedades elásticas y la geometría de la zona de contacto, constituye un campo del conocimiento de alto impacto tecnológico. El conocimiento de estas relaciones permite entender mejor el comportamiento de los sistemas tribológicos para mejorar su diseño y desempeño. Este artículo busca dar a conocer una herramienta matricial útil para el modelado de problemas bidimiensionales de contactos elásticos. Basada en una generalización del problema de Flamant, dicha matriz constituye un vínculo entre los desplazamientos perpendiculares a la superficie que experimentan los puntos de ésta y la forma como se distribuye la carga en la zona de contacto, permitiendo encontrar una de estas variables en función de la otra. Esta es una herramienta sencilla y de gran utilidad para la solución de problemas complejos de este tipo. Para mostrar su utilidad, esta matriz fue empleada para resolver el problema del contacto elástico entre dos cilindros largos, problema inicialmente planteado por Hertz; los resultados encontrados son iguales a los obtenidos por Hertz en su solución analítica.

  11. O problema da roteirização periódica de veículos

    Directory of Open Access Journals (Sweden)

    Luciele Wu

    2009-06-01

    Full Text Available

    Este artigo trata do problema de roteirização periódica, uma generalização do problema clássico de roteirização de veículos. Neste problema, os pontos a serem atendidos podem ter diferentes freqüências de visitas e a roteirização deve considerar um período de planejamento. Portanto, é preciso decidir quais são os melhores dias de visita para cada ponto (respeitando sua freqüência de visitas, para que a roteirização seja otimizada para todo o horizonte de planejamento. Este problema ocorre no contexto da logística inbound na indústria automobilística. Neste caso, não só os roteiros de coleta devem ser determinados como também os dias em que cada fornece- dor pode ser visitado, dado que os diferentes fornecedores podem ter diferentes freqüências. Com a finalidade de explorar novas abor- dagens para este tipo de problema de maneira que houvesse um aumento na qualidade de soluções e diminuição do tempo de proces- samento computacional, são propostas três estratégias heurísticas de solução, baseadas em inserção, GRASP e algoritmos genéticos. As estratégias foram implementadas e testadas para problemas encontrados na literatura, bem como problemas gerados aleatoriamente.

    Abstract: This article deals with the period vehicle routing problem, which can be viewed as a generalization of the classical vehicle routing problem. In this problem, points to be serviced may have different frequencies and the routing is accomplished over a given planning horizon. Thus, one must decide which are the best days to visit each point (respecting its given frequency, so that the routing over the overall planning horizon is optimized. This problem arises in the context of inbound logistics in the automotive industry. In this case, pick-up routes should be determined as well as the days each supplier must be visited, given that the different suppliers may have different

  12. Violência urbana: um problema social Urban violence: a social problem

    Directory of Open Access Journals (Sweden)

    Álvaro de Aquino e Silva Gullo

    1998-05-01

    Full Text Available O presente artigo reúne um conjunto de reflexões sobre diversos aspectos em que se manifesta a violência social. Essas reflexões, apresentadas em momentos diferentes, como aulas, debates e num congresso, foram agrupadas sob o título de Violência Urbana porque concorrem para a compreensão da violência cotidiana enquanto problema da sociedade urbana. Dos cursos regulares, registro a concepção inicial, tomada da antropologia social, que leva à caracterização da violência na sociedade rural para fundamentar a gênese do problema na sociedade contemporânea de classes sociais, focalizado na perspectiva da marginalidade estrutural. Dos debates sucitados por acontecimentos traumáticos envolvendo o aparato policial, resultou uma discussão sobre as causas da violência inerente ao desempenho da função institucional atribuída às polícias militar e civil. Da participação em congresso sobre o novo Código de Trânsito Brasileiro, resultou a parte final deste artigo que discute o papel e, particularmente, o significado dos símbolos sociais divulgados pelos meios de comunicação de massa, como fatores responsáveis pela crescente violência no trânsito.This article contains some reflections on how social violence expresses itself. These reflections, presented in former moments as lectures, public debates and at a congress, have been gathered under the title of Urban Violence because they all try to comprehend everyday violence as a problem of urban society. Based on the lectures I have formulated the first part of this article, which deals with a conception taken from social anthropology: the characterization of violence in rural society under the perspective of structural marginality, in order to explain the genesis of this problem in the actual social class society. The debates, that took place because of traumatic happenings related to the police apparatus, have brought about a discussion of the causes of violence inherent to the

  13. A numerical homogenization method for heterogeneous, anisotropic elastic media based on multiscale theory

    KAUST Repository

    Gao, Kai; Chung, Eric T.; Gibson, Richard L.; Fu, Shubin; Efendiev, Yalchin R.

    2015-01-01

    The development of reliable methods for upscaling fine-scale models of elastic media has long been an important topic for rock physics and applied seismology. Several effective medium theories have been developed to provide elastic parameters

  14. A model of non-Gaussian diffusion in heterogeneous media

    Science.gov (United States)

    Lanoiselée, Yann; Grebenkov, Denis S.

    2018-04-01

    Recent progress in single-particle tracking has shown evidence of the non-Gaussian distribution of displacements in living cells, both near the cellular membrane and inside the cytoskeleton. Similar behavior has also been observed in granular materials, turbulent flows, gels and colloidal suspensions, suggesting that this is a general feature of diffusion in complex media. A possible interpretation of this phenomenon is that a tracer explores a medium with spatio-temporal fluctuations which result in local changes of diffusivity. We propose and investigate an ergodic, easily interpretable model, which implements the concept of diffusing diffusivity. Depending on the parameters, the distribution of displacements can be either flat or peaked at small displacements with an exponential tail at large displacements. We show that the distribution converges slowly to a Gaussian one. We calculate statistical properties, derive the asymptotic behavior and discuss some implications and extensions.

  15. Situação-problema como disparador do processo de ensino-aprendizagem em metodologias ativas de ensino

    Directory of Open Access Journals (Sweden)

    Raphaela Barroso Guedes-Granzotti

    2015-12-01

    Full Text Available RESUMO: Objetivo: descrever o processo de elaboração de uma Situação-Problema e de um Módulo de aprendizagem e refletir a importância destes na formação do Fonoaudiólogo. Métodos: estudo descritivo do processo de elaboração de uma Situação-Problema e de um Módulo de aprendizagem de um curso de graduação em Fonoaudiologia - uma experiência precursora na área em que toda a estrutura curricular tem como base Metodologias Ativas de ensino. Resultado: o Módulo Estudo da Linguagem Infantil ocorre no Ciclo II do Curso e é constituído por nove Situações-Problema sendo, cada uma, discutida em duas sessões tutoriais com até dez discentes e conduzida por um professor tutor. As Situações-Problema, assim como o Módulo, são elaboradas por uma comissão de docentes doutores e especialistas em Linguagem de acordo com o Projeto Pedagógico do Curso. Discute-se, neste artigo, a terceira Situação-Problema que tem como título - "Mesmas características, mas diagnósticos diferentes... Por quê?"; O título tem o papel de despertar a curiosidade do discente e apresentar o enfoque principal do problema. Todas as Situações-Problema são avaliadas por docentes e discentes com objetivo de promover aperfeiçoamentos constantes. Conclusão: o contexto problematizador construído a partir das Situações-Problema permite ao discente a busca de respostas diariamente, de forma ativa e autônoma, pela vivência e discussão do trabalho em equipe, dos aspectos biopsicossociais do indivíduo e das questões éticas na atuação profissional. Possibilitando assim a formação de profissionais resolutivos, competentes para aperfeiçoar seu conhecimento constantemente e de atuar em consonância com as práticas de Saúde Pública do País.

  16. A Review Paper On Exploring Text Link And Spacial-Temporal Information In Social Media Networks

    Directory of Open Access Journals (Sweden)

    Dr. Mamta Madan

    2015-03-01

    Full Text Available ABSTRACT The objective of this paper is to have a literature review on the various methods to mine the knowledge from the social media by taking advantage of embedded heterogeneous information. Specifically we are trying to review different types of mining framework which provides us useful information from these networks that have heterogeneous data types including text spacial-temporal and data association LINK information. Firstly we will discuss the link mining to study the link structure with respect to Social Media SM. Secondly we summarize the various text mining models thirdly we shall review spacial as well the temporal models to extract or detect the frequent related topics from SM. Fourthly we will try to figure out few improvised models that take advantage of the link textual temporal and spacial information which motivates to discover progressive principles and fresh methodologies for DM Data Mining in social media networks SMNs.

  17. The geological basis and the representation of spatial variability in sedimentary heterogeneous media

    International Nuclear Information System (INIS)

    Cliffe, K.A.; Franklin, D.J.; Jones, P.I.R.; Macleod, E.J.; Porter, J.D.

    1998-01-01

    The impact of different conceptual models was investigated of the heterogeneity of the Sherwood Sandstone Group (SSG) at Sellafield on calculations of flow and transport. Detailed models of the heterogeneity of the Undifferentiated St Bees Sandstone (USBS) of the SSG were produced. The models took into account directly the geological structures at the facies level. The software package STORM (STOchastic Reservoir Modelling), was used to construct the models. The data required by the model are those that characterise the geometry of the channel bodies and the properties of the various sub-facies within the channels. It was found that for the case in which all of the variability was within channels, the larger scale permeabilities did not exhibit any significant correlation structure. The up-scaled effective permeabilities also exhibited correlation lengths that were comparable with the channel dimensions. Flow and transport calculations were also performed on 90 realizations of a detailed facies scale three-dimensional representation of a larger block of the USBS. The results are broadly consistent with the analytical results for transport through a random permeability field. (R.P.)

  18. Problemas éticos al final de la vida

    Directory of Open Access Journals (Sweden)

    Maria Graciela De Ortuzar

    2014-06-01

    Full Text Available El presente informe trata sobre el análisis filosófico de un tema complejo y controvertido, como lo es la ?definición de muerte?. Por ello, es importante subrayar que no desarrollaré aquí los aspectos antropológicos, sicológicos, médicos y técnicos de la muerte. Sólo me centraré en las teorías filosóficas principales que justifican diferentes definiciones de muerte (esencialista vs. biológica y sus consecuentes problemas prácticos. La necesidad de realizar esta investigación surge a partir del reconocimiento de confusiones conceptuales y contradicciones cuando se comunica ?la muerte? (falta de concordancia entre la definición filosófica, criterios y tests; contradicciones reflejadas cotidianamente en el lenguaje y en las actitudes del personal médico y de enfermería de nuestras Unidades de Terapia Intensiva (UTIs. Hablar de paciente al referirse a un cadáver al que se le ha diagnosticado la muerte encefálica; hablar de muerte cuando se produce el paro cardiorespitariaco (¿dos muertes?; hablar de eutanasia cuando se retira el respirador al individuo muerto cuyos órganos están siendo mantenidos artificialmente; éstas situaciones -entre otras- reflejan conflictos y falta de claridad conceptual sobre los conceptos básicos de muerte y eutanasia. Dichos conflictos constituyen problemas éticos claves al final de la vida, los cuáles nacen a partir del reciente cambio en el criterio de muerte en un contexto de acelerada ?tecnologización? de la salud. He aquí la necesidad del análisis crítico sobre el marco teórico-conceptual requerido en UTIs y su confrontación aplicada, con el fin de esclarecer los citados problemas. Para ello, estudiaré la teoría moral unificada de Bernard Gert, examinando su justificación teórica y su aplicabilidad práctica, como así también las posiciones alternativas a la misma (Wikler. En términos generales, considero que la defensa de la coherencia, sistematicidad y aplicabilidad de las

  19. Discontinuous Galerkin Subgrid Finite Element Method for Heterogeneous Brinkman’s Equations

    KAUST Repository

    Iliev, Oleg P.

    2010-01-01

    We present a two-scale finite element method for solving Brinkman\\'s equations with piece-wise constant coefficients. This system of equations model fluid flows in highly porous, heterogeneous media with complex topology of the heterogeneities. We make use of the recently proposed discontinuous Galerkin FEM for Stokes equations by Wang and Ye in [12] and the concept of subgrid approximation developed for Darcy\\'s equations by Arbogast in [4]. In order to reduce the error along the coarse-grid interfaces we have added a alternating Schwarz iteration using patches around the coarse-grid boundaries. We have implemented the subgrid method using Deal.II FEM library, [7], and we present the computational results for a number of model problems. © 2010 Springer-Verlag Berlin Heidelberg.

  20. Monte Carlo simulation of radioactive contaminant transport in fractured geologic media: Disorder and long-range correlations

    International Nuclear Information System (INIS)

    Mukhopadhyay, S.; Cushman, J.H.

    1997-01-01

    The geologic media near Yucca mountain site consist of fractured welded tuffs along with less fractured unwelded tuff. Numerical simulation of flow and transport in such media poses a number of challenging problems, due mainly to the heterogeneities and disorder in the media. In addition, because of different dominant transport mechanisms in different regions of the media, investigations need to be carried out at different time-scales. Time-marching will pose a considerable problem in analyzing such multi-scale transient problems. The authors develop a field-scale network model of fractures and study transport of radionuclides through geologic media as a function of disorder and correlated fracture-permeabilities

  1. Designing Mixed Media Devices for support of healthcare professionals

    DEFF Research Database (Denmark)

    Kramp, Gunnar

    2008-01-01

    at tilføje en lokation til et fotografi. I denne afhandling betegnes denne type objekter som Mixed-Media-Devices på grund af deres heterogene natur.   For at Mixed-Media-Devices kan forbinde sig til hinanden, er det nødvendigt med en software arkitektur, som understøtter denne heterogenitet. Ydermere, må......”. Med andre ord, at udvikle den nødvendige software til at kunne orkestrere de fremspirende Mixed-Media-Devices i vores omgivelser. Arbejdet, der ligger til grund for denne afhandling er, blevet til indenfor Palcom projektets rammer.   Palcom projektet koordineres af Datalogi på Århus Universitet...... virkelighedens brugere har Palcom projektet arbejdet med en række indsatsområder som katastrofeindsats, graviditet og barsel, hånd-kirurgi og en neonatal afdeling. Sammen med brugerne fra disse områder er der udviklet en række Mixed-Media-Devices med henblik på at informere om og afprøve den udviklede software...

  2. What makes papers visible on social media? An analysis of various document characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Zahedi, Z.; Costas, R.; Lariviere, V.; Haustein, S.

    2016-07-01

    In this study we have investigated the relationship between different document characteristics and the number of Mendeley readership counts, tweets, Facebook posts, mentions in blogs and mainstream media for 1.3 million papers published in journals covered by the Web of Science (WoS). It aims to demonstrate that how factors affecting various social media-based indicators differ from those influencing citations and which document types are more popular across different platforms. Our results highlight the heterogeneous nature of altmetrics, which encompasses different types of uses and user groups engaging with research on social media. (Author)

  3. FASES DE RESOLUCIÓN DE UNA SITUACIÓN-PROBLEMA UTILIZANDO ELEMENTOS DE COMPETENCIAS

    Directory of Open Access Journals (Sweden)

    Ester Ruda

    2012-01-01

    Full Text Available El objetivo de este trabajo fue analizar las fases utilizadas para resolver una situación-problema a través de elementos de competencias en el proceso de enseñanza y aprendizaje de una asignatura universitaria. Se analizan las fases a desarrollar (análisis de la situación-problema, identificación de los esquemas de actuación, selección, disposición y aplicación estratégica de los esquemas de actuación; conocimiento, dominio y transferencia de los componentes de la competencia y las evidencias de logro del dominio de los componentes de la competencia. Se aplican los conceptos a un ejemplo para una asignatura del ciclo superior de una carrera relacionada con la química y se discuten los resultados obtenidos. La resolución de una situación-problema implica que los alumnos han adquirido elementos de competencias, han sorteado distintos pasos que implican el dominio de procedimientos que aparecen en toda acción competente y han aplicado interrelacionadamente contenidos conceptuales, actitudinales y procedimentales.

  4. La comunicación corno quehacer y como problema

    Directory of Open Access Journals (Sweden)

    Javier Luis Mier

    2015-01-01

    Full Text Available Este número aborda la comunicación desde las tres interpretaciones más importantes: la tradicionalista, la militar y mercantilista y el arte popular tan inestable, cuestionado y cambiante. Canclini cuestiona la compartamentalización de cultura: popular y de medios y esboza los problemas que plantea la tradicional miopía de no reconocer la universalización y ubicuidad de la cultura de masas. Se agregan otros temas como: ¿Re-intelección de los medios? apuntes sobre un libro de los Mattelart, ¿"Ética" o "Deontología"?, El lenguaje del vestido y de la fiesta,Talleres de cultura Popular en Santiago de Chile, El dilema del arte popular en Bolivia,¿Sobrevivirán las artesanías aborígenes argentinas?, Los tejedores de El Tintorero, Tecnologías de computación y Tercer Mundo, La cobertura del terremoto en México, La comunicación como quehacer y como problema, la comunicación planificada sirve al desarrollo

  5. Veridicção: um problema de verdade

    Directory of Open Access Journals (Sweden)

    Maria de Lourdes Ortiz Gandin Baldan

    2001-02-01

    Full Text Available

    A teoria semiótica greimasiana provocou, com a definição de veridicção, um avanço considerável rias teorias que tratam do texto. O presente trabalho fornece algumas reflexões, principalmente no sentido de repensar o problema da referencialidade nos discursos através do estatuto cientifico que a teoria greimasiana propõe no seu procedimento descritivo.

  6. Tratamiento fisioterapico en pacientes con lesión en territorio de la arteria cerebral media.

    OpenAIRE

    Bays Moneo, Ana Beatriz

    2014-01-01

    Paciente de 70 años que padece una hemiparesia derecha con afasia de Broca de casi dos años de evolución como consecuencia de una oclusión de arteria carótida interna que provocó un infarto en el territorio de la arteria cerebral media. Para su tratamiento se ha utilizado el concepto Bobath. Durante el mismo, tuvo una frecuencia de tres sesiones por semana de 45 minutos durante cuatro meses. El paciente mostraba como problema principal, un pie con gran tendencia al equ...

  7. Modeling multicomponent ionic transport in groundwater with IPhreeqc coupling: Electrostatic interactions and geochemical reactions in homogeneous and heterogeneous domains

    DEFF Research Database (Denmark)

    Muniruzzaman, Muhammad; Rolle, Massimo

    2016-01-01

    is coupled with the geochemical code PHREEQC-3 by utilizing the IPhreeqc module, thus enabling to perform the geochemical calculations included in the PHREEQC's reaction package. The multicomponent reactive transport code is benchmarked with different 1-D and 2-D transport problems. Successively...... the electrostatic interactions during transport of charged ions in physically and chemically heterogeneous porous media. The modeling approach is based on the local charge balance and on the description of compound-specific and spatially variable diffusive/dispersive fluxes. The multicomponent ionic transport code......, conservative and reactive transport examples are presented to demonstrate the capability of the proposed model to simulate transport of charged species in heterogeneous porous media with spatially variable physical and chemical properties. The results reveal that the Coulombic cross-coupling between dispersive...

  8. A theoretical framework for modeling dilution enhancement of non-reactive solutes in heterogeneous porous media.

    Science.gov (United States)

    de Barros, F P J; Fiori, A; Boso, F; Bellin, A

    2015-01-01

    Spatial heterogeneity of the hydraulic properties of geological porous formations leads to erratically shaped solute clouds, thus increasing the edge area of the solute body and augmenting the dilution rate. In this study, we provide a theoretical framework to quantify dilution of a non-reactive solute within a steady state flow as affected by the spatial variability of the hydraulic conductivity. Embracing the Lagrangian concentration framework, we obtain explicit semi-analytical expressions for the dilution index as a function of the structural parameters of the random hydraulic conductivity field, under the assumptions of uniform-in-the-average flow, small injection source and weak-to-mild heterogeneity. Results show how the dilution enhancement of the solute cloud is strongly dependent on both the statistical anisotropy ratio and the heterogeneity level of the porous medium. The explicit semi-analytical solution also captures the temporal evolution of the dilution rate; for the early- and late-time limits, the proposed solution recovers previous results from the literature, while at intermediate times it reflects the increasing interplay between large-scale advection and local-scale dispersion. The performance of the theoretical framework is verified with high resolution numerical results and successfully tested against the Cape Cod field data. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. O Problema Habitacional na América Latina: Exemplos do Brasil e Chile

    OpenAIRE

    Rubin, Graziela

    2013-01-01

    DOI: 10.12957/geouerj.2013.3873O presente artigo faz um resgate histórico da problemática habitacional na América Latinae traz como exemplos o Brasil e o Chile, países que apresentaram políticas interessantes para tentarresolver o problema da habitação. A partir do século XIX, com a industrialização e,consequentemente,o aumento da urbanização, as cidades da América Latina passaram a sofrer com osproblemas urbanos. Entre eles, a questão habitacional se destaca por ser um problema que afeta nos...

  10. Problemas fundamentales de elasticidad en suelos. Aplicaciones del círculo de Mohr

    OpenAIRE

    Alhama Manteca, Iván; García Ros, Gonzalo; Alhama López, Francisco

    2017-01-01

    El libro contiene fundamentos teóricos relacionados con la elasticidad aplicada a mecánica de suelos, junto con 61 problemas y 155 figuras. Describe la elasticidad aplicada a geotecnia desde sus principios fundamentales: concepto de esfuerzo y tipos, Ley de Hooke, matrices de esfuerzos y deformaciones y resolución de problemas de mecánica de suelos a través del círculo de Mohr, extendiendo su aplicación a los criterios de fallo en suelos, teoría y uso del polo, círculo de Mohr de deformacione...

  11. Relaxações Lagrangianas e planos de corte faciais na resolução de problemas de particionamento de conjuntos

    OpenAIRE

    Andrei de Almeida Sampaio Braga

    2011-01-01

    Resumo: O problema de particionamento de conjuntos (SPP, do inglês set partitioning problem) é considerado um dos problemas de otimização combinatória com mais vasta gama de aplicações. Para solucioná-lo, utilizam-se comumente métodos tradicionais para a resolução de problemas NP - Difíceis. Nesta dissertação, estuda-se o uso da combinação de relaxação Lagrangiana com planos de corte. Relaxação Lagrangiana é uma técnica que tem sido usada com bastante sucesso para atacar vários problemas NP-D...

  12. Energy-Reduction Offloading Technique for Streaming Media Servers

    Directory of Open Access Journals (Sweden)

    Yeongpil Cho

    2016-01-01

    Full Text Available Recent growth in popularity of mobile video services raises a demand for one of the most popular and convenient methods of delivering multimedia data, video streaming. However, heterogeneity of currently existing mobile devices involves an issue of separate video transcoding for each type of mobile devices such as smartphones, tablet PCs, and smart TVs. As a result additional burden comes to media servers, which pretranscode multimedia data for number of clients. Regarding even higher increase of video data in the Internet in the future, the problem of media servers overload is impending. To struggle against the problem an offloading method is introduced in this paper. By the use of SorTube offloading framework video transcoding process is shifted from the centralized media server to the local offloading server. Thus, clients can receive personally customized video stream; meanwhile the overload of centralized servers is reduced.

  13. Analysis and Visualization of Internet QA Bulletin Boards Represented as Heterogeneous Networks

    Science.gov (United States)

    Murata, Tsuyoshi; Ikeya, Tomoyuki

    Visualizing and analyzing social interactions of CGM (Consumer Generated Media) are important for understanding overall activities on the internet. Social interactions are often represented as simple networks that are composed of homogeneous nodes and edges between them. However, related entities in real world are often not homogeneous. Such relations are naturally represented as heterogeneous networks composed of more than one kind of nodes and edges connecting them. In the case of CGM, for example, users and their contents constitute nodes of heterogeneous networks. There are related users (user communities) and related contents (contents communities) in the heterogeneous networks. Discovering both communities and finding correspondence among them will clarify the characteristics of the communites. This paper describes an attempt for visualizing and analyzing social interactions of Yahoo! Chiebukuro (Japanese Yahoo! Answers). New criteria for measuring correspondence between user communities and board communites are defined, and characteristics of both communities are analyzed using the criteria.

  14. Health-related media use among youth audiences in Senegal.

    Science.gov (United States)

    Glik, Deborah; Massey, Philip; Gipson, Jessica; Dieng, Thierno; Rideau, Alexandre; Prelip, Michael

    2016-03-01

    Lower- and middle-income countries (LMICs) are experiencing rapid changes in access to and use of new internet and digital media technologies. The purpose of this study was to better understand how younger audiences are navigating traditional and newer forms of media technologies, with particular emphasis on the skills and competencies needed to obtain, evaluate and apply health-related information, also defined as health and media literacy. Sixteen focus group discussions were conducted throughout Senegal in September 2012 with youth aged 15-25. Using an iterative coding process based on grounded theory, four themes emerged related to media use for health information among Senegalese youth. They include the following: (i) media utilization; (ii) barriers and conflicts regarding media utilization; (iii) uses and gratifications and (iv) health and media literacy. Findings suggest that Senegalese youth use a heterogeneous mix of media platforms (i.e. television, radio, internet) and utilization often occurs with family members or friends. Additionally, the need for entertainment, information and connectedness inform media use, mostly concerning sexual and reproductive health information. Importantly, tensions arise as youth balance innovative and interactive technologies with traditional and conservative values, particularly concerning ethical and privacy concerns. Findings support the use of multipronged intervention approaches that leverage both new media, as well as traditional media strategies, and that also address lack of health and media literacy in this population. Implementing health-related interventions across multiple media platforms provides an opportunity to create an integrated, as opposed to a disparate, user experience. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Adaptive mesh refinement for a finite volume method for flow and transport of radionuclides in heterogeneous porous media

    International Nuclear Information System (INIS)

    Amaziane, Brahim; Bourgeois, Marc; El Fatini, Mohamed

    2014-01-01

    In this paper, we consider adaptive numerical simulation of miscible displacement problems in porous media, which are modeled by single phase flow equations. A vertex-centred finite volume method is employed to discretize the coupled system: the Darcy flow equation and the diffusion-convection concentration equation. The convection term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion-dispersion term is discretized by piecewise linear conforming finite elements. We introduce two kinds of indicators, both of them of residual type. The first one is related to time discretization and is local with respect to the time discretization: thus, at each time, it provides an appropriate information for the choice of the next time step. The second is related to space discretization and is local with respect to both the time and space variable and the idea is that at each time it is an efficient tool for mesh adaptivity. An error estimation procedure evaluates where additional refinement is needed and grid generation procedures dynamically create or remove fine-grid patches as resolution requirements change. The method was implemented in the software MELODIE, developed by the French Institute for Radiological Protection and Nuclear Safety (IRSN, Institut de Radioprotection et de Surete Nucleaire). The algorithm is then used to simulate the evolution of radionuclide migration from the waste packages through a heterogeneous disposal, demonstrating its capability to capture complex behavior of the resulting flow. (authors)

  16. Un sistema de calefacción sustentable: decisiones sobre un problema auténtico

    OpenAIRE

    Federico Agraso, Marta; Eirexas Santamaría, Fins; Jiménez Aleixandre, María Pilar; Gutiérrez Roger, Xulio

    2007-01-01

    En este trabajo se discute un ejemplo de cómo incorporar las dimensiones de la educación ambiental al trabajo de aula en el marco de la asignatura de Ciencias de la Tierra y del Medio Ambiente. Para ello se implica activamente a los estudiantes en la resolución de los problemas reales de su entorno persiguiendo que desarrollen la conciencia y la preocupación por los problemas ambientales así como el reconocimiento de su responsabilidad en los mismos.

  17. Modeling mixed retention and early arrivals in multidimensional heterogeneous media using an explicit Lagrangian scheme

    Science.gov (United States)

    Zhang, Yong; Meerschaert, Mark M.; Baeumer, Boris; LaBolle, Eric M.

    2015-08-01

    This study develops an explicit two-step Lagrangian scheme based on the renewal-reward process to capture transient anomalous diffusion with mixed retention and early arrivals in multidimensional media. The resulting 3-D anomalous transport simulator provides a flexible platform for modeling transport. The first step explicitly models retention due to mass exchange between one mobile zone and any number of parallel immobile zones. The mobile component of the renewal process can be calculated as either an exponential random variable or a preassigned time step, and the subsequent random immobile time follows a Hyper-exponential distribution for finite immobile zones or a tempered stable distribution for infinite immobile zones with an exponentially tempered power-law memory function. The second step describes well-documented early arrivals which can follow streamlines due to mechanical dispersion using the method of subordination to regional flow. Applicability and implementation of the Lagrangian solver are further checked against transport observed in various media. Results show that, although the time-nonlocal model parameters are predictable for transport with retention in alluvial settings, the standard time-nonlocal model cannot capture early arrivals. Retention and early arrivals observed in porous and fractured media can be efficiently modeled by our Lagrangian solver, allowing anomalous transport to be incorporated into 2-D/3-D models with irregular flow fields. Extensions of the particle-tracking approach are also discussed for transport with parameters conditioned on local aquifer properties, as required by transient flow and nonstationary media.

  18. El papel de los esquemas en la resolución de problemas de enunciado verbal

    OpenAIRE

    Nesher, Pearla

    1999-01-01

    En el artículo se pretende demostrar que la capacidad para resolver problemas de matemáticas depende de los niveles de esquemas y en las estructuras que tienen los chicos y chicas. Se sugiere que si los profesores son conscientes de los esquemas necesarios para asentar cada nivel de aprendizaje y presentan los problemas de los alumnos de la forma más general posible, eso facilitar la resolución.

  19. Influence of interface scattering on shock waves in heterogeneous solids

    International Nuclear Information System (INIS)

    Zhuang Shiming; Ravichandran, Guruswami; Grady, Dennis E.

    2002-01-01

    In heterogeneous media, the scattering due to interfaces between dissimilar materials play an important role in shock wave dissipation and dispersion. In this work the influence of interface scattering effect on shock waves was studied by impacting flyer plates onto periodically layered polycarbonate/6061 aluminum, polycarbonate/304 stainless steel and polycarbonate/glass composites. The experimental results (using VISAR and stress gauges) indicate that the rise time of the shock front decreases with increasing shock strength, and increases with increasing mechanical impedance mismatch between layers; the strain rate at the shock front increases by about the square of the shock stress. Experimental and numerical results also show that due to interface scattering effect the shock wave velocity in periodically layered composites decreases. In some cases the shock velocity of a layered heterogeneous composite can be lower than that of either of its components

  20. On POD-based Deflation Vectors for DPCG applied to porous media problems

    NARCIS (Netherlands)

    Diaz Cortes, G.B.; Vuik, C.; Jansen, J.D.

    2018-01-01

    We study fast and robust iterative solvers for large systems of linear equations resulting from simulation of flow trough strongly heterogeneous porous media. We propose the use of preconditioning and deflation techniques, based on information obtained frfrom the system, to reduce the time spent in

  1. Experimental investigation of transverse mixing in porous media under helical flow conditions

    DEFF Research Database (Denmark)

    Ye, Yu; Chiogna, Gabriele; Cirpka, Olaf A.

    2016-01-01

    Plume dilution and transverse mixing can be considerably enhanced by helical flow occurring in three-dimensional heterogeneous anisotropic porous media. In this study, we perform tracer experiments in a fully three-dimensional flow-through chamber to investigate the effects of helical flow on plume...

  2. Mapping moveout approximations in TI media

    KAUST Repository

    Stovas, Alexey; Alkhalifah, Tariq Ali

    2013-01-01

    Moveout approximations play a very important role in seismic modeling, inversion, and scanning for parameters in complex media. We developed a scheme to map one-way moveout approximations for transversely isotropic media with a vertical axis of symmetry (VTI), which is widely available, to the tilted case (TTI) by introducing the effective tilt angle. As a result, we obtained highly accurate TTI moveout equations analogous with their VTI counterparts. Our analysis showed that the most accurate approximation is obtained from the mapping of generalized approximation. The new moveout approximations allow for, as the examples demonstrate, accurate description of moveout in the TTI case even for vertical heterogeneity. The proposed moveout approximations can be easily used for inversion in a layered TTI medium because the parameters of these approximations explicitly depend on corresponding effective parameters in a layered VTI medium.

  3. Mapping moveout approximations in TI media

    KAUST Repository

    Stovas, Alexey

    2013-11-21

    Moveout approximations play a very important role in seismic modeling, inversion, and scanning for parameters in complex media. We developed a scheme to map one-way moveout approximations for transversely isotropic media with a vertical axis of symmetry (VTI), which is widely available, to the tilted case (TTI) by introducing the effective tilt angle. As a result, we obtained highly accurate TTI moveout equations analogous with their VTI counterparts. Our analysis showed that the most accurate approximation is obtained from the mapping of generalized approximation. The new moveout approximations allow for, as the examples demonstrate, accurate description of moveout in the TTI case even for vertical heterogeneity. The proposed moveout approximations can be easily used for inversion in a layered TTI medium because the parameters of these approximations explicitly depend on corresponding effective parameters in a layered VTI medium.

  4. Measurement and modeling of flow through unsaturated heterogeneous rock in the context of geologic disposal of nuclear waste

    International Nuclear Information System (INIS)

    Sagar, B.; Bagtzoglou, A.C.; Green, R.T.; Stothoff, S.A.

    1995-01-01

    Deep geologic disposal of high-level and transuranic waste is currently being pursued vigorously. Assessing long-term performance of such repositories involves laboratory and field measurements, and numerical modeling. There exist two primary characteristics, associated with assessing repository performance, that define problems of modeling and measurement of non-isothermal flow through geologic media exposed to variable boundary conditions (e.g., climatic changes). These are: (1) the large time scale (tens of thousands of years) and highly variable space scale (from one meter to 10 5 meters); and (2) the hierarchy of heterogeneities and discontinuities characterizing the medium. This paper provides an overview of recent work, conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA), related to laboratory experiments, consideration of similitude, and numerical modeling of flow through heterogeneous media under non-homogeneous boundary conditions. As discussed, there exist neither good methods of measuring flows at these scales nor are there adequate similitude analyses that would allow reasonable scaling up of laboratory-scale experiments. Reliable assessment of long-term geologic repositories will require sophisticated geostatistical models capable of addressing variables scales of heterogeneities conditioned with observed results from adequately sized field-scale experiments conducted for sufficiently long durations

  5. O Problema de Roteamento de Estoques: um olhar sobre a literatura

    Directory of Open Access Journals (Sweden)

    Fernando Leme Franco

    2003-03-01

    Full Text Available A globalização e o aumento da competitividade nas empresas têm levado pesquisadores a desenvolver, dos pontos de vista teórico e prático, o problema de roteamento de estoques (PRE. Este artigo é uma revisão da produção do conhecimento na área do PRE. Aborda primeiramente os conceitos envolvidos do PRE assim como as diferenças entre o problema em questão e do roteamento de veículos (PRV. Os artigos pesquisados são olhados de acordo com o horizonte de planejamento e a modelagem da demanda, a partir da abordagem explicitada em cada um. Finaliza sugerindo caminhos futuros neste campo de pesquisa. Palavras- chave: Roteamento de Estoques, Roteamento de Veículos, Controle de Estoques, Logística, Revisão Bibliográfica.

  6. Calculation of breaking radiation dose fields in heterogenous media by a method of the transformation of axial distribution

    International Nuclear Information System (INIS)

    Mil'shtejn, R.S.

    1988-01-01

    Analysis of dose fields in a heterogeneous tissue equivalent medium has shown that dose distributions have radial symmetry and can be described by a curve of axial distribution with renormalization of maximum ionization depth. A method of the calculation of a dose field in a heterogeneous medium using the principle of radial symmetry is presented

  7. PEN, modelo de los Cinco Factores y problemas de conducta en la adolescencia

    Directory of Open Access Journals (Sweden)

    Víctor Abella

    2014-06-01

    Full Text Available En este estudio se ha investigado la implicación de la personalidad en los problemas de conducta durante la adolescencia. La muestra estaba compuesta por 264 adolescentes, 145 varones y 119 mujeres, entre 16 y 18 años de edad. Los adolescentes contestaron anónimamente a cuestionarios de personalidad y problemas de conducta. La aproximación centrada en personas permitió descubrir cuatro tipos de adolescentes, mediante análisis de conglomerados basados en seis puntuaciones sobre conductas disruptivas. Los problemas eran máximos en el tipo disruptivo, mientras que en el resiliente eran mucho más moderados. Las características de personalidad de los cuatro tipos presentan perfiles claramente diferenciables. La aproximación centrada en variables mostró, mediante análisis de regresión, que Neuroticismo y Psicoticismo en el modelo de Eysenck y Neuroticismo, Amabilidad y Responsabilidad en el modelo de los Cinco Factores, eran los principales predictores de las conductas disruptivas. Los resultados sugieren las características de personalidad han mostrado que pueden ser eficaces para entender y prevenir la aparición de conductas antisociales en los centros escolares.

  8. Contabilidad de Costos I. - Problemas sobre el Ciclo de la Contabilidad de Costo, a través del estado de costos de producción y ventas

    OpenAIRE

    Morillo Moreno, Marysela C.

    2008-01-01

    ÍNDICE Introducción Problemas sobre terminología básica Problemas básicos sobre el Ciclo de la Contabilidad de Costos Problemas sobre contabilización de las actividades relacionadas con los materiales Problemas sobre la contabilización de las actividades relacionadas con la mano de obra Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación Problemas sobre el Ciclo de la Contabilida...

  9. Problemas enfrentados por los extensionistas rurales argentinos en el ejercicio de su labor desde su propia perspectiva

    Directory of Open Access Journals (Sweden)

    Fernando Pablo Landini

    2013-01-01

    Full Text Available El presente artículo se propone identificar, describir y analizar los problemas que los extensionistas argentinos enfrentan en su práctica. Con este fin se aplicó una encuesta, la cual fue respondida por 219 extensionistas. Las respuestas fueron categorizadas con apoyo del software Atlas Ti a partir de la identificación de problemas que iban repitiéndose en distintas encuestas. Seguidamente, los resultados fueron cuantificados, considerándose presencia de la variable en una encuesta cuando la categoría que la expresaba había aparecido al menos una vez en ella. Mediante el uso del programa SPSS, también se estudió la asociación de los principales problemas identificados con diversas variables de interés. Se concluye que las dificultades más importantes enfrentadas por los extensionistas encuestados son (1 el individualismo, la desconfianza y la falta de asociaciones de productores, (2 los problemas para la comercialización y (3 la falta de apoyo público y de políticas de desarrollo rural.

  10. Uma revisão comentada das abordagens do problema quadrático de alocação

    Directory of Open Access Journals (Sweden)

    Loiola Eliane Maria

    2004-01-01

    Full Text Available O Problema Quadrático de Alocação, PQA, um dos mais difíceis da classe NP-hard, modela diversas aplicações em diferentes áreas como pesquisa operacional, computação paralela e análise estatística de dados discretos. Além disso, problemas conhecidos como o do caixeiro viajante, o da clique maximal, o de particionamento e o de isomorfismo de grafos podem ser formulados como um PQA. Na tentativa de identificar novas propriedades estruturais para este problema, diversas formulações aparecem na literatura. Reunimos tais formulações, destacando suas principais características para classificá-las segundo as técnicas matemáticas nelas adotadas. Finalizamos o artigo avaliando a extensão das contribuições dadas ao problema, quer na elaboração de algoritmos, quer no cálculo de limites inferiores ou na caracterização de classes de exemplares polinomiais ou não, oriundas das diferentes abordagens aqui estudadas.

  11. O problema do fisicalismo/cognitivismo na ergonomia e segurança do trabalho

    Directory of Open Access Journals (Sweden)

    Gilbert Cardoso Bouyer

    2014-12-01

    Full Text Available Este estudo investigou os problemas causados pelo fisicalismo/cognitivismo na ergonomia e segurança do trabalho. Fisicalismo é uma abordagem ontológica para a qual tudo é físico. O centro da discussão é que a metáfora "trabalhador como máquina" não é meramente uma crença isolada nas práticas ergonômicas no Brasil. Ela é a base da estrutura experiencial que envolve valores, interesses, objetivos, práticas e teorias. Isso é um sério problema porque o fisicalismo/cognitivismo tornou-se causa de acidentes de trabalho e doenças ocupacionais.

  12. Problemas de comportamento exteriorizado e as relações familiares: revisão de literatura Problemas de comportamiento exteriorizado y las relaciones familiares: revisión de literatura Externalized behavior problems and family relationships: a review of the literature

    Directory of Open Access Journals (Sweden)

    Adriane Corrêa Szelbracikowski

    2007-04-01

    Full Text Available Pesquisadores têm estudado as relações familiares de crianças com problemas de comportamento exteriorizado, sobretudo, por suas implicações no desenvolvimento humano, ao longo do curso de vida. Os fatores de risco que contribuem para o surgimento e manutenção desses problemas estão relacionados às características da criança, aos processos familiares e às influências dos pares, comunidades e escolas. Neste artigo, discutimos, brevemente, a influência das relações parentais e conjugais em famílias de crianças pré-escolares com problemas de comportamento exteriorizado. No primeiro caso, ênfase é dada às práticas parentais e ao nível de estresse parental; no que tange às relações conjugais, destaque é dado aos padrões de interação em famílias casadas e recasadas e suas possíveis implicações nas relações parentais. Por fim, tecemos algumas considerações a respeito do papel da cultura no desenvolvimento de problemas de comportamento exteriorizado e da necessidade de investigar este tipo de problema sob a perspectiva do desenvolvimento humano.Investigadores han estudiado las relaciones familiares de niños con problemas de comportamiento exteriorizado, sobretodo por sus implicaciones en el desarrollo humano, a lo largo del curso de vida. Los factores de riesgo que contribuyen para el surgimiento y manutención de esos problemas están relacionados a las características del niño, a los procesos familiares y a las influencias de los pares, comunidades y escuelas. En este artículo, discutimos, brevemente, la influencia de las relaciones parentales y conyugales en familias de niños preescolares con problemas de comportamiento exteriorizado. En el primer caso, el énfasis es dado a las prácticas parentales y al nivel de estrés parental; en lo que toca a las relaciones conyugales, es dado destaque a los modelos de interacción en familias casadas y re-casadas y sus posibles implicaciones en las relaciones

  13. Design of SIP transformation server for efficient media negotiation

    Science.gov (United States)

    Pack, Sangheon; Paik, Eun Kyoung; Choi, Yanghee

    2001-07-01

    Voice over IP (VoIP) is one of the advanced services supported by the next generation mobile communication. VoIP should support various media formats and terminals existing together. This heterogeneous environment may prevent diverse users from establishing VoIP sessions among them. To solve the problem an efficient media negotiation mechanism is required. In this paper, we propose the efficient media negotiation architecture using the transformation server and the Intelligent Location Server (ILS). The transformation server is an extended Session Initiation Protocol (SIP) proxy server. It can modify an unacceptable session INVITE message into an acceptable one using the ILS. The ILS is a directory server based on the Lightweight Directory Access Protocol (LDAP) that keeps userí*s location information and available media information. The proposed architecture can eliminate an unnecessary response and re-INVITE messages of the standard SIP architecture. It takes only 1.5 round trip times to negotiate two different media types while the standard media negotiation mechanism takes 2.5 round trip times. The extra processing time in message handling is negligible in comparison to the reduced round trip time. The experimental results show that the session setup time in the proposed architecture is less than the setup time in the standard SIP. These results verify that the proposed media negotiation mechanism is more efficient in solving diversity problems.

  14. Tema 10. Ondas electromagnéticas (Enunciados de los problemas)

    OpenAIRE

    Beléndez Vázquez, Augusto

    1999-01-01

    Enunciados de los problemas del Tema 10: "Ondas electromagnéticas" que se imparte en la asignatura "Fundamentos Físicos de la Ingeniería" de primer curso de la titulación de Ingeniero Técnico de Telecomunicación, especialidad Sonido e Imagen, de la Universidad de Alicante.

  15. MAPA CONCEPTUAL PARA EL APRENDIZAJE BASADO EN PROBLEMAS

    Directory of Open Access Journals (Sweden)

    YURI GORBANEFF

    2009-01-01

    Full Text Available Se presentan los resultados del experimento sobre el uso de mapas conceptuales en el contexto del aprendizaje basado en problemas (ABP. El experimento fue realizado en la Universidad Javeriana (Bogotá, Colombia en el pregrado de administración. Se encontró que el mapa conceptual mejora el aprendizaje pero no afecta la percepción de los alumnos del método de ABP. Se recomienda incluir mapas conceptuales en los ejercicios de ABP.

  16. Mapa Conceptual Para El Aprendizaje Basado En Problemas

    Directory of Open Access Journals (Sweden)

    Yuri Gorbaneff

    2009-01-01

    Full Text Available Se presentan los resultados del experimento sobre el uso de mapas conceptuales en el contexto del aprendizaje basado en problemas (ABP. El experimento fue realizado en la Universidad Javeriana (Bogotá, Colombia en el pregrado de administración. Se encontró que el mapa conceptual mejora el aprendizaje pero no afecta la percepción de los alumnos del método de ABP. Se recomienda incluir mapas conceptuales en los ejercicios de ABP.

  17. Osteoporosi e fratture femorali: attualitá sanitaria e scarsa percezione di un grave problema di sanitá pubblica

    Directory of Open Access Journals (Sweden)

    G. Guida

    2003-05-01

    Full Text Available

    Obiettivi: questo workshop viene proposto per
    approfondire in una sede prestigiosa e appropriata,
    che vede riuniti i maggiori esponenti e decisori della
    sanità pubblica italiana, la consapevolezza e la conoscenza delle fratture osteoporotiche quale problema
    di sanità pubblica di grande attualità nel nostro
    Paese, nel contesto del progressivo invecchiamento
    della popolazione italiana.

    Metodi: i due lavori che vengono presentati hanno condotto precise valutazioni epidemiologiche, a partire
    dalle considerazioni demografiche sull’aumento della
    vita media degli italiani, fino alla ricerca dei dati di prevalenza di patologie quali l’osteoporosi. I lavori qui presentati forniscono dati sull’incidenza delle fratture
    femorali negli anziani in Italia, dati sugli interventi chirurgici di riduzione di fratture femorali, dati relativi alla comorbosità ed alla riabilitazione dei pazienti con frattura femorale e si spingono fino alla stima dei costi
    diretti delle fratture femorali. Per meglio stimolare una
    vera consapevolezza dell’entità del fenomeno, abbiamo
    eseguito un confronto con una patologia percepita
    come “severa” e “ad alto impatto” sulla salute degli
    ultaquarantacinquenni: l’infarto miocardico acuto.

    Risultati: l’incidenza ed i costi dei ricoveri per fratture
    femorali negli anziani in Italia soni paragonabili
    all’Infarto Miocardico Acuto e le conseguenze in termini di qualità di vita (riabilitazione, problemi di deambulazione etc. sono tali da richiedere una maggiore
    attenzione in termini di programmazione di
    interventi di prevenzione.


    Conclusioni: le fratture femorali in italia sono un problema di sanità pubblica che è doveroso non sottovalutare e pertanto non interessano esclusivamente l

  18. La escuela media en la encrucijada de la ciudadanía: Un estado del conocimiento y de su investigación The secondary school in the crossroad of the citizenship: The state of knowledge and its investigation

    Directory of Open Access Journals (Sweden)

    M. Silvina Areste

    2006-12-01

    Full Text Available El artículo delinea un estado del conocimiento sobre la problemática de la formación ciudadana en el nivel medio, orientado hacia los estudios empíricos, nacionales e internacionales que la investigan, configurando un campo de problemas multidimensional. Con este propósito se revisan diversas perspectivas e investigaciones que también han contribuido a acotar el objeto de estudio de la tesis de maestría en curso, "La Educación Ciudadana en la escuela media: el punto de vista de los docentes y alumnos", que contrasta las significaciones de los actores educativos atribuidas a esta educación, en escuelas secundarias de la ciudad de Buenos Aires. Se concluye que en la educación ciudadana del nivel cohabitan significaciones y concepciones divergentes, contenidos escolares heterogéneos, dificultades en la enseñanza y aprendizaje de saberes políticos, y problemas propios de la escuela secundaria. Este escenario convoca a realizar investigaciones en el área, que posibiliten esclarecer problemas específicos del nivel.The article delineates one state of knowledge on the problematic of the citizen formation in the half level oriented towards empirical studies, national and international, that revealed a multidimensional field of problems. With this purpose it reviews diverse perspective and investigations that have also contributed to limit the object of study of the thesis of masters in course, "the Citizen Education in the secondary school: the point of view of educational and the students", that resist the meanings of the educative actors attributed to this education, in secondary schools of the city of Buenos Aires. It concludes that in the citizen education of this level divergent meaning and conceptions cohabit with heterogeneous scholastic contents, difficulties in education and learning of politics knowledge and own problems of the secondary school. This scene summons to make investigations in the area, that could possible clarify

  19. The impacts of pore-scale physical and chemical heterogeneities on the transport of radionuclide-carrying colloids

    Energy Technology Data Exchange (ETDEWEB)

    WU, Ning

    2018-04-24

    Independent of the methods of nuclear waste disposal, the degradation of packaging materials could lead to mobilization and transport of radionuclides into the geosphere. This process can be significantly accelerated due to the association of radionuclides with the backfill materials or mobile colloids in groundwater. The transport of these colloids is complicated by the inherent coupling of physical and chemical heterogeneities (e.g., pore space geometry, grain size, charge heterogeneity, and surface hydrophobicity) in natural porous media that can exist on the length scale of a few grains. In addition, natural colloids themselves are often heterogeneous in their surface properties (e.g., clay platelets possess opposite charges on the surface and along the rim). Both physical and chemical heterogeneities influence the transport and retention of radionuclides under various groundwater conditions. However, the precise mechanisms how these coupled heterogeneities influence colloidal transport are largely elusive. This knowledge gap is a major source of uncertainty in developing accurate models to represent the transport process and to predict distribution of radionuclides in the geosphere.

  20. El Método de los Elementos Finitos en problemas electromagnéticos: planteamiento y aplicaciones

    OpenAIRE

    Sarrate Ramos, Josep; Clarisó, Ramon

    2001-01-01

    En el presente trabajo se analizan y comparan diferentes alternativas para resolver mediante el Método de los Elementos Finitos (MEF) problemas electromagnéticos. Asimismo, se repasan diversos conceptos físicos a fin de justificar los posteriores desarrollos numéricos. Las formulaciones para la resolución de dichos problemas se clasifican en dos grandes grupos: 1. formulaciones basadas en potenciales escalares y/o vectoriales y 2. formulaciones basadas en la resolución de las ecua...

  1. La conducta de los públicos para legitimar el acoso escolar como problema social a través de la agenda de los medios

    Directory of Open Access Journals (Sweden)

    Maria Carmen Carretón Ballester

    2017-05-01

    Full Text Available Las noticias sobre acoso escolar en los medios de comunicación en España están despertando interés político, mediático y social en general. Este aumento de contenido en las agendas de los medios junto con el anuncio del Gobierno de elaborar una estrategia conjunta, ha suscitado nuestra hipótesis de que el acoso escolar es un problema social de interés público. No se conoce la estrategia y las acciones tomadas parecen no responder a un plan estratégico diseñado por los actores sociales y políticos. Analizar dos años de noticias, nos permite averiguar esta premisa para la campaña de prevención del acoso desde una estrategia proactiva de relaciones con los públicos. Behaviour of the general public in establishing school bullying as a social problem through the media. Abstract News about bullying in the media in Spain is raising political, media and social interest in general. This increase in media coverage, together with the declared intention of the Government of developing a joint strategy, has given rise to the hypothesis that bullying is a social problem of public interest. The strategy for this has not yet been defined and actions undertaken to date do not seem to respond to any strategic plan of social and political agents. By analysing two years of news, we have been able to examine this premise about the campaign to prevent bullying through a proactive public relations strategy. Keywords Bullying, proactive strategy, public interest, public relations, social problem.

  2. Meta-raps: Un enfoque de solución eficaz para problemas combinatorios

    Directory of Open Access Journals (Sweden)

    Reinaldo Moraga

    2003-07-01

    Full Text Available Este artículo introduce una metaheurística denominada Meta-RaPS (Meta-heuristic for Randomized Priority Search para problemas de optimización combinatoria. Meta-RaPS es un sistema de múltiples iteraciones que balancea el uso de heurísticas de construcción y mejoramiento de soluciones en cada iteración. Una de las características principales de Meta-RaPS es la dosificación del uso de aleatoriedad como mecanismo para mejorar heurísticas de construcción. En este artículo se presenta el enfoque y se entregan resultados de aplicaciones a cuatro problemas de optimización combinatoria. Este artículo es un extracto de la tesis doctoral titulada: “Meta-RaPS: An Effective Solution Approach for Combinatorial Problems” (Moraga, 2002. La tesis representa la culminación de una investigación desarrollada por las Universidades de Central Florida y Louisville en un esfuerzo por extender un enfoque heurístico clásico denominado COMSOAL a problemas combinatorios. (Nota: esta tesis doctoral es una de las tres tesis que recientemente obtuvieron el Premio “2003 Pritsker Doctoral Dissertation Award”, otorgado por el Institute of Industrial Engineering en la última Conferencia de Investigación en Ingeniería Industrial celebrada en Portland, Oregon, USA, Mayo 2003.

  3. PROBLEMAS DE PRIMERA Y SEGUNDA GENERACIÓN EN LA DEMOCRACIA REGIONAL EN MÉXICO

    Directory of Open Access Journals (Sweden)

    Alberto Aziz Nassif

    2003-01-01

    Full Text Available Durante muchos años se pensó que todo el autoritarismo mexicano estaba protegido por un sistema electoral que distorsionaba la voluntad ciudadana y la posibilidad de que hubiera alternancia en el poder. Después de que el sistema electoral generó la competencia y la alternancia en el poder, existió la tentación de pensar que la construcción democrática se llevaría a cabo de forma casi automática. Sin embargo, ahora se puede afirmar que la democracia mexicana tiene problemas importantes que van más lejos que los que rondaban el espacio de los votos y la representación. El trabajo plantea una hipótesis para reflexionar sobre lo que hemos llamado problemas de primera y segunda generación en la democracia mexicana. Los primeros responden a la interrogante: ¿cómo lograr elecciones competidas, asegurar la posibilidad de la alternancia y el pluralismo? Sus problemas son: reglas equitativas, transparencia, y posibilidad de alternancia. La segunda generación de problemas tiene como objetivo central investigar cómo se logran buenos gobiernos o por qué razones no se dan. Se trata de saber cuáles son los márgenes para desterrar los modos autoritarios de gobernar, los abusos de poder, las decisiones arbitrarias, el manejo patrimonial de los recursos públicos y la sistemática corrupción que ha impregnado el espacio público durante décadas. Se toman dos ejemplos regionales, Chihuahua y Jalisco.

  4. Distributing intelligence and organizing diversity in new media projects

    Directory of Open Access Journals (Sweden)

    Monique Girard

    2002-06-01

    Full Text Available This paper examines how web design firms in the new media industry probe and experiment with possible forms and sources of value giving shape to the new economy. Focusing on the collaborative engineering of cross-disciplinary web-design project teams, we examine how websites emerge as provisional settlements among the heterogeneous disciplines as they negotiate working compromises across competing performance criteria.

  5. La construcción discursiva de los problemas globales. El multiculturalismo: residuos, commodities y seudofusiones

    Directory of Open Access Journals (Sweden)

    Aníbal Ford

    2012-01-01

    Full Text Available Este artículo aborda el ingreso de los problemas globales en las agendas de los medios de comunicación y la publicidad contemporánea. Se asume que, si bien las agendas del sufrimiento, las desigualdades, la pobreza y las migraciones han estado presentes en la producción massmediática, su ingreso actual se torna de manera "discutible" porque estamos ante un proceso típico de la sociocultura contemporánea que traslada la información sobre problemas críticos hacia géneros que ingresan más en el ámbito del imaginario social que en el de la opinión pública. De ahí la generación, por ejemplo, en la publicidad, del impacto de marca que juega con la representación y la cultura de "los otros" o que utiliza los problemas globales señalados al principio como dispositivos de efecto, residuos, seudofusiones o bienes de consumo.

  6. Problemas de Crecimiento Pondo Estatural

    Directory of Open Access Journals (Sweden)

    Ernesto Plata Rueda

    1979-10-01

    Full Text Available

    Quizás sorprenda un poco que este capítulo no se denomine Desnutrición o Distrofia o Síndrome pluricarencial o Malnutrición proteico calórica o Kwashiorkor o Hambre como preferiría llamarla con no poco sarcasmo el pediatra colombiano Gustavo González Ochoá.

    Al denominarlo por los signos de somatometría (peso y talla queremos proseguir la línea general de este libro de tratar los problemas con base en el motivo de consulta y de este modo, solo por no emplear lenguaje familiar en los títulos de los capítulos, no hicimos como hubiéramos preferido llamarlo: "el niño flaco y pequeño" o algo por el estilo_ Quizás el empleo de terminología científica pero rebuscada o lo que es, como en el caso de Kwashiorkor, referida solo a un signo circunstancial (niño rojo, no frecuente entre nosotros y propio solo de estados muy avanzados de desnutrición, ha contribuído a que los' médicos dejen pasar inadvertidos por su consulta los casos mucho más frecuentes de subalimentación incipiente (desnutrición de primer grado que se manifiestan solo por detención de peso y que en términos de manejo oportuno de los problemas, son en extremo importantes pues como bien lo ha señalado Rafael Ramos Galván (Diagnóstico y Tratamiento de la Desnutrición a nivel individual 'Y colectivo. Impresiones Modernas. México (1.968 p. 39, "en desnutrición el tiempo perdido no se recupera" y las carencias cuando
    ocurren en los períodos de mayor crecimiento y se prolongan, si no matan, dejan una huella imborrable en el individuo, tanto en lo físico (nanismo nutricional como en lo psíquico (retardo psicomotor.

    Con la enumeración de términos hecha al principio no queremos embarcarnos en una discusión por demás bizantina sobre semántica, pero sí queremos señalar un hecho que contrista el ánimo cual es el del muy escaso reconocimiento que de la literatura médica latinoamericana se hace en los medios anglosajones. Durante todo lo que

  7. Classical radiation theory of charged particles moving in electromagnetic fields in nonabsorbable isotropic media

    International Nuclear Information System (INIS)

    Konstantinovich, A.V.; Melnychuk, S.V.; Konstantinovich, I.A.

    2002-01-01

    The integral expressions for spectral-angular and spectral distributions of the radiation power of heterogeneous charged particles system moving on arbitrary trajectory in nonabsorbable isotropic media media with ε≠1 , μ≠1 are obtained using the Lorentz's self-interaction method. In this method a proper electromagnetic field, acting on electron, is defined as a semi difference between retarded and advanced potentials (Dirac, 1938). The power spectrum of Cherenkov radiation for the linear uniformly moving heterogeneous system of charged particles are obtained. It is found that the expression for the radiation power of heterogeneous system of charged particles becomes simplified when a system of charged particles is homogeneous. In this case the radiation power includes the coherent factor. It is shown what the redistribution effects in energy of the radiation spectrum of the studied system are caused by the coherent factor. The radiation spectrum of the system of electrons moving in a circle in this medium is discrete. The Doppler effect causes the appearance of the new harmonics for the system of electrons moving in a spiral. These harmonics form the region of continuous radiation spectrum. (authors)

  8. Donar: ¿Un problema bioético?

    OpenAIRE

    Ángel Alonso Salas

    2017-01-01

    El filósofo australiano, Peter Singer escribió un texto que se titula Salvar una vida. Cómo terminar con la pobreza que hace referencia a los motivos que se tienen para que las personas efectúen donaciones y el deber que el ser humano tiene para ayudar a los más necesitados. En este sentido, el presente texto tiene como finalidad, preguntarse acerca del problema bioético que supone el que un sujeto o una institución otorguen algún tipo de donación, bajo el supuesto de ¿cuáles son los motivos ...

  9. Meta-Analysis of the Association of Alcohol-Related Social Media Use with Alcohol Consumption and Alcohol-Related Problems in Adolescents and Young Adults.

    Science.gov (United States)

    Curtis, Brenda L; Lookatch, Samantha J; Ramo, Danielle E; McKay, James R; Feinn, Richard S; Kranzler, Henry R

    2018-06-01

    Despite the pervasive use of social media by young adults, there is comparatively little known about whether, and how, engagement in social media influences this group's drinking patterns and risk of alcohol-related problems. We examined the relations between young adults' alcohol-related social media engagement (defined as the posting, liking, commenting, and viewing of alcohol-related social media content) and their drinking behavior and problems. We conducted a systematic review and meta-analysis of studies evaluating the association of alcohol consumption and alcohol-related problems with alcohol-related social media engagement. Summary baseline variables regarding the social media platform used (e.g., Facebook and Twitter), social media measures assessed (e.g., number of alcohol photographs posted), alcohol measures (e.g., Alcohol Use Disorders Identification Test and Timeline Follow back Interview), and the number of time points at which data were collected were extracted from each published study. We used the Q statistic to examine heterogeneity in the correlations between alcohol-related social media engagement and both drinking behavior and alcohol-related problems. Because there was significant heterogeneity, we used a random-effects model to evaluate the difference from zero of the weighted aggregate correlations. We used metaregression with study characteristics as moderators to test for moderators of the observed heterogeneity. Following screening, 19 articles met inclusion criteria for the meta-analysis. The primary findings indicated a statistically significant relationship and moderate effect sizes between alcohol-related social media engagement and both alcohol consumption (r = 0.36, 95% CI: 0.29 to 0.44, p social media engagement and drinking behavior or these were measured on different occasions and (ii) whether measurements were taken by self-report or observation of social media engagement. We found moderate-sized effects across the 19

  10. Problemas de la promulgación de una constitución británica

    OpenAIRE

    Bogdanor, Vernor; Vogenauer, Stefan

    2010-01-01

    De vez en cuando se apunta que sería mejor que Gran Bretaña contase con una constitución cuyos términos se encontrasen en un documento impreso, conocido y accesible a todos los ciudadanos. La finalidad de este artículo es considerar la cuestión de la factibilidad, o, mejor dicho, los problemas que hay que resolver si se decide promulgar una Constitución Británica. El primer problema fundamental consiste en determinar qué debería incluirse en dicha constitución, y, el segundo, d...

  11. Sobre el uso del problema de complementariedad lineal extendido para el control óptimo de semáforos

    Directory of Open Access Journals (Sweden)

    Lema Fernández, Carmen S.

    2007-01-01

    Full Text Available En el trabajo titulado “Modelo de optimización con restricciones de equilibrio para el control de semáforos” que presentamos en las XIV Jornadas de ASEPUMA (2006 analizábamos un problema de control óptimo de semáforos para un cruce de dos carreteras con los dos sentidos de circulación; allí interpretábamos las restricciones del problema como un problema de complementariedad lineal extendido (ELCP. También proponíamos un método híbrido de solución basado en una propiedad que demostraba que mediante un cambio de variable adecuado, las restricciones de ELCP describen un problema de complementariedad lineal (LCP. Nos interesa pues, estudiar bajo que condiciones dichos problemas tienen solución y además única. Así introducimos tres propiedades importantes para los ELCP y como caso particular para los LCP:• La propiedad de suficiencia en columnas que caracteriza la convexidad del conjunto solución.• La propiedad de suficiencia en filas que describe una clase importante de pares de matrices (respecto a K para las cuales la factibilidad del ELCP(M,N,K implica su solucionabilidad.• La P-propiedad (que para el caso del LCP(M,q significa que M ha de ser una P-matriz, que caracteriza la unicidad de solución.

  12. LA FORMACIÓN DE LA HABILIDAD PARA RESOLVER PROBLEMAS DE

    Directory of Open Access Journals (Sweden)

    Israel Mazario Triana

    2010-11-01

    Full Text Available El siguiente artículo muestra los resultados de una experiencia pedagógica sobre el desarrollo de habilidades en la resolución de problemas de matemáticas en estudiantes de primer año. La investigación se llevó cabo en el Departamento de Matemáticas de la Universidad de Matanzas, Cuba. Basado en el enfoque histórico cultural de L. S. Vygotsky, el trabajo presenta una nueva visión de la educación como desarrollo integral de la personalidad, que tiene lugar mediante la interacción social, la actividad conjunta y las relaciones entre profesor-estudiantes-conocimientos matemáticos, que se integran en la noción de enseñanza-aprendizaje que sustentamos. Con la investigación realizada durante varios cursos se ha logrado que los estudiantes desarrollen las acciones relacionadas con la resolución de problemas de matemáticas. En las conclusiones se enumeran los avances obtenidos hasta el momento.

  13. El Principio de Pareto en el control documental de programas informativos televisivos: implicaciones en el Media Asset Management

    Directory of Open Access Journals (Sweden)

    Jorge Caldera-Serrano

    2015-09-01

    Full Text Available Se analiza la reutilización de las colecciones audiovisuales de las cadenas de televisión con el fin de detectar si se cumple el Índice de Pareto, facilitando mecanismos para su control y explotación de la parte de la colección audiovisual menos utilizada. Se detecta que la correlación de Pareto se establece no sólo en el uso sino también en la presencia de elementos temáticos y elementos onomásticos en el archivo y en la difusión de contenidos, por lo que se plantea formas de control en la integración de información en la colección y de recursos en la difusión. Igualmente se describe el Índice de Pareto, los Media Asset Management y el cambio de paradigma al digital, elementos fundamentales para entender los problemas y las soluciones para la eliminación de problemas en la recuperación y en la conformación de la colección. Abstract: Reuse of audiovisual collections television networks in order to detect whether the Pareto index, providing mechanisms for control and exploitation of the least used part of the audiovisual collection holds analyzed. It is found that the correlation of Pareto is established not only in the use but also the presence of thematic elements and onomastic elements in the file and in the distribution of content, so forms of control arises in the integration of information collection and distributing resources. Likewise, the Pareto index, the Media Asset Management and the paradigm shift to digital, essential to understanding the problems and solutions to eliminate problems in recovery and in the establishment of collection elements described. Keywords:  Information processing. Television. Electronic media. Information systems evaluation.

  14. La medición de la capacidad de resolución de problemas en las ciencias experimentales

    Directory of Open Access Journals (Sweden)

    José Joaquín García García

    2012-01-01

    Full Text Available Este trabajo presenta un estudio, sobre el diseño de una prueba para medir la capacidad de resolución de problemas utilizando la técnica de análisis factorial. La prueba presentó un alfa de Cronbach (α de 0,76 y 16 peguntas distribuidas en 7 factores ordenados de acuerdo al porcentaje en el cual explicaban la varianza de la capacidad: predicción y transferencia, capacidad de síntesis, lectura crítica del enunciado, análisis, interpretación de información, comprensión metacognitiva de enunciados y procesos, delimitación del problema. Así, la resolución de problemas es una capacidad que está más relacionada con factores de carácter estructural y global, como la selección de soluciones e hipótesis más adecuadas y la representación misma del problema, y en menor medida con aspectos estratégicos de delimitación, precisión y planeación, tal vez por la usual ausencia de dichos aspectos en las aulas de clase.

  15. LA CUESTIÓN AGRARIA COMO ENFOQUE Y COMO PROBLEMA

    Directory of Open Access Journals (Sweden)

    Carlos Salgado

    2000-01-01

    Full Text Available Este ensayo trata de llamar la atención sobre los problemas del agro hoy, colocando especial énfasis en la disrupción entre las razones tecnológicas -que se asumen como ideológicas-, económicas y políticas que han inspirado el desarrollo del agro, o mejor, sobre las cuales se han basado las políticas de crecimiento agropecuario.

  16. Modelo matemático para resolver el problema de localización y ruteo con restricciones de capacidad considerando flota propia y subcontratada

    OpenAIRE

    Toro-Ocampo, Eliana Mirledy; Franco-Baquero, John Fredy; Gallego-Rendón, Ramón Alfonso

    2016-01-01

    Resumen: El problema de localización y ruteo con restricciones de capacidad (CLRP) consiste en la selección de depósitos y rutas para atender un conjunto de clientes para obtener el mínimo costo. Una variante de este problema, en la que se considera existe la posibilidad de subcontratar la operación de algunas (o todas) las rutas, es el problema de localización y ruteo con flota propia y flota subcontratada (CLRPPC). Este problema aparece cuando la flota propia es insuficiente para atender la...

  17. Los Supuestos Metafísicos del Problema de la Experiencia Consciente en la Filosofía de David Chalmers

    OpenAIRE

    Fontcuberta Llavata, Alejandro

    2016-01-01

    El problema difícil de la experiencia consciente se resume en la cuestión de cómo es posible que el cerebro sea la base de la experiencia consciente. El objetivo general de la tesis es llevar a cabo una crítica general de los supuestos metafísicos que subyacen a la formulación del problema difícil de la experiencia consciente, centrándose en el análisis que se lleva a cabo del problema en la obra de David Chalmers. Los argumentos presentados tratan de establecer tres clases de resultados que ...

  18. Estrategias de solución de problemas aplicadas por ajedrecistas de diferente nivel

    Directory of Open Access Journals (Sweden)

    Luis Lázaro Agüero Jiménez

    2017-01-01

    Full Text Available En el presente trabajo se estudiaron las diferen - tes estrategias de solución de problemas aplicadas por ajedrecistas de distinto nivel, y así desarrollar programas más integradores que permitan perfec - cionar el entrenamiento de ajedrecistas de todas las edades. Por esto, lo estudiado en la presente investigación sirve como guía para la captación de jóvenes talentos que deseen integrar las escuelas deportivas que posee el país; y desde el punto de vista psicológico, lo más relevante es la manera en que los ajedrecistas dan soluciones a problemas que se les presentan en la vida cotidiana a partir del aprendizaje que reciben en el juego de ajedrez. Se tuvo como objetivo identificar las estrategias de so - lución de problemas en ajedrecistas de diferentes niveles, del cual se derivan los objetivos específicos de: determinar las estrategias que utilizan los aje - drecistas de la muestra en tareas de pensamiento lógico, definir las estrategias que utilizan los ajedre - cistas de la muestra en la solución de partidas de ajedrez y el determinar si los ajedrecistas con mayor experiencia practicando este deporte utilizan estra - tegias de solución de problemas más eficaces; de estos objetivos específicos se extrajeron las variables: resolución de problemas, pensamiento, pensamiento lógico, estrategia, y eficacia, las cuales fueron medidas con el test de ajedrez propuesto por Przewoznik y Soszynski (2004 y por el test de pensamiento lógico de Tobin y Capie (1981 La muestra estuvo conformada por siete sujetos y los resultados de ambos test fueron procesadas con el programa Microsoft Excel. Se logró constatar en los resultados que en el test de ajedrez también se aplican los cinco esquemas propuestos en el test de pensamiento lógico (proporcionalidad, control de variables, probabilidad, correlación y operaciones combinatorias, y aquellos jugadores de más experiencia fueron más eficaces en la solución de las posiciones de

  19. Earthquake ground-motion in presence of source and medium heterogeneities

    KAUST Repository

    Vyas, Jagdish Chandra

    2017-01-01

    This dissertation work investigates the effects of earthquake rupture complexity and heterogeneities in Earth structure on near-field ground-motions. More specifically, we address two key issues in seismology: (1) near-field ground-shaking variability as function of distance and azimuth for unilateral directive ruptures, and (2) impact of rupture complexity and seismic scattering on Mach wave coherence associated with supershear rupture propagation. We examine earthquake ground-motion variability associated with unilateral ruptures based on ground-motion simulations of the MW 7.3 1992 Landers earthquake, eight simplified source models, and a MW 7.8 rupture simulation (ShakeOut) for the San Andreas fault. Our numerical modeling reveals that the ground-shaking variability in near-fault distances (< 20 km) is larger than that given by empirical ground motion prediction equations. In addition, the variability decreases with increasing distance from the source, exhibiting a power-law decay. The high near-field variability can be explained by strong directivity effects whose influence weaken as we move away from the fault. At the same time, the slope of the power-law decay is found to be dominantly controlled by slip heterogeneity. Furthermore, the ground-shaking variability is high in the rupture propagation direction whereas low in the directions perpendicular to it. However, the variability expressed as a function of azimuth is not only sensitive to slip heterogeneity, but also to rupture velocity. To study Mach wave coherence for supershear ruptures, we consider heterogeneities in rupture parameters (variations in slip, rise time and rupture speed) and 3D scattering media having small-scale random heterogeneities. The Mach wave coherence is reduced at near-fault distances (< 10 km) by the source heterogeneities. At the larger distances from the source, medium scattering plays the dominant role in reducing the Mach wave coherence. Combined effect of the source and

  20. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

    Science.gov (United States)

    Yang, Hui; Tang, Ming; Gross, Thilo

    2015-08-01

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

  1. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

    Science.gov (United States)

    Yang, Hui; Tang, Ming; Gross, Thilo

    2015-08-21

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

  2. Discretization-dependent model for weakly connected excitable media

    Science.gov (United States)

    Arroyo, Pedro André; Alonso, Sergio; Weber dos Santos, Rodrigo

    2018-03-01

    Pattern formation has been widely observed in extended chemical and biological processes. Although the biochemical systems are highly heterogeneous, homogenized continuum approaches formed by partial differential equations have been employed frequently. Such approaches are usually justified by the difference of scales between the heterogeneities and the characteristic spatial size of the patterns. Under different conditions, for example, under weak coupling, discrete models are more adequate. However, discrete models may be less manageable, for instance, in terms of numerical implementation and mesh generation, than the associated continuum models. Here we study a model to approach discreteness which permits the computer implementation on general unstructured meshes. The model is cast as a partial differential equation but with a parameter that depends not only on heterogeneities sizes, as in the case of quasicontinuum models, but also on the discretization mesh. Therefore, we refer to it as a discretization-dependent model. We validate the approach in a generic excitable media that simulates three different phenomena: the propagation of action membrane potential in cardiac tissue, in myelinated axons of neurons, and concentration waves in chemical microemulsions.

  3. Contribution to solving the problem of neutron thermalization in heterogeneous reactor; Prilog resavanju problema termalizacije neutron u heterognom reaktoru

    Energy Technology Data Exchange (ETDEWEB)

    Pop-Jordanov, J P [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1963-12-15

    A method for calculating of neutron termalization in heterogeneous rector core was developed. It is more precise than the diffusion method but more complcated. Concerning accuracy it is comparable to non-diffusion methods. Sonce the approach was analytical need for powerful computer is avoided and the description of physical phenomena is more transparent. Convergence is satsfactory. Constraints of the proposed method are: low neutron absorption in the moderator, negligible slowing down in the fuel, and big lattice pitch. The method is applicable for heavy water and graphite moderator systems. Based on the application of this method, procedures were developed for calculating thermal utilzation and neutron temperature. Since 1/v dependence of cross sections is not estimated this metof could be used for long-term reactivity changes.

  4. Seismic wave propagation in heterogeneous multiphasic media: numerical modelling, sensibility and inversion of poro-elastic parameters

    International Nuclear Information System (INIS)

    Dupuy, B.

    2011-11-01

    Seismic wave propagation in multiphasic porous media have various environmental (natural risks, geotechnics, groundwater pollutions...) and resources (aquifers, oil and gas, CO 2 storage...) issues. When seismic waves are crossing a given material, they are distorted and thus contain information on fluid and solid phases. This work focuses on the characteristics of seismic waves propagating in multiphasic media, from the physical complex description to the parameter characterisation by inversion, including 2D numerical modelling of the wave propagation. The first part consists in the description of the physics of multiphasic media (each phase and their interactions), using several up-scaling methods, in order to obtain an equivalent mesoscale medium defined by seven parameters. Thus, in simple porosity saturated media and in complex media (double porosity, patchy saturation, visco-poro-elasticity), I can compute seismic wave propagation without any approximation. Indeed, I use a frequency-space domain for the numerical method, which allows to consider all the frequency dependent terms. The spatial discretization employs a discontinuous finite elements method (discontinuous Galerkin), which allows to take into account complex interfaces.The computation of the seismic attributes (velocities and attenuations) of complex porous media shows strong variations in respect with the frequency. Waveforms, computed without approximation, are strongly different if we take into account the full description of the medium or an homogenisation by averages. The last part of this work deals with the poro-elastic parameters characterisation by inversion. For this, I develop a two-steps method: the first one consists in a classical inversion (tomography, full waveform inversion) of seismograms data to obtain macro-scale parameters (seismic attributes). The second step allows to recover, from the macro-scale parameters, the poro-elastic micro-scale properties. This down-scaling step

  5. A notação escrita na resolução de problemas por crianças pré-escolares

    Directory of Open Access Journals (Sweden)

    Selva Ana Coêlho Vieira

    2000-01-01

    Full Text Available O estudo investigou como crianças de 4 a 6 anos resolvem problemas de subtração usando a notação escrita. Trinta crianças nas séries de Alfabetização, Jardim II e Jardim I foram solicitadas a resolverem quatro problemas (dois do tipo mudança e dois de comparação, envolvendo pares numéricos maiores e menores que dez. Os problemas foram inseridos em uma situação que buscou dar maior significado para o uso do registro no papel. Os protocolos das entrevistas com as crianças foram analisados a partir de dois eixos: a influência do registro no papel para o processo de resolução dos problemas e os tipos de registros produzidos. Observamos que o registro escrito foi utilizado para apoiar os cálculos realizados, possibilitar o acompanhamento do processo de raciocínio e favorecer o avanço no registro das operações matemáticas. Concluímos que resolver problemas no papel pode se constituir em uma alternativa interessante para a educação infantil.

  6. A notação escrita na resolução de problemas por crianças pré-escolares

    Directory of Open Access Journals (Sweden)

    Ana Coêlho Vieira Selva

    Full Text Available O estudo investigou como crianças de 4 a 6 anos resolvem problemas de subtração usando a notação escrita. Trinta crianças nas séries de Alfabetização, Jardim II e Jardim I foram solicitadas a resolverem quatro problemas (dois do tipo mudança e dois de comparação, envolvendo pares numéricos maiores e menores que dez. Os problemas foram inseridos em uma situação que buscou dar maior significado para o uso do registro no papel. Os protocolos das entrevistas com as crianças foram analisados a partir de dois eixos: a influência do registro no papel para o processo de resolução dos problemas e os tipos de registros produzidos. Observamos que o registro escrito foi utilizado para apoiar os cálculos realizados, possibilitar o acompanhamento do processo de raciocínio e favorecer o avanço no registro das operações matemáticas. Concluímos que resolver problemas no papel pode se constituir em uma alternativa interessante para a educação infantil.

  7. Problemas de saúde mental e tabagismo em adolescentes do sul do Brasil Problemas de salud mental y tabaquismo en adolescentes del sur de Brasil Mental health problems and smoking among adolescents from Southern Brazil

    Directory of Open Access Journals (Sweden)

    Ana M B Menezes

    2011-08-01

    Full Text Available OBJETIVO: Analisar a associação entre problemas de saúde mental e uso de tabaco em adolescentes. MÉTODOS: Foram analisados 4.325 adolescentes de 15 anos da coorte de nascimentos de 1993 da cidade de Pelotas, RS. Tabagismo foi definido como fumar um ou mais cigarros nos últimos 30 dias. Saúde mental foi avaliada de acordo com o escore total do questionário Strengths and Difficulties Questionnaire e escore maior ou igual a 20 pontos foi considerado como positivo. Os dados foram analisados por regressão de Poisson, com ajuste robusto para variância. RESULTADOS: A prevalência de tabagismo foi 6,0% e cerca de 30% dos adolescentes apresentaram algum tipo de problema de saúde mental. Na análise bruta, a razão de prevalências para tabagismo foi de 3,3 (IC95% 2,5; 4,2. Após ajuste (para sexo, idade, cor da pele, renda familiar, escolaridade da mãe, grupo de amigos fumantes, trabalho no último ano, repetência escolar, atividade física de lazer e uso experimental de bebida alcoólica, diminuiu para 1,7 (IC95% 1,2; 2,3 entre aqueles com problemas de saúde mental. CONCLUSÕES: Problemas de saúde mental na adolescência podem ter relação com o consumo de tabaco.OBJETIVO: Analizar la asociación entre problemas de salud mental y uso de cigarro en adolescentes. MÉTODOS: Se analizaron 4.325 adolescentes de 15 años de la cohorte de nacimientos de 1993 de la ciudad de Pelotas, Sur de Brasil. Tabaquismo fue definido como fumar uno o más cigarros en los últimos 30 días. Salud mental fue evaluada de acuerdo con el escore total del cuestionario Strengths and Difficulties Questionnaire y escore mayor o igual a 20 puntos fue considerado como positivo. Los datos fueron analizados por regresión de Poisson, con ajuste robusto para varianza. RESULTADOS: La prevalencia de tabaquismo fue 6,0% y cerca de 30% de los adolescentes presentaron algún tipo de problema de salud mental. En el análisis bruto, la tasa de prevalencias de problema de

  8. Un nuevo enfoque para la resolución de problemas: redes neuronales

    Directory of Open Access Journals (Sweden)

    Jonatán Gómez Perdomo

    2015-05-01

    Full Text Available RESUMEN El siguiente artículo  expone los lineamientos generales de un nuevo enfoque para la resolución de problemas mediante computador. Inspiradas en las redes neuronales biológicas, las redes neuronales artifíciales han  mostrado mayor efectividad para resolver problemas que los enfoques tradicionales no han  solucionado o lo han hecho de manera parcial. En la actualidad este enfoque ha ganado un gran auge, lo cual ha generado en el país grupos de investigación que están trabajando sobre sí mismo. Como parte de su trabajo  en el grupo de la Universidad Nacional, los autores desarrollan una herramienta para el diseño, entrenamiento y simulación de redes neuronales artificiales. Las características generales de esta herramienta  se exponen al final.

  9. The Parabolic Variational Inequalities for Variably Saturated Water Flow in Heterogeneous Fracture Networks

    Directory of Open Access Journals (Sweden)

    Zuyang Ye

    2018-01-01

    Full Text Available Fractures are ubiquitous in geological formations and have a substantial influence on water seepage flow in unsaturated fractured rocks. While the matrix permeability is small enough to be ignored during the partially saturated flow process, water seepage in heterogeneous fracture systems may occur in a non-volume-average manner as distinguished from a macroscale continuum model. This paper presents a systematic numerical method which aims to provide a better understanding of the effect of fracture distribution on the water seepage behavior in such media. Based on the partial differential equation (PDE formulations with a Signorini-type complementary condition on the variably saturated water flow in heterogeneous fracture networks, the equivalent parabolic variational inequality (PVI formulations are proposed and the related numerical algorithm in the context of the finite element scheme is established. With the application to the continuum porous media, the results of the numerical simulation for one-dimensional infiltration fracture are compared to the analytical solutions and good agreements are obtained. From the application to intricate fracture systems, it is found that water seepage flow can move rapidly along preferential pathways in a nonuniform fashion and the variably saturated seepage behavior is intimately related to the geometrical characteristics orientation of fractures.

  10. La observación del problema ambiental en un contexto de diferenciación funcional

    Directory of Open Access Journals (Sweden)

    Anahí Urquiza

    2015-01-01

    Full Text Available El presente trabajo es fruto de una investigación social cualitativa realizada el año 2014 en el marco del Núcleo Interdisciplinario de Estudios Socioambientales de la Universidad de Chile (NIES y con el apo yo del Centro de Ciencia del Clima y Resiliencia (CR2. La investigación se centra en el problema ambiental desde tres ámbitos sociales: público, privado y conocimiento experto. El estudio identificó la existencia de tres tipos de obstáculos que dificultar ían el diálogo entre los actores que son parte de la discusión, así como el tratamiento del problema socioambiental, estos son: obstáculos a nivel de institucionalidad y normativa vigente; obstáculos a nivel del actuar y de las relaciones entre los actores ; y obstáculos que se presentan a nivel de los significados asignados al problema. En el presente artículo se abordan los últimos dos tipos de obstáculos desde una perspectiva sistémico constructivista.

  11. Diffusion, Coulombic interactions and multicomponent ionic transport of charged species in saturated porous media

    DEFF Research Database (Denmark)

    Rolle, Massimo; Muniruzzaman, Muhammad

    water are cross-coupled due to the effects of Coulombic interactions. Such effects are illustrated in flow-through experiments in saturated porous media. Simple strong electrolytes (i.e., salts and strong acid solutions) were selected as tracers and their transport was studied under different advection......-dominated conditions in homogeneous and heterogeneous porous media [2-3]. The model-based interpretation of the experimental results is challenging since it requires a multicomponent ionic formulation with an accurate description of local hydrodynamic dispersion and explicitly accounting for the cross-coupling...

  12. Effect of reservoir heterogeneity on air injection performance in a light oil reservoir

    Directory of Open Access Journals (Sweden)

    Hu Jia

    2018-03-01

    Full Text Available Air injection is a good option to development light oil reservoir. As well-known that, reservoir heterogeneity has great effect for various EOR processes. This also applies to air injection. However, oil recovery mechanisms and physical processes for air injection in heterogeneous reservoir with dip angle are still not well understood. The reported setting of reservoir heterogeneous for physical model or simulation model of air injection only simply uses different-layer permeability of porous media. In practice, reservoir heterogeneity follows the principle of geostatistics. How much of contrast in permeability actually challenges the air injection in light oil reservoir? This should be investigated by using layered porous medial settings of the classical Dykstra-Parsons style. Unfortunately, there has been no work addressing this issue for air injection in light oil reservoir. In this paper, Reservoir heterogeneity is quantified based on the use of different reservoir permeability distribution according to classical Dykstra-Parsons coefficients method. The aim of this work is to investigate the effect of reservoir heterogeneity on physical process and production performance of air injection in light oil reservoir through numerical reservoir simulation approach. The basic model is calibrated based on previous study. Total eleven pseudo compounders are included in this model and ten complexity of reactions are proposed to achieve the reaction scheme. Results show that oil recovery factor is decreased with the increasing of reservoir heterogeneity both for air and N2 injection from updip location, which is against the working behavior of air injection from updip location. Reservoir heterogeneity sometimes can act as positive effect to improve sweep efficiency as well as enhance production performance for air injection. High O2 content air injection can benefit oil recovery factor, also lead to early O2 breakthrough in heterogeneous reservoir. Well

  13. Generic, network schema agnostic sparse tensor factorization for single-pass clustering of heterogeneous information networks.

    Science.gov (United States)

    Wu, Jibing; Meng, Qinggang; Deng, Su; Huang, Hongbin; Wu, Yahui; Badii, Atta

    2017-01-01

    Heterogeneous information networks (e.g. bibliographic networks and social media networks) that consist of multiple interconnected objects are ubiquitous. Clustering analysis is an effective method to understand the semantic information and interpretable structure of the heterogeneous information networks, and it has attracted the attention of many researchers in recent years. However, most studies assume that heterogeneous information networks usually follow some simple schemas, such as bi-typed networks or star network schema, and they can only cluster one type of object in the network each time. In this paper, a novel clustering framework is proposed based on sparse tensor factorization for heterogeneous information networks, which can cluster multiple types of objects simultaneously in a single pass without any network schema information. The types of objects and the relations between them in the heterogeneous information networks are modeled as a sparse tensor. The clustering issue is modeled as an optimization problem, which is similar to the well-known Tucker decomposition. Then, an Alternating Least Squares (ALS) algorithm and a feasible initialization method are proposed to solve the optimization problem. Based on the tensor factorization, we simultaneously partition different types of objects into different clusters. The experimental results on both synthetic and real-world datasets have demonstrated that our proposed clustering framework, STFClus, can model heterogeneous information networks efficiently and can outperform state-of-the-art clustering algorithms as a generally applicable single-pass clustering method for heterogeneous network which is network schema agnostic.

  14. Sobre el uso de las desigualdades variacionales para el cálculo del problema de complementariedad no lineal.

    Directory of Open Access Journals (Sweden)

    Pedreira Andrade, Luis P.

    2003-01-01

    Full Text Available El nacimiento de los problemas de complementariedad no lineal (NCP y de los problemas de desigualdades variacionales (VIP fuertemente ligados a la programación matemática ha dado lugar a numerosos esfuerzos investigadores orientados a resolverlos. En los últimos años ha resultado de vital importancia para la resolución de los VIP el uso de funciones D-gap para reformular el problema como uno de optimización diferenciable sin restricciones. Este artículo pretende ser una presentación de la aplicabilidad de la función D-gap a los NCP con algoritmos recogidos de la literatura, así como un punto de partida para investigaciones que reduzcan las hipótesis para este caso particular.

  15. Laboratory-scale in situ bioremediation in heterogeneous porous media: biokinetics-limited scenario.

    Science.gov (United States)

    Song, Xin; Hong, Eunyoung; Seagren, Eric A

    2014-03-01

    Subsurface heterogeneities influence interfacial mass-transfer processes and affect the application of in situ bioremediation by impacting the availability of substrates to the microorganisms. However, for difficult-to-degrade compounds, and/or cases with inhibitory biodegradation conditions, slow biokinetics may also limit the overall bioremediation rate, or be as limiting as mass-transfer processes. In this work, a quantitative framework based on a set of dimensionless coefficients was used to capture the effects of the competing interfacial and biokinetic processes and define the overall rate-limiting process. An integrated numerical modeling and experimental approach was used to evaluate application of the quantitative framework for a scenario in which slow-biokinetics limited the overall bioremediation rate of a polycyclic aromatic hydrocarbon (naphthalene). Numerical modeling was conducted to simulate the groundwater flow and naphthalene transport and verify the system parameters, which were used in the quantitative framework application. The experiments examined the movement and biodegradation of naphthalene in a saturated, heterogeneous intermediate-scale flow cell with two layers of contrasting hydraulic conductivities. These experiments were conducted in two phases: Phase I, simulating an inhibited slow biodegradation; and Phase II, simulating an engineered bioremediation, with system perturbations selected to enhance the slow biodegradation rate. In Phase II, two engineered perturbations to the system were selected to examine their ability to enhance in situ biodegradation. In the first perturbation, nitrogen and phosphorus in excess of the required stoichiometric amounts were spiked into the influent solution to mimic a common remedial action taken in the field. The results showed that this perturbation had a moderate positive impact, consistent with slow biokinetics being the overall rate-limiting process. However, the second perturbation, which was to

  16. Hydraulic Parameter Generation Technique Using a Discrete Fracture Network with Bedrock Heterogeneity in Korea

    Directory of Open Access Journals (Sweden)

    Jae-Yeol Cheong

    2017-12-01

    Full Text Available In instances of damage to engineered barriers containing nuclear waste material, surrounding bedrock is a natural barrier that retards radionuclide movement by way of adsorption and delay due to groundwater flow through highly tortuous fractured rock pathways. At the Gyeongju nuclear waste disposal site, groundwater mainly flows through granitic and sedimentary rock fractures. Therefore, to understand the nuclide migration path, it is necessary to understand discrete fracture networks based on heterogeneous fracture orientations, densities, and size characteristics. In this study, detailed heterogeneous fracture distribution, including the density and orientation of the fractures, was considered for a region that has undergone long periods of change from various geological activities at and around the Gyeongju site. A site-scale discrete fracture network (DFN model was constructed taking into account: (i regional fracture heterogeneity constrained by a multiple linear regression analysis of fracture intensity on faults and electrical resistivity; and (ii the connectivity of conductive fractures having fracture hydraulic parameters, using transient flow simulation. Geometric and hydraulic heterogeneity of the DFN was upscaled into equivalent porous media for flow and transport simulation for a large-scale model.

  17. VIOLÊNCIA CONTRA A MULHER POR PARCEIRO ÍNTIMO: (IN VISIBILIDADE DO PROBLEMA

    Directory of Open Access Journals (Sweden)

    Daniele Ferreira Acosta

    2015-01-01

    Full Text Available El objetivo del estudio fue identificar las razones que llevan a la violencia contra la mujer y describir los actos perpetrados por su pareja. Investigación documental, cualitativa realizada en el Servicio de Policía Especializada en Atención a Mujeres. Se analizaron 902 informes registrados entre Agosto/2009 y Diciembre/2011, cuyas víctimas tenían al menos dieciocho años. Se recolectaron los datos de las ocurrencias, describiendo literalmente, las historias de las víctimas y su tratamiento fue a través del análisis de contenido. Fue identificados como factores desencadenantes de la violencia: la supremacía masculina como generadora de sufrimiento y sumisión, los problemas derivados del uso de drogas, los problemas relacionados con los niños y la división de los bienes. La gravedad fue escalada por las consecuencias a la víctima y su familia. El personal de enfermería como parte de la red de apoyo, debe entender este fenómeno como un problema de salud y esforzarse por romper las barreras que impidan el servicio eficaz y eficiente, auxiliando en el fortalecimiento de la autonomía de las mujeres, incluyendo a los hombres en acciones de combate y prevención de la violencia contra las mujeres.

  18. Numerical modeling of macrodispersion in heterogeneous media: a comparison of multi-Gaussian and non-multi-Gaussian models

    Science.gov (United States)

    Wen, Xian-Huan; Gómez-Hernández, J. Jaime

    1998-03-01

    The macrodispersion of an inert solute in a 2-D heterogeneous porous media is estimated numerically in a series of fields of varying heterogeneity. Four different random function (RF) models are used to model log-transmissivity (ln T) spatial variability, and for each of these models, ln T variance is varied from 0.1 to 2.0. The four RF models share the same univariate Gaussian histogram and the same isotropic covariance, but differ from one another in terms of the spatial connectivity patterns at extreme transmissivity values. More specifically, model A is a multivariate Gaussian model for which, by definition, extreme values (both high and low) are spatially uncorrelated. The other three models are non-multi-Gaussian: model B with high connectivity of high extreme values, model C with high connectivity of low extreme values, and model D with high connectivities of both high and low extreme values. Residence time distributions (RTDs) and macrodispersivities (longitudinal and transverse) are computed on ln T fields corresponding to the different RF models, for two different flow directions and at several scales. They are compared with each other, as well as with predicted values based on first-order analytical results. Numerically derived RTDs and macrodispersivities for the multi-Gaussian model are in good agreement with analytically derived values using first-order theories for log-transmissivity variance up to 2.0. The results from the non-multi-Gaussian models differ from each other and deviate largely from the multi-Gaussian results even when ln T variance is small. RTDs in non-multi-Gaussian realizations with high connectivity at high extreme values display earlier breakthrough than in multi-Gaussian realizations, whereas later breakthrough and longer tails are observed for RTDs from non-multi-Gaussian realizations with high connectivity at low extreme values. Longitudinal macrodispersivities in the non-multi-Gaussian realizations are, in general, larger than

  19. Filosofía y ciencia: el problema de las otras mentes y las neuronas espejo

    OpenAIRE

    Raúl Robles Chamorro

    2014-01-01

    Resumen El propósito del siguiente artículo es mostrar cómo el descubrimiento de las neuronas espejo ayudó a resolver uno de los tantos y eternos problemas de la filosofía: el problema de las otras mentes, y cómo este hecho particular es solo el síntoma de una enfermedad que acosa a la filosofía desde hace bastante tiempo: el haber llegado a su limite y sin embargo no acudir a las herramientas que la ciencia le puede proporcionar para superar su actual estancamiento y así volver a ser una ...

  20. A perfectly matched layer for the time-dependent wave equation in heterogeneous and layered media

    KAUST Repository

    Duru, Kenneth

    2014-01-01

    , and derive energy estimates for discontinuous media with piecewise smooth coefficients. We consider a computational setup consisting of smaller structured subdomains that are discretized using high order accurate finite difference operators for approximating

  1. Aplicação de sistemas híbridos em problemas de otimização

    OpenAIRE

    Antonio Rogerio Machado Ramos

    1996-01-01

    Este trabalho discorre sobre o emprego de sistemas híbridos voltados resolução de problemas de otimizando. Como problemas de otimizando entende-se como sendo o emprego de técnicas que visam aumentar a produtividade de alguma tarefa, otimizando seus procedimentos. Desta forma, utiliza-se neste trabalho o paradigma de Algoritmos Genéticos sobre um modelo de Redes Neurais para otimizar seu funcionamento, tornando-o mais rapido e de tamanho menor na tarefa de reconhecimento de padrões. O modelo d...

  2. Problemas asociados al equilibrio en estructuras de membrana con bordes rígidos

    Directory of Open Access Journals (Sweden)

    Martínez, F.

    2009-12-01

    Full Text Available This paper presents the equilibrium analysis of a membrane with rigid boundary. The idea of using membranes in applications such as footbridges, a new technology being developed in Spain, implies a more accurate analysis procedure. Due to the tension stresses, membrane is identifi ed to a negative gaussian curvature surface. Equilibrium is directly expressed by means of partial differential equations, in terms of the membrane shape and stress tensor. Starting from these equations, two dual approaches can be defi ned, namely direct problem and dual problem. Both problems are analyzed, studying their possible solutions in order to obtain practical results. In particular, the main analytical aspects of the direct problem are discussed, a numerical resolution procedure is proposed and, fi nally, analytical and numerical solution examples are presented.Este trabajo aborda el análisis del equilibrio de una membrana con borde rígido. La idea de utilizar las membranas en aplicaciones tales como las pasarelas, una nueva tecnología que se está desarrollando en España, requiere un análisis estructural muy ajustado. Debido a los esfuerzos de tracción, la membrana se identifi ca a una superficie con curvatura de Gauss negativa. De esta forma, el equilibrio se expresa directamente por medio de ecuaciones diferenciales en derivadas parciales, en términos de la forma de la membrana y del tensor de esfuerzos. A partir de dichas ecuaciones, se pueden considerar dos enfoques complementarios, aquí llamados problema directo y problema dual. Se analizan ambos problemas, estudiando sus posibles soluciones con el objetivo de obtener resultados prácticos. En particular, se profundizan los principales aspectos analíticos del problema directo, se propone un método numérico para la resolución y, fi nalmente, se presentan ejemplos de solución analítica y numérica.

  3. Problemas de Metafísica y Ontología en América Latina

    Directory of Open Access Journals (Sweden)

    Juan Cepeda H.

    2009-01-01

    Full Text Available El problema del ser plantea algunos interrogantes específicos cuando se le estudia desde América Latina: ¿los pueblos precolombinos se preguntaron por el ser?, ¿cómo se nos enseñó metafísica en el periodo colonial?, ¿desde Latinoamérica se han hecho propuestas originales en metafísica y ontología?, y hacia futuro ¿se nos posibilita develar una ontología propiamente latinoamericana? Este artículo evidencia algunos avances de las probables respuestas a los citados interrogantes, fruto del desarrollo del Proyecto de Investigación Problemas de Metafísica en América Latina (2008-2010.

  4. DIFICULTADES EN LA APLICACIÓN DEL CÁLCULO DIFERENCIAL E INTEGRAL EN LA RESOLUCIÓN DE PROBLEMAS DE CAMPO ELÉCTRICO

    Directory of Open Access Journals (Sweden)

    Silvia Coello

    2013-12-01

    Full Text Available El propósito de este estudio fue el determinar los conceptos en acción y teoremas en acción que tienen los estudiantes cuando aplican el cálculo diferencial e integral en la resolución de problemas de campo eléctrico utilizando la teoría de los campos conceptuales de Vergnaud.  Participaron en este estudio seis estudiantes registrados en un curso de física básico con cálculo en el tópico de electromagnetismo y que tiene como prerrequisito el cálculo diferencial y como correquisito el cálculo integral. Los estudiantes resolvieron un problema de campo eléctrico que involucró el uso del cálculo diferencial e integral utilizando el pensamiento en voz alta y a partir de la resolución del problema se establecieron los conceptos en acción y teoremas en acción equivocados. Los conceptos en acción y teoremas de acción incorrectos se presentan principalmente en la representación gráfica del problema y se concentran más en el dominio del cálculo diferencial e integral. Esto en gran medida se debe a que los esquemas de resolución de problemas del cálculo diferencial e integral no se transfieren adecuadamente a la resolución de problemas de física con este componente.

  5. Design and fabrication of a realistic anthropomorphic heterogeneous head phantom for MR purposes.

    Directory of Open Access Journals (Sweden)

    Sossena Wood

    Full Text Available The purpose of this study is to design an anthropomorphic heterogeneous head phantom that can be used for MRI and other electromagnetic applications.An eight compartment, physical anthropomorphic head phantom was developed from a 3T MRI dataset of a healthy male. The designed phantom was successfully built and preliminarily evaluated through an application that involves electromagnetic-tissue interactions: MRI (due to it being an available resource. The developed phantom was filled with media possessing electromagnetic constitutive parameters that correspond to biological tissues at ~297 MHz. A preliminary comparison between an in-vivo human volunteer (based on whom the anthropomorphic head phantom was created and various phantoms types, one being the anthropomorphic heterogeneous head phantom, were performed using a 7 Tesla human MRI scanner.Echo planar imaging was performed and minimal ghosting and fluctuations were observed using the proposed anthropomorphic phantom. The magnetic field distributions (during MRI experiments at 7 Tesla and the scattering parameter (measured using a network analyzer were most comparable between the anthropomorphic heterogeneous head phantom and an in-vivo human volunteer.The developed anthropomorphic heterogeneous head phantom can be used as a resource to various researchers in applications that involve electromagnetic-biological tissue interactions such as MRI.

  6. OpenSWPC: an open-source integrated parallel simulation code for modeling seismic wave propagation in 3D heterogeneous viscoelastic media

    Science.gov (United States)

    Maeda, Takuto; Takemura, Shunsuke; Furumura, Takashi

    2017-07-01

    We have developed an open-source software package, Open-source Seismic Wave Propagation Code (OpenSWPC), for parallel numerical simulations of seismic wave propagation in 3D and 2D (P-SV and SH) viscoelastic media based on the finite difference method in local-to-regional scales. This code is equipped with a frequency-independent attenuation model based on the generalized Zener body and an efficient perfectly matched layer for absorbing boundary condition. A hybrid-style programming using OpenMP and the Message Passing Interface (MPI) is adopted for efficient parallel computation. OpenSWPC has wide applicability for seismological studies and great portability to allowing excellent performance from PC clusters to supercomputers. Without modifying the code, users can conduct seismic wave propagation simulations using their own velocity structure models and the necessary source representations by specifying them in an input parameter file. The code has various modes for different types of velocity structure model input and different source representations such as single force, moment tensor and plane-wave incidence, which can easily be selected via the input parameters. Widely used binary data formats, the Network Common Data Form (NetCDF) and the Seismic Analysis Code (SAC) are adopted for the input of the heterogeneous structure model and the outputs of the simulation results, so users can easily handle the input/output datasets. All codes are written in Fortran 2003 and are available with detailed documents in a public repository.[Figure not available: see fulltext.

  7. ATRIBUTOS DEL PROBLEMA DINÁMICO DE CONTROL OPERACIONAL DE AGVS EN LA DISTRIBUCIÓN DE MATERIALES

    Directory of Open Access Journals (Sweden)

    Isidro Ramos Torres

    2016-06-01

    Full Text Available En este trabajo se estudian los atributos del problema dinámico del control operacional de AGVs. Se discuten las implicaciones del uso de la información on-line como el principal elemento del carácter dinámico de los problemas. Se utiliza la taxonomía de Psaraftis para identificar los atributos (evolución, calidad, disponibiliad, y procesamiento de la información utilizada. Se obtuvieron resultados parciales sobre las tendencias de los estudios dinámicos y sus características.

  8. Estudio de existencia de soluciones por elementos finitos de un problema del tipo de capa limite

    OpenAIRE

    Toro, Jose

    1988-01-01

    Se estudia la existencia de soluciones a las ecuaciones algebraicas asociadas a la discretización de un problema modelo similar a las ecuaciones de capa límite. El problema modelo retiene la forma de las no linealidades de la capa limite pero ignora la ecuación de continuidad. De este análisis se siguen criterios que permiten determinar la influencia de parámetros como viscosidad, norma de la velocidad, e incremento en la dirección de avance sobre la existencia de las soluciones algebraicas. ...

  9. Non destructive testing of heterogeneous structures with a step frequency radar

    International Nuclear Information System (INIS)

    Cattin, V.; Chaillout, J.J.

    1998-01-01

    Ground penetrating radar have shown increasing potential in diagnostic of soils or concrete, but the realisation of such a system and the interpretation of data produced by this technique require a clear understanding of the physical electromagnetic processes that appear between media and waves. In this paper are studied the performances of a step frequency radar as a nondestructive technique to evaluate different heterogeneous laboratory size structures. Some critical points are studied like material properties, antenna effect and image reconstruction algorithm, to determine its viability to distinguish smallest region of interest

  10. Modelos de aplicación de ecuaciones diferenciales de primer orden con geogebra: actividades para resolver problemas de mezclas

    Directory of Open Access Journals (Sweden)

    Cesar Augusto Hernández-Suarez

    2016-09-01

    Full Text Available El objetivo del estudio es diseñar una actividad para abordar los problemas de mezclas en un curso de ecuaciones diferenciales que permita realizar cambios de representación en los registros gráfico, algebraico y lengua natural mediante la ayuda de software libre Geogebra, esperando así reducir la dificultad que presentan los estudiantes al momento de plantear la ecuación diferencial que modela un problema de mezclas. La actividad se fundamenta en dos marcos, el didáctico y el matemático, los cuales fueron elaborados con los aportes de distintas fuentes consultadas acerca del objeto de investigación. La selección de los participantes fue realizada mediante muestreo intencional y durante el desarrollo de este proceso se eligieron dieciocho (18 estudiantes de un programa académico de Ingeniería Civil de un curso de ecuaciones diferenciales. Se aplicó una encuesta a los estudiantes sobre los modelos de aplicación de ecuaciones diferenciales de primer orden para determinar el modelo a utilizar; los modelos con mayor porcentaje de elección fueron: Mezclas y ley de enfriamiento de Newton, razón por la cual se eligió el modelo de mezclas para el diseño de una actividad tipo test con 3 problemas que para ser resueltos con el Geogebra. Se analizan las respuestas dadas por los estudiantes al resolver una serie de problemas de aplicación de primer orden con el software libre Geogebra. Estos problemas permiten realizar traspasos del registro lenguaje natural al algebraico mediante representaciones ejecutables y preguntas que pretenden orientar al estudiante durante el desarrollo de la misma, con el fin de proporcionar herramientas para plantear la ecuación diferencial que se ajusta a los problemas planteados. Como resultados se obtiene una propuesta del uso del Geogebra como un recurso didáctico para favorecer la resolución de problemas de aplicación de ecuaciones diferenciales de primer orden (problemas de mezclas. Se puede concluir

  11. Clases de cachorros y problemas de comportamiento en perros

    OpenAIRE

    González Alonso, Almudena

    2017-01-01

    Traballo Fin de Grao en Veterinaria. Curso 2016-2017 [ES] Los perros que son debidamente socializados durante las primeras semanas de vida son menos propensos a la aparición de problemas de comportamiento, que pueden deteriorar el vínculo propietario-animal y provocar el abandono y eutanasia de las mascotas. La evidencia de los beneficios de las clases de cachorros no está tan clara, algunos estudios muestran que las clases impactan positivamente en el comportamiento de los adultos, reduci...

  12. Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media

    KAUST Repository

    Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin R.

    2015-01-01

    , anisotropic media, where we construct basis functions from multiple local problems for both boundaries and the interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property

  13. Desarrollo de la competencia social y prevención de problemas de conducta en el aula infantil

    Directory of Open Access Journals (Sweden)

    M. Carmen Pichardo Martínez

    2016-01-01

    Full Text Available Objetivo. El propósito del estudio es analizar el efecto longitudinal del programa de prevención universal Aprender a Convivir sobre la competencia social y los problemas de conducta infantiles. Método. 197 niños de tres años participaron en el programa durante tres años consecutivos y fueron evaluados por sus maestros en distintas variables relacionadas con la competencia social y los problemas de conducta. El análisis de datos se llevó a cabo mediante un ANOVA simple de medidas repetidas, incluyendo como factor intragrupo el momento de evaluación pretest (3 años de edad y postest (5 años de edad. Resultados. Los resultados mostraron una mejora significativa del grupo experimental, tanto en las variables de competencia social (cooperación social d = 1.55; interacción social d = 1.91; e independencia social d = 1.32 como en las de problemas de conducta (interiorizados d = 0.40; y exteriorizados d = 0.48 analizadas. Conclusión. El programa de intervención Aprender a Convivir contribuye al desarrollo de la competencia social del alumnado de Educación Infantil, también tiene un efecto indirecto sobre la reducción de problemas de conducta interiorizados y exteriorizados en niños.

  14. Oficina de Aritmética: o Uso dos Números Primos na Resolução de Problemas e Algumas curiosidades

    OpenAIRE

    REIS, C. C.

    2014-01-01

    Este projeto traz uma proposta de oficina-didática para professores e alunos dos ensinos fundamental e médio trabalharem, nas aulas ou mesmo no aprimoramento para turmas que se preparam para as olimpíadas de matemática, técnicas de resolução de problemas envolvendo números primos. A sequência dos capítulos expõe a teoria básica, breve argumentação sobre resolução de problemas, problemas diversos sobre números primos e suas resoluções e, por fim, artigos sobre curiosidades no mundo inteiro a r...

  15. Disecciones de cubos, juegos de persecución y otros problemas

    OpenAIRE

    Rupérez, José Antonio; García, Manuel

    2010-01-01

    Presentamos algunas soluciones y enlaces de las disecciones de cubos presentados en el artículo anterior e introducimos los Juegos de Persecución, como otro recurso didáctico para el análisis, planteamiento, búsqueda, discusión y comprobación de soluciones, siguiendo la metodología de resolución de problemas.

  16. Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma.

    Science.gov (United States)

    Kan, Monica W K; Leung, Lucullus H T; So, Ronald W K; Yu, Peter K N

    2013-03-01

    in a heterogeneous medium, produced the best agreement with the AXB_Dw. For the verification of point doses within the target using TLD in the anthropomorphic phantom, the absolute percentage deviations between the calculated and measured data when averaged over all IMRT and RA plans were 1.8%, 1.7%, and 1.8% for AAA, AXB_Dm and AXB_Dw, respectively. From all the verification results, no significant difference was found between the IMRT and RA plans. The target dose analysis of the real patient plans showed that the discrepancies in mean doses to the PTV component in tissue among the three dose calculation options were within 2%, but up to about 4% in the bone content, with AXB_Dm giving the lowest values and AXB_Dw giving the highest values. In general, the verification measurements demonstrated that both algorithms produced acceptable accuracy when compared to the measured data. GafChromic(®) film results indicated that AXB produced slightly better accuracy compared to AAA for dose calculation adjacent to and within the heterogeneous media. Users should be aware of the differences in calculated target doses between options AXB_Dm and AXB_Dw, especially in bone, for IMRT and RA in NPC cases.

  17. Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma

    International Nuclear Information System (INIS)

    Kan, Monica W. K.; Leung, Lucullus H. T.; So, Ronald W. K.; Yu, Peter K. N.

    2013-01-01

    dose close to unit density water in a heterogeneous medium, produced the best agreement with the AXB Dw . For the verification of point doses within the target using TLD in the anthropomorphic phantom, the absolute percentage deviations between the calculated and measured data when averaged over all IMRT and RA plans were 1.8%, 1.7%, and 1.8% for AAA, AXB Dm and AXB Dw , respectively. From all the verification results, no significant difference was found between the IMRT and RA plans. The target dose analysis of the real patient plans showed that the discrepancies in mean doses to the PTV component in tissue among the three dose calculation options were within 2%, but up to about 4% in the bone content, with AXB Dm giving the lowest values and AXB Dw giving the highest values. Conclusions: In general, the verification measurements demonstrated that both algorithms produced acceptable accuracy when compared to the measured data. GafChromic ® film results indicated that AXB produced slightly better accuracy compared to AAA for dose calculation adjacent to and within the heterogeneous media. Users should be aware of the differences in calculated target doses between options AXB Dm and AXB Dw , especially in bone, for IMRT and RA in NPC cases.

  18. Aprendizaje basado en problemas y educación en ingeniería

    DEFF Research Database (Denmark)

    Numerosos reportes científicos alrededor del mundo identifican al aprendizaje basado en problemas (PBL) como una práctica educativa efectiva para que los estudiantes desarrollen habilidades y competencias para el ejercicio profesional durante su aprendizaje. En la comunidad académica se han formu...

  19. Experiencia docente mediante la Metodología de Aprendizaje Basado en Problemas

    Directory of Open Access Journals (Sweden)

    José Manuel López-Guede

    2015-07-01

    Full Text Available En este artículo se describe una experiencia docente de implantación de Aprendizaje Basado en Problemas (ABP llevada a cabo en la Escuela Universitaria de Ingeniería de Vitoria-Gasteiz, de la Universidad del País Vasco (UPV/EHU. La asignatura objeto de la implantación ha sido Arquitectura de Computadores, del Grado en Ingeniería Informática de Gestión y Sistemas de Información. En el artículo se recogen los elementos principales a considerar en toda implantación como son las competencias específicas y transversales a adquirir por el alumnado, por lo que se recoge el temario y los resultados del aprendizaje a lograr y evaluar. Se detalla el problema estructurante diseñado y su división en subproblemas, así como los logros alcanzados, siendo estos altamente satisfactorios tanto para el alumnado en general como para el profesorado.

  20. Fuel micro-mechanics: homogenization, cracking, granular media

    International Nuclear Information System (INIS)

    Monerie, Yann

    2010-01-01

    This work summarizes about fifteen years of research in the field of micro-mechanics of materials. Emphasis is placed on the most recent work carried out in the context of nuclear safety. Micro-mechanics finds a natural place there, aiming to predict the behavior of heterogeneous materials with an evolving microstructure. The applications concerned mainly involve the nuclear fuel and its tubular cladding. The uranium dioxide fuel is modeled, according to the scales under consideration, as a porous ceramic or a granular medium. The strongly irradiated Zircaloy claddings are identified with a composite medium with a metal matrix and a gradient of properties. The analysis of these classes of material is rich in problems of a more fundamental nature. Three main themes are discussed: 1/ Homogenization, 2/ cracking, rupture and fragmentation, 3/ discrete media and fluid-grain couplings. Homogenization: The analytical scale change methods proposed aim to estimate or limit the linear and equivalent nonlinear behaviors of isotropic porous media and anisotropic composites with a metal matrix. The porous media under consideration are saturated or drained, with a compressible or incompressible matrix, and have one or two scales of spherical or ellipsoid pores, or cracks. The composites studied have a macroscopic anisotropy related to that of the matrix, and to the shape and spatial distribution of the inclusions. Thermoelastic, elastoplastic, and viscoplastic behaviors and ductile damage of these media are examined using different techniques: extensions of classic approaches, linear in particular, variational approaches and approaches using elliptical potentials with thermally activated elementary mechanisms. The models developed are validated on numerical finite element simulations, and their functional relevance is illustrated in comparison to experimental data obtained from the literature. The significant results obtained include a plasticity criterion for Gurson matrix

  1. Aplicación del método de elementos naturales a problemas estructurales

    Directory of Open Access Journals (Sweden)

    Libardo Andrés González Torres

    2008-01-01

    Full Text Available El objetivo del presente artículo se enmarca en la revisión de la teoría y la implementación numérica de uno de los métodos numéricos sin malla usados para la solución de problemas de tipo estructural, el método de los elementos naturales (MEN, junto con la contrastación de los resultados obtenidos para dos problemas estructurales elástico-lineales en dos dimensiones con la solución analítica exacta y la aproximada por el método de los elementos finitos (MEF. Se describe la técnica de interpolación usada por el MEN para obtener las funciones de forma y se presen-tan las características más importantes del método en su forma estándar. Se presentan los resultados de dos simula-ciones de problemas estructurales realizadas usando un código escrito en Matlab 6.5 para la solución de ecuacio-nes diferenciales de elasticidad lineal en dominios bidimensionales. Se concluye que el método de los elementos naturales es similar al de los elementos finitos en cuanto a estabilidad y convergencia, con la ventaja de que la ma-lla es generada automáticamente y la no dependencia de la solución aproximada con la distribución de la nube de puntos que define la geometría.

  2. Contribuição dos Indicadores de Problemas Emocionais e de Comportamento para o Rendimento Escolar

    Directory of Open Access Journals (Sweden)

    Bruna Mainardi Rosso Borba

    2017-07-01

    Full Text Available Este estudo investigou se há contribuição e em que medida os problemas e os indicadores comportamentais emocionais e de conduta explicam o rendimento escolar dos adolescentes. Setenta estudantes participaram, 70 famílias e 21 profes-sores. Os adolescentes responderam ao inventário de comportamentos da juventude (YSR, a família do inventário dos professores da criança e o comportamento dos adolescentes (CBCL e o inventário de conduta do Adolescente (TRF e crianças. O desempenho escolar foi avaliado a partir da média final nas disciplinas de português e matemática. Na ava-liação dos adolescentes, suas famílias e professores, os problemas de atenção explicam o mau desempenho escolar, bem como a terceirização dos problemas identificados pelos adolescentes e os sintomas de isolamento/depressão indicada pelos professores. É realçada a importância de atender tais indicadores, visto sua influência nos adolescentes.

  3. SAM: Secure Access of Media Independent Information Service with User Anonymity

    Directory of Open Access Journals (Sweden)

    Li Guangsong

    2010-01-01

    Full Text Available Seamless handover across different access technologies is very important in the future wireless networks. To optimize vertical handover in heterogeneous networks, IEEE 802.21 standard defines Media Independent Handover (MIH services. The MIH services can be a new target to attackers, which will be the main concern for equipment vendors and service providers. In this paper, we focus specifically on security of Media Independent Information Service (MIIS and present a new access authentication scheme with user anonymity for MIIS. The protocol can be used to establish a secure channel between the mobile node and the information server. Security and performance of the protocol are also analyzed in this paper.

  4. Media Education Initiatives by Media Organizations: The Uses of Media Literacy in Hong Kong Media

    Science.gov (United States)

    Chu, Donna; Lee, Alice Y. L.

    2014-01-01

    As more media organizations have engaged in media education, this paper investigates the goals and practices of these activities. This article coins media education initiatives by media organizations with the term "media-organization media literac"y (MOML). Four MOML projects in Hong Kong were selected for examination. Built on critical…

  5. Darcy-Forchheimer flow with Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions.

    Science.gov (United States)

    Hayat, Tasawar; Haider, Farwa; Muhammad, Taseer; Alsaedi, Ahmed

    2017-01-01

    Here Darcy-Forchheimer flow of viscoelastic fluids has been analyzed in the presence of Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions. Results for two viscoelastic fluids are obtained and compared. A linear stretching surface has been used to generate the flow. Flow in porous media is characterized by considering the Darcy-Forchheimer model. Modified version of Fourier's law through Cattaneo-Christov heat flux is employed. Equal diffusion coefficients are employed for both reactants and auto catalyst. Optimal homotopy scheme is employed for solutions development of nonlinear problems. Solutions expressions of velocity, temperature and concentration fields are provided. Skin friction coefficient and heat transfer rate are computed and analyzed. Here the temperature and thermal boundary layer thickness are lower for Cattaneo-Christov heat flux model in comparison to classical Fourier's law of heat conduction. Moreover, the homogeneous and heterogeneous reactions parameters have opposite behaviors for concentration field.

  6. Scale dependence of effective media properties

    International Nuclear Information System (INIS)

    Tidwell, V.C.; VonDoemming, J.D.; Martinez, K.

    1992-01-01

    For problems where media properties are measured at one scale and applied at another, scaling laws or models must be used in order to define effective properties at the scale of interest. The accuracy of such models will play a critical role in predicting flow and transport through the Yucca Mountain Test Site given the sensitivity of these calculations to the input property fields. Therefore, a research programhas been established to gain a fundamental understanding of how properties scale with the aim of developing and testing models that describe scaling behavior in a quantitative-manner. Scaling of constitutive rock properties is investigated through physical experimentation involving the collection of suites of gas permeability data measured over a range of discrete scales. Also, various physical characteristics of property heterogeneity and the means by which the heterogeneity is measured and described are systematically investigated to evaluate their influence on scaling behavior. This paper summarizes the approach that isbeing taken toward this goal and presents the results of a scoping study that was conducted to evaluate the feasibility of the proposed research

  7. Social media mining and visualization for point-of-interest recommendation

    Institute of Scientific and Technical Information of China (English)

    Ren Xingyi; Song Meina; E Haihong; Song Junde

    2017-01-01

    With the rapid growth of location-based social networks (LBSNs),point-of-interest (POI) recommendation has become an important research problem.As one of the most representative social media platforms,Twitter provides various real-life information for POI recommendation in real time.Despite that POI recommendation has been actively studied,tweet images have not been well utilized for this research problem.State-of-the-art visual features like convolutional neural network (CNN) features have shown significant performance gains over the traditional bag-of-visual-words in unveiling the image's semantics.Unfortunately,they have not been employed for POI recommendation from social websites.Hence,how to make the most of tweet images to improve the performance of POI recommendation and visualization remains open.In this paper,we thoroughly study the impact of tweet images on POI recommendation for different POI categories using various visual features.A novel topic model called social media Twitter-latent Dirichlet allocation (SM-TwitterLDA) which jointly models five Twitter features,(i.e.,text,image,location,timestamp and hashtag) is designed to discover POIs from the sheer amount of tweets.Moreover,each POI is visualized by representative images selected on three predefined criteria.Extensive experiments have been conducted on a real-life tweet dataset to verify the effectiveness of our method.

  8. Trabajo infantil y problemas del comportamiento en menores trabajadores

    OpenAIRE

    Cardenas Ramirez, Luz Stella

    2016-01-01

    Objetivo: Identificar la relación de los factores de riesgo ocupacional del trabajo infantil con los problemas de comportamiento en menores de edad trabajadores de una plaza de mercado en Colombia Materiales y métodos: Se realizó un estudio de corte transversal con 100 niños trabajadores de la plaza de Mercaneiva. Se aplicó un cuestionario para evaluar los factores ocupacionales en la población, evaluando aspectos sociodemográficos y condiciones laborales; para establecer la prevalencia d...

  9. Experiencias de utilización del método de búsqueda TABU en la resolución de problemas de organización universitaria

    OpenAIRE

    J.M. Tamarit; E. Crespo; R. Álvarez-Valdés1

    2000-01-01

    A lo largo de los 10 últimos años hemos trabajado en problemas de organización académica de grandes dimensiones. En problemas universitarios hemos tratado la confección de calendarios de exámenes, la asignación de estudiantes a grupos vinculada al problema de la automatrícula y también la confección de horarios. Todos estos problemas son difíciles (NP-hard) por lo que en todos los casos los algoritmos de resolución implementados han sido complejos y basados en procedimientos adaptados a cad...

  10. Preliminary Groundwater Simulations To Compare Different Reconstruction Methods of 3-d Alluvial Heterogeneity

    Science.gov (United States)

    Teles, V.; de Marsily, G.; Delay, F.; Perrier, E.

    Alluvial floodplains are extremely heterogeneous aquifers, whose three-dimensional structures are quite difficult to model. In general, when representing such structures, the medium heterogeneity is modeled with classical geostatistical or Boolean meth- ods. Another approach, still in its infancy, is called the genetic method because it simulates the generation of the medium by reproducing sedimentary processes. We developed a new genetic model to obtain a realistic three-dimensional image of allu- vial media. It does not simulate the hydrodynamics of sedimentation but uses semi- empirical and statistical rules to roughly reproduce fluvial deposition and erosion. The main processes, either at the stream scale or at the plain scale, are modeled by simple rules applied to "sediment" entities or to conceptual "erosion" entities. The model was applied to a several kilometer long portion of the Aube River floodplain (France) and reproduced the deposition and erosion cycles that occurred during the inferred climate periods (15 000 BP to present). A three-dimensional image of the aquifer was gener- ated, by extrapolating the two-dimensional information collected on a cross-section of the floodplain. Unlike geostatistical methods, this extrapolation does not use a statis- tical spatial analysis of the data, but a genetic analysis, which leads to a more realistic structure. Groundwater flow and transport simulations in the alluvium were carried out with a three-dimensional flow code or simulator (MODFLOW), using different rep- resentations of the alluvial reservoir of the Aube River floodplain: first an equivalent homogeneous medium, and then different heterogeneous media built either with the traditional geostatistical approach simulating the permeability distribution, or with the new genetic model presented here simulating sediment facies. In the latter case, each deposited entity of a given lithology was assigned a constant hydraulic conductivity value. Results of these

  11. A new media optimizer based on the mean-variance model

    Directory of Open Access Journals (Sweden)

    Pedro Jesus Fernandez

    2007-01-01

    Full Text Available In the financial markets, there is a well established portfolio optimization model called generalized mean-variance model (or generalized Markowitz model. This model considers that a typical investor, while expecting returns to be high, also expects returns to be as certain as possible. In this paper we introduce a new media optimization system based on the mean-variance model, a novel approach in media planning. After presenting the model in its full generality, we discuss possible advantages of the mean-variance paradigm, such as its flexibility in modeling the optimization problem, its ability of dealing with many media performance indices - satisfying most of the media plan needs - and, most important, the property of diversifying the media portfolios in a natural way, without the need to set up ad hoc constraints to enforce diversification.No mercado financeiro, existem modelos de otimização de portfólios já bem estabelecidos, denominados modelos de média-variância generalizados, ou modelos de Markowitz generalizados. Este modelo considera que um investidor típico, enquanto espera altos retornos, espera também que estes retornos sejam tão certos quanto possível. Neste artigo introduzimos um novo sistema otimizador de mídia baseado no modelo de média-variância, uma abordagem inovadora na área de planejamento de mídia. Após apresentar o modelo em sua máxima generalidade, discutimos possíveis vantagens do paradigma de média-variância, como sua flexibilidade na modelagem do problema de otimização, sua habilidade de lidar com vários índices de performance - satisfazendo a maioria dos requisitos de planejamento - e, o mais importante, a propriedade de diversificar os portfólios de mídia de uma forma natural, sem a necessidade de estipular restrições ad hoc para forçar a diversificação.

  12. On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations

    DEFF Research Database (Denmark)

    Fogliata, Antonella; Vanetti, Eugenio; Albers, Dirk

    2007-01-01

    A comparative study was performed to reveal differences and relative figures of merit of seven different calculation algorithms for photon beams when applied to inhomogeneous media. The following algorithms were investigated: Varian Eclipse: the anisotropic analytical algorithm, and the pencil beam...... a systematic deficiency in managing the presence of heterogeneous media. In contrast, complicated patterns were observed for the advanced algorithms with significant discrepancies observed between algorithms in the lighter materials (rho = 0.035 g cm(-3)), enhanced for the most energetic beam. For denser...

  13. Tratamiento ortodóntico interceptivo para paciente pediátrico con problema periodontal ocasionado por trauma oclusal primario. Reporte de caso

    Directory of Open Access Journals (Sweden)

    Johana Maldonado-Villamizar

    2016-07-01

    Full Text Available El diagnóstico correcto puede evitar la evolución de patologías que lleven al paciente pediátrico a padecer de problemas graves en el futuro. Este diagnóstico junto con un tratamiento interceptivo a tiempo, puede ayudar a resolver problemas de tipo periodontal causado por el inadecuado posicionamiento dental o injurias oclusales. El objetivo de este artículo es realizar el reporte de caso de un paciente pediátrico que presenta una maloclusion dental tipo mordida cruzada anterior acompañada por un trauma oclusal primario, el cual causo un problema periodontal localizado, a su vez, describir la terapéutica interceptiva basada en el correcto diagnóstico odontopediátrico, ortodóntico y periodontal. Concluyendo que al seleccionar la aparatología adecuada se puede solventar diversos problemas dentales que puedan ocasionar un daño mayor a las estructuras comprometidas.

  14. PROBLEMA DE ALOCAÇÃO DE CONFIABILIDADE-REDUNDÂNCIA USANDO EVOLUÇÃO DIFERENCIAL AUTO-ADAPTATIVA

    OpenAIRE

    Spengler, Hellen Cristina; Loch, Gustavo Valentim

    2017-01-01

    Resumo. Esse trabalho considera a otimização não-linear inteira-mista do problema de alocação de confiabilidade-redundância, determinando simultaneamente a confiabilidade e redundância dos componentes de um sistema em série. Grande número de métodos (exatos e metaheurísticos) já abordaram esse problema, apresentando soluções satisfatórias. Nesse trabalho é utilizado um algoritmo de evolução diferencial auto-adaptativa (SaMDE) junto a um algoritmo de busca local. O exemplo numérico resolvido i...

  15. Impact of local diffusion on macroscopic dispersion in three-dimensional porous media

    Science.gov (United States)

    Dartois, Arthur; Beaudoin, Anthony; Huberson, Serge

    2018-02-01

    While macroscopic longitudinal and transverse dispersion in three-dimensional porous media has been simulated previously mostly under purely advective conditions, the impact of diffusion on macroscopic dispersion in 3D remains an open question. Furthermore, both in 2D and 3D, recurring difficulties have been encountered due to computer limitation or analytical approximation. In this work, we use the Lagrangian velocity covariance function and the temporal derivative of second-order moments to study the influence of diffusion on dispersion in highly heterogeneous 2D and 3D porous media. The first approach characterizes the correlation between the values of Eulerian velocity components sampled by particles undergoing diffusion at two times. The second approach allows the estimation of dispersion coefficients and the analysis of their behaviours as functions of diffusion. These two approaches allowed us to reach new results. The influence of diffusion on dispersion seems to be globally similar between highly heterogeneous 2D and 3D porous media. Diffusion induces a decrease in the dispersion in the direction parallel to the flow direction and an increase in the dispersion in the direction perpendicular to the flow direction. However, the amplification of these two effects with the permeability variance is clearly different between 2D and 3D. For the direction parallel to the flow direction, the amplification is more important in 3D than in 2D. It is reversed in the direction perpendicular to the flow direction.

  16. Helicobacter pylori y dispepsia, un problema de salud comunitario

    Directory of Open Access Journals (Sweden)

    Miguel González-Carbajal Pascual

    2002-06-01

    Full Text Available Mientras la relación causal entre el Helicobacter pylori y la gastritis crónica, así como la importante conexión entre esta infección, la úlcera gastroduodenal y el cáncer gástrico han sido bien establecidas, la asociación entre la infección por Helicobacter pylori y la dispepsia "no ulcerosa" es un problema que dista mucho de estar esclarecido. Hay autores que no dudan en utilizar tratamiento de erradicación en la dispepsia "no ulcerosa" con Helicobacter pylori, pero existen enfoques alternativos a este problema. La realización de tratamiento de erradicación en los pacientes con dispepsia "no ulcerosa" pudiera beneficiar o no a los enfermos y a la comunidad, pero seguramente no puede dejar de beneficiar a las transnacionales productoras de medicamentos que cosechan cuantiosas ganancias con la comercialización de los bloqueadores de la bomba de protones y los antibióticos que se incluyen en cualquier esquema de terapia erradicadora de la infección por Helicobacter pylori. El alivio de los síntomas dispépticos como consecuencia del tratamiento de erradicación del Helicobacter pylori no ha sido comprobado. El problema de realizar tratamiento de erradicación de la infección a los pacientes con dispepsia "no ulcerosa" continúa siendo un dilema y, por tanto, no debe indicarse sistemáticamente.Although the causative relationship between Helicobacter pylori and chronic gastritis as well as the important connection of this infection with gastric-duodenal ulcer and gastric cancer are well established, the association of Helicobacter pylori infection and non-ulcer dispepsia is a problem that is still unclear. Some authors do not hesitate in using Helicobacter pylori eradication treatment in cases of non-ulcer dispepsia but there are other alternative approaches to this problem. The eradication treatment in patients with non-ulcer dispepsia may or may not benefit patients and the community, but will benefit for sure the big drug

  17. The fluid control mechanism of bionic structural heterogeneous composite materials and its potential application in enhancing pump efficiency

    Directory of Open Access Journals (Sweden)

    Limei Tian

    2015-11-01

    Full Text Available Studies have shown that the structure of dolphin skin controls fluid media dynamically. Gaining inspiration from this phenomenon, a kind of bionic structural heterogeneous composite material was designed. The bionic structural heterogeneous composite material is composed of two materials: a rigid metal base layer with bionic structures and an elastic polymer surface layer with the corresponding mirror structures. The fluid control mechanism of the bionic structural heterogeneous composite material was investigated using a fluid–solid interaction method in ANSYS Workbench. The results indicated that the bionic structural heterogeneous composite material’s fluid control mechanism is its elastic deformation, which is caused by the coupling action between the elastic surface material and the bionic structure. This deformation can decrease the velocity gradient of the fluid boundary layer through changing the fluid–solid actual contact surface and reduce the frictional force. The bionic structural heterogeneous composite material can also absorb some energy through elastic deformation and avoid energy loss. The bionic structural heterogeneous composite material was applied to the impeller of a centrifugal pump in a contrast experiment, increasing the pump efficiency by 5% without changing the hydraulic model of the impeller. The development of this bionic structural heterogeneous composite material will be straightforward from an engineering point of view, and it will have valuable practical applications.

  18. A new approach to tracer transport analysis: From fracture systems to strongly heterogeneous porous media

    International Nuclear Information System (INIS)

    Tsang, Chin-Fu.

    1989-02-01

    Many current development and utilization of groundwater resources include a study of their flow and transport properties. These properties are needed in evaluating possible changes in groundwater quality and potential transport of hazardous solutes through the groundwater system. Investigation of transport properties of fractured rocks is an active area of research. Most of the current approaches to the study of flow and transport in fractured rocks cannot be easily used for analysis of tracer transport field data. A new approach is proposed based on a detailed study of transport through a fracture of variable aperture. This is a two-dimensional strongly heterogeneous permeable system. It is suggested that tracer breakthrough curves can be analyzed based on an aperture or permeability probability distribution function that characterizes the tracer flow through the fracture. The results are extended to a multi-fracture system and can be equally applied to a strongly heterogeneous porous medium. Finally, the need for multi-point or line and areal tracer injection and observation tests is indicated as a way to avoid the sensitive dependence of point measurements on local permeability variability. 30 refs., 15 figs

  19. Parametric study of boiling heat transfer in porous media

    International Nuclear Information System (INIS)

    Shi, B.; Jones, B.G.; Pan, C.

    1996-01-01

    Detailed numerical modeling and parametric variation studies were conducted on boiling heat transfer processes in porous deposits with emphasis on applications associated with light water nuclear power reactor systems. The processes of boiling heat transfer in the porous corrosion deposits typically involve phase changes in finite volumetric regions in the porous media. The study examined such processes in two porous media configurations, without chimneys (homogeneous porous structures) and with chimneys (heterogeneous porous structures). A 1-D model and a 2-D model were developed to simulate two-phase flows with phase changes, without dry-out, inside the porous media for both structural configurations. For closure of the governing equations, an empirical correlation of the evaporation rate for phase changes inside the porous media was introduced. In addition, numerical algorithms were developed to solve the coupled nonlinear equations of mass, momentum, energy, capillary pressure, and evaporation rate. The distributions of temperature, thermodynamic saturation, liquid pressure, vapor pressure, liquid velocity, and vapor velocity were predicted. Furthermore, the effects of heat flux, system pressure, porosity, particle diameter, chimney population density, chimney radius, and crud thickness on the all superheat, critical heat flux, and minimum saturation were examined. The predictions were found to be in good agreement with the available experimental results

  20. Sleep problems and social support: Frailty in a Brazilian Elderly Multicenter Study Problemas de sueño y soporte social: estudio multicéntrico sobre Fragilidad en Ancianos Brasileños Problemas de sono e suporte social: estudo multicêntrico Fragilidade em Idosos Brasileiros

    Directory of Open Access Journals (Sweden)

    Shintia Viana da Costa

    2011-08-01

    Full Text Available This study identifies relationships among the quality of perceived social support and sleep problems and napping habits in community-dwelling elderly. This study is part of a larger multicenter project entitled "Frailty in Brazilian Elderly Individuals", conducted in 17 Brazilian cities. A total of 498 elderly individuals capable of participating in interviews and free of cognitive deficits or functional impairment were found. The following instruments were used in data collection: Questionnaire addressing socio-demographic data; Interpersonal Support Evaluation Scale; questions concerning sleep patterns (Nottingham Health Profile; questions related to napping habits (Minnesota Leisure Activity Questionnaire. Descriptive statistics and the Mann-Whitney test were used for data analysis. The elderly individuals who reported having sleep problems in general, taking longer to fall asleep and sleeping poorly at night had lower scores on the Interpersonal Support Evaluation Scale than the elderly who denied such problems. Strategies to improve the quality of social support could also help reduce sleep problems.Este artículo tiene como objetivo identificar relaciones entre calidad del soporte social percibido, problemas de sueño y hábito de dormitar, en ancianos de la comunidad. Se trata de un recorte del estudio Fragilidad en Ancianos Brasileiros (FIBRA, proyecto multicéntrico desarrollado en 17 ciudades brasileñas. Participaron 498 ancianos, capaces de responder a las entrevistas, sin déficit cognitivo o funcional grave. Se adoptó para la recolección de datos: el Cuestionario Sociodemográfico; la Escala de Percepción de la Calidad del Soporte Social; preguntas sobre problemas de sueño (Perfil de Salud de Nottingham; y, preguntas sobre el hábito de dormitar (Minnesota Leisure Activity Questionnaire. Se utilizó estadística descriptiva y prueba de Mann-Whitney para tratamiento de los datos. Los ancianos que refirieron problemas de sue

  1. The use of laboratory experiments for the study of conservative solute transport in heterogeneous porous media

    Science.gov (United States)

    Silliman, S. E.; Zheng, L.; Conwell, P.

    Laboratory experiments on heterogeneous porous media (otherwise known as intermediate scale experiments, or ISEs) have been increasingly relied upon by hydrogeologists for the study of saturated and unsaturated groundwater systems. Among the many ongoing applications of ISEs is the study of fluid flow and the transport of conservative solutes in correlated permeability fields. Recent advances in ISE design have provided the capability of creating correlated permeability fields in the laboratory. This capability is important in the application of ISEs for the assessment of recent stochastic theories. In addition, pressure-transducer technology and visualization methods have provided the potential for ISEs to be used in characterizing the spatial distributions of both hydraulic head and local water velocity within correlated permeability fields. Finally, various methods are available for characterizing temporal variations in the spatial distribution (and, thereby, the spatial moments) of solute concentrations within ISEs. It is concluded, therefore, that recent developments in experimental techniques have provided an opportunity to use ISEs as important tools in the continuing study of fluid flow and the transport of conservative solutes in heterogeneous, saturated porous media. Résumé Les hydrogéologues se sont progressivement appuyés sur des expériences de laboratoire sur des milieux poreux hétérogènes (connus aussi par l'expression "Expériences àéchelle intermédiaire", ISE) pour étudier les zones saturées et non saturées des aquifères. Parmi les nombreuses applications en cours des ISE, il faut noter l'étude de l'écoulement de fluide et le transport de solutés conservatifs dans des champs aux perméabilités corrélées. Les récents progrès du protocole des ISE ont donné la possibilité de créer des champs de perméabilités corrélées au laboratoire. Cette possibilité est importante dans l'application des ISE pour l'évaluation des th

  2. Upscaling in porous media : Consequences of reducing the phase on the dynamic behavior of a homogenized medium

    NARCIS (Netherlands)

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

    2014-01-01

    Effective-medium approaches are widely used to model initially heterogeneous systems: it saves computational time. In poroelasticity (two-phase media), it is advantageous to use one-phase effective medium if possible: it simplifies computations even more. In this paper we discuss situations where

  3. PROBLEMAS DE ESTIMACIÓN DE MAGNITUDES NO ALCANZABLES: ESTRATEGIAS Y ÉXITO EN LA RESOLUCIÓN (Unreachable Magnitude Estimation Problems: Strategies and Solving Success

    Directory of Open Access Journals (Sweden)

    Núria Gorgorió

    2013-03-01

    Full Text Available Llamamos problemas de Fermi a aquellos problemas que, siendo de difícil resolución, admiten una aproximación a su solución a base de romper el problema en partes más pequeñas y resolverlas por separado. En este artículo presentamos los problemas de estimación de magnitudes no alcanzables (PEMNA como un subconjunto de los problemas de Fermi. A partir de los datos recopilados en un estudio hecho con alumnos de 12 a 16 años, caracterizamos las distintas estrategias de resolución propuestas por estos y discutimos sobre la potencialidad de estas estrategias para resolver los problemas con éxito. Fermi problems are problems that, being difficult to solve, can be satisfactorily solved if they are broken down into smaller pieces that are solved separately. In this article, we present inconceivable magnitude estimation problems as a subset of Fermi problems. Based on data collected from a study carried out with 12 to 16 years old students, we describe the different strategies for solving the problems that were proposed by the students, and discuss the potential of these strategies to successfully solve the problems.

  4. When Factorization Meets Heterogeneous Latent Topics:An Interpretable Cross-Site Recommendation Framework

    Institute of Scientific and Technical Information of China (English)

    辛欣; 林钦佑; 魏骁驰; 黄河燕

    2015-01-01

    Data sparsity is a well-known challenge in recommender systems. Previous studies alleviate this problem by incorporating the information within the corresponding social media site. In this paper, we solve this challenge by exploring cross-site information. Specifically, we examine: 1) how to effectively and efficiently utilize cross-site ratings and content features to improve recommendation performance and 2) how to make the recommendation interpretable by utilizing content features. We propose a joint model of matrix factorization and latent topic analysis. Heterogeneous content features are modeled by multiple kinds of latent topics. In addition, the combination of matrix factorization and latent topics makes the recommendation result interpretable. Therefore, the above two issues are simultaneously solved. Through a real-world dataset, where user behaviors in three social media sites are collected, we demonstrate that the proposed model is effective in improving recommendation performance and interpreting the rationale of ratings.

  5. O problema da falácia naturalista para o projeto de uma ética evolucionista

    Directory of Open Access Journals (Sweden)

    Karla Chediak

    2006-06-01

    Full Text Available Um dos problemas mais difíceis enfrentados pelos defensores de uma ética evolucionista é a falácia naturalista. Neste artigo, analisamos as soluções propostas por W. Rottschaefer e por R. Richards e verificamos não serem elas suficientes para eliminar o problema da falácia naturalista sem comprometer a especificidade da moral.One of the most difficult problems for who defends an evolutionary ethics is the naturalist fallacy. In this article, we examine the solutions proposed by W. Rottschaefer and R. Richards. We believe that these solutions are not good enough to completely eliminate the problem of the naturalist fallacy without compromising the specificity of morality.

  6. On the importance of aqueous diffusion and electrostatic interactions in advection-dominated transport in saturated porous media

    DEFF Research Database (Denmark)

    Rolle, Massimo

    2015-01-01

    to multicomponent ionic dispersion: the dispersive fluxes of the different ions are cross-coupled due to the effects of Coulombic interactions. Such effects are illustrated in flow-through experiments in saturated porous media. Simple strong electrolytes were selected as tracers and their transport was studied...... under different advection-dominated conditions and in homogeneous and heterogeneous porous media. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion and explicitly accounting for the cross-coupling...

  7. Pollutant transport in clayey sands: reactive flows in saturated porous media and unsaturated flows

    International Nuclear Information System (INIS)

    Cadalen, Sebastien

    2008-01-01

    In the context of nuclear risk control associated to nuclear waste storage, the french nuclear agency plays an increasing role in terms of research and development in the area of subsurface contamination. This study focuses on an homogeneous porous media constituted of Fontainebleau sand and clay grains (illite) presenting sorption capacities. The modeling of the complex geometry and physical phenomena at different scales enables us to describe the average transport at Darcy's scale. The two main axes developed are the impact of an heterogeneous sorption on transport phenomena and the dispersivity of an unsaturated porous media. (author) [fr

  8. APRENDIZAJE BASADO EN PROBLEMAS Y RAZONAMIENTO BASADO EN CASOS EN LA ENSEÑANZA

    Directory of Open Access Journals (Sweden)

    Juan Pedro Febles Rodríguez

    2002-05-01

    Full Text Available

    El el trabajo se hace una valoración sobre la utilización del Razonamiento Basado en Caso, como eficaz complemento en la formación profesional del alumno de Medicina, ya que este tipo de sistema utiliza un mecanismo de razonamiento por analogías o asociaciones de forma automática, muy similar a como lo realiza el humano. Esto permitirá que ante la presentación de un problema (teniendo en cuenta los principales aspectos destacados sobre el Aprendizaje Basado en Problemas, PBL, en las distintas bases de conocimientos que se conformen y que estarán constituidas por casos reales o supuestos, prototipos y excepcionales, en número suficiente y aportadas por los profesores, quienes fungirán como expertos, los educandos busquen respuestas a sus inquietudes.

  9. Media Komunitas dan Media Literacy

    Directory of Open Access Journals (Sweden)

    Pawito .

    2013-12-01

    Full Text Available Abstract:This essay deals with community media in relation to media literacy. After a short discussion on a number of community media characters is made the essay goes further with somewhat detail theoretical presumptions of the roles of media community with respect primarily to the development as Amartya Sen mentioned about. The author suggests that community media may play some significant roles in the development including (a disseminating information (from varieties of perspective, (b facilitating public discussion, (c helping to reach solutions of problems, (d encouraging participations, and (e encouraging the development of media literacy. Regarding the last point the author remarks that media community may have a dual-roles i.e facilitating community’s member in media participation and facilitating community’s member in media education.

  10. Experiencias de utilización del método de búsqueda TABU en la resolución de problemas de organización universitaria

    Directory of Open Access Journals (Sweden)

    J.M. Tamarit

    2000-01-01

    Full Text Available A lo largo de los 10 últimos años hemos trabajado en problemas de organización académica de grandes dimensiones. En problemas universitarios hemos tratado la confección de calendarios de exámenes, la asignación de estudiantes a grupos vinculada al problema de la automatrícula y también la confección de horarios. Todos estos problemas son difíciles (NP-hard por lo que en todos los casos los algoritmos de resolución implementados han sido complejos y basados en procedimientos adaptados a cada problema. Sin embargo, en todos ellos el método de Búsqueda Tabú (Tabu Search ha constituído el elemento esencial en la obtención de buenas soluciones. En el presente trabajo exponemos algunas enseñanzas de estas experiencias. Tanto aquellos elementos que se han mostrado útiles en el conjunto de los problemas como los que han mostrado una validez diferente en los diversos casos planteados. Asimismo se examinan diferentes posibilidades de uso de los elementos del Tabú y se exponen conclusiones.

  11. INAPLICABILIDAD Y VICIOS DE FORMA: ¿UN PROBLEMA RESUELTO?

    OpenAIRE

    Verdugo Ramírez, Sergio

    2010-01-01

    La discusión acerca de la idoneidad de la acción de inaplicabilidad para revisar los vicios de forma de las leyes generados en el proceso legislativo, que existía cuando esta acción era de competencia de la Corte Suprema, aún tiene asidero. El autor, luego de revisar la reacción de la doctrina a la reforma constitucional de 2005, de la cual se muestra crítico, detecta incoherencias en las sentencias del actual Tribunal Constitucional. Luego propone un marco para solucionar el problema, el que...

  12. Internal fracture heterogeneity in discrete fracture network modelling: Effect of correlation length and textures with connected and disconnected permeability field

    Science.gov (United States)

    Frampton, A.; Hyman, J.; Zou, L.

    2017-12-01

    Analysing flow and transport in sparsely fractured media is important for understanding how crystalline bedrock environments function as barriers to transport of contaminants, with important applications towards subsurface repositories for storage of spent nuclear fuel. Crystalline bedrocks are particularly favourable due to their geological stability, low advective flow and strong hydrogeochemical retention properties, which can delay transport of radionuclides, allowing decay to limit release to the biosphere. There are however many challenges involved in quantifying and modelling subsurface flow and transport in fractured media, largely due to geological complexity and heterogeneity, where the interplay between advective and dispersive flow strongly impacts both inert and reactive transport. A key to modelling transport in a Lagrangian framework involves quantifying pathway travel times and the hydrodynamic control of retention, and both these quantities strongly depend on heterogeneity of the fracture network at different scales. In this contribution, we present recent analysis of flow and transport considering fracture networks with single-fracture heterogeneity described by different multivariate normal distributions. A coherent triad of fields with identical correlation length and variance are created but which greatly differ in structure, corresponding to textures with well-connected low, medium and high permeability structures. Through numerical modelling of multiple scales in a stochastic setting we quantify the relative impact of texture type and correlation length against network topological measures, and identify key thresholds for cases where flow dispersion is controlled by single-fracture heterogeneity versus network-scale heterogeneity. This is achieved by using a recently developed novel numerical discrete fracture network model. Furthermore, we highlight enhanced flow channelling for cases where correlation structure continues across

  13. Modeling solute transport in a heterogeneous unsaturated porous medium under dynamic boundary conditions on different spatial scales

    Science.gov (United States)

    Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel

    2013-04-01

    Understanding transport of solutes/contaminants through unsaturated soil in the shallow subsurface is vital to assess groundwater quality, nutrient cycling or to plan remediation projects. Alternating precipitation and evaporation conditions causing upward and downward flux with differing flow paths, changes in saturation and related structural heterogeneity make the description of transport in the unsaturated zone near the soil-surface a complex problem. Preferential flow paths strongly depend, among other things, on the saturation of a medium. Recent studies (e.g. Bechtold et al., 2011) showed lateral flow and solute transport during evaporation conditions (upward flux) in vertically layered sand columns. Results revealed that during evaporation water and solute are redistributed laterally from coarse to fine media deeper in the soil, and towards zones of lowest hydraulic head near to the soil surface. These zones at the surface can be coarse or fine grained depending on saturation status and evaporation flux. However, if boundary conditions are reversed and precipitation is applied, the flow field is not reversed in the same manner, resulting in entirely different transport patterns for downward and upward flow. Therefore, considering net-flow rates alone is misleading when describing transport in the shallow unsaturated zone. In this contribution, we analyze transport of a solute in the shallow subsurface to assess effects resulting from the superposition of heterogeneous soil structures and dynamic flow conditions on various spatial scales. Two-dimensional numerical simulations of unsaturated flow and transport in heterogeneous porous media under changing boundary conditions are carried out using a finite-volume code coupled to a particle tracking algorithm to quantify solute transport and leaching rates. In order to validate numerical simulations, results are qualitatively compared to those of a physical experiment (Bechtold et al., 2011). Numerical

  14. Transport of Chemotactic Bacteria in Porous Media with Structured Heterogeneity

    Science.gov (United States)

    Ford, R. M.; Wang, M.; Liu, J.; Long, T.

    2008-12-01

    Chemical contaminants that become trapped in low permeability zones (e.g. clay lenses) are difficult to remediate using conventional pump-and-treat approaches. Chemotactic bacteria that are transported by groundwater through more permeable regions may migrate toward these less permeable zones in response to chemical gradients created by contaminant diffusion from the low permeability source, thereby enhancing the remediation process by directing bacteria to the contaminants they degrade. What effect does the heterogeneity associated with coarse- and fine-grained layers that are characteristic of natural groundwater environments have on the transport of microorganisms and their chemotactic response? To address this question experiments were conducted over a range of scales from a single capillary tube to a laboratory- scale column in both static and flowing systems with and without chemoattractant gradients. In static capillary assays, motile bacteria accumulated at the interface between an aqueous solution and a suspension of agarose particulates. In microfluidic devices with an array of staggered cylinders, chemotactic bacteria migrated transverse to flow in response to a chemoattractant gradient. In sand columns packed with a coarse-grained core and surrounded by a fine-grained annulus, chemotactic bacteria migrated preferentially toward a chemoattractant source along the centerline. Mathematical models and computer simulations were developed to analyze the experimental observations in terms of transport parameters from the advection- disperson-sorption equation.

  15. Spatially resolved D-T(2) correlation NMR of porous media.

    Science.gov (United States)

    Zhang, Yan; Blümich, Bernhard

    2014-05-01

    Within the past decade, 2D Laplace nuclear magnetic resonance (NMR) has been developed to analyze pore geometry and diffusion of fluids in porous media on the micrometer scale. Many objects like rocks and concrete are heterogeneous on the macroscopic scale, and an integral analysis of microscopic properties provides volume-averaged information. Magnetic resonance imaging (MRI) resolves this spatial average on the contrast scale set by the particular MRI technique. Desirable contrast parameters for studies of fluid transport in porous media derive from the pore-size distribution and the pore connectivity. These microscopic parameters are accessed by 1D and 2D Laplace NMR techniques. It is therefore desirable to combine MRI and 2D Laplace NMR to image functional information on fluid transport in porous media. Because 2D Laplace resolved MRI demands excessive measuring time, this study investigates the possibility to restrict the 2D Laplace analysis to the sum signals from low-resolution pixels, which correspond to pixels of similar amplitude in high-resolution images. In this exploratory study spatially resolved D-T2 correlation maps from glass beads and mortar are analyzed. Regions of similar contrast are first identified in high-resolution images to locate corresponding pixels in low-resolution images generated with D-T2 resolved MRI for subsequent pixel summation to improve the signal-to-noise ratio of contrast-specific D-T2 maps. This method is expected to contribute valuable information on correlated sample heterogeneity from the macroscopic and the microscopic scales in various types of porous materials including building materials and rock. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Wave propagation simulation in the upper core of sodium-cooled fast reactors using a spectral-element method for heterogeneous media

    Science.gov (United States)

    Nagaso, Masaru; Komatitsch, Dimitri; Moysan, Joseph; Lhuillier, Christian

    2018-01-01

    ASTRID project, French sodium cooled nuclear reactor of 4th generation, is under development at the moment by Alternative Energies and Atomic Energy Commission (CEA). In this project, development of monitoring techniques for a nuclear reactor during operation are identified as a measure issue for enlarging the plant safety. Use of ultrasonic measurement techniques (e.g. thermometry, visualization of internal objects) are regarded as powerful inspection tools of sodium cooled fast reactors (SFR) including ASTRID due to opacity of liquid sodium. In side of a sodium cooling circuit, heterogeneity of medium occurs because of complex flow state especially in its operation and then the effects of this heterogeneity on an acoustic propagation is not negligible. Thus, it is necessary to carry out verification experiments for developments of component technologies, while such kind of experiments using liquid sodium may be relatively large-scale experiments. This is why numerical simulation methods are essential for preceding real experiments or filling up the limited number of experimental results. Though various numerical methods have been applied for a wave propagation in liquid sodium, we still do not have a method for verifying on three-dimensional heterogeneity. Moreover, in side of a reactor core being a complex acousto-elastic coupled region, it has also been difficult to simulate such problems with conventional methods. The objective of this study is to solve these 2 points by applying three-dimensional spectral element method. In this paper, our initial results on three-dimensional simulation study on heterogeneous medium (the first point) are shown. For heterogeneity of liquid sodium to be considered, four-dimensional temperature field (three spatial and one temporal dimension) calculated by computational fluid dynamics (CFD) with Large-Eddy Simulation was applied instead of using conventional method (i.e. Gaussian Random field). This three-dimensional numerical

  17. Problemas asociados al equilibrio en estructuras de membrana con bordes rígidos y cables

    Directory of Open Access Journals (Sweden)

    Viglialoro, G.

    2011-12-01

    Full Text Available This paper presents the equilibrium analysis of a membrane with rigid and cable boundaries for the so called prestressing phase. The idea of using membranes in Civil Engineering applications such as footbridges, a new technology being developed in Spain, implies higher structural responsibility and more accurate analysis procedure. The membrane and its boundary are respectively identified to a regular and negative gaussian curvature surface and a set of regular curves whose curvature depends on the structural elements, rigid or cable. Equilibrium is directly expressed by means of boundary differential problems, in terms of the membrane shape and its stress tensor. We must outline that membrane-cable interface equilibrium leads to take into account a singular condition that makes the problem more difficult. Therefore, starting from the equilibrium equations, two dual problems can be considered namely direct problem and dual problem. Both problems will be defined and analyzed, studying their principal qualitative aspects. Particularly, for the direct problem a numerical resolution procedure is proposed, in order to obtain practical results.

    Este trabajo aborda el análisis del equilibrio de una membrana con bordes rígidos y cables de borde para la fase de pretensado. La idea de utilizar las membranas en aplicaciones como las pasarelas, una nueva tecnología que está siendo desarrollada en España, implica niveles más altos de responsabilidad y de esfuerzos, requiriendo así un anáisis estructural ajustado. La membrana y sus bordes se identifican, respectivamente, a una superficie con curvatura de Gauss negativa y a curvas cuya curvatura depende de las características estructurales de los bordes. El equilibrio se expresa mediante problemas de contorno con ecuaciones en derivadas parciales, en términos de la forma de la membrana y de su tensor de esfuerzos, así como de la forma y las cargas de los bordes. En particular, el equilibrio

  18. Role of medium heterogeneity and viscosity contrast in miscible flow regimes and mixing zone growth: A computational pore-scale approach

    Science.gov (United States)

    Afshari, Saied; Hejazi, S. Hossein; Kantzas, Apostolos

    2018-05-01

    Miscible displacement of fluids in porous media is often characterized by the scaling of the mixing zone length with displacement time. Depending on the viscosity contrast of fluids, the scaling law varies between the square root relationship, a sign for dispersive transport regime during stable displacement, and the linear relationship, which represents the viscous fingering regime during an unstable displacement. The presence of heterogeneities in a porous medium significantly affects the scaling behavior of the mixing length as it interacts with the viscosity contrast to control the mixing of fluids in the pore space. In this study, the dynamics of the flow and transport during both unit and adverse viscosity ratio miscible displacements are investigated in heterogeneous packings of circular grains using pore-scale numerical simulations. The pore-scale heterogeneity level is characterized by the variations of the grain diameter and velocity field. The growth of mixing length is employed to identify the nature of the miscible transport regime at different viscosity ratios and heterogeneity levels. It is shown that as the viscosity ratio increases to higher adverse values, the scaling law of mixing length gradually shifts from dispersive to fingering nature up to a certain viscosity ratio and remains almost the same afterwards. In heterogeneous media, the mixing length scaling law is observed to be generally governed by the variations of the velocity field rather than the grain size. Furthermore, the normalization of mixing length temporal plots with respect to the governing parameters of viscosity ratio, heterogeneity, medium length, and medium aspect ratio is performed. The results indicate that mixing length scales exponentially with log-viscosity ratio and grain size standard deviation while the impact of aspect ratio is insignificant. For stable flows, mixing length scales with the square root of medium length, whereas it changes linearly with length during

  19. Aggiornamento cartografico speditivo Un problema di cultura o mancanza di strumenti?

    Directory of Open Access Journals (Sweden)

    Redazione Redazione

    2006-10-01

    Full Text Available Il problema dell’aggiornamento cartografico e’ un tema che tocca una comunità molto estesa, le cui componenti vanno dai singoli professionisti come urbanisti, progettisti ambientali, progettisti di infrastrutture, alla maggior parte degli uffici tecnici della Pubblica Amministrazione locale e centrale. Nel corso del breve articolo affronteremo il tema specifico dell’aggiornamento cartografico speditivo, altrimenti definibile come aggiornamento cartografico di limitate dimensioni.

  20. Conceptualizing Media Generations: the Print-, Online- and Individualized Generations

    DEFF Research Database (Denmark)

    Westlund, Oscar; A Färdigh, Mathias

    2012-01-01

    During the 1990s news publishers established an online presence and in the 2000s they developed cross-media news work. This has resulted in changing news accessing habits, with varied magnitude among generations. This article aims to construct theoretically sound news media generations, through...... statistical analysis of data from a nationally representative scientific omnibus survey conducted in 2010. Firstly the article presents a descriptive and explanatory analysis of how eight generational cohorts utilize news in print and/or online and/or mobile. Secondly these findings are used for merging...... highest of online only news accessing (Pearson’s r = .135). The heterogeneous news usage patterns exhibited by the individualized generation (1980s-1990s) were accommodated for by two cohorts. The online cohort shows high probability for online-only news usage (49%) and a positive correlation (Pearson’s r...