Science.gov

Sample records for process transition models

  1. The clinical practice developmental model: the transition process.

    PubMed

    Nuccio, S A; Lingen, D; Burke, L J; Kramer, A; Ladewig, N; Raaum, J; Shearer, B

    1996-12-01

    The authors report their hospital's experience in replicating Benner's novice-to-expert clinical nursing practice model, called the Clinical Practice Developmental Model. The authors describe the outcomes of an exploratory, qualitative study conducted to understand staff nurses' perceptions of their transition experience from a traditional clinical ladder for advancement and recognition to the theoretically based clinical practice developmental model. The findings of this study identify critical factors that influenced nurses' perceptions and describe positive and negative outcomes of transition. Specific recommendations to facilitate organizational changes for the nurse executive and the individual nurse are discussed. PMID:8968322

  2. The spatial pattern of transition (spot): linking pattern, process, and scale to state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field implementation of conceptual state-and-transition models will benefit from explicit representations of spatial patterns of vegetation, soils and topography and the hydrological/eolian processes that link them. Here, we introduce the concept "spatial pattern of transition” (SPOT) as a means to ...

  3. Teacher in Transition: A Model of One Teacher's Change Process.

    ERIC Educational Resources Information Center

    Mahurt, Sarah Fleming

    Change in teaching practice is a popular theme in literacy education. A case study examined the nature of the change process in a teacher in a large Caribbean island school district who made a personal decision to change instructional practices from skills-based methods to whole language methods. Through data collection and analysis, a metaphor,…

  4. Transit Model Fitting in Processing Four Years of Kepler Science Data: New Features and Performance

    NASA Astrophysics Data System (ADS)

    Li, Jie; Burke, Christopher; Jenkins, Jon Michael; Quintana, Elisa; Rowe, Jason; Seader, Shawn; Tenenbaum, Peter; Twicken, Joseph

    2015-08-01

    We present new transit model fitting features and performance of the latest release (9.3, March 2015) of the Kepler Science Operations Center (SOC) Pipeline, which will be used for the final processing of four years of Kepler science data later this year. Threshold Crossing Events (TCEs), which represent transiting planet detections, are generated by the Transiting Planet Search (TPS) component of the pipeline and subsequently processed in the Data Validation (DV) component. The transit model is used in DV to fit TCEs and derive parameters that are used in various diagnostic tests to validate the planet detections. The standard limb-darkened transit model includes five fit parameters: transit epoch time (i.e. central time of first transit), orbital period, impact parameter, ratio of planet radius to star radius and ratio of semi-major axis to star radius. In the latest Kepler SOC pipeline codebase, the light curve of the target for which a TCE is generated is also fitted by a trapezoidal transit model with four parameters: transit epoch time, depth, duration and ratio of ingress time to duration. The fitted trapezoidal transit model is used in the diagnostic tests when the fit with the standard transit model fails or when the fit is not performed, e.g. for suspected eclipsing binaries. Additional parameters, such as the equilibrium temperature and effective stellar flux (i.e. insolation) of the planet candidate, are derived from the transit model fit parameters to characterize pipeline candidates for the search of Earth-size planets in the habitable zone. The uncertainties of all derived parameters are updated in the latest codebase to account for the propagated errors of the fit parameters as well as the uncertainties in stellar parameters. The results of the transit model fitting for the TCEs identified by the Kepler SOC Pipeline are included in the DV reports and one-page report summaries, which are accessible by the science community at NASA Exoplanet Archive

  5. Performance of Transit Model Fitting in Processing Four Years of Kepler Science Data

    NASA Astrophysics Data System (ADS)

    Li, Jie; Burke, Christopher J.; Jenkins, Jon Michael; Quintana, Elisa V.; Rowe, Jason; Seader, Shawn; Tenenbaum, Peter; Twicken, Joseph D.

    2014-06-01

    We present transit model fitting performance of the Kepler Science Operations Center (SOC) Pipeline in processing four years of science data, which were collected by the Kepler spacecraft from May 13, 2009 to May 12, 2013. Threshold Crossing Events (TCEs), which represent transiting planet detections, are generated by the Transiting Planet Search (TPS) component of the pipeline and subsequently processed in the Data Validation (DV) component. The transit model is used in DV to fit TCEs and derive parameters that are used in various diagnostic tests to validate planetary candidates. The standard transit model includes five fit parameters: transit epoch time (i.e. central time of first transit), orbital period, impact parameter, ratio of planet radius to star radius and ratio of semi-major axis to star radius. In the latest Kepler SOC pipeline codebase, the light curve of the target for which a TCE is generated is initially fitted by a trapezoidal model with four parameters: transit epoch time, depth, duration and ingress time. The trapezoidal model fit, implemented with repeated Levenberg-Marquardt minimization, provides a quick and high fidelity assessment of the transit signal. The fit parameters of the trapezoidal model with the minimum chi-square metric are converted to set initial values of the fit parameters of the standard transit model. Additional parameters, such as the equilibrium temperature and effective stellar flux of the planet candidate, are derived from the fit parameters of the standard transit model to characterize pipeline candidates for the search of Earth-size planets in the Habitable Zone. The uncertainties of all derived parameters are updated in the latest codebase to take into account for the propagated errors of the fit parameters as well as the uncertainties in stellar parameters. The results of the transit model fitting of the TCEs identified by the Kepler SOC Pipeline, including fitted and derived parameters, fit goodness metrics and

  6. Generalized Hammersley Process and Phase Transition for Activated Random Walk Models

    NASA Astrophysics Data System (ADS)

    Rolla, Leonardo T.

    2008-12-01

    * ACTIVATED RANDOM WALK MODEL * This is a conservative particle system on the lattice, with a Markovian continuous-time evolution. Active particles perform random walks without interaction, and they may as well change their state to passive, then stopping to jump. When particles of both types occupy the same site, they all become active. This model exhibits phase transition in the sense that for low initial densities the system locally fixates and for high densities it keeps active. Though extensively studied in the physics literature, the matter of giving a mathematical proof of such phase transition remained as an open problem for several years. In this work we identify some variables that are sufficient to characterize fixation and at the same time are stochastically monotone in the model's parameters. We employ an explicit graphical representation in order to obtain the monotonicity. With this method we prove that there is a unique phase transition for the one-dimensional finite-range random walk. Joint with V. Sidoravicius. * BROKEN LINE PROCESS * We introduce the broken line process and derive some of its properties. Its discrete version is presented first and a natural generalization to the continuum is then proposed and studied. The broken lines are related to the Young diagram and the Hammersley process and are useful for computing last passage percolation values and finding maximal oriented paths. For a class of passage time distributions there is a family of boundary conditions that make the process stationary and reversible. One application is a simple proof of the explicit law of large numbers for last passage percolation with exponential and geometric distributions. Joint with V. Sidoravicius, D. Surgailis, and M. E. Vares.

  7. Limited ability driven phase transitions in the coevolution process in Axelrod's model

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Han, Yuexing; Chen, Luonan; Aihara, Kazuyuki

    2009-04-01

    We study the coevolution process in Axelrod's model by taking into account of agents' abilities to access information, which is described by a parameter α to control the geographical range of communication. We observe two kinds of phase transitions in both cultural domains and network fragments, which depend on the parameter α. By simulation, we find that not all rewiring processes pervade the dissemination of culture, that is, a very limited ability to access information constrains the cultural dissemination, while an exceptional ability to access information aids the dissemination of culture. Furthermore, by analyzing the network characteristics at the frozen states, we find that there exists a stage at which the network develops to be a small-world network with community structures.

  8. The Application of Global Kinetic Models to HMX Beta-Delta Transition and Cookoff Processes

    SciTech Connect

    Wemhoff, A P; Burnham, A K; Nichols III, A L

    2006-12-07

    The reduction of the number of reactions in kinetic models for both the HMX beta-delta phase transition and thermal cookoff provides an attractive alternative to traditional multi-stage kinetic models due to reduced calibration effort requirements. In this study, we use the LLNL code ALE3D to provide calibrated kinetic parameters for a two-reaction bidirectional beta-delta HMX phase transition model based on Sandia Instrumented Thermal Ignition (SITI) and Scaled Thermal Explosion (STEX) temperature history curves, and a Prout-Tompkins cookoff model based on One-Dimensional Time to Explosion (ODTX) data. Results show that the two-reaction bidirectional beta-delta transition model presented here agrees as well with STEX and SITI temperature history curves as a reversible four-reaction Arrhenius model, yet requires an order of magnitude less computational effort. In addition, a single-reaction Prout-Tompkins model calibrated to ODTX data provides better agreement with ODTX data than a traditional multi-step Arrhenius model, and can contain up to 90% less chemistry-limited time steps for low-temperature ODTX simulations. Manual calibration methods for the Prout-Tompkins kinetics provide much better agreement with ODTX experimental data than parameters derived from Differential Scanning Calorimetry (DSC) measurements at atmospheric pressure. The predicted surface temperature at explosion for STEX cookoff simulations is a weak function of the cookoff model used, and a reduction of up to 15% of chemistry-limited time steps can be achieved by neglecting the beta-delta transition for this type of simulation. Finally, the inclusion of the beta-delta transition model in the overall kinetics model can affect the predicted time to explosion by 1% for the traditional multi-step Arrhenius approach, while up to 11% using a Prout-Tompkins cookoff model.

  9. Modeling Relations among Discrete Developmental Processes: A General Approach to Associative Latent Transition Analysis

    ERIC Educational Resources Information Center

    Bray, Bethany C.; Lanza, Stephanie T.; Collins, Linda M.

    2010-01-01

    To understand one developmental process, it is often helpful to investigate its relations with other developmental processes. Statistical methods that model development in multiple processes simultaneously over time include latent growth curve models with time-varying covariates, multivariate latent growth curve models, and dual trajectory models.…

  10. Models for transition clinics.

    PubMed

    Carrizosa, Jaime; An, Isabelle; Appleton, Richard; Camfield, Peter; Von Moers, Arpad

    2014-08-01

    Transition is a purposeful, planned process that addresses the medical, psychosocial, educational, and vocational needs of adolescents and young adults with chronic medical conditions, as they advance from a pediatric and family-centered to an adult, individual focused health care provider. This article describes some of the models for transition clinics or services for epilepsy in five countries (Canada, France, Colombia, Germany, and the United Kingdom). These models include joint adult and pediatric clinics, algorithm-driven service, and a check list system in the context of pediatric care. Evaluation of these models is limited, and it is not possible to choose an optimal program. The attitude and motivation of health care providers may be the most important elements. PMID:25209087

  11. Dynamics model of the IBR-2M pulsed reactor for analysis of fast transition processes

    NASA Astrophysics Data System (ADS)

    Pepelyshev, Yu. N.; Popov, A. K.; Sumkhuu, D.; Sangaa, D.

    2015-05-01

    A nonlinear model of the IBR-2M pulsed reactor dynamics relating values of variables at discreet instants of time (when power pulses appear) is developed on the basis of the MATLAB program system. The tests of the model by simulating calculated processes in the IBR-2M reactor proved the correctness of the model. A tentative estimate of the transfer coefficient for the linear part of the automatic regulator is obtained.

  12. PyTransit: Transit light curve modeling

    NASA Astrophysics Data System (ADS)

    Parviainen, Hannu

    2015-05-01

    PyTransit implements optimized versions of the Giménez and Mandel & Agol transit models for exoplanet transit light-curves. The two models are implemented natively in Fortran with OpenMP parallelization, and are accessed by an object-oriented python interface. PyTransit facilitates the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations. It offers efficient model evaluation for multicolour observations and transmission spectroscopy, built-in supersampling to account for extended exposure times, and routines to calculate the projected planet-to-star distance for circular and eccentric orbits, transit durations, and more.

  13. Phase transitions in multiplicative competitive processes

    SciTech Connect

    Shimazaki, Hideaki; Niebur, Ernst

    2005-07-01

    We introduce a discrete multiplicative process as a generic model of competition. Players with different abilities successively join the game and compete for finite resources. Emergence of dominant players and evolutionary development occur as a phase transition. The competitive dynamics underlying this transition is understood from a formal analogy to statistical mechanics. The theory is applicable to bacterial competition, predicting novel population dynamics near criticality.

  14. UTM: Universal Transit Modeller

    NASA Astrophysics Data System (ADS)

    Deeg, Hans J.

    2014-12-01

    The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.

  15. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-01

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2-6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  16. State and transition models: Theory, applications, and challenges. In: Briske, D.D. Rangeland Systems: Processes, Management and Challenges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State and transition models (STMs) are used for communicating about ecosystem change in rangelands and other ecosystems, especially the implications for management. The fundamental premise that rangelands can exhibit multiple states is now widely accepted. The current application of STMs for managem...

  17. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    SciTech Connect

    Ren, X. D. Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-05

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  18. Conducting a Labor Market Trend Analysis: Process and Results. Working Paper 85-3. COMPETE: Community-Based Model for Public-School Exit and Transition to Employment.

    ERIC Educational Resources Information Center

    Sitlington, Patricia L.; Easterday, Joseph R.

    The purpose of Project COMPETE is to use previous research and exemplary practices to develop and validate a model and training sequence to assist retarded youth to make the transition from school to employment in the most competitive environment possible. This project working paper describes the process of using existing information sources to…

  19. Hidden percolation transition in kinetic replication process

    NASA Astrophysics Data System (ADS)

    Timonin, P. N.; Chitov, G. Y.

    2015-04-01

    The one-dimensional kinetic contact process with parallel update is introduced and studied by the mean-field approximation and Monte Carlo (MC) simulations. Contrary to a more conventional scenario with single active phase for 1d models with Ising-like variables, we find two different adjacent active phases in the parameter space of the proposed model with a second-order transition between them and a multiphase point where the active and the absorbing phases meet. While one of the active phases is quite standard with a smooth average filling of the space-time lattice, the second active phase demonstrates a very subtle (hidden) percolating order which becomes manifest only after certain transformation from the original model. We determine the percolation order parameter for active-active phase transition and discuss such hidden orders in other low-dimensional systems. Our MC data demonstrate finite-size critical and near-critical scaling of the order parameter relaxation for the two phase transitions. We find three independent critical indices for them and conclude that they both belong to the directed percolation universality class.

  20. Exoplanet Transit Database. Reduction and processing of the photometric data of exoplanet transits

    NASA Astrophysics Data System (ADS)

    Poddaný, Stanislav; Brát, Luboš; Pejcha, Ondřej

    2010-03-01

    We demonstrate the newly developed resource for exoplanet researchers - The Exoplanet Transit Database. This database is designed to be a web application and it is open for any exoplanet observer. It came on-line in September 2008. The ETD consists of three individual sections. One serves for predictions of the transits, the second one for processing and uploading new data from the observers. We use a simple analytical model of the transit to calculate the central time of transit, its duration and the depth of the transit. These values are then plotted into the observed-computed diagrams (O-C), that represent the last part of the application.

  1. Modelling the transitional boundary layer

    NASA Technical Reports Server (NTRS)

    Narasimha, R.

    1990-01-01

    Recent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone.

  2. Transition-Independent Decentralized Markov Decision Processes

    NASA Technical Reports Server (NTRS)

    Becker, Raphen; Silberstein, Shlomo; Lesser, Victor; Goldman, Claudia V.; Morris, Robert (Technical Monitor)

    2003-01-01

    There has been substantial progress with formal models for sequential decision making by individual agents using the Markov decision process (MDP). However, similar treatment of multi-agent systems is lacking. A recent complexity result, showing that solving decentralized MDPs is NEXP-hard, provides a partial explanation. To overcome this complexity barrier, we identify a general class of transition-independent decentralized MDPs that is widely applicable. The class consists of independent collaborating agents that are tied up by a global reward function that depends on both of their histories. We present a novel algorithm for solving this class of problems and examine its properties. The result is the first effective technique to solve optimally a class of decentralized MDPs. This lays the foundation for further work in this area on both exact and approximate solutions.

  3. Soil, resilience, and state and transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State and transition models are based on the assumption that less resilient systems are more susceptible to state changes. The objective of this paper is to show how two different types of soil properties contribute to resilience through their direct and indirect effects on ecosystem processes, and ...

  4. Hybrid Percolation Transition in Cluster Merging Processes: Continuously Varying Exponents.

    PubMed

    Cho, Y S; Lee, J S; Herrmann, H J; Kahng, B

    2016-01-15

    Consider growing a network, in which every new connection is made between two disconnected nodes. At least one node is chosen randomly from a subset consisting of g fraction of the entire population in the smallest clusters. Here we show that this simple strategy for improving connection exhibits a more unusual phase transition, namely a hybrid percolation transition exhibiting the properties of both first-order and second-order phase transitions. The cluster size distribution of finite clusters at a transition point exhibits power-law behavior with a continuously varying exponent τ in the range 2<τ(g)≤2.5. This pattern reveals a necessary condition for a hybrid transition in cluster aggregation processes, which is comparable to the power-law behavior of the avalanche size distribution arising in models with link-deleting processes in interdependent networks. PMID:26824550

  5. Application of Glass Transition in Food Processing.

    PubMed

    Balasubramanian, S; Devi, Apramita; Singh, K K; Bosco, S J D; Mohite, Ashish M

    2016-04-25

    The phenomenon of glass transition has been employed to food products to study their stability. It can be applied as an integrated approach along with water activity and physical and chemical changes in food in processing and storage to determine the food stability. Also associated with the changes during agglomeration crystallization, caking, sticking, collapse, oxidation reactions, nonenzymatic browning, and microbial stability of food system. Various techniques such as Differential Scanning Calorimetry, Nuclear Magnetic Resonance, etc. have been developed to determine the glass transition temperature (Tg) of food system. Also, various theories have been applied to explain the concept of Tg and its relation to changes in food system. This review summarizes the understanding of concept of glass transition, its measurement, and application in food technology. PMID:25118113

  6. Discontinuous transition in a boundary driven contact process

    NASA Astrophysics Data System (ADS)

    Costa, A.; Blythe, R. A.; Evans, M. R.

    2010-09-01

    The contact process is a stochastic process which exhibits a continuous, absorbing state phase transition in the directed percolation (DP) universality class. In this work, we consider a contact process with a bias in conjunction with an active wall. This model exhibits waves of activity emanating from the active wall and, when the system is supercritical, propagating indefinitely as travelling (Fisher) waves. In the subcritical phase the activity is localized near the wall. We study the phase transition numerically and show that certain properties of the system, notably the wave velocity, are discontinuous across the transition. Using a modified Fisher equation to model the system we elucidate the mechanism by which the discontinuity arises. Furthermore we establish relations between properties of the travelling wave and DP critical exponents.

  7. A Latent Transition Model with Logistic Regression

    ERIC Educational Resources Information Center

    Chung, Hwan; Walls, Theodore A.; Park, Yousung

    2007-01-01

    Latent transition models increasingly include covariates that predict prevalence of latent classes at a given time or transition rates among classes over time. In many situations, the covariate of interest may be latent. This paper describes an approach for handling both manifest and latent covariates in a latent transition model. A Bayesian…

  8. Transit Model Fitting in the Kepler Science Operations Center Pipeline

    NASA Astrophysics Data System (ADS)

    Li, Jie; Burke, C. J.; Jenkins, J. M.; Quintana, E. V.; Rowe, J. F.; Seader, S. E.; Tenenbaum, P.; Twicken, J. D.

    2012-05-01

    We describe the algorithm and performance of the transit model fitting of the Kepler Science Operations Center (SOC) Pipeline. Light curves of long cadence targets are subjected to the Transiting Planet Search (TPS) component of the Kepler SOC Pipeline. Those targets for which a Threshold Crossing Event (TCE) is generated in the transit search are subsequently processed in the Data Validation (DV) component. The light curves may span one or more Kepler observing quarters, and data may not be available for any given target in all quarters. Transit model parameters are fitted in DV to transit-like signatures in the light curves of target stars with TCEs. The fitted parameters are used to generate a predicted light curve based on the transit model. The residual flux time series of the target star, with the predicted light curve removed, is fed back to TPS to search for additional TCEs. The iterative process of transit model fitting and transiting planet search continues until no TCE is generated from the residual flux time series or a planet candidate limit is reached. The transit model includes five parameters to be fitted: transit epoch time (i.e. central time of first transit), orbital period, impact parameter, ratio of planet radius to star radius and ratio of semi-major axis to star radius. The initial values of the fit parameters are determined from the TCE values provided by TPS. A limb darkening model is included in the transit model to generate the predicted light curve. The transit model fitting results are used in the diagnostic tests in DV, such as the centroid motion test, eclipsing binary discrimination tests, etc., which helps to validate planet candidates and identify false positive detections. Funding for the Kepler Mission has been provided by the NASA Science Mission Directorate.

  9. Phase transitions in contagion processes mediated by recurrent mobility patterns

    NASA Astrophysics Data System (ADS)

    Balcan, Duygu; Vespignani, Alessandro

    2011-07-01

    Human mobility and activity patterns mediate contagion on many levels, including the spatial spread of infectious diseases, diffusion of rumours, and emergence of consensus. These patterns however are often dominated by specific locations and recurrent flows and poorly modelled by the random diffusive dynamics generally used to study them. Here we develop a theoretical framework to analyse contagion within a network of locations where individuals recall their geographic origins. We find a phase transition between a regime in which the contagion affects a large fraction of the system and one in which only a small fraction is affected. This transition cannot be uncovered by continuous deterministic models because of the stochastic features of the contagion process and defines an invasion threshold that depends on mobility parameters, providing guidance for controlling contagion spread by constraining mobility processes. We recover the threshold behaviour by analysing diffusion processes mediated by real human commuting data.

  10. The Community Transition Center (CTC) Model.

    ERIC Educational Resources Information Center

    Coker, Charles C.; Costello, James

    This paper describes the Community Transition Center (CTC) model, being tested in six districts in rural Wisconsin. The model is a way of conceptualizing and organizing the employment-related needs of mainstreamed mildly handicapped youths who are exiting secondary schools. The model emphasizes the role of secondary school transition programming,…

  11. Presidential Transition Teams: Fostering a Collaborative Transition Process

    ERIC Educational Resources Information Center

    Artman, Richard B.; Franz, Mark

    2009-01-01

    Whether hiring a sitting president or one beginning a first presidency, the board of trustees should be keenly interested in ensuring that the new president's first months in office flow as smoothly as possible. Increasing attention has been paid in recent years to the idea of using a transition team to assist the new president. Using a transition…

  12. Phase transitions in Hidden Markov Models

    NASA Astrophysics Data System (ADS)

    Bechhoefer, John; Lathouwers, Emma

    In Hidden Markov Models (HMMs), a Markov process is not directly accessible. In the simplest case, a two-state Markov model ``emits'' one of two ``symbols'' at each time step. We can think of these symbols as noisy measurements of the underlying state. With some probability, the symbol implies that the system is in one state when it is actually in the other. The ability to judge which state the system is in sets the efficiency of a Maxwell demon that observes state fluctuations in order to extract heat from a coupled reservoir. The state-inference problem is to infer the underlying state from such noisy measurements at each time step. We show that there can be a phase transition in such measurements: for measurement error rates below a certain threshold, the inferred state always matches the observation. For higher error rates, there can be continuous or discontinuous transitions to situations where keeping a memory of past observations improves the state estimate. We can partly understand this behavior by mapping the HMM onto a 1d random-field Ising model at zero temperature. We also present more recent work that explores a larger parameter space and more states. Research funded by NSERC, Canada.

  13. Correcting transit time distributions in coarse MODFLOW-MODPATH models.

    PubMed

    Abrams, Daniel

    2013-01-01

    In low to medium resolution MODFLOW models, the area occupied by sink cells often far exceeds the surface area of the streams they represent. As a result, MODPATH will calculate inaccurate particle traces and transit times. A frequency distribution of transit times for a watershed will also be in error. Such a distribution is used to assess the long-term impact of nonpoint source pollution on surface waters and wells. Although the inaccuracies for individual particles can only be avoided by increased model grid resolution or other advanced modeling techniques, the frequency distribution can be improved by scaling the particle transit times by an adjustment factor during post-processing. PMID:22974377

  14. Semiclassical theory of electronically nonadiabatic transitions in molecular collision processes

    NASA Technical Reports Server (NTRS)

    Lam, K. S.; George, T. F.

    1979-01-01

    An introductory account of the semiclassical theory of the S-matrix for molecular collision processes is presented, with special emphasis on electronically nonadiabatic transitions. This theory is based on the incorporation of classical mechanics with quantum superposition, and in practice makes use of the analytic continuation of classical mechanics into the complex space of time domain. The relevant concepts of molecular scattering theory and related dynamical models are described and the formalism is developed and illustrated with simple examples - collinear collision of the A+BC type. The theory is then extended to include the effects of laser-induced nonadiabatic transitions. Two bound continuum processes collisional ionization and collision-induced emission also amenable to the same general semiclassical treatment are discussed.

  15. A Correlation-Based Transition Model using Local Variables. Part 1; Model Formation

    NASA Technical Reports Server (NTRS)

    Menter, F. R.; Langtry, R. B.; Likki, S. R.; Suzen, Y. B.; Huang, P. G.; Volker, S.

    2006-01-01

    A new correlation-based transition model has been developed, which is based strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) approaches, such as unstructured grids and massive parallel execution. The model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models) but from a framework for the implementation of correlation-based models into general-purpose CFD methods.

  16. Modelling of phase transitions: do it yourself

    NASA Astrophysics Data System (ADS)

    Medved', I.; Huckaby, D. A.; Trník, A.; Valovičová, L'

    2013-01-01

    We present the basics of a powerful contemporary statistical mechanical technique that can be used by students to explore first-order phase transitions by themselves and for models of their own construction. The technique is a generalization of the well-known Peierls argument and is applicable to various models on a lattice. We illustrate the technique with the help of two simple models that were recently used to simulate phase transitions on surfaces.

  17. Mathematical modeling and investigations of the processes of heat conduction of ammonium perchlorate with phase transitions in thermal decomposition and gasification

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. V.; Lagun, I. M.; Polyakov, E. P.

    2013-01-01

    Transient heat-conduction processes occurring in the period of thermal decomposition and gasification of a crystalline oxidant — ammonium perchlorate — have been investigated and analyzed on the basis of the developed mathematical model.

  18. Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes

    NASA Astrophysics Data System (ADS)

    Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem

    2014-02-01

    The Gd5Ge2Si2 alloy and the off-stoichiometric Ni50Mn35In15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd5Ge2Si2 and Ni50Mn35In15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis.

  19. Phase Transitions in Models of Bird Flocking

    NASA Astrophysics Data System (ADS)

    Christodoulidi, H.; van der Weele, K.; Antonopoulos, Ch. G.; Bountis, T.

    2014-12-01

    The aim of the present paper is to elucidate the transition from collective to random behavior exhibited by various mathematical models of bird flocking. In particular, we compare Vicsek's model [Vicsek et al., Phys. Rev. Lett. 75, 1226-1229 (1995)] with one based on topological considerations. The latter model is found to exhibit a first order phase transition from flocking to decoherence, as the "noise parameter" of the problem is increased, whereas Vicsek's model gives a second order transition. Refining the topological model in such a way that birds are influenced mostly by the birds in front of them, less by the ones at their sides and not at all by those behind them (because they do not see them), we find a behavior that lies in between the two models. Finally, we propose a novel mechanism for preserving the flock's cohesion, without imposing artificial boundary conditions or attractive forces.

  20. Factors and processes in children's transitive deductions

    PubMed Central

    Wright, Barlow C.; Smailes, Jennifer

    2015-01-01

    Transitive tasks are important for understanding how children develop socio-cognitively. However, developmental research has been restricted largely to questions surrounding maturation. We asked 6-, 7- and 8-year-olds (N = 117) to solve a composite of five different transitive tasks. Tasks included conditions asking about item-C (associated with the marked relation) in addition to the usual case of asking only about item-A (associated with the unmarked relation). Here, children found resolving item-C much easier than resolving item-A, a finding running counter to long-standing assumptions about transitive reasoning. Considering gender perhaps for the first time, boys exhibited higher transitive scores than girls overall. Finally, analysing in the context of one recent and well-specified theory of spatial transitive reasoning, we generated the prediction that reporting the full series should be easier than deducing any one item from that series. This prediction was not upheld. We discuss amendments necessary to accommodate all our earlier findings. PMID:26635950

  1. Application of epidemic models to phase transitions

    NASA Astrophysics Data System (ADS)

    Bilge, A. H.; Pekcan, Ö.; Gürol, M. V.

    2012-11-01

    The Susceptible-Infected-Recovered (SIR) and Susceptible-Exposed-Infected-Recovered (SEIR) models describe the spread of epidemics in a society. In the typical case, the ratio of the susceptible individuals fall from a value S 0 close to 1 to a final value Sf , while the ratio of recovered individuals rise from 0 to Rf = 1 - Sf . The sharp passage from the level zero to the level Rf allows also the modeling of phase transitions by the number of "recovered" individuals R(t) of the SIR or SEIR model. In this article, we model the sol-gel transition for polyacrylamide-sodium alginate (SA) composite with different concentrations of SA as SIR and SEIR dynamical systems by solving the corresponding differential equations numerically and we show that the phase transitions of "classical" and "percolation" types are represented, respectively, by the SEIR and SIR models.

  2. A Process for Transition to Sustainability: Implementation

    ERIC Educational Resources Information Center

    Wooltorton, Sandra; Palmer, Marilyn; Steele, Fran

    2011-01-01

    This paper reports the outcomes of the second action cycle of an ongoing project at Edith Cowan University (ECU) called "Transition to Sustainability: ECU South West" which is located in a small, single faculty regional university campus. The overall project has comprised three action research cycles, the first of which was the planning cycle…

  3. Modeling continuum of epithelial mesenchymal transition plasticity.

    PubMed

    Mandal, Mousumi; Ghosh, Biswajoy; Anura, Anji; Mitra, Pabitra; Pathak, Tanmaya; Chatterjee, Jyotirmoy

    2016-02-01

    Living systems respond to ambient pathophysiological changes by altering their phenotype, a phenomenon called 'phenotypic plasticity'. This program contains information about adaptive biological dynamism. Epithelial-mesenchymal transition (EMT) is one such process found to be crucial in development, wound healing, and cancer wherein the epithelial cells with restricted migratory potential develop motile functions by acquiring mesenchymal characteristics. In the present study, phase contrast microscopy images of EMT induced HaCaT cells were acquired at 24 h intervals for 96 h. The expression study of relevant pivotal molecules viz. F-actin, vimentin, fibronectin and N-cadherin was carried out to confirm the EMT process. Cells were intuitively categorized into five distinct morphological phenotypes. A population of 500 cells for each temporal point was selected to quantify their frequency of occurrence. The plastic interplay of cell phenotypes from the observations was described as a Markovian process. A model was formulated empirically using simple linear algebra, to depict the possible mechanisms of cellular transformation among the five phenotypes. This work employed qualitative, semi-quantitative and quantitative tools towards illustration and establishment of the EMT continuum. Thus, it provides a newer perspective to understand the embedded plasticity across the EMT spectrum. PMID:26762753

  4. Modeling and Fitting Exoplanet Transit Light Curves

    NASA Astrophysics Data System (ADS)

    Millholland, Sarah; Ruch, G. T.

    2013-01-01

    We present a numerical model along with an original fitting routine for the analysis of transiting extra-solar planet light curves. Our light curve model is unique in several ways from other available transit models, such as the analytic eclipse formulae of Mandel & Agol (2002) and Giménez (2006), the modified Eclipsing Binary Orbit Program (EBOP) model implemented in Southworth’s JKTEBOP code (Popper & Etzel 1981; Southworth et al. 2004), or the transit model developed as a part of the EXOFAST fitting suite (Eastman et al. in prep.). Our model employs Keplerian orbital dynamics about the system’s center of mass to properly account for stellar wobble and orbital eccentricity, uses a unique analytic solution derived from Kepler’s Second Law to calculate the projected distance between the centers of the star and planet, and calculates the effect of limb darkening using a simple technique that is different from the commonly used eclipse formulae. We have also devised a unique Monte Carlo style optimization routine for fitting the light curve model to observed transits. We demonstrate that, while the effect of stellar wobble on transit light curves is generally small, it becomes significant as the planet to stellar mass ratio increases and the semi-major axes of the orbits decrease. We also illustrate the appreciable effects of orbital ellipticity on the light curve and the necessity of accounting for its impacts for accurate modeling. We show that our simple limb darkening calculations are as accurate as the analytic equations of Mandel & Agol (2002). Although our Monte Carlo fitting algorithm is not as mathematically rigorous as the Markov Chain Monte Carlo based algorithms most often used to determine exoplanetary system parameters, we show that it is straightforward and returns reliable results. Finally, we show that analyses performed with our model and optimization routine compare favorably with exoplanet characterizations published by groups such as the

  5. The R-γ transition prediction model

    NASA Astrophysics Data System (ADS)

    Goldberg, Uriel C.; Batten, Paul; Peroomian, Oshin; Chakravarthy, Sukumar

    2015-01-01

    The Rt turbulence closure (Goldberg 2003) is coupled with an intermittency transport equation, γ, to enable prediction of laminar-to-turbulent flow by-pass transition. The model is not correlation-based and is completely topography-parameter-free, thus ready for use in parallelized Computational Fluid Dynamics (CFD) solvers based on unstructured book-keeping. Several examples compare the R-γ model's performance with experimental data and with predictions by the Langtry-Menter γ-Reθ transition closure (2009). Like the latter, the R-γ model is very sensitive to freestream turbulence levels, limiting its utility for engineering purposes.

  6. Operationalizing resilience using state and transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In management, restoration, and policy contexts, the notion of resilience can be confusing. Systematic development of conceptual models of ecological state change (state transition models; STMs) can help overcome semantic confusion and promote a mechanistic understanding of resilience. Drawing on ex...

  7. Transitional Employment Experimental Model (TEEM). Final Report.

    ERIC Educational Resources Information Center

    California State Personnel Board, Sacramento.

    The final report of the Transitional Employemnt Experimental Model (TEEM) Project, a research and development project providing a potential model for a large scale manpower absorption program in times of economic need, is presented. One major purpose of the project was to demonstrate the viability of providing suitable job placement for the…

  8. Transition mixing study empirical model report

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; White, C.

    1988-01-01

    The empirical model developed in the NASA Dilution Jet Mixing Program has been extended to include the curvature effects of transition liners. This extension is based on the results of a 3-D numerical model generated under this contract. The empirical model results agree well with the numerical model results for all tests cases evaluated. The empirical model shows faster mixing rates compared to the numerical model. Both models show drift of jets toward the inner wall of a turning duct. The structure of the jets from the inner wall does not exhibit the familiar kidney-shaped structures observed for the outer wall jets or for jets injected in rectangular ducts.

  9. A Model of Mental State Transition Network

    NASA Astrophysics Data System (ADS)

    Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo

    Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.

  10. A Conceptual Model Facilitating the Transition of Involuntary Migrant Families

    PubMed Central

    Samarasinghe, Kerstin Linnéa

    2011-01-01

    Refugee families face a complex transition due to the nature of involuntary migration and the process of acculturation. There are several risk factors to the family adaptation process during the transition period, which are sociocontextually environmental dependant. Facilitating a healthy transition for refugee families, therefore, requires the role of nursing to incorporate sociopolitics into the discipline. This paper introduces a sociopolitically oriented and community-driven assessment and intervention model which is based on a family systematic approach. Interventions that aid the families in their acculturation process as well as empowers them to a well-functioning daily life, as per the SARFI model, should be adopted. As such, the future of nursing may provide additional primary health care services for refugee families; this is through a team-led “family nurse” who provides quality care for the family unit in collaboration with other health care professionals and societal authorities. PMID:22191055

  11. Explosive percolation: Unusual transitions of a simple model

    NASA Astrophysics Data System (ADS)

    Bastas, N.; Giazitzidis, P.; Maragakis, M.; Kosmidis, K.

    In this paper we review the recent advances in explosive percolation, a very sharp phase transition first observed by Achlioptas et al. (2009). There a simple model was proposed, which changed slightly the classical percolation process so that the emergence of the spanning cluster is delayed. This slight modification turns out to have a great impact on the percolation phase transition. The resulting transition is so sharp that it was termed explosive, and it was at first considered to be discontinuous. This surprising fact stimulated considerable interest in “Achlioptas processes”. Later work, however, showed that the transition is continuous (at least for Achlioptas processes on Erdös networks), but with very unusual finite size scaling. We present a review of the field, indicate open “problems” and propose directions for future research.

  12. The Work of Cultural Transition: An Emerging Model

    PubMed Central

    Ryba, Tatiana V.; Stambulova, Natalia B.; Ronkainen, Noora J.

    2016-01-01

    In today’s uncertain, fluid job market, transnational mobility has intensified. Though the concept of cultural transition is increasingly used in sport and career research, insight into the processes of how individuals produce their own development through work and relationships in shifting cultural patterns of meaning remains limited. The transnational industry of sports, in which athletes’ psychological adjustment to cultural transitions has implications for both performance and meaningful life, serves as a backdrop for this article. This study applied the life story method to interviews with 15 professional and semi-professional athletes, focusing particularly on the cultural transition aspect of their transnational athletic careers. The aims of the study were to identify the developmental tasks of cultural transitions and strategies/mechanisms through which cultural transitions were enacted. Three underlying mechanisms of the transition process that assisted athletic career adaptability were social repositioning, negotiation of cultural practices, and meaning reconstruction. Based on the data analyses, a temporal model of cultural transition is proposed. The results of this research provide professionals working in the fields of career counseling and migrant support with a content framework for enhancing migrant workers’ adaptabilities and psychological wellbeing. PMID:27047436

  13. The Work of Cultural Transition: An Emerging Model.

    PubMed

    Ryba, Tatiana V; Stambulova, Natalia B; Ronkainen, Noora J

    2016-01-01

    In today's uncertain, fluid job market, transnational mobility has intensified. Though the concept of cultural transition is increasingly used in sport and career research, insight into the processes of how individuals produce their own development through work and relationships in shifting cultural patterns of meaning remains limited. The transnational industry of sports, in which athletes' psychological adjustment to cultural transitions has implications for both performance and meaningful life, serves as a backdrop for this article. This study applied the life story method to interviews with 15 professional and semi-professional athletes, focusing particularly on the cultural transition aspect of their transnational athletic careers. The aims of the study were to identify the developmental tasks of cultural transitions and strategies/mechanisms through which cultural transitions were enacted. Three underlying mechanisms of the transition process that assisted athletic career adaptability were social repositioning, negotiation of cultural practices, and meaning reconstruction. Based on the data analyses, a temporal model of cultural transition is proposed. The results of this research provide professionals working in the fields of career counseling and migrant support with a content framework for enhancing migrant workers' adaptabilities and psychological wellbeing. PMID:27047436

  14. Phase Transitions in the Quadratic Contact Process on Complex Networks

    NASA Astrophysics Data System (ADS)

    Varghese, Chris; Durrett, Rick

    2013-03-01

    The quadratic contact process (QCP) is a natural extension of the well studied linear contact process where a single infected (1) individual can infect a susceptible (0) neighbor and infected individuals are allowed to recover (1 --> 0). In the QCP, a combination of two 1's is required to effect a 0 --> 1 change. We extend the study of the QCP, which so far has been limited to lattices, to complex networks as a model for the change in a population via sexual reproduction and death. We define two versions of the QCP - vertex centered (VQCP) and edge centered (EQCP) with birth events 1 - 0 - 1 --> 1 - 1 - 1 and 1 - 1 - 0 --> 1 - 1 - 1 respectively, where ` -' represents an edge. We investigate the effects of network topology by considering the QCP on regular, Erdős-Rényi and power law random graphs. We perform mean field calculations as well as simulations to find the steady state fraction of occupied vertices as a function of the birth rate. We find that on the homogeneous graphs (regular and Erdős-Rényi) there is a discontinuous phase transition with a region of bistability, whereas on the heavy tailed power law graph, the transition is continuous. The critical birth rate is found to be positive in the former but zero in the latter.

  15. Modeling Developmental Transitions in Adaptive Resonance Theory

    ERIC Educational Resources Information Center

    Raijmakers, Maartje E. J.; Molenaar, Peter C. M.

    2004-01-01

    Neural networks are applied to a theoretical subject in developmental psychology: modeling developmental transitions. Two issues that are involved will be discussed: discontinuities and acquiring qualitatively new knowledge. We will argue that by the appearance of a bifurcation, a neural network can show discontinuities and may acquire…

  16. Stochastic Modeling of Laminar-Turbulent Transition

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Choudhari, Meelan

    2002-01-01

    Stochastic versions of stability equations are developed in order to develop integrated models of transition and turbulence and to understand the effects of uncertain initial conditions on disturbance growth. Stochastic forms of the resonant triad equations, a high Reynolds number asymptotic theory, and the parabolized stability equations are developed.

  17. Transition Services Model: Partnership for Student Success

    ERIC Educational Resources Information Center

    Pearman, Elizabeth; Elliott, Twila; Aborn, Lucinda

    2004-01-01

    In 1995, the Southwest Special Education Local Plan Area (SELPA) of the Los Angeles County School District, and El Camino College pioneered a partnership to serve students with disabilities on the community college campus. SELPA transition services serve as a model for alliances between community colleges and school districts throughout…

  18. A synergetic model for human gait transitions

    NASA Astrophysics Data System (ADS)

    Abdolvahab, Mohammad

    2015-09-01

    Gait transitions have been considered as bifurcations between states (e.g. walking or running modes) of a nonlinear dynamical system. A top-down synergetic approach to model gait transitions has been adapted from Frank et al. (2009) and applied to two sets of empirical observations. In this approach, it is assumed that the amplitudes of the spatio-temporal modes of locomotion satisfy a generic form of evolution equations that are known to hold for animate and inanimate self-organizing systems. The presented experimental results focus on hysteresis in human walk-to-run and run-to-walk transitions on a treadmill as a function of treadmill inclination and acceleration, the rate at which speed was increased or decreased during experimental trials. The bi-stability in the synergetic model is assumed to account for the hysteretic transitions. Accordingly, the relevant parameters of the model were estimated from the empirical data and the model's efficacy in predicting the observed hysteresis effects was evaluated.

  19. The physician's alternative career transition model: a stepwise approach.

    PubMed

    Bernard, S; Moore, D L

    1995-03-01

    The recent intense focus on marketplace reform has stimulated a reassessment of career planning options for some physicians. These socioeconomic changes have created unique opportunities beyond the traditional arenas of clinical practice and medical management for physicians to leverage their medical degrees and experiences in the business world. This paper presents three case reports of physician executives who have successfully pursued medically related business career options, each following different motivations at various stages of their medical careers. It then discusses the Physicians' Alternative Career Transition (PACT) model developed by the authors to assist other physicians who are considering making transitions into business-related careers. The PACT model is based on four critical steps for practicing physicians to make these transitions successfully: an internal self-evaluation process, an external environmental evaluation process, seeking the best "career match," and securing the career match. PMID:10161175

  20. Transition matrix model for evolutionary game dynamics

    NASA Astrophysics Data System (ADS)

    Ermentrout, G. Bard; Griffin, Christopher; Belmonte, Andrew

    2016-03-01

    We study an evolutionary game model based on a transition matrix approach, in which the total change in the proportion of a population playing a given strategy is summed directly over contributions from all other strategies. This general approach combines aspects of the traditional replicator model, such as preserving unpopulated strategies, with mutation-type dynamics, which allow for nonzero switching to unpopulated strategies, in terms of a single transition function. Under certain conditions, this model yields an endemic population playing non-Nash-equilibrium strategies. In addition, a Hopf bifurcation with a limit cycle may occur in the generalized rock-scissors-paper game, unlike the replicator equation. Nonetheless, many of the Folk Theorem results are shown to hold for this model.

  1. Transition matrix model for evolutionary game dynamics.

    PubMed

    Ermentrout, G Bard; Griffin, Christopher; Belmonte, Andrew

    2016-03-01

    We study an evolutionary game model based on a transition matrix approach, in which the total change in the proportion of a population playing a given strategy is summed directly over contributions from all other strategies. This general approach combines aspects of the traditional replicator model, such as preserving unpopulated strategies, with mutation-type dynamics, which allow for nonzero switching to unpopulated strategies, in terms of a single transition function. Under certain conditions, this model yields an endemic population playing non-Nash-equilibrium strategies. In addition, a Hopf bifurcation with a limit cycle may occur in the generalized rock-scissors-paper game, unlike the replicator equation. Nonetheless, many of the Folk Theorem results are shown to hold for this model. PMID:27078323

  2. Phase Transitions in Delaunay Potts Models

    NASA Astrophysics Data System (ADS)

    Adams, Stefan; Eyers, Michael

    2016-01-01

    We establish phase transitions for certain classes of continuum Delaunay multi-type particle systems (continuum Potts models) with infinite range repulsive interaction between particles of different type. In one class of the Delaunay Potts models studied the repulsive interaction is a triangle (multi-body) interaction whereas in the second class the interaction is between pairs (edges) of the Delaunay graph. The result for the edge model is an extension of finite range results in Bertin et al. (J Stat Phys 114(1-2):79-100, 2004) for the Delaunay graph and in Georgii and Häggström (Commun Math Phys 181:507-528, 1996) for continuum Potts models to an infinite range repulsion decaying with the edge length. This is a proof of an old conjecture of Lebowitz and Lieb. The repulsive triangle interactions have infinite range as well and depend on the underlying geometry and thus are a first step towards studying phase transitions for geometry-dependent multi-body systems. Our approach involves a Delaunay random-cluster representation analogous to the Fortuin-Kasteleyn representation of the Potts model. The phase transitions manifest themselves in the percolation of the corresponding random-cluster model. Our proofs rely on recent studies (Dereudre et al. in Probab Theory Relat Fields 153:643-670, 2012) of Gibbs measures for geometry-dependent interactions.

  3. Phase transition model for community detection

    NASA Astrophysics Data System (ADS)

    Wu, Jianshe; Lu, Rui; Jiao, Licheng; Liu, Fang; Yu, Xin; Wang, Da; Sun, Bo

    2013-03-01

    Motivated by social and biological interactions, a novel type of phase transition model is provided in order to investigate the emergence of the clustering phenomenon in networks. The model has two types of interactions: one is attractive and the other is repulsive. In each iteration, the phase of a node (or an agent) moves toward the average phase of its neighbors and moves away from the average phase of its non-neighbors. The velocities of the two types of phase transition are controlled by two parameters, respectively. It is found that the phase transition phenomenon is closely related to the topological structure of the underlying network, and thus can be applied to identify its communities and overlapping groups. By giving each node of the network a randomly generated initial phase and updating these phases by the phase transition model until they reach stability, one or two communities will be detected according to the nodes’ stable phases, confusable nodes are moved into a set named Of. By removing the detected communities and the nodes in Of, another one or two communities will be detected by an iteration of the algorithm, …. In this way, all communities and the overlapping nodes are detected. Simulations on both real-world networks and the LFR benchmark graphs have verified the efficiency of the proposed scheme.

  4. Process for making transition metal nitride whiskers

    SciTech Connect

    Bamberger, Carlos E.

    1989-01-01

    A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites.

  5. Process for making transition metal nitride whiskers

    DOEpatents

    Bamberger, C.E.

    1988-04-12

    A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites. 1 fig., 1 tab.

  6. MODELING TREE LEVEL PROCESSES

    EPA Science Inventory

    An overview of three main types of simulation approach (explanatory, abstraction, and estimation) is presented, along with a discussion of their capabilities limitations, and the steps required for their validation. A process model being developed through the Forest Response Prog...

  7. Biosphere Process Model Report

    SciTech Connect

    J. Schmitt

    2000-05-25

    To evaluate the postclosure performance of a potential monitored geologic repository at Yucca Mountain, a Total System Performance Assessment (TSPA) will be conducted. Nine Process Model Reports (PMRs), including this document, are being developed to summarize the technical basis for each of the process models supporting the TSPA model. These reports cover the following areas: (1) Integrated Site Model; (2) Unsaturated Zone Flow and Transport; (3) Near Field Environment; (4) Engineered Barrier System Degradation, Flow, and Transport; (5) Waste Package Degradation; (6) Waste Form Degradation; (7) Saturated Zone Flow and Transport; (8) Biosphere; and (9) Disruptive Events. Analysis/Model Reports (AMRs) contain the more detailed technical information used to support TSPA and the PMRs. The AMRs consists of data, analyses, models, software, and supporting documentation that will be used to defend the applicability of each process model for evaluating the postclosure performance of the potential Yucca Mountain repository system. This documentation will ensure the traceability of information from its source through its ultimate use in the TSPA-Site Recommendation (SR) and in the National Environmental Policy Act (NEPA) analysis processes. The objective of the Biosphere PMR is to summarize (1) the development of the biosphere model, and (2) the Biosphere Dose Conversion Factors (BDCFs) developed for use in TSPA. The Biosphere PMR does not present or summarize estimates of potential radiation doses to human receptors. Dose calculations are performed as part of TSPA and will be presented in the TSPA documentation. The biosphere model is a component of the process to evaluate postclosure repository performance and regulatory compliance for a potential monitored geologic repository at Yucca Mountain, Nevada. The biosphere model describes those exposure pathways in the biosphere by which radionuclides released from a potential repository could reach a human receptor

  8. Modeling robot contour processes

    NASA Astrophysics Data System (ADS)

    Whitney, D. E.; Edsall, A. C.

    Robot contour processes include those with contact force like car body grinding or deburring of complex castings, as well as those with little or no contact force like inspection. This paper describes ways of characterizing, identifying, and estimating contours and robot trajectories. Contour and robot are modeled as stochastic processes in order to emphasize that both successive robot cycles and successive industrial workpieces are similar but not exactly the same. The stochastic models can be used to identify the state of a workpiece or process, or to design a filter to estimate workpiece, shape and robot position from robot-based measurements.

  9. Liberty High School Transition Project: Model Process for Assimilating School, Community, Business, Government and Service Groups of the Least Restrictive Environment for Nondisabled and Disabled.

    ERIC Educational Resources Information Center

    Grimes, Michael K.

    The panel presentation traces the development of and describes the operation of a Brentwood (California) project to prepare approximately 75 severely disabled individuals, ages 12-22, to function in the least restrictive recreation/leisure, vocational, and general community environments. Transition Steering Committee developed such project…

  10. Approaches to retrospective sampling for longitudinal transition regression models

    PubMed Central

    Hunsberger, Sally; Albert, Paul S.; Thoma, Marie

    2016-01-01

    For binary diseases that relapse and remit, it is often of interest to estimate the effect of covariates on the transition process between disease states over time. The transition process can be characterized by modeling the probability of the binary event given the individual’s history. Designing studies that examine the impact of time varying covariates over time can lead to collection of extensive amounts of data. Sometimes it may be possible to collect and store tissue, blood or images and retrospectively analyze this covariate information. In this paper we consider efficient sampling designs that do not require biomarker measurements on all subjects. We describe appropriate estimation methods for transition probabilities and functions of these probabilities, and evaluate efficiency of the estimates from the proposed sampling designs. These new methods are illustrated with data from a longitudinal study of bacterial vaginosis, a common relapsing-remitting vaginal infection of women of child bearing age.

  11. MODEL UPDATING: TRANSITION FROM RESEARCH TO PRACTICE?

    SciTech Connect

    D. C. ZIMMERMAN; F. M. HEMEZ

    2000-10-01

    This session offers an open forum to discuss issues associated with the transition of nearly two decades of engineering research into computational guided model updating into industry state-of-the-practice. Related technical issues are the model updating technology, model reduction, test-analysis correlation and optimization strategies. The session is organized as follows. Technical presentations review the state-of-the-art in finite element model updating and present examples of industrial applications. The results of a recent survey on the potential and usefulness of the model updating technology are discussed. Panel discussions and interaction with the audience discuss industrial needs, future trends and challenges and why negative model updating results are never discussed within the structural dynamics community.

  12. Engineering models of deflagration-to-detonation transition

    SciTech Connect

    Bdzil, J.B.; Son, S.F.

    1995-07-01

    For the past two years, Los Alamos has supported research into the deflagration-to-detonation transition (DDT) in damaged energetic materials as part of the explosives safety program. This program supported both a theory/modeling group and an experimentation group. The goal of the theory/modeling group was to examine the various modeling structures (one-phase models, two-phase models, etc.) and select from these a structure suitable to model accidental initiation of detonation in damaged explosives. The experimental data on low-velocity piston supported DDT in granular explosive was to serve as a test bed to help in the selection process. Three theoretical models have been examined in the course of this study: (1) the Baer-Nunziato (BN) model, (2) the Stewart-Prasad-Asay (SPA) model and (3) the Bdzil-Kapila-Stewart model. Here we describe these models, discuss their properties, and compare their features.

  13. Microwave sintering process model.

    PubMed

    Peng, Hu; Tinga, W R; Sundararaj, U; Eadie, R L

    2003-01-01

    In order to simulate and optimize the microwave sintering of a silicon nitride and tungsten carbide/cobalt toolbits process, a microwave sintering process model has been built. A cylindrical sintering furnace was used containing a heat insulating layer, a susceptor layer, and an alumina tube containing the green toolbit parts between parallel, electrically conductive, graphite plates. Dielectric and absorption properties of the silicon nitride green parts, the tungsten carbide/cobalt green parts, and an oxidizable susceptor material were measured using perturbation and waveguide transmission methods. Microwave absorption data were measured over a temperature range from 20 degrees C to 800 degrees C. These data were then used in the microwave process model which assumed plane wave propagation along the radial direction and included the microwave reflection at each interface between the materials and the microwave absorption in the bulk materials. Heat transfer between the components inside the cylindrical sintering furnace was also included in the model. The simulated heating process data for both silicon nitride and tungsten carbide/cobalt samples closely follow the experimental data. By varying the physical parameters of the sintering furnace model, such as the thickness of the susceptor layer, the thickness of the allumina tube wall, the sample load volume and the graphite plate mass, the model data predicts their effects which are helpful in optimizing those parameters in the industrial sintering process. PMID:15323110

  14. Camera-Model Identification Using Markovian Transition Probability Matrix

    NASA Astrophysics Data System (ADS)

    Xu, Guanshuo; Gao, Shang; Shi, Yun Qing; Hu, Ruimin; Su, Wei

    Detecting the (brands and) models of digital cameras from given digital images has become a popular research topic in the field of digital forensics. As most of images are JPEG compressed before they are output from cameras, we propose to use an effective image statistical model to characterize the difference JPEG 2-D arrays of Y and Cb components from the JPEG images taken by various camera models. Specifically, the transition probability matrices derived from four different directional Markov processes applied to the image difference JPEG 2-D arrays are used to identify statistical difference caused by image formation pipelines inside different camera models. All elements of the transition probability matrices, after a thresholding technique, are directly used as features for classification purpose. Multi-class support vector machines (SVM) are used as the classification tool. The effectiveness of our proposed statistical model is demonstrated by large-scale experimental results.

  15. Foam process models.

    SciTech Connect

    Moffat, Harry K.; Noble, David R.; Baer, Thomas A.; Adolf, Douglas Brian; Rao, Rekha Ranjana; Mondy, Lisa Ann

    2008-09-01

    In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.

  16. Introducing Modeling Transition Diagrams as a Tool to Connect Mathematical Modeling to Mathematical Thinking

    ERIC Educational Resources Information Center

    Czocher, Jennifer A.

    2016-01-01

    This study contributes a methodological tool to reconstruct the cognitive processes and mathematical activities carried out by mathematical modelers. Represented as Modeling Transition Diagrams (MTDs), individual modeling routes were constructed for four engineering undergraduate students. Findings stress the importance and limitations of using…

  17. A Correlation-Based Transition Model using Local Variables. Part 2; Test Cases and Industrial Applications

    NASA Technical Reports Server (NTRS)

    Langtry, R. B.; Menter, F. R.; Likki, S. R.; Suzen, Y. B.; Huang, P. G.; Volker, S.

    2006-01-01

    A new correlation-based transition model has been developed, which is built strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) methods using unstructured grids and massive parallel execution. The model is based on two transport equations, one for the intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models), but form a framework for the implementation of correlation-based models into general-purpose CFD methods.

  18. Unified Model Deformation and Flow Transition Measurements

    NASA Technical Reports Server (NTRS)

    Burner, Alpheus W.; Liu, Tianshu; Garg, Sanjay; Bell, James H.; Morgan, Daniel G.

    1999-01-01

    The number of optical techniques that may potentially be used during a given wind tunnel test is continually growing. These include parameter sensitive paints that are sensitive to temperature or pressure, several different types of off-body and on-body flow visualization techniques, optical angle-of-attack (AoA), optical measurement of model deformation, optical techniques for determining density or velocity, and spectroscopic techniques for determining various flow field parameters. Often in the past the various optical techniques were developed independently of each other, with little or no consideration for other techniques that might also be used during a given test. Recently two optical techniques have been increasingly requested for production measurements in NASA wind tunnels. These are the video photogrammetric (or videogrammetric) technique for measuring model deformation known as the video model deformation (VMD) technique, and the parameter sensitive paints for making global pressure and temperature measurements. Considerations for, and initial attempts at, simultaneous measurements with the pressure sensitive paint (PSP) and the videogrammetric techniques have been implemented. Temperature sensitive paint (TSP) has been found to be useful for boundary-layer transition detection since turbulent boundary layers convect heat at higher rates than laminar boundary layers of comparable thickness. Transition is marked by a characteristic surface temperature change wherever there is a difference between model and flow temperatures. Recently, additional capabilities have been implemented in the target-tracking videogrammetric measurement system. These capabilities have permitted practical simultaneous measurements using parameter sensitive paint and video model deformation measurements that led to the first successful unified test with TSP for transition detection in a large production wind tunnel.

  19. Applying Gaussian processes to Spitzer/IRAC transit lightcurves

    NASA Astrophysics Data System (ADS)

    Evans, Thomas

    2015-08-01

    For the past decade, transit and eclipse measurements made with Spitzer/IRAC have been used to characterize dozens of exoplanet atmospheres. However, lightcurves obtained with IRAC are affected by systematics that swamp the faint atmosphere signals being sought, as the instrument was not designed for ~100ppm photometry over >3hr timescales. Robustly quantifying the degeneracies between these systematics and the planet signal is therefore crucial for obtaining realistic uncertainty estimates, to avoid over-interpreting what the data have to tell us. This is challenging, because the nature of the instrumental systematics are not well-understood from a first principles standpoint. I will describe the application of Gaussian process (GPs) models to this problem, which is a relatively new approach in the exoplanet literature. Specifically, I will present transmission and emission results for the hot Jupiter HD209458b, and summarise how the new GP analysis draws into question a number of previous results, including inferences of strong water absorption in transmission and an inverted pressure-temperature profile for the dayside hemisphere. I will also outline the main challenges in applying GP models to datasets like the IRAC lightcurves, which typically contain well over 1000 data points and exhibit non-stationary systematics.

  20. Intelligent card processing terminal of urban rail transit in Nanjing

    NASA Astrophysics Data System (ADS)

    Xia, Dechuan; Zhang, Xiaojun; Song, Yana; He, Tiejun

    2011-10-01

    In order to improve the compatibility, security and expandability of Automatic Fare Collection System in rail transit, and reduce the maintenance cost, intelligent card processing terminal is proposed in this paper. The operation flow and features of intelligent card processing terminal are analyzed in detailed, and the software and hardware structures and business treatment process are designed. Finally, the security mechanism of intelligent card processing terminal is summarized. The application results shows that Intelligent card processing terminal makes interconnection among lines easier, creates considerable economic efficiency and the social efficiency, and can be widely used.

  1. How can models support a transition to sustainability: The role of simulations in sustainable resource management

    NASA Astrophysics Data System (ADS)

    Halbe, Johannes; Reusser, Dominik E.; Holtz, Gerog; Stosius, Annette; Kwakkel, Jan; Haasnoot, Marjolijn; Avenhaus, Wiebke

    2013-04-01

    The delineation of transition pathways towards sustainability and the implementation of associated measures are challenged by uncertainty, structural barriers, and conflicts among affected stakeholders. Experiences from other research domains suggest that the effective application of models to tackle these challenges require the explicit consideration of modeling purposes and roles. We present a classification of modeling roles for the analysis and governance of transitions. Models can support understanding of transitions processes, detect barriers and drivers of change, support the exploration of pathways towards sustainability, and help to actively engage relevant stakeholder groups. For each application area, examples are provided from the transition community and related research fields like environmental modeling and integrated assessment.

  2. Facility Will Help Transition Models Into Operations

    NASA Astrophysics Data System (ADS)

    Kumar, Mohi

    2009-02-01

    The U.S. National Oceanic and Atmospheric Administration's Space Weather Prediction Center (NOAA SWPC), in partnership with the U.S. Air Force Weather Agency (AFWA), is establishing a center to promote and facilitate the transition of space weather models to operations. The new facility, called the Developmental Testbed Center (DTC), will take models used by researchers and rigorously test them to see if they can withstand continued use as viable warning systems. If a model used in a space weather warning system crashes or fails to perform well, severe consequences can result. These include increased radiation risks to astronauts and people traveling on high-altitude flights, national security vulnerabilities from the loss of military satellite communications, and the cost of replacing damaged military and commercial spacecraft.

  3. Modeling the Polycentric Transition of Cities

    NASA Astrophysics Data System (ADS)

    Louf, Rémi; Barthelemy, Marc

    2013-11-01

    Empirical evidence suggests that most urban systems experience a transition from a monocentric to a polycentric organization as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city, which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the instability of the monocentric regime and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predictions that are in agreement with data gathered for around 9000 U.S. cities between 1994 and 2010.

  4. Modeling the polycentric transition of cities.

    PubMed

    Louf, Rémi; Barthelemy, Marc

    2013-11-01

    Empirical evidence suggests that most urban systems experience a transition from a monocentric to a polycentric organization as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city, which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the instability of the monocentric regime and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predictions that are in agreement with data gathered for around 9000 U.S. cities between 1994 and 2010. PMID:24266493

  5. Sabin-to-Mahoney Transition Model of Quasispecies Replication

    SciTech Connect

    2009-05-31

    Qspp is an agent-based stochastic simulation model of the Poliovirus Sabin-to-Mahoney transition. This code simulates a cell-to-cell model of Poliovirus replication. The model tracks genotypes (virus genomes) as they are replicated in cells, and as the cells burst and release particles into the medium of a culture dish. An inoculum is then taken from the pool of virions and is used to inoculate cells on a new dish. This process repeats. The Sabin genotype comprises the initial inoculum. Nucleotide positions that match the Sabin1 (vaccine strain) and Mahoney (wild type) genotypes, as well as the neurovirulent phenotype (from the literature) are enumerated as constants.

  6. Becoming Counselors through Growth and Learning: The Entry Transition Process

    ERIC Educational Resources Information Center

    Wagner, Holly H.; Hill, Nicole R.

    2015-01-01

    This article explored counselor development within the entry transition into counselor education programs using 4 interviews and interpretive dialogues with 8 beginning counselors. Six categories resulted from the authors' grounded theory analysis: Anticipation, Evolving Identity, Growth and Learning, Coping, Choosing to Trust the Process, and…

  7. Adding Structure to the Transition Process to Advanced Mathematical Activity

    ERIC Educational Resources Information Center

    Engelbrecht, Johann

    2010-01-01

    The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical…

  8. Software Transition Project Retrospectives and the Application of SEL Effort Estimation Model and Boehm's COCOMO to Complex Software Transition Projects

    NASA Technical Reports Server (NTRS)

    McNeill, Justin

    1995-01-01

    The Multimission Image Processing Subsystem (MIPS) at the Jet Propulsion Laboratory (JPL) has managed transitions of application software sets from one operating system and hardware platform to multiple operating systems and hardware platforms. As a part of these transitions, cost estimates were generated from the personal experience of in-house developers and managers to calculate the total effort required for such projects. Productivity measures have been collected for two such transitions, one very large and the other relatively small in terms of source lines of code. These estimates used a cost estimation model similar to the Software Engineering Laboratory (SEL) Effort Estimation Model. Experience in transitioning software within JPL MIPS have uncovered a high incidence of interface complexity. Interfaces, both internal and external to individual software applications, have contributed to software transition project complexity, and thus to scheduling difficulties and larger than anticipated design work on software to be ported.

  9. Detecting critical state before phase transition of complex systems by hidden Markov model

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Chen, Pei; Li, Yongjun; Chen, Luonan

    Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e., before-transition state, pre-transition state, and after-transition state, which can be considered as three different Markov processes. Thus, based on this dynamical feature, we present a novel computational method, i.e., hidden Markov model (HMM), to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e., the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin, and HCV-induced dysplasia and hepatocellular carcinoma.

  10. When University Faculty Retire: A Study of the Transition Process.

    ERIC Educational Resources Information Center

    Pappas, John G.; Goodman, Jane

    This study examined the retirement transitions of college faculty based on the Schlossberg (1984) model, which suggests that successful coping depends on an evaluation of the retiree's unique situation, the qualities of the individual, the support available, and the strategies employed. A total of 55 emeritus faculty from the College of Education…

  11. A new model for broadband waveguide to microstrip transition design

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Downey, Alan N.

    1986-01-01

    A new model is presented which permits the prediction of the resonant frequencies created by antipodal finline waveguide to microstrip transitions. The transition is modeled as a tapered transmission line in series with an infinite set of coupled resonant circuits. The resonant circuits are modeled as simple microwave resonant cavities of which the resonant frequencies are easily determined. The model is developed and the resonant frequencies determined for several different transitions. Experimental results are given to confirm the models.

  12. Transition from a planar interface to cellular and dendritic structures during rapid solidification processing

    NASA Technical Reports Server (NTRS)

    Laxmanan, V.

    1986-01-01

    The development of theoretical models which characterize the planar-cellular and cell-dendrite transitions is described. The transitions are analyzed in terms of the Chalmers number, the solute Peclet number, and the tip stability parameter, which correlate microstructural features and processing conditions. The planar-cellular transition is examined using the constitutional supercooling theory of Chalmers et al., (1953) and it is observed that the Chalmers number is between 0 and 1 during dendritic and cellular growth. Analysis of cell-dendrite transition data reveal that the transition occurs when the solute Peclet number goes through a minimum, the primary arm spacings go through a maximum, and the Chalmers number is equal to 1/2. The relation between the tip stability parameter and the solute Peclet number is investigated and it is noted that the tip stability parameter is useful for studying dendritic growth in alloys.

  13. Transitioning GONG data processing to NOAA SWPC operations

    NASA Astrophysics Data System (ADS)

    Reinard, Alysha; Marble, Andrew R.; Berger, Thomas

    2016-05-01

    The NOAA Space Weather Prediction Center (SWPC) is the nation's official source of space weather watches, warnings, and alerts, providing 24x7 forecasting and support to critical infrastructure operators around the world. Observations of the conditions on the Sun are crucial for determining when and if a warning is needed. The Global Oscillation Network Group (GONG) operated by the National Solar Observatory (NSO) consists of six ground stations, allowing continuous observations of the Sun. Of particular interest for space weather purposes are the H-alpha images and magnetograms. The H-alpha data are used to identify filaments and their eruptions, to assess active region evolution and plage extent, and to help localize flare locations. The magnetograms are used to identify neutral lines, to examine potential shearing areas and to characterize the magnetic structure of active regions. GONG magnetograms also provide the initial condition for models of solar wind expansion through the heliosphere such as the WSA-Enlil model. Although beyond the scope of current space weather applications, GONG helioseismology products can be used to assess active region emergence on the far side of the Sun and to indicate the flaring potential of a front-side active region. These products are being examined as future tools in flare prediction.NSO has operated GONG as a science facility since 1995 and has provided processed space weather data products to NOAA via for the past several years. In 2014 the White House Office of Management and Budget (OMB) requested that NOAA transition the GONG network to an operational space weather asset in order to ensure the continued flow of critical data for solar wind models. NSO will continue to operate and manage the instruments and sites, but the H-alpha images and 10 minute averaged magnetogram data will be sent directly to SWPC for processing and use in space weather modeling. SWPC will make these data available to NSO and the public via the

  14. Transitioning GONG data processing to NOAA SWPC operations

    NASA Astrophysics Data System (ADS)

    Reinard, A.; Marble, A.; Hill, F.; Berger, T. E.

    2015-12-01

    The NOAA Space Weather Prediction Center (SWPC) is the nation's official source of space weather watches, warnings, and alerts, providing 24x7 forecasting and support to critical infrastructure operators around the world. Observations of the conditions on the Sun are crucial for determining when and if a warning is needed. The Global Oscillation Network Group (GONG) operated by the National Solar Observatory (NSO) consists of six ground stations, allowing continuous observations of the Sun. Of particular interest for space weather purposes are the H-alpha images and magnetograms. The H-alpha data are used to identify filaments and their eruptions, to assess active region evolution and plage extent, and to help localize flare locations. The magnetograms are used to identify neutral lines, to examine potential shearing areas and to characterize the magnetic structure of active regions. GONG magnetograms also provide the initial condition for models of solar wind expansion through the heliosphere such as the WSA-Enlil model. Although beyond the scope of current space weather applications, GONG helioseismology products can be used to assess active region emergence on the far side of the Sun and to indicate the flaring potential of a front-side active region. These products are being examined as future tools in flare prediction. NSO has operated GONG as a science facility since 1995 and has provided processed space weather data products to NOAA via public internet connections for the past several years. In 2014 the White House Office of Management and Budget (OMB) requested that NOAA transition the GONG network to an operational space weather asset in order to ensure the continued flow of critical magnetogram data for solar wind models. NSO will continue to operate and manage the instruments and sites, but the H-alpha images and 10 minute averaged magnetogram data will be sent directly to SWPC for processing and use in space weather modeling. SWPC will make these data

  15. Chaos Theory as a Model for Life Transitions Counseling: Nonlinear Dynamics and Life's Changes

    ERIC Educational Resources Information Center

    Bussolari, Cori J.; Goodell, Judith A.

    2009-01-01

    Chaos theory is presented for counselors working with clients experiencing life transitions. It is proposed as a model that considers disorder, unpredictability, and lack of control as normal parts of transition processes. Nonlinear constructs from physics are adapted for use in counseling. The model provides a method clients can use to…

  16. Relaxation processes in a lower disorder order transition diblock copolymer

    SciTech Connect

    Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  17. A simple hydrodynamic model for transition boiling

    NASA Astrophysics Data System (ADS)

    Joo, Sang W.; Davis, Stephen H.; Bankoff, S. George

    2000-01-01

    A vertical column of an inviscid fluid, heated uniformly from below through a horizontal rigid bottom, is studied, with focus on the dynamics of the vapour/liquid interface near the three-phase (contact) line. The interfacial motion is induced by the competing effects of liquid feeding from above and evaporative mass loss through the interface. A linearized solution is obtained that describes the location of the contact line. The solution is used to study the transition processes to and from film boiling, where part of the liquid, lying on top of a vapour layer, can spontaneously be drawn downward and touch the heated bottom. Recession or advancement of the contact line then determines whether the film boiling is sustained or broken. It is seen that the correct contact-line dynamics cannot be predicted solely from a global mass balance in the liquid column.

  18. 'Biogeneric' developmental processes: drivers of major transitions in animal evolution.

    PubMed

    Newman, Stuart A

    2016-08-19

    Using three examples drawn from animal systems, I advance the hypothesis that major transitions in multicellular evolution often involved the constitution of new cell-based materials with unprecedented morphogenetic capabilities. I term the materials and formative processes that arise when highly evolved cells are incorporated into mesoscale matter 'biogeneric', to reflect their commonality with, and distinctiveness from, the organizational properties of non-living materials. The first transition arose by the innovation of classical cell-adhesive cadherins with transmembrane linkage to the cytoskeleton and the appearance of the morphogen Wnt, transforming some ancestral unicellular holozoans into 'liquid tissues', and thereby originating the metazoans. The second transition involved the new capabilities, within a basal metazoan population, of producing a mechanically stable basal lamina, and of planar cell polarization. This gave rise to the eumetazoans, initially diploblastic (two-layered) forms, and then with the addition of extracellular matrices promoting epithelial-mesenchymal transformation, three-layered triploblasts. The last example is the fin-to-limb transition. Here, the components of a molecular network that promoted the development of species-idiosyncratic endoskeletal elements in gnathostome ancestors are proposed to have evolved to a dynamical regime in which they constituted a Turing-type reaction-diffusion system capable of organizing the stereotypical arrays of elements of lobe-finned fish and tetrapods. The contrasting implications of the biogeneric materials-based and neo-Darwinian perspectives for understanding major evolutionary transitions are discussed.This article is part of the themed issue 'The major synthetic evolutionary transitions'. PMID:27431521

  19. Simplified modeling of transition to detonation in porous energetic materials

    SciTech Connect

    Stewart, D.S. ); Asay, B.W. ); Prasad, K. )

    1994-07-01

    A simplified model that can predict the transitions from compaction to detonation and shock to detonation is given with the aim of describing experiments in beds of porous HMX. In the case of compaction to detonation, the energy of early impact generates a slowly moving, convective-reactive deflagration that expands near the piston face and evolves in a manner that is characteristic of confined deflagration to detonation transition. A single-phase state variable theory is adopted in contrast to a two-phase axiomatic mixture theory. The ability of the porous material to compact is treated as an endothermic process. Reaction is treated as an exothermic process. The algebraic (Rankine--Hugoniot) steady wave analysis is given for inert compaction waves and steady detonation waves in a piston supported configuration, typical of the experiments carried out in porous HMX. A structure analysis of the steady compaction wave is given. Numerical simulations of deflagration to detonation are carried out for parameters that describe an HMX-like material and compared with the experiments. The simple model predicts the high density plug that is observed in the experiments and suggests that the leading front of the plug is a secondary compaction wave. A shock to detonation transition is also numerically simulated.

  20. Phase transitions in Thirring’s model

    NASA Astrophysics Data System (ADS)

    Campa, Alessandro; Casetti, Lapo; Latella, Ivan; Pérez-Madrid, Agustín; Ruffo, Stefano

    2016-07-01

    In his pioneering work on negative specific heat, Walter Thirring introduced a model that is solvable in the microcanonical ensemble. Here, we give a complete description of the phase-diagram of this model in both the microcanonical and the canonical ensemble, highlighting the main features of ensemble inequivalence. In both ensembles, we find a line of first-order phase transitions which ends in a critical point. However, neither the line nor the point have the same location in the phase-diagram of the two ensembles. We also show that the microcanonical and canonical critical points can be analytically related to each other using a Landau expansion of entropy and free energy, respectively, in analogy with what has been done in (Cohen and Mukamel 2012 J. Stat. Mech. P12017). Examples of systems with certain symmetries restricting the Landau expansion have been considered in this reference, while no such restrictions are present in Thirring’s model. This leads to a phase diagram that can be seen as a prototype for what happens in systems of particles with kinematic degrees of freedom dominated by long-range interactions.

  1. Quantitative modeling of soil genesis processes

    NASA Technical Reports Server (NTRS)

    Levine, E. R.; Knox, R. G.; Kerber, A. G.

    1992-01-01

    For fine spatial scale simulation, a model is being developed to predict changes in properties over short-, meso-, and long-term time scales within horizons of a given soil profile. Processes that control these changes can be grouped into five major process clusters: (1) abiotic chemical reactions; (2) activities of organisms; (3) energy balance and water phase transitions; (4) hydrologic flows; and (5) particle redistribution. Landscape modeling of soil development is possible using digitized soil maps associated with quantitative soil attribute data in a geographic information system (GIS) framework to which simulation models are applied.

  2. Phase Transitions in Model Active Systems

    NASA Astrophysics Data System (ADS)

    Redner, Gabriel S.

    The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these

  3. Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model

    PubMed Central

    Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P.; Terrace, Herbert S.

    2015-01-01

    Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort’s success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models. PMID:26407227

  4. Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model.

    PubMed

    Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P; Terrace, Herbert S

    2015-01-01

    Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort's success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models. PMID:26407227

  5. Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System

    PubMed Central

    Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201

  6. A multinomial choice model approach for dynamic driver vision transitions.

    PubMed

    Huang, Shih-Hsuan; Wong, Jinn-Tsai

    2015-01-01

    Exploring the continual process of drivers allocating their attention under varying conditions could be vital for preventing motor vehicle crashes. This study aims to model visual behaviors and to estimate the effects of various contributing factors on driver's vision transitions. A visual attention allocation framework, based on certain contributing attributes related to driving tasks and environmental conditions, has been developed. The associated logit type models for determining driver choices for focal points were successfully formulated and estimated by using naturalistic glance data from the 100-car event database. The results offer insights into driver visual behavior and patterns of visual attention allocation. The three focal points that drivers most frequently rely on and glance at are the forward, left and rear view mirror. The sample drivers were less likely to demonstrate troublesome transition patterns, particularly in mentally demanding situations. Additionally, instead of shifting vision directly between two non-forward focal points, the sample drivers frequently had an intermediate forward glance. Thus, seemingly unrelated paths could be grouped into explanatory patterns of driver attention allocation. Finally, in addition to the vision-transition patterns, the potential pitfalls of such patterns and possible countermeasures to improving safety are illustrated, focusing on situations when drivers are distracted, traveling at high speeds and approaching intersections. PMID:25463950

  7. Human driven transitions in complex model ecosystems

    NASA Astrophysics Data System (ADS)

    Harfoot, Mike; Newbold, Tim; Tittinsor, Derek; Purves, Drew

    2015-04-01

    Human activities have been observed to be impacting ecosystems across the globe, leading to reduced ecosystem functioning, altered trophic and biomass structure and ultimately ecosystem collapse. Previous attempts to understand global human impacts on ecosystems have usually relied on statistical models, which do not explicitly model the processes underlying the functioning of ecosystems, represent only a small proportion of organisms and do not adequately capture complex non-linear and dynamic responses of ecosystems to perturbations. We use a mechanistic ecosystem model (1), which simulates the underlying processes structuring ecosystems and can thus capture complex and dynamic interactions, to investigate boundaries of complex ecosystems to human perturbation. We explore several drivers including human appropriation of net primary production and harvesting of animal biomass. We also present an analysis of the key interactions between biotic, societal and abiotic earth system components, considering why and how we might think about these couplings. References: M. B. J. Harfoot et al., Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model., PLoS Biol. 12, e1001841 (2014).

  8. Data support for a state-and-transition model: What have we learned?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State-and-transition models (STMs) were conceived as a means to synthesize knowledge about alternative plant communities and the processes that lead to transitions among them for specific land areas. STMs that have been developed over the past decade have often been limited by 1) a lack of detail on...

  9. Transition region models for Be stars

    NASA Astrophysics Data System (ADS)

    Fontenla, J. M.; Rovira, M.; Ringuelet, A. E.

    1981-12-01

    A preliminary model that reproduces the general characteristics of equivalent widths and profiles of ultraviolet spectral lines corresponding to ions such as C IV, Si IV, and N V which frequently exhibit asymmetric profiles and which are particularly observed in early type objects undergoing mass loss, is presented. The model considers terms due to kinetic and potential energies as well as radiative losses in solving for the energy balance equation. In a first approximation, it is shown how the kinetic energy can account for the heating of the material up to temperatures compatible with the formation of ions like C IV and Si IV by collisional processes. Agreement, at least as to the order of magnitude, between the model and the observations is found if the existence of some kind of braking mechanism is postulated.

  10. GREENSCOPE: Sustainable Process Modeling

    EPA Science Inventory

    EPA researchers are responding to environmental problems by incorporating sustainability into process design and evaluation. EPA researchers are also developing a tool that allows users to assess modifications to existing and new chemical processes to determine whether changes in...

  11. Electronic Relaxation Processes of Transition Metal Atoms in Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Kautsch, Andreas; Lindebner, Friedrich; Koch, Markus; Ernst, Wolfgang E.

    2014-06-01

    Spectroscopy of doped superfluid helium nanodroplets (He_N) gives information about the influence of this cold, chemically inert, and least interacting matrix environment on the excitation and relaxation dynamics of dopant atoms and molecules. We present the results from laser induced fluorescence (LIF), photoionization (PI), and mass spectroscopy of Cr and Cu doped He_N. From these results, we can draw a comprehensive picture of the complex behavior of such transition metal atoms in He_N upon photo-excitation. The strong Cr and Cu ground state transitions show an excitation blueshift and broadening with respect to the bare atom transitions which can be taken as indication for the solvation inside the droplet. From the originally excited states the atoms relax to energetically lower states and are ejected from the He_N. The relaxation processes include bare atom spin-forbidden transitions, which clearly bears the signature of the He_N influence. Two-color resonant two-photon ionization (2CR2PI) also shows the formation of bare atoms and small Cr-He_n and Cu-He_n clusters in their ground and metastable states ^c. Currently, Cr dimer excitation studies are in progress and a brief outlook on the available results will be given. C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, 2011. A. Kautsch, M. Koch, and W. E. Ernst, J. Phys. Chem. A, 117 (2013) 9621-9625, DOI: 10.1021/jp312336m F. Lindebner, A. Kautsch, M. Koch, and W. E. Ernst, Int. J. Mass Spectrom. (2014) in press, DOI: 10.1016/j.ijms.2013.12.022 M. Koch, A. Kautsch, F. Lackner, and W. E. Ernst, submitted to J. Phys. Chem. A

  12. Thermodynamic model of nonequilibrium phase transitions.

    PubMed

    Martyushev, L M; Konovalov, M S

    2011-07-01

    Within the scope of a thermodynamic description using the maximum entropy production principle, transitions from one nonequilibrium (kinetic) regime to another are considered. It is shown that in the case when power-law dependencies of thermodynamic flux on force are similar for two regimes, only a transition accompanied by a positive jump of thermodynamic flux is possible between them. It is found that the difference in powers of the dependencies of thermodynamic fluxes on forces results in a number of interesting nonequilibrium transitions between kinetic regimes, including the reentrant one with a negative jump of thermodynamic flux. PMID:21867119

  13. Visual Modelling of Learning Processes

    ERIC Educational Resources Information Center

    Copperman, Elana; Beeri, Catriel; Ben-Zvi, Nava

    2007-01-01

    This paper introduces various visual models for the analysis and description of learning processes. The models analyse learning on two levels: the dynamic level (as a process over time) and the functional level. Two types of model for dynamic modelling are proposed: the session trace, which documents a specific learner in a particular learning…

  14. Sabin-to-Mahoney Transition Model of Quasispecies Replication

    Energy Science and Technology Software Center (ESTSC)

    2009-05-31

    Qspp is an agent-based stochastic simulation model of the Poliovirus Sabin-to-Mahoney transition. This code simulates a cell-to-cell model of Poliovirus replication. The model tracks genotypes (virus genomes) as they are replicated in cells, and as the cells burst and release particles into the medium of a culture dish. An inoculum is then taken from the pool of virions and is used to inoculate cells on a new dish. This process repeats. The Sabin genotype comprisesmore » the initial inoculum. Nucleotide positions that match the Sabin1 (vaccine strain) and Mahoney (wild type) genotypes, as well as the neurovirulent phenotype (from the literature) are enumerated as constants.« less

  15. Transitional paleointensities from Kauai, Hawaii, and geomagnetic reversal models

    USGS Publications Warehouse

    Bogue, Scott W.; Coe, Robert S.

    1984-01-01

    Previously presented paleointensity results from an R-N transition zone in Kauai, Hawaii, show that field intensity dropped from 0. 431 Oe to 0. 101 Oe while the field remained within 30 degree of the reversed axial dipole direction. A recovery in intensity and the main directional change followed this presumably short period of low field strength. As the reversal neared completion, the field has an intensity of 0. 217 Oe while still 40 degree from the final direction. The relationship of paleointensity to field direction during the early part of the reversal thus differs from that toward the end, a feature that only some reversal models are consistent with. For example, a model in which a standing nondipole component persists through the dipole reversal predicts only symmetric intensity patterns. In contrast, zonal flooding models generate suitably complex field behavior if multiple flooding schemes operate during a single reversal or if the flooding process is itself asymmetric.

  16. A random matrix model with localization and ergodic transitions

    NASA Astrophysics Data System (ADS)

    Kravtsov, V. E.; Khaymovich, I. M.; Cuevas, E.; Amini, M.

    2015-12-01

    Motivated by the problem of many-body localization and the recent numerical results for the level and eigenfunction statistics on the random regular graphs, a generalization of the Rosenzweig-Porter random matrix model is suggested that possesses two transitions. One of them is the Anderson localization transition from the localized to the extended states. The other one is the ergodic transition from the extended non-ergodic (multifractal) states to the extended ergodic states. We confirm the existence of both transitions by computing the two-level spectral correlation function, the spectrum of multifractality f(α ) and the wave function overlap which consistently demonstrate these two transitions.

  17. A Parent-Professional Collaboration Model of Transitional Planning.

    ERIC Educational Resources Information Center

    Wittenstein, S. H.

    1993-01-01

    A transitional planning model implemented at St. Joseph's School for the Blind in Jersey City, New Jersey, incorporates a broad conceptualization of transition that includes social skills, independent living skills, and overall competence in adjustment to the community. The model considers parental involvement, advocacy, and leadership as…

  18. Transitional Jobs: Background, Program Models, and Evaluation Evidence

    ERIC Educational Resources Information Center

    Bloom, Dan

    2010-01-01

    The budget for the U.S. Department of Labor for Fiscal Year 2010 includes a total of $45 million to support and study transitional jobs. This paper describes the origins of the transitional jobs models that are operating today, reviews the evidence on the effectiveness of this approach and other subsidized employment models, and offers some…

  19. Topology changing transitions in supersymmetric linear σ-models

    NASA Astrophysics Data System (ADS)

    Ryang, Shijong

    1995-02-01

    We analyze the two-dimensional supersymmetric linear σ-model with U(1) gauge symmetries that includes a Calabi-Yau phase and a possible Landau-Ginzburg phase. We demonstrate the topology changing transitions among the generic vacua of various linear σ-models. In the supersymmetric transition the determinantal contraction naturally arises.

  20. Implementation and Validation of a Laminar-to-Turbulent Transition Model in the Wind-US Code

    NASA Technical Reports Server (NTRS)

    Denissen, Nicholas A.; Yoder, Dennis A.; Georgiadis, Nicholas J.

    2008-01-01

    A bypass transition model has been implemented in the Wind-US Reynolds Averaged Navier-Stokes (RANS) solver. The model is based on the Shear Stress Transport (SST) turbulence model and was built starting from a previous SST-based transition model. Several modifications were made to enable (1) consistent solutions regardless of flow field initialization procedure and (2) fully turbulent flow beyond the transition region. This model is intended for flows where bypass transition, in which the transition process is dominated by large freestream disturbances, is the key transition mechanism as opposed to transition dictated by modal growth. Validation of the new transition model is performed for flows ranging from incompressible to hypersonic conditions.

  1. Transition and Turbulence Modeling for Blunt-Body Wake Flows

    NASA Technical Reports Server (NTRS)

    Nance, Robert P.; Horvath, Thomas J.; Hassan, H. A.

    1997-01-01

    This study attempts t o improve the modeling and computational prediction of high- speed transitional wake flows. The recently developed kappa - zeta (Enstrophy) turbulence model is coupled with a newly developed transition prediction method and implemented in an implicit flow solver well-suited to hypersonic flows. In this model, transition onset is determined as part of the solution. Results obtained using the new model for a 70- deg blunted cone/sting geometry demonstrate better agreement with experimental heat- transfer measurements when compared to laminar calculations as well as solutions using the kappa - omega model. Results are also presented for the situation where transition onset is preselected. It is shown that, in this case, results are quite sensitive to location of the transition point.

  2. Hearing loss severity: impaired processing of formant transition duration.

    PubMed

    Coez, A; Belin, P; Bizaguet, E; Ferrary, E; Zilbovicius, M; Samson, Y

    2010-08-01

    Normal hearing listeners exploit the formant transition (FT) detection to identify place of articulation for stop consonants. Neuro-imaging studies revealed that short FT induced less cortical activation than long FT. To determine the ability of hearing impaired listeners to distinguish short and long formant transitions (FT) from vowels of the same duration, 84 mild to severe hearing impaired listeners and 5 normal hearing listeners were asked to detect 10 synthesized stimuli with long (200 ms) or short (40 ms) FT among 30 stimuli of the same duration without FT. Hearing impaired listeners were tested with and without hearing aids. The effect of the difficulty of the task (short/long FT) was analysed as a function of the hearing loss with and without hearing aids. Normal hearing listeners were able to detect every FT (short and long). For hearing impaired listeners, the detection of long FT was better than that of short ones irrespective of their degree of hearing loss. The use of hearing aids improved detection of both kinds of FT; however, the detection of long FT remained much better than the detection of the short ones. The length of FT modified the ability of hearing impaired patients to detect FT. Short FT had access to less cortical processing than long FT and cochlea damages enhanced this specific deficit in short FT brain processing. These findings help to understand the limit of deafness rehabilitation in the time domain and should be taken into account in future devices development. PMID:20600193

  3. Correlated Percolation Models of Jamming and Glass Transitions

    NASA Astrophysics Data System (ADS)

    Jeng, Monwhea; Schwarz, Jennifer

    2007-03-01

    Toninelli, Biroli, and Fisher recently introduced a model of correlated percolation called the Knight model, which they claimed to prove underwent a dynamical glass transition. This transition had novel properties, with a discontinuous jump in the order parameter, but with diverging time scales and correlation lengths. We show that their proof misidentified the critical point, so that these properties are currently unproven for this model. However, we show that these novel properties can in fact be proven for suitably modified models of correlated percolation, with qualitatively similar culling rules. We discuss the features of the models necessary for a rigorous proof to be possible. We also discuss properties of models such as the force balance model and the original Knight model, which appear to undergo novel transitions despite the lack of a rigorous proof of such a transition.

  4. Dynamic network modelling to understand flowering transition and floral patterning.

    PubMed

    Davila-Velderrain, J; Martinez-Garcia, J C; Alvarez-Buylla, E R

    2016-04-01

    Differentiation and morphogenetic processes during plant development are particularly robust. At the cellular level, however, plants also show great plasticity in response to environmental conditions, and can even reverse apparently terminal differentiated states with remarkable ease. Can we understand and predict both robust and plastic systemic responses as a general consequence of the non-trivial interplay between intracellular regulatory networks, extrinsic environmental signalling, and tissue-level mechanical constraints? Flower development has become an ideal model system to study these general questions of developmental biology, which are especially relevant to understanding stem cell patterning in plants, animals, and human disease. Decades of detailed study of molecular developmental genetics, as well as novel experimental techniques for in vivo assays in both wild-type and mutant plants, enable the postulation and testing of experimentally grounded mathematical and computational network dynamical models. Research in our group aims to explain the emergence of robust transitions that occur at the shoot apical meristem, as well as flower development, as the result of the collective action of key molecular components in regulatory networks subjected to intra-organismal signalling and extracellular constraints. Here we present a brief overview of recent work from our group, and that of others, focusing on the use of simple dynamical models to address cell-fate specification and cell-state stochastic dynamics during flowering transition and cell-state transitions at the shoot apical meristem of Arabidopsis thaliana. We also focus on how our work fits within the general field of plant developmental modelling, which is being developed by many others. PMID:27025221

  5. A Simple Model for Complex Dynamical Transitions in Epidemics

    NASA Astrophysics Data System (ADS)

    Earn, David J. D.; Rohani, Pejman; Bolker, Benjamin M.; Grenfell, Bryan T.

    2000-01-01

    Dramatic changes in patterns of epidemics have been observed throughout this century. For childhood infectious diseases such as measles, the major transitions are between regular cycles and irregular, possibly chaotic epidemics, and from regionally synchronized oscillations to complex, spatially incoherent epidemics. A simple model can explain both kinds of transitions as the consequences of changes in birth and vaccination rates. Measles is a natural ecological system that exhibits different dynamical transitions at different times and places, yet all of these transitions can be predicted as bifurcations of a single nonlinear model.

  6. Magnetization Processes During FM Transitions of Supercooled Er Films

    NASA Astrophysics Data System (ADS)

    Durfee, C. S.; Flynn, C. P.

    2000-03-01

    FM transitions are generally accompanied by dimensional changes of the crystal lattice. In magnetic films, the in-plane dimensional changes are inhibited by clamping to the substrate, creating a rich variety of phenomena (e.g. supercooling, dislocation formation and motion, bowing of dislocations, and altered magnetization processes), which can be directly observed with x-rays. Here we characterize the magnetization processes exhibited by unstrained Er films. Below the Curie temperature, the film exhibits supercooling, remaining in a metastable non-FM state and only relaxing to the FM state when a magnetic field is applied. This occurs by two distinct processes. The first process, which broadens the x-ray line shape, is nucleation and growth of FM domains. The second, which produces no line broadening, is isotropic magnetization of the entire film. Once magnetized, the film remains in the FM state until the temperature is raised several degrees above the Curie temperature, at which point the film relaxes to the non-FM state via one of these two paths. This process depends on the temperature when the field is removed.

  7. Processed foods and the nutrition transition: evidence from Asia.

    PubMed

    Baker, P; Friel, S

    2014-07-01

    This paper elucidates the role of processed foods and beverages in the 'nutrition transition' underway in Asia. Processed foods tend to be high in nutrients associated with obesity and diet-related non-communicable diseases: refined sugar, salt, saturated and trans-fats. This paper identifies the most significant 'product vectors' for these nutrients and describes changes in their consumption in a selection of Asian countries. Sugar, salt and fat consumption from processed foods has plateaued in high-income countries, but has rapidly increased in the lower-middle and upper-middle-income countries. Relative to sugar and salt, fat consumption in the upper-middle- and lower-middle-income countries is converging most rapidly with that of high-income countries. Carbonated soft drinks, baked goods, and oils and fats are the most significant vectors for sugar, salt and fat respectively. At the regional level there appears to be convergence in consumption patterns of processed foods, but country-level divergences including high levels of consumption of oils and fats in Malaysia, and soft drinks in the Philippines and Thailand. This analysis suggests that more action is needed by policy-makers to prevent or mitigate processed food consumption. Comprehensive policy and regulatory approaches are most likely to be effective in achieving these goals. PMID:24735161

  8. First-order phase transitions in outbreaks of co-infectious diseases and the extended general epidemic process

    NASA Astrophysics Data System (ADS)

    Janssen, Hans-Karl; Stenull, Olaf

    2016-01-01

    In co-infections, positive feedback between multiple diseases can accelerate outbreaks. In a recent letter Chen, Ghanbarnejad, Cai, and Grassberger (CGCG) introduced a spatially homogeneous mean-field model system for such co-infections, and studied this system numerically with focus on the possible existence of discontinuous phase transitions. We show that their model coincides in mean-field theory with the homogenous limit of the extended general epidemic process (EGEP). Studying the latter analytically, we argue that the discontinuous transition observed by CGCG is basically a spinodal phase transition and not a first-order transition with phase coexistence. We derive the conditions for this spinodal transition along with predictions for important quantities such as the magnitude of the discontinuity. We also shed light on a true first-order transition with phase coexistence by discussing the EGEP with spatial inhomogeneities.

  9. Correlation-based Transition Modeling for External Aerodynamic Flows

    NASA Astrophysics Data System (ADS)

    Medida, Shivaji

    Conventional turbulence models calibrated for fully turbulent boundary layers often over-predict drag and heat transfer on aerodynamic surfaces with partially laminar boundary layers. A robust correlation-based model is developed for use in Reynolds-Averaged Navier-Stokes simulations to predict laminar-to-turbulent transition onset of boundary layers on external aerodynamic surfaces. The new model is derived from an existing transition model for the two-equation k-omega Shear Stress Transport (SST) turbulence model, and is coupled with the one-equation Spalart-Allmaras (SA) turbulence model. The transition model solves two transport equations for intermittency and transition momentum thickness Reynolds number. Experimental correlations and local mean flow quantities are used in the model to account for effects of freestream turbulence level and pressure gradients on transition onset location. Transition onset is triggered by activating intermittency production using a vorticity Reynolds number criterion. In the new model, production and destruction terms of the intermittency equation are modified to improve consistency in the fully turbulent boundary layer post-transition onset, as well as ensure insensitivity to freestream eddy viscosity value specified in the SA model. In the original model, intermittency was used to control production and destruction of turbulent kinetic energy. Whereas, in the new model, only the production of eddy viscosity in SA model is controlled, and the destruction term is not altered. Unlike the original model, the new model does not use an additional correction to intermittency for separation-induced transition. Accuracy of drag predictions are improved significantly with the use of the transition model for several two-dimensional single- and multi-element airfoil cases over a wide range of Reynolds numbers. The new model is able to predict the formation of stable and long laminar separation bubbles on low-Reynolds number airfoils that

  10. Continuous percolation transition in suppressed random cluster growth model

    NASA Astrophysics Data System (ADS)

    Roy, Bappaditya; Santra, S. B.

    2016-05-01

    A new suppressed cluster growth model on 2D square lattice combining Hoshen-Kopelman and Leath approaches is studied here. The lattice sites are initially occupied randomly with probability (ρ). The empty perimeter sites of the clusters of occupied sites are grown with a cluster size dependent probability. The growth probability is then lowest for the largest cluster and highest for the smallest cluster. At the end of growth process all the cluster related quantities are estimated and they are found to display power law scaling as in percolation transition. However, the values of the critical exponents vary continuously with ρ, the initial seed concentration. At higher values of ρ, the model belongs the percolation universality class.

  11. Glass transition and relaxation processes of nanocomposite polymer electrolytes.

    PubMed

    Money, Benson K; Hariharan, K; Swenson, Jan

    2012-07-01

    This study focus on the effect of δ-Al(2)O(3) nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO(4). The results show that there are three dielectric relaxation processes, α, β, and γ, in the systems, although the structural α-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % δ-Al(2)O(3) added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden α-relaxation, even in the presence of nanofillers (at least in the case of δ-Al(2)O(3) nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the α-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces. PMID:22686254

  12. Entropy, chaos, and excited-state quantum phase transitions in the Dicke model.

    PubMed

    Lóbez, C M; Relaño, A

    2016-07-01

    We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy. PMID:27575109

  13. Curriculum Outline for Tennessee Transition Model.

    ERIC Educational Resources Information Center

    Esch, B. J.

    This curriculum outline for the Sevier County, Tennessee, transition program for special needs students provides goals and objectives for the following domains: domestic, vocational, community functioning, and recreation/leisure. The domestic domain covers personal hygiene/grooming, first aid, home nursing, birth control/pregnancy, parenting, drug…

  14. Processing-induced-transformations (PITs) during direct compression: Impact of tablet composition and compression load on phase transition of caffeine.

    PubMed

    Juban, Audrey; Briançon, Stéphanie; Puel, François

    2016-03-30

    In the pharmaceutical field, solid-state transitions that may occur during manufacturing of pharmaceuticals are of great importance. The phase transition of a model API, caffeine Form I (CFI), was studied during direct compression process by analysing the impacts of the operating conditions (process and formulation). This work is focused on two formulation parameters: nature of the diluent and impact of the caffeine dilution, and one process parameter: the compression pressure that may impact the phase transition of CFI. Tablets were made from pure CFI and from binary mixture of CFI/diluent (microcrystalline cellulose or anhydrous dicalcium phosphate). A kinetic study performed during six months helped to highlight the influence of these parameters on the CFI transition degree. Results showed a triggering effect of the direct compression process, transformation was higher in tablets than in uncompressed powders. Whatever the pressure applied, CFI transition degree was almost constant and uniformly occurring throughout the tablet volume. Nevertheless, several differences on the evolution of the CFI transition degree were observed between binary mixtures of CFI/diluent. An analysis of the transition mechanism with a stretched exponential law of the Johnson-Mehl-Avrami model shows that tableting accelerates the polymorphic transition without modifying its mechanism controlled by nucleation only. PMID:26853314

  15. Using the Research and Development in Organisations Model to Improve Transition to High School

    ERIC Educational Resources Information Center

    Ashton, Rebecca

    2009-01-01

    This article describes the application of the Research and Development in Organisations (RADIO) model to five action research projects carried out in schools around transition processes. The RADIO model is mapped onto all five studies, and adapting the model in order to include greater stakeholder participation is suggested. Reflections are made…

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

    PubMed

    Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter

    2012-07-01

    Discontinuous percolation transitions and the associated tricritical points are manifest in a wide range of both equilibrium and nonequilibrium cooperative phenomena. To demonstrate this, we present and relate the continuous and first-order behaviors in two different classes of models: The first are generalized epidemic processes that describe in their spatially embedded version--either on or off a regular lattice--compact or fractal cluster growth in random media at zero temperature. A random graph version of these processes is mapped onto a model previously proposed for complex social contagion. We compute detailed phase diagrams and compare our numerical results at the tricritical point in d = 3 with field theory predictions of Janssen et al. [Phys. Rev. E 70, 026114 (2004)]. The second class consists of exponential ("Hamiltonian," i.e., formally equilibrium) random graph models and includes the Strauss and the two-star model, where "chemical potentials" control the densities of links, triangles, or two-stars. When the chemical potentials in either graph model are O(logN), the percolation transition can coincide with a first-order phase transition in the density of links, making the former also discontinuous. Hysteresis loops can then be of mixed order, with second-order behavior for decreasing link fugacity, and a jump (first order) when it increases. PMID:23005389

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

    NASA Astrophysics Data System (ADS)

    Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter

    2012-07-01

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

  18. Cost Models for MMC Manufacturing Processes

    NASA Technical Reports Server (NTRS)

    Elzey, Dana M.; Wadley, Haydn N. G.

    1996-01-01

    Processes for the manufacture of advanced metal matrix composites are rapidly approaching maturity in the research laboratory and there is growing interest in their transition to industrial production. However, research conducted to date has almost exclusively focused on overcoming the technical barriers to producing high-quality material and little attention has been given to the economical feasibility of these laboratory approaches and process cost issues. A quantitative cost modeling (QCM) approach was developed to address these issues. QCM are cost analysis tools based on predictive process models relating process conditions to the attributes of the final product. An important attribute, of the QCM approach is the ability to predict the sensitivity of material production costs to product quality and to quantitatively explore trade-offs between cost and quality. Applications of the cost models allow more efficient direction of future MMC process technology development and a more accurate assessment of MMC market potential. Cost models were developed for two state-of-the art metal matrix composite (MMC) manufacturing processes: tape casting and plasma spray deposition. Quality and Cost models are presented for both processes and the resulting predicted quality-cost curves are presented and discussed.

  19. Radiolysis Process Model

    SciTech Connect

    Buck, Edgar C.; Wittman, Richard S.; Skomurski, Frances N.; Cantrell, Kirk J.; McNamara, Bruce K.; Soderquist, Chuck Z.

    2012-07-17

    Assessing the performance of spent (used) nuclear fuel in geological repository requires quantification of time-dependent phenomena that may influence its behavior on a time-scale up to millions of years. A high-level waste repository environment will be a dynamic redox system because of the time-dependent generation of radiolytic oxidants and reductants and the corrosion of Fe-bearing canister materials. One major difference between used fuel and natural analogues, including unirradiated UO2, is the intense radiolytic field. The radiation emitted by used fuel can produce radiolysis products in the presence of water vapor or a thin-film of water (including OH• and H• radicals, O2-, eaq, H2O2, H2, and O2) that may increase the waste form degradation rate and change radionuclide behavior. H2O2 is the dominant oxidant for spent nuclear fuel in an O2 depleted water environment, the most sensitive parameters have been identified with respect to predictions of a radiolysis model under typical conditions. As compared with the full model with about 100 reactions it was found that only 30-40 of the reactions are required to determine [H2O2] to one part in 10–5 and to preserve most of the predictions for major species. This allows a systematic approach for model simplification and offers guidance in designing experiments for validation.

  20. A Symmetrized Basis for Transitions in the Heisenberg Model

    NASA Astrophysics Data System (ADS)

    Haydock, Roger; Nex, C. M. M.

    2013-03-01

    The spin-S Heisenberg model has 2S+1 states on each site, for which there are (2S+1)2 possible transitions between these states. For N sites there are (2S+1)N states and (2S+1)2N transitions between states. This rapid increase in the number of transitions with sites appears to limit calculations to just a few sites. However for transitions induced by spin-spin interactions, we construct a symmetrized basis which only grows as 2N-3, making possible computations for much larger systems. Supported by the Richmond F. Snyder Fund.

  1. Security Transition Program Office (STPO), technology transfer of the STPO process, tools, and techniques

    SciTech Connect

    Hauth, J.T.; Forslund, C.R.J.; Underwood, J.A.

    1994-09-01

    In 1990, with the transition from a defense mission to environmental restoration, the U.S. Department of Energy`s (DOE`s) Hanford Site began a significant effort to diagnose, redesign, and implement new safeguards and security (SAS) processes. In 1992 the Security Transition Program Office (STPO) was formed to address the sweeping changes that were being identified. Comprised of SAS and other contractor staff with extensive experience and supported by staff experienced in organizational analysis and work process redesign, STPO undertook a series of tasks designed to make fundamental changes to SAS processes throughout the Hanford Site. The goal of STPO is to align the SAS work and organization with the new Site mission. This report describes the key strategy, tools, methods, and techniques used by STPO to change SAS processes at Hanford. A particular focus of this review is transferring STPO`s experience to other DOE sites and federal agency efforts: that is, to extract, analyze, and provide a critical review of the approach, tools, and techniques used by STPO that will be useful to other DOE sites and national laboratories in transitioning from a defense production mode to environmental restoration and other missions. In particular, what lessons does STPO provide as a pilot study or model for implementing change in other transition activities throughout the DOE complex? More broadly, what theoretical and practical contributions do DOE transition efforts, such as STPO, provide to federal agency streamlining efforts and attempts to {open_quotes}reinvent{close_quotes} government enterprises in the public sector? The approach used by STPO should provide valuable information to those examining their own processes in light of new mission requirements.

  2. Wake interaction effects on the transition process on turbine blades

    NASA Astrophysics Data System (ADS)

    Ainsworth, R. W.; Lagraff, J. E.

    1987-10-01

    The characterization of the nozzle guide vane inlet and exit conditions in the Oxford University Isentropic Light Piston Tunnel fully 3-D annular rotating stage has been undertaken. Measurements included hot wire anemometry and pressure/Mach number distributions. Preparations for the rotor heat transfer instrumentation/data acquisition hardware and software are also in progress. Further development of a numerical model to predict the effects of wake passing and transition is reported. The convection of the wake through the passage is predicted, allowing for estimations of the expected times for which the boundary layer is disturbed by the wake fluid. The new model for the random generation and subsequent growth and convection of the turbulent spots produces a time-resolved prediction of the intermittent heat transfer signals by use of a time-marching procedure. By superimposing the two numerical models it is possible to simulate the measured instantaneous heat transfer characteristics and to estimate the effective average intermittency along the blade surface and compare the results to the measured intermittency values.

  3. Business Process Modeling: Perceived Benefits

    NASA Astrophysics Data System (ADS)

    Indulska, Marta; Green, Peter; Recker, Jan; Rosemann, Michael

    The process-centered design of organizations and information systems is globally seen as an appropriate response to the increased economic pressure on organizations. At the methodological core of process-centered management is process modeling. However, business process modeling in large initiatives can be a time-consuming and costly exercise, making it potentially difficult to convince executive management of its benefits. To date, and despite substantial interest and research in the area of process modeling, the understanding of the actual benefits of process modeling in academia and practice is limited. To address this gap, this paper explores the perception of benefits derived from process modeling initiatives, as reported through a global Delphi study. The study incorporates the views of three groups of stakeholders - academics, practitioners and vendors. Our findings lead to the first identification and ranking of 19 unique benefits associated with process modeling. The study in particular found that process modeling benefits vary significantly between practitioners and academics. We argue that the variations may point to a disconnect between research projects and practical demands.

  4. [Succession in forest coenoses: a model of second-order phase transition].

    PubMed

    Isaev, A S; Sukhovol'skiĭ, V G; Buzykin, A I; Ovchinnikova, T M

    2009-01-01

    The changes of arboreous coenoses composition resulting from natural and anthropogenic impacts are considered. The mathematical model is proposed and verified that describes arboreous cenoses transition from one succession state into another by analogy with phase transition in statistical physics. It is demonstrated that the model is concordant with the data of full-scale observations. The model allows to explain the trend of succession processes and determine the stage of forestation process at which succession transitions should be expected. The analysis of full-scale observations data by means of the proposed approach makes it possible to calculate, for given regions and forest types, the critical values of planting phytomass that, upon being attained, initiate the succession transition. Those values are important to be known for middle- and long-term forecasting of forest cover dynamics. PMID:20063768

  5. The electroweak phase transition in the Inert Doublet Model

    SciTech Connect

    Blinov, Nikita; Profumo, Stefano; Stefaniak, Tim

    2015-07-21

    We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.

  6. PYTRANSIT: fast and easy exoplanet transit modelling in PYTHON

    NASA Astrophysics Data System (ADS)

    Parviainen, Hannu

    2015-07-01

    We present a fast and user friendly exoplanet transit light-curve modelling package PYTRANSIT, implementing optimized versions of the Giménez and Mandel & Agol transit models. The package offers an object-oriented PYTHON interface to access the two models implemented natively in FORTRAN with OpenMP parallelization. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PYTRANSIT is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations, as a part of a researcher's programming toolkit for building complex, problem-specific analyses.

  7. The folding transition state theory in simple model systems

    NASA Astrophysics Data System (ADS)

    Niewieczerzał, Szymon; Cieplak, Marek

    2008-06-01

    We present the results of an exact analysis of several model free energy landscapes of a protein to clarify the notion of the transition state and the physical meaning of the phi values determined in protein engineering experiments. We argue that a proper search strategy for the transition state in more realistic models should involve identification of a common part of various methods. Two of the models considered involve explicit conformations instead of just points on the free energy axis. These models are minimalistic as they are endowed only with five or 36 states to enumerate folding paths and to identify the transition state easily. Even though they display much of the two-state behavior, the phi values are found not to correspond to the conformation of the transition state.

  8. Immunolocalization of endocan during the endothelial-mesenchymal transition process

    PubMed Central

    Carrillo, L.M.; Arciniegas, E.; Rojas, H.; Ramírez, R.

    2011-01-01

    Endocan is a dermatan sulfate proteoglycan (DSPG) that has been observed in the cytoplasm of endothelial cells of small and large vessels in lung, kidney, liver, colon, ovary and brain tumors. This DSPG has been implicated in the regulation of cellular activities such as adhesion, migration, and proliferation. Given the important roles played by endocan in such processes, we sought to determine whether this DSPG is present in the chicken embryo aortic wall in embryonic days 12 and 14, when intimal thickening and endothelial transformation are notorious. Immunolabeling of serial paraffin cross-sections revealed endocan immunoreactivity at the endothelium and some mesenchymal cells constituting the intimal thickening but not in the cells arranged in lamellar layers. We also investigated whether endocan was present in monolayers of primary embryonic aortic endothelial cells attached to fibronectin when they were deprived of serum and stimulated with epidermal growth factor. Immunofluorescence determined that in the epidermal growth factor (EGF) condition where separating, detaching, and migrating cells were observed, endocan appeared organized in arrays typical of focal complexes in the leading edge of these cells. In serum-free medium condition in which the endothelial cells displayed a cobblestone appearance, endocan appeared mainly delineating the margin of many cells. This study demonstrates for the first time the presence of endocan during the aortic wall remodeling, and provides evidence that suggests a possible contribution of this DSPG in the endothelial-mesenchymal transition (EndoMT) process. PMID:22201190

  9. Business process modeling in healthcare.

    PubMed

    Ruiz, Francisco; Garcia, Felix; Calahorra, Luis; Llorente, César; Gonçalves, Luis; Daniel, Christel; Blobel, Bernd

    2012-01-01

    The importance of the process point of view is not restricted to a specific enterprise sector. In the field of health, as a result of the nature of the service offered, health institutions' processes are also the basis for decision making which is focused on achieving their objective of providing quality medical assistance. In this chapter the application of business process modelling - using the Business Process Modelling Notation (BPMN) standard is described. Main challenges of business process modelling in healthcare are the definition of healthcare processes, the multi-disciplinary nature of healthcare, the flexibility and variability of the activities involved in health care processes, the need of interoperability between multiple information systems, and the continuous updating of scientific knowledge in healthcare. PMID:22925789

  10. Conceptual models of information processing

    NASA Technical Reports Server (NTRS)

    Stewart, L. J.

    1983-01-01

    The conceptual information processing issues are examined. Human information processing is defined as an active cognitive process that is analogous to a system. It is the flow and transformation of information within a human. The human is viewed as an active information seeker who is constantly receiving, processing, and acting upon the surrounding environmental stimuli. Human information processing models are conceptual representations of cognitive behaviors. Models of information processing are useful in representing the different theoretical positions and in attempting to define the limits and capabilities of human memory. It is concluded that an understanding of conceptual human information processing models and their applications to systems design leads to a better human factors approach.

  11. Modeling nuclear processes by Simulink

    NASA Astrophysics Data System (ADS)

    Rashid, Nahrul Khair Alang Md

    2015-04-01

    Modelling and simulation are essential parts in the study of dynamic systems behaviours. In nuclear engineering, modelling and simulation are important to assess the expected results of an experiment before the actual experiment is conducted or in the design of nuclear facilities. In education, modelling can give insight into the dynamic of systems and processes. Most nuclear processes can be described by ordinary or partial differential equations. Efforts expended to solve the equations using analytical or numerical solutions consume time and distract attention from the objectives of modelling itself. This paper presents the use of Simulink, a MATLAB toolbox software that is widely used in control engineering, as a modelling platform for the study of nuclear processes including nuclear reactor behaviours. Starting from the describing equations, Simulink models for heat transfer, radionuclide decay process, delayed neutrons effect, reactor point kinetic equations with delayed neutron groups, and the effect of temperature feedback are used as examples.

  12. Modeling nuclear processes by Simulink

    SciTech Connect

    Rashid, Nahrul Khair Alang Md

    2015-04-29

    Modelling and simulation are essential parts in the study of dynamic systems behaviours. In nuclear engineering, modelling and simulation are important to assess the expected results of an experiment before the actual experiment is conducted or in the design of nuclear facilities. In education, modelling can give insight into the dynamic of systems and processes. Most nuclear processes can be described by ordinary or partial differential equations. Efforts expended to solve the equations using analytical or numerical solutions consume time and distract attention from the objectives of modelling itself. This paper presents the use of Simulink, a MATLAB toolbox software that is widely used in control engineering, as a modelling platform for the study of nuclear processes including nuclear reactor behaviours. Starting from the describing equations, Simulink models for heat transfer, radionuclide decay process, delayed neutrons effect, reactor point kinetic equations with delayed neutron groups, and the effect of temperature feedback are used as examples.

  13. Reversal Transition Records from Intrusions: Implications for the Reversal Process.

    NASA Astrophysics Data System (ADS)

    Fuller, M. D.; Williams, I. S.

    2014-12-01

    The nature of reversals of the geomagnetic field and the details of the transition fields remain controversial. However, reversal records from the Agno batholith and Tatoosh intrusion confirm the suggestion of Valet et al., (2012) from studies of lava records, that there is a threefold division in reversal transition directions. In the Agno, the first phase, or precursor, consists of a CCW loop of the VGP moving from high southerly latitude reverse poles to reach North America. The second phase takes the VGP along a half CCW loop from the tip of South America to northern latitudes at the intensity minimum. The third phase, or rebound is a smaller CCW loop and the main intensity recovery begins. The first and third phases appear to be paleosecular variation loops analogous to present London-Paris secular variation loops. The Tatoosh intrusion gives a similar, but less complete record with the VGPs again confined to the East Pacific and the Americas. Away from the reversal region, secular variation loops in the Tatoosh were shown to be comparable in duration to the precursor in the transition record, consistent with the first phase being a paleosecular variation loop in the Agno. Using westward drift estimates from the present field, this should last about1800 years. This gives ~3300 for phase 2, in an intensity low of >16,000 years. A feature of R to N reversal field models is a low latitude magnetic field flux concentration of the same sign as the polar vortex of the south geographic pole. This is followed by northward flux flow, e.g. Shao et al., (1999). The reversal is achieved by northward motion of this flux feature. The feature is locked in longitudinal mantle coordinates and similarly the VGPs in the Agno and Tatoosh records are confined to the longitudes of the eastern Pacific and the Americas. Whether we are approaching a reversal remains to be seen, although judging by these intrusion records the field intensity would need to decrease much further before

  14. A Transitional Care Model Using Faith Community Nurses.

    PubMed

    Ziebarth, Deborah; Campbell, Katora P

    2016-01-01

    The Medicare mandatory readmission reduction program has hospitals scrambling to reduce 30-day readmissions. A Faith Community Nurse (FCN) Transitional Care Model was developed from systematic literature review of predictive factors of readmission and pre- and postdischarge interventions that decrease readmission. The model presents specific FCN care that occurs pre- and posthospital discharge to support the patient in transitioning from one level of care to another, move toward wholistic health, and avoid unnecessary readmission. PMID:27119808

  15. Variability in Response to Life Transitions: Application of a Transition Model.

    ERIC Educational Resources Information Center

    Kampfe, Charlene M.

    The modified House Model of Social Stress is used to discuss the variability of individual responses to potentially stressful events or transitions. The model graphically depicts the variety of ways people respond to the potentially complex interaction among variables associated with stress. It also depicts the potential relationship among…

  16. Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

    NASA Astrophysics Data System (ADS)

    Voudouris, P.; Gomopoulos, N.; Le Grand, A.; Hadjichristidis, N.; Floudas, G.; Ediger, M. D.; Fytas, G.

    2010-02-01

    The primary α-relaxation time (τα) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M∗. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the α-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and τα is system dependent. In PI and PP, the former is more than one order of magnitude faster than τα, whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the α-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers.

  17. Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

    PubMed

    Voudouris, P; Gomopoulos, N; Le Grand, A; Hadjichristidis, N; Floudas, G; Ediger, M D; Fytas, G

    2010-02-21

    The primary alpha-relaxation time (tau(alpha)) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M*. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the alpha-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and tau(alpha) is system dependent. In PI and PP, the former is more than one order of magnitude faster than tau(alpha), whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the alpha-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers. PMID:20170250

  18. Modeling the Polydomain–Monodomain transition of Liquid Crystal Elastomers

    PubMed Central

    Whitmer, Jonathan K.; Roberts, Tyler F.; Shekhar, Raj; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    We study the mechanism of the polydomain–monodomain transition in liquid crystalline elastomers at the molecular scale. A coarse-grained model is proposed in which mesogens are described as ellipsoidal particles. Molecular dynamics simulations are used to examine the transition from a polydomain state to a monodomain state in the presence of uniaxial strain. Our model demonstrates soft elasticity, similar to that exhibited by side-chain elastomers in the literature. By analysing the growth dynamics of nematic domains during uniaxial extension, we provide direct evidence that at a molecular level the polydomain–monodomain transition proceeds through cluster rotation and domain growth. PMID:23496448

  19. Model potential calculations of lithium transitions.

    NASA Technical Reports Server (NTRS)

    Caves, T. C.; Dalgarno, A.

    1972-01-01

    Semi-empirical potentials are constructed that have eigenvalues close in magnitude to the binding energies of the valence electron in lithium. The potentials include the long range polarization force between the electron and the core. The corresponding eigenfunctions are used to calculate dynamic polarizabilities, discrete oscillator strengths, photoionization cross sections and radiative recombination coefficients. A consistent application of the theory imposes a modification on the transition operator, but its effects are small for lithium. The method presented can be regarded as a numerical generalization of the widely used Coulomb approximation.

  20. TGF-β induced epithelial-mesenchymal transition modeling

    NASA Astrophysics Data System (ADS)

    Xenitidis, P.; Seimenis, I.; Kakolyris, S.; Adamopoulos, A.

    2015-09-01

    Epithelial cells may undergo a process called epithelial to mesenchymal transition (EMT). During EMT, cells lose their epithelial characteristics and acquire a migratory ability. Transforming growth factor-beta (TGF-β) signaling is considered to play an important role in EMT by regulating a set of genes through a gene regulatory network (GRN). This work aims at TGF-β induced EMT GRN modeling using publicly available experimental data (gene expression microarray data). The time-series network identification (TSNI) algorithm was used for inferring the EMT GRN. Receiver operating characteristic (ROC) and precision-recall (P-R) curves were constructed and the areas under them were used for evaluating the algorithm performance regarding network inference.

  1. Electrophysiological models of neural processing.

    PubMed

    Nelson, Mark E

    2011-01-01

    The brain is an amazing information processing system that allows organisms to adaptively monitor and control complex dynamic interactions with their environment across multiple spatial and temporal scales. Mathematical modeling and computer simulation techniques have become essential tools in understanding diverse aspects of neural processing ranging from sub-millisecond temporal coding in the sound localization circuity of barn owls to long-term memory storage and retrieval in humans that can span decades. The processing capabilities of individual neurons lie at the core of these models, with the emphasis shifting upward and downward across different levels of biological organization depending on the nature of the questions being addressed. This review provides an introduction to the techniques for constructing biophysically based models of individual neurons and local networks. Topics include Hodgkin-Huxley-type models of macroscopic membrane currents, Markov models of individual ion-channel currents, compartmental models of neuronal morphology, and network models involving synaptic interactions among multiple neurons. PMID:21064164

  2. TRANSIT MODEL FITTING IN THE KEPLER SCIENCE OPERATIONS CENTER PIPELINE: NEW FEATURES AND PERFORMANCE

    NASA Astrophysics Data System (ADS)

    Li, Jie; Burke, C. J.; Jenkins, J. M.; Quintana, E. V.; Rowe, J. F.; Seader, S. E.; Tenenbaum, P.; Twicken, J. D.

    2013-10-01

    We describe new transit model fitting features and performance of the latest release (9.1, July 2013) of the Kepler Science Operations Center (SOC) Pipeline. The targets for which a Threshold Crossing Event (TCE) is generated in the Transiting Planet Search (TPS) component of the pipeline are subsequently processed in the Data Validation (DV) component. Transit model parameters are fitted in DV to transit-like signatures in the light curves of the targets with TCEs. The transit model fitting results are used in diagnostic tests in DV, which help to validate planet candidates and identify false positive detections. The standard transit model includes five fit parameters: transit epoch time (i.e. central time of first transit), orbital period, impact parameter, ratio of planet radius to star radius and ratio of semi-major axis to star radius. Light curves for many targets do not contain enough information to uniquely determine the impact parameter, which results in poor convergence performance of the fitter. In the latest release of the Kepler SOC pipeline, a reduced parameter fit is included in DV: the impact parameter is set to a fixed value and the four remaining parameters are fitted. The standard transit model fit is implemented after a series of reduced parameter fits in which the impact parameter is varied between 0 and 1. Initial values for the standard transit model fit parameters are determined by the reduced parameter fit with the minimum chi-square metric. With reduced parameter fits, the robustness of the transit model fit is improved significantly. Diagnostic plots of the chi-square metrics and reduced parameter fit results illustrate how the fitted parameters vary as a function of impact parameter. Essentially, a family of transiting planet characteristics is determined in DV for each Pipeline TCE. Transit model fitting performance of release 9.1 of the Kepler SOC pipeline is demonstrated with the results of the processing of 16 quarters of flight data

  3. Thermal and Nonthermal Processes on Single Crystal Transition Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Guo, Xingcai

    investigated with polarized light. Photon-induced desorption of CO from oxidized Ni(111) (Chapter 13) is observed to be initiated by substrate interband transition. The photodesorption process is first -order in photon flux and in CO coverage. The cross section is measured to be 5 times 10 ^{-18} cm^2 at a photon energy of 4.1 eV. The appendices list abstracts of additional published results on HCN/Pt(111),(112); HCN + O/Pt(111),(112); HCN + O_2/Pt(111); CN + H(s)/Pd(111); HCN/Pd(111); Azo-methane/Pd(111); Methanol/Pd(111); Dimethyl methyl phosphonate/Pd(111), Ni(111); NO + O,S/Ni(111); Xe/Pt(111), (557), (112).

  4. Models of the Reading Process

    PubMed Central

    Rayner, Keith; Reichle, Erik D.

    2010-01-01

    Reading is a complex skill involving the orchestration of a number of components. Researchers often talk about a “model of reading” when talking about only one aspect of the reading process (for example, models of word identification are often referred to as “models of reading”). Here, we review prominent models that are designed to account for (1) word identification, (2) syntactic parsing, (3) discourse representations, and (4) how certain aspects of language processing (e.g., word identification), in conjunction with other constraints (e g., limited visual acuity, saccadic error, etc.), guide readers’ eyes. Unfortunately, it is the case that these various models addressing specific aspects of the reading process seldom make contact with models dealing with other aspects of reading. Thus, for example, the models of word identification seldom make contact with models of eye movement control, and vice versa. While this may be unfortunate in some ways, it is quite understandable in other ways because reading itself is a very complex process. We discuss prototypical models of aspects of the reading process in the order mentioned above. We do not review all possible models, but rather focus on those we view as being representative and most highly recognized. PMID:21170142

  5. Thermodynamics and phase transitions in the Overhauser model

    NASA Astrophysics Data System (ADS)

    Duffield, N. G.; Pulé, J. V.

    1989-01-01

    We analyze the thermodynamics of the Overhauser model and demonstrate rigorously the existence of a phase transition. This is achieved by extending techniques previously developed to treat the BCS model in the quasi-spin formulation. Additionally, we compare the thermodynamics of the quasi-spin and full-trace BCS models. The results are identical up to a temperature rescaling.

  6. Development of one-equation transition/turbulence models

    SciTech Connect

    Edwards, J.R.; Roy, C.J.; Blottner, F.G.; Hassan, H.A.

    2000-01-14

    This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity--transport equation for nonturbulent fluctuation growth based on that proposed by Warren and Hassan is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittency function based on the work of Dhawan and Narasimha. The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the grid-dependence of selected predictions is analyzed.

  7. Analog modelling of obduction processes

    NASA Astrophysics Data System (ADS)

    Agard, P.; Zuo, X.; Funiciello, F.; Bellahsen, N.; Faccenna, C.; Savva, D.

    2012-04-01

    Obduction corresponds to one of plate tectonics oddities, whereby dense, oceanic rocks (ophiolites) are presumably 'thrust' on top of light, continental ones, as for the short-lived, almost synchronous Peri-Arabic obduction (which took place along thousands of km from Turkey to Oman in c. 5-10 Ma). Analog modelling experiments were performed to study the mechanisms of obduction initiation and test various triggering hypotheses (i.e., plate acceleration, slab hitting the 660 km discontinuity, ridge subduction; Agard et al., 2007). The experimental setup comprises (1) an upper mantle, modelled as a low-viscosity transparent Newtonian glucose syrup filling a rigid Plexiglas tank and (2) high-viscosity silicone plates (Rhodrosil Gomme with PDMS iron fillers to reproduce densities of continental or oceanic plates), located at the centre of the tank above the syrup to simulate the subducting and the overriding plates - and avoid friction on the sides of the tank. Convergence is simulated by pushing on a piston at one end of the model with velocities comparable to those of plate tectonics (i.e., in the range 1-10 cm/yr). The reference set-up includes, from one end to the other (~60 cm): (i) the piston, (ii) a continental margin containing a transition zone to the adjacent oceanic plate, (iii) a weakness zone with variable resistance and dip (W), (iv) an oceanic plate - with or without a spreading ridge, (v) a subduction zone (S) dipping away from the piston and (vi) an upper, active continental margin, below which the oceanic plate is being subducted at the start of the experiment (as is known to have been the case in Oman). Several configurations were tested and over thirty different parametric tests were performed. Special emphasis was placed on comparing different types of weakness zone (W) and the extent of mechanical coupling across them, particularly when plates were accelerated. Displacements, together with along-strike and across-strike internal deformation in all

  8. Phase transition of the one-dimensional coagulation-production process

    SciTech Connect

    Odor, Geza

    2001-06-01

    Recently an exact solution has been found by M. Henkel and H. Hinrichsen [J. Phys. A >34, 1561 (2001)] for the one-dimensional coagulation-production process: 2A{r_arrow}A, A0A{r_arrow}3A with equal diffusion and coagulation rates. This model evolves into the inactive phase independently of the production rate with t{sup {minus}1/2} density decay law. This paper shows that cluster mean-field approximations and Monte Carlo simulations predict a continuous phase transition for higher diffusion/coagulation rates as considered by the exact solution. Numerical evidence is given that the phase transition universality agrees with that of the annihilation-fission model with low diffusions.

  9. Modeled and Observed Transitions Between Rip Currents and Alongshore Flows

    NASA Astrophysics Data System (ADS)

    Moulton, M.; Elgar, S.; Warner, J. C.; Raubenheimer, B.

    2014-12-01

    Predictions of rip currents, alongshore currents, and the temporal transitions between these circulation patterns are important for swimmer safety and for estimating the transport of sediments, biota, and pollutants in the nearshore. Here, field observations are combined with hydrodynamic modeling to determine the dominant processes that lead rip currents to turn on and off with changing waves, bathymetry, and tidal elevation. Waves, currents, mean sea levels, and bathymetry were measured near and within five shore-perpendicular channels (on average 2-m deep, 30-m wide) that were dredged with the propellers of a landing craft at different times on a long straight Atlantic Ocean beach near Duck, NC in summer 2012. The circulation was measured for a range of incident wave conditions and channel sizes, and included rapid transitions between strong (0.5 to 1 m/s) rip current jets flowing offshore through the channels and alongshore currents flowing across the channels with no rip currents. Meandering alongshore currents (alongshore currents combined with an offshore jet at the downstream edge of the channel) also were observed. Circulation patterns near and within idealized rip channels simulated with COAWST (a three-dimensional phase-averaged model that couples ROMS and SWAN) are compared with the observations. In addition, the model is used to investigate the hydrodynamic response to a range of wave conditions (angle, height, period) and bathymetries (channel width, depth, and length; tidal elevations; shape of sandbar or terrace). Rip current speeds are largest for the deepest perturbations, and decrease as incident wave angles become more oblique. For obliquely incident waves, the rip currents are shifted in the direction of the alongshore flow, with an increasing shift for increasing alongshore current speed or increasing bathymetric perturbation depth.

  10. Social Influence and Selection Processes as Predictors of Normative Perceptions and Alcohol Use across the Transition to College

    ERIC Educational Resources Information Center

    Abar, Caitlin C.; Maggs, Jennifer L.

    2010-01-01

    Research indicates that social influences impact college students' alcohol consumption; however, how selection processes may serve as an influential factor predicting alcohol use in this population has not been widely addressed. A model of influence and selection processes contributing to alcohol use across the transition to college was examined…

  11. Lifshitz transition in two-dimensional spin density wave models.

    SciTech Connect

    Lin, J.; Materials Science Division

    2010-11-09

    We argue that both pocket-disappearing and neck-disrupting types of Lifshitz transitions can be realized in two-dimensional spin-density wave models for underdoped cuprates, and study both types of transitions with impurity scattering treated in the self-consistent Born approximation. We first solve for the electron self-energy from the self-consistent equation, and then study the low-temperature electrical conductivity and thermopower. Close to the Lifshitz transition, the thermopower is strongly enhanced. For the pocket-disappearing type, it has a sharp peak while for the neck-disrupting type, it changes sign at the transition, with its absolute value peaked on both sides of the transition. We discuss possible applications to underdoped cuprates.

  12. Testing a Theoretical Model of Immigration Transition and Physical Activity.

    PubMed

    Chang, Sun Ju; Im, Eun-Ok

    2015-01-01

    The purposes of the study were to develop a theoretical model to explain the relationships between immigration transition and midlife women's physical activity and test the relationships among the major variables of the model. A theoretical model, which was developed based on transitions theory and the midlife women's attitudes toward physical activity theory, consists of 4 major variables, including length of stay in the United States, country of birth, level of acculturation, and midlife women's physical activity. To test the theoretical model, a secondary analysis with data from 127 Hispanic women and 123 non-Hispanic (NH) Asian women in a national Internet study was used. Among the major variables of the model, length of stay in the United States was negatively associated with physical activity in Hispanic women. Level of acculturation in NH Asian women was positively correlated with women's physical activity. Country of birth and level of acculturation were significant factors that influenced physical activity in both Hispanic and NH Asian women. The findings support the theoretical model that was developed to examine relationships between immigration transition and physical activity; it shows that immigration transition can play an essential role in influencing health behaviors of immigrant populations in the United States. The NH theoretical model can be widely used in nursing practice and research that focus on immigrant women and their health behaviors. Health care providers need to consider the influences of immigration transition to promote immigrant women's physical activity. PMID:26502554

  13. Student Engagement and Leadership of the Transition Planning Process

    ERIC Educational Resources Information Center

    Martin, James E.; Williams-Diehm, Kendra

    2013-01-01

    The Council for Exceptional Children's Division on Career Development and Transition (DCDT) has been a longstanding leader and advocate in the field of secondary education for students with disabilities. This paper traces the history of student engagement in transition planning primarily through the lens of DCDT's journal "Career…

  14. Kinetic Modeling of Microbiological Processes

    SciTech Connect

    Liu, Chongxuan; Fang, Yilin

    2012-08-26

    Kinetic description of microbiological processes is vital for the design and control of microbe-based biotechnologies such as waste water treatment, petroleum oil recovery, and contaminant attenuation and remediation. Various models have been proposed to describe microbiological processes. This editorial article discusses the advantages and limiation of these modeling approaches in cluding tranditional, Monod-type models and derivatives, and recently developed constraint-based approaches. The article also offers the future direction of modeling researches that best suit for petroleum and environmental biotechnologies.

  15. A process algebra model of QED

    NASA Astrophysics Data System (ADS)

    Sulis, William

    2016-03-01

    The process algebra approach to quantum mechanics posits a finite, discrete, determinate ontology of primitive events which are generated by processes (in the sense of Whitehead). In this ontology, primitive events serve as elements of an emergent space-time and of emergent fundamental particles and fields. Each process generates a set of primitive elements, using only local information, causally propagated as a discrete wave, forming a causal space termed a causal tapestry. Each causal tapestry forms a discrete and finite sampling of an emergent causal manifold (space-time) M and emergent wave function. Interactions between processes are described by a process algebra which possesses 8 commutative operations (sums and products) together with a non-commutative concatenation operator (transitions). The process algebra possesses a representation via nondeterministic combinatorial games. The process algebra connects to quantum mechanics through the set valued process and configuration space covering maps, which associate each causal tapestry with sets of wave functions over M. Probabilities emerge from interactions between processes. The process algebra model has been shown to reproduce many features of the theory of non-relativistic scalar particles to a high degree of accuracy, without paradox or divergences. This paper extends the approach to a semi-classical form of quantum electrodynamics.

  16. Social Models: Blueprints or Processes?

    ERIC Educational Resources Information Center

    Little, Graham R.

    1981-01-01

    Discusses the nature and implications of two different models for societal planning: (1) the problem-solving process approach based on Karl Popper; and (2) the goal-setting "blueprint" approach based on Karl Marx. (DC)

  17. Some Results on the Analysis of Stochastic Processes with Uncertain Transition Probabilities and Robust Optimal Control

    SciTech Connect

    Keyong Li; Seong-Cheol Kang; I. Ch. Paschalidis

    2007-09-01

    This paper investigates stochastic processes that are modeled by a finite number of states but whose transition probabilities are uncertain and possibly time-varying. The treatment of uncertain transition probabilities is important because there appears to be a disconnection between the practice and theory of stochastic processes due to the difficulty of assigning exact probabilities to real-world events. Also, when the finite-state process comes as a reduced model of one that is more complicated in nature (possibly in a continuous state space), existing results do not facilitate rigorous analysis. Two approaches are introduced here. The first focuses on processes with one terminal state and the properties that affect their convergence rates. When a process is on a complicated graph, the bound of the convergence rate is not trivially related to that of the probabilities of individual transitions. Discovering the connection between the two led us to define two concepts which we call 'progressivity' and 'sortedness', and to a new comparison theorem for stochastic processes. An optimality criterion for robust optimal control also derives from this comparison theorem. In addition, this result is applied to the case of mission-oriented autonomous robot control to produce performance estimate within a control framework that we propose. The second approach is in the MDP frame work. We will introduce our preliminary work on optimistic robust optimization, which aims at finding solutions that guarantee the upper bounds of the accumulative discounted cost with prescribed probabilities. The motivation here is to address the issue that the standard robust optimal solution tends to be overly conservative.

  18. The improved code TAC maker for modeling of planet transits

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Dimitrov, D.; Vladev, A.

    We present improvements of the code TAC-maker for modeling of planet transits. While the initial version of the code calculated synthetic transits for certain values of the input parameters, the new version TAC-maker 1.1.0 gives a possibility to obtain simultaneously numerous synthetic transits corresponding to chosen ranges of values for each fitted parameter. The most valuable property of the improved version of the code is the ability to obtain the global minimum of χ^{2} in the multidimensional parametric space and to estimate the errors of the searched parameters.

  19. Transitions.

    ERIC Educational Resources Information Center

    Nathanson, Jeanne H., Ed.

    1993-01-01

    This theme issue on transitions for individuals with disabilities contains nine papers discussing transition programs and issues. "Transition Issues for the 1990s," by Michael J. Ward and William D. Halloran, discusses self-determination, school responsibility for transition, continued educational engagement of at-risk students, and service…

  20. Phase transitions in models of human cooperation

    NASA Astrophysics Data System (ADS)

    Perc, Matjaž

    2016-08-01

    If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.

  1. Role of secondary instability theory and parabolized stability equations in transition modeling

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.; Dinavahi, Surya P.; Chang, Chau-Lyan; Zang, Thomas A.

    1993-01-01

    In modeling the laminar-turbulent transition region, the designer depends largely on benchmark data from experiments and/or direct numerical simulations that are usually extremely expensive. An understanding of the evolution of the Reynolds stresses, turbulent kinetic energy, and quantifies in the transport equations like the dissipation and production is essential in the modeling process. The secondary instability theory and the parabolized stability equations method are used to calculate these quantities, which are then compared with corresponding quantities calculated from available direct numerical simulation data for the incompressible boundary-layer flow of laminar-turbulent transition conditions. The potential of the secondary instability theory and the parabolized stability equations approach in predicting these quantities is discussed; results indicate that inexpensive data that are useful for transition modeling in the early stages of the transition region can be provided by these tools.

  2. Transitions in a probabilistic interface growth model

    NASA Astrophysics Data System (ADS)

    Alves, S. G.; Moreira, J. G.

    2011-04-01

    We study a generalization of the Wolf-Villain (WV) interface growth model based on a probabilistic growth rule. In the WV model, particles are randomly deposited onto a substrate and subsequently move to a position nearby where the binding is strongest. We introduce a growth probability which is proportional to a power of the number ni of bindings of the site i: p_i\\propto n_i^\

  3. Diffraction model of a step-out transition

    SciTech Connect

    Chao, A.W.; Zimmermann, F.

    1996-06-01

    The diffraction model of a cavity, suggested by Lawson, Bane and Sands is generalized to a step out transition. Using this model, the high frequency impedance is calculated explicitly for the case that the transition step is small compared with the beam pipe radius. In the diffraction model for a small step out transition, the total energy is conserved, but, unlike the cavity case, the diffracted waves in the geometric shadow and the pipe region, in general, do not always carry equal energy. In the limit of small step sizes, the impedance derived from the diffraction model agrees with that found by Balakin, Novokhatsky and also Kheifets. This impedance can be used to compute the wake field of a round collimator whose half aperture is much larger than the bunch length, as existing in the SLC final focus.

  4. The remarkable ability of turbulence model equations to describe transition

    NASA Technical Reports Server (NTRS)

    Wilcox, David C.

    1992-01-01

    This paper demonstrates how well the k-omega turbulence model describes the nonlinear growth of flow instabilities from laminar flow into the turbulent flow regime. Viscous modifications are proposed for the k-omega model that yield close agreement with measurements and with Direct Numerical Simulation results for channel and pipe flow. These modifications permit prediction of subtle sublayer details such as maximum dissipation at the surface, k approximately y(exp 2) as y approaches 0, and the sharp peak value of k near the surface. With two transition specific closure coefficients, the model equations accurately predict transition for an incompressible flat-plate boundary layer. The analysis also shows why the k-epsilon model is so difficult to use for predicting transition.

  5. Metrics for Business Process Models

    NASA Astrophysics Data System (ADS)

    Mendling, Jan

    Up until now, there has been little research on why people introduce errors in real-world business process models. In a more general context, Simon [404] points to the limitations of cognitive capabilities and concludes that humans act rationally only to a certain extent. Concerning modeling errors, this argument would imply that human modelers lose track of the interrelations of large and complex models due to their limited cognitive capabilities and introduce errors that they would not insert in a small model. A recent study by Mendling et al. [275] explores in how far certain complexity metrics of business process models have the potential to serve as error determinants. The authors conclude that complexity indeed appears to have an impact on error probability. Before we can test such a hypothesis in a more general setting, we have to establish an understanding of how we can define determinants that drive error probability and how we can measure them.

  6. Modeling non-equilibrium phase transitions in isentropically compressed Bi

    SciTech Connect

    Kane, J; Smith, R

    2005-09-19

    We report here on modeling of non-equilibrium phase transitions in Bi samples isentropically compressed to 120 GPa by a ramped drive, which is produced using the Janus laser. In the experiments, the Bi samples are attached to windows of LiF or sapphire, and the velocity history of the sample-window interface is recorded with line VISAR. The 1D response of the targets is modeled using a multiphase Bi EOS, the Andrews-Hayes method for non-equilibrium transitions, and a Boettger-Wallace kinetics model. The pressure drive is deduced by back integration of VISAR data from shots performed with Al samples.

  7. Command Process Modeling & Risk Analysis

    NASA Technical Reports Server (NTRS)

    Meshkat, Leila

    2011-01-01

    Commanding Errors may be caused by a variety of root causes. It's important to understand the relative significance of each of these causes for making institutional investment decisions. One of these causes is the lack of standardized processes and procedures for command and control. We mitigate this problem by building periodic tables and models corresponding to key functions within it. These models include simulation analysis and probabilistic risk assessment models.

  8. Processing-induced-transformations (PITs) during direct compression: impact of compression speeds on phase transition of caffeine.

    PubMed

    Juban, Audrey; Briancon, Stephanie; Puel, François

    2016-11-01

    For pharmaceutical industry, understanding solid-phase transition of the active pharmaceutical ingredient (API) induced by the manufacturing process is a key issue. Caffeine was chosen as a model API since it exhibits a polymorphic transformation during tableting. This study investigated the impact of the compression speed on the phase transition of anhydrous Form I (CFI) into Form II. Tablets were made from pure CFI and binary mixtures of CFI/microcrystalline cellulose, with an electric press well instrumented at three different compression speeds (50, 500 and 4500 mm min(-1)). For each velocity of the mobile punch studied, tablets made from three compression pressures (50, 100 and 200 MPa) were analyzed. The determination of the CFI transition degree was performed using a Differential Scanning Calorimetry (DSC). The CFI transition degree was monitored during three months in order to obtain the transformation profile of the API in tablets and in uncompressed powder. The modeling of the profile with a stretched exponential kinetic law (Johnson-Mehl-Avrami model) was used for the identification of the transition mechanism. The direct compression process triggered the polymorphic transformation in tablet when a sufficient compression pressure is applied. The velocity of the punch did neither impact the transition degree just after compression nor the transformation profile. The transition mechanism remained driven by nucleation for several operating conditions. Consequently, the punch velocity is not a decisive process parameter for avoiding such phase transition in tableting. As already observed, the compression pressure did not influence the transition whatever the compression speed and the velocity. PMID:27109544

  9. Testing of transition-region models: Test cases and data

    NASA Technical Reports Server (NTRS)

    Singer, Bart A.; Dinavahi, Surya; Iyer, Venkit

    1991-01-01

    Mean flow quantities in the laminar turbulent transition region and in the fully turbulent region are predicted with different models incorporated into a 3-D boundary layer code. The predicted quantities are compared with experimental data for a large number of different flows and the suitability of the models for each flow is evaluated.

  10. Conformational transitions in random heteropolymer models

    NASA Astrophysics Data System (ADS)

    Blavatska, Viktoria; Janke, Wolfhard

    2014-01-01

    We study the conformational properties of heteropolymers containing two types of monomers A and B, modeled as self-attracting self-avoiding random walks on a regular lattice. Such a model can describe in particular the sequences of hydrophobic and hydrophilic residues in proteins [K. F. Lau and K. A. Dill, Macromolecules 22, 3986 (1989)] and polyampholytes with oppositely charged groups [Y. Kantor and M. Kardar, Europhys. Lett. 28, 169 (1994)]. Treating the sequences of the two types of monomers as quenched random variables, we provide a systematic analysis of possible generalizations of this model. To this end we apply the pruned-enriched Rosenbluth chain-growth algorithm, which allows us to obtain the phase diagrams of extended and compact states coexistence as function of both the temperature and fraction of A and B monomers along the heteropolymer chain.

  11. Conformational transitions in random heteropolymer models.

    PubMed

    Blavatska, Viktoria; Janke, Wolfhard

    2014-01-21

    We study the conformational properties of heteropolymers containing two types of monomers A and B, modeled as self-attracting self-avoiding random walks on a regular lattice. Such a model can describe in particular the sequences of hydrophobic and hydrophilic residues in proteins [K. F. Lau and K. A. Dill, Macromolecules 22, 3986 (1989)] and polyampholytes with oppositely charged groups [Y. Kantor and M. Kardar, Europhys. Lett. 28, 169 (1994)]. Treating the sequences of the two types of monomers as quenched random variables, we provide a systematic analysis of possible generalizations of this model. To this end we apply the pruned-enriched Rosenbluth chain-growth algorithm, which allows us to obtain the phase diagrams of extended and compact states coexistence as function of both the temperature and fraction of A and B monomers along the heteropolymer chain. PMID:25669411

  12. Transition modeling of neuropsychiatric impairment in HIV.

    PubMed

    Bisaso, Kuteesa R; Mukonzo, Jackson K; Ette, Ene I

    2016-06-01

    Few studies have reported analyses of neuropsychiatric impairment (NPI) data from HIV patients, in a real world clinical setting with the aim of establishing association between anti-retroviral drug concentrations and NPI development and resolution. No study has modeled the effect of efavirenz exposure beyond the pre-steady state period on the frequency and duration of NPI. The data used consists of 196 HIV patients whose efavirenz pharmacokinetic parameters were previously determined. Neuropsychiatric evaluation was done at baseline, week 2 and week 12. Patients were classified into NORMAL and NPI states. The duration of NPI was further classified as transient (NPI at week 2 but not at week 12), persistent (NPI at week 2 and 12) and delayed (NPI at week 12 but not at week 2). The proportion of patients in each duration category out of the total NPI patients was calculated. A continuous time Markov model was developed in NONMEM 7.3 and used to describe the relationship between efavirenz exposure and the duration of NPI. Monte Carlo simulations with the model were used to describe the effect of efavirenz dose reduction from 600mg to 400mg on the duration of NPI. The model adequately described the data. The influence of efavirenz exposure on the rate of development of NPI decayed with a half-life of 8.4 days. Efavirenz dose reduction to 400mg significantly reduces the duration of NPI, but has no impact on delayed NPI symptoms or efficacy. PMID:27107677

  13. Tinto's Model and Successful College Transitions.

    ERIC Educational Resources Information Center

    Tucker, John E.

    1999-01-01

    Compares the themes of academic and social integration in Tinto's model of college student attrition with the themes of "vision" and "sense of community" as described in a recent ethnographic study. It is argued that vision and sense of community are more useful theoretical considerations in helping address college student retention than is…

  14. Predictive Aspects of a Stochastic Model for Citation Processes.

    ERIC Educational Resources Information Center

    Glanzel, W.; Schubert, A.

    1995-01-01

    A statistical model for citation processes is presented as a particular version of a nonhomogenous birth process. The mean value function and special transition probabilities, which can readily be calculated on the basis of known and estimated parameters, give essential information on the change of citation impact in time. (10 references) (KRN)

  15. How to measure the agroecological performance of farming in order to assist with the transition process.

    PubMed

    Trabelsi, Meriam; Mandart, Elisabeth; Le Grusse, Philippe; Bord, Jean-Paul

    2016-01-01

    The use of plant protection products enables farmers to maximize economic performance and yields, but in return, the environment and human health can be greatly affected because of their toxicity. There are currently strong calls for farmers to reduce the use of these toxic products for the preservation of the environment and the human health, and it has become urgent to invest in more sustainable models that help reduce these risks. One possible solution is the transition toward agroecological production systems. These new systems must be beneficial economically, socially, and environmentally in terms of human health. There are many tools available, based on a range of indicators, for assessing the sustainability of agricultural systems on conventional farm holdings. These methods are little suitable to agroecological farms and do not measure the performance of agroecological transition farms. In this article, we therefore develop a model for the strategic definition, guidance, and assistance for a transition to agroecological practices, capable of assessing performance of this transition and simulating the consequences of possible changes. This model was built by coupling (i) a decision-support tool and a technico-economic simulator with (ii) a conceptual model built from the dynamics of agroecological practices. This tool is currently being tested in the framework of a Compte d'Affectation Spéciale pour le Développement Agricole et Rural (CASDAR) project (CASDAR: project launched in 2013 by the French Ministry of Agriculture, Food and Forestry, on the theme "collective mobilisation for agroecology," http://agriculture.gouv.fr/Appel-a-projets-CASDAR ) using data from farms, most of which are engaged in agroenvironmental process and reducing plant protection treatments since 2008. PMID:26527345

  16. A MATLAB GUI to study Ising model phase transition

    NASA Astrophysics Data System (ADS)

    Thornton, Curtislee; Datta, Trinanjan

    We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.

  17. Geometry in Transition: A Model of Emergent Geometry

    SciTech Connect

    Delgadillo-Blando, Rodrigo; O'Connor, Denjoe; Ydri, Badis

    2008-05-23

    We study a three matrix model with global SO(3) symmetry containing at most quartic powers of the matrices. We find an exotic line of discontinuous transitions with a jump in the entropy, characteristic of a 1st order transition, yet with divergent critical fluctuations and a divergent specific heat with critical exponent {alpha}=1/2. The low temperature phase is a geometrical one with gauge fields fluctuating on a round sphere. As the temperature increased the sphere evaporates in a transition to a pure matrix phase with no background geometrical structure. Both the geometry and gauge fields are determined dynamically. It is not difficult to invent higher dimensional models with essentially similar phenomenology. The model presents an appealing picture of a geometrical phase emerging as the system cools and suggests a scenario for the emergence of geometry in the early Universe.

  18. Numerical study of a disordered model for DNA denaturation transition.

    PubMed

    Coluzzi, Barbara

    2006-01-01

    We numerically study a disordered version of the model for DNA denaturation transition consisting of two interacting self-avoiding walks in three dimensions, which undergoes a first order transition in the homogeneous case. The two possible values epsilonAT and epsilonGC of the interactions between base pairs are taken as quenched random variables distributed with equal probability along the chain. We measure quantities averaged over disorder such as the energy density, the specific heat, and the probability distribution of the loop lengths. When applying the scaling laws used in the homogeneous case we find that the transition seems to be smoother in the presence of disorder, in agreement with general theoretical arguments, although we cannot rule out the possibility of a first order transition. PMID:16486189

  19. Neuroscientific Model of Motivational Process

    PubMed Central

    Kim, Sung-il

    2013-01-01

    Considering the neuroscientific findings on reward, learning, value, decision-making, and cognitive control, motivation can be parsed into three sub processes, a process of generating motivation, a process of maintaining motivation, and a process of regulating motivation. I propose a tentative neuroscientific model of motivational processes which consists of three distinct but continuous sub processes, namely reward-driven approach, value-based decision-making, and goal-directed control. Reward-driven approach is the process in which motivation is generated by reward anticipation and selective approach behaviors toward reward. This process recruits the ventral striatum (reward area) in which basic stimulus-action association is formed, and is classified as an automatic motivation to which relatively less attention is assigned. By contrast, value-based decision-making is the process of evaluating various outcomes of actions, learning through positive prediction error, and calculating the value continuously. The striatum and the orbitofrontal cortex (valuation area) play crucial roles in sustaining motivation. Lastly, the goal-directed control is the process of regulating motivation through cognitive control to achieve goals. This consciously controlled motivation is associated with higher-level cognitive functions such as planning, retaining the goal, monitoring the performance, and regulating action. The anterior cingulate cortex (attention area) and the dorsolateral prefrontal cortex (cognitive control area) are the main neural circuits related to regulation of motivation. These three sub processes interact with each other by sending reward prediction error signals through dopaminergic pathway from the striatum and to the prefrontal cortex. The neuroscientific model of motivational process suggests several educational implications with regard to the generation, maintenance, and regulation of motivation to learn in the learning environment. PMID:23459598

  20. Neuroscientific model of motivational process.

    PubMed

    Kim, Sung-Il

    2013-01-01

    Considering the neuroscientific findings on reward, learning, value, decision-making, and cognitive control, motivation can be parsed into three sub processes, a process of generating motivation, a process of maintaining motivation, and a process of regulating motivation. I propose a tentative neuroscientific model of motivational processes which consists of three distinct but continuous sub processes, namely reward-driven approach, value-based decision-making, and goal-directed control. Reward-driven approach is the process in which motivation is generated by reward anticipation and selective approach behaviors toward reward. This process recruits the ventral striatum (reward area) in which basic stimulus-action association is formed, and is classified as an automatic motivation to which relatively less attention is assigned. By contrast, value-based decision-making is the process of evaluating various outcomes of actions, learning through positive prediction error, and calculating the value continuously. The striatum and the orbitofrontal cortex (valuation area) play crucial roles in sustaining motivation. Lastly, the goal-directed control is the process of regulating motivation through cognitive control to achieve goals. This consciously controlled motivation is associated with higher-level cognitive functions such as planning, retaining the goal, monitoring the performance, and regulating action. The anterior cingulate cortex (attention area) and the dorsolateral prefrontal cortex (cognitive control area) are the main neural circuits related to regulation of motivation. These three sub processes interact with each other by sending reward prediction error signals through dopaminergic pathway from the striatum and to the prefrontal cortex. The neuroscientific model of motivational process suggests several educational implications with regard to the generation, maintenance, and regulation of motivation to learn in the learning environment. PMID:23459598

  1. Suggestion for a theoretical model for secondary-tertiary transition in mathematics

    NASA Astrophysics Data System (ADS)

    Clark, Megan; Lovric, Miroslav

    2008-09-01

    One of most notable features of existing body of research in transition seems to be the absence of a theoretical model. The suggestion we present in this paper—to view and understand the high school to university transition in mathematics as a modern-day rite of passage—is an attempt at defining such framework. Although dominantly reflecting North-American reality, we believe that the model could be found useful in other countries as well. Let us emphasize that our model is not new in the sense that it recognizes the transition as such. In this paper, we try to determine whether (and, if so, how) the notion of a rite of passage—which is a well-understood concept in anthropology, as well as in some other disciplines (e.g. culture shock in cultural studies)—can help us understand mathematics transition issues better. Can it help us systematize existing body of research, and enhance our understanding of transition in mathematics; does it point at something new? We believe so, and by elaborating some traditional aspects of rites of passage, we hope to provide a useful lens through which we can examine the process of transition in mathematics, and make suggestions for improved management of some transitional issues.

  2. Characterizing Phase Transitions in a Model of Neutral Evolutionary Dynamics

    NASA Astrophysics Data System (ADS)

    Scott, Adam; King, Dawn; Bahar, Sonya

    2013-03-01

    An evolutionary model was recently introduced for sympatric, phenotypic evolution over a variable fitness landscape with assortative mating (Dees & Bahar 2010). Organisms in the model are described by coordinates in a two-dimensional phenotype space, born at random coordinates with limited variation from their parents as determined by a mutation parameter, mutability. The model has been extended to include both neutral evolution and asexual reproduction in Scott et al (submitted). It has been demonstrated that a second order, non-equilibrium phase transition occurs for the temporal dynamics as the mutability is varied, for both the original model and for neutral conditions. This transition likely belongs to the directed percolation universality class. In contrast, the spatial dynamics of the model shows characteristics of an ordinary percolation phase transition. Here, we characterize the phase transitions exhibited by this model by determining critical exponents for the relaxation times, characteristic lengths, and cluster (species) mass distributions. Missouri Research Board; J.S. McDonnell Foundation

  3. Transitions.

    ERIC Educational Resources Information Center

    Field, David; And Others

    1992-01-01

    Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)

  4. Modeling Production Plant Forming Processes

    SciTech Connect

    Rhee, M; Becker, R; Couch, R; Li, M

    2004-09-22

    Engineering has simulation tools and experience in modeling forming processes. Y-12 personnel have expressed interest in validating our tools and experience against their manufacturing process activities such as rolling, casting, and forging etc. We have demonstrated numerical capabilities in a collaborative DOE/OIT project with ALCOA that is nearing successful completion. The goal was to use ALE3D to model Alcoa's slab rolling process in order to demonstrate a computational tool that would allow Alcoa to define a rolling schedule that would minimize the probability of ingot fracture, thus reducing waste and energy consumption. It is intended to lead to long-term collaboration with Y-12 and perhaps involvement with other components of the weapons production complex. Using simulations to aid in design of forming processes can: decrease time to production; reduce forming trials and associated expenses; and guide development of products with greater uniformity and less scrap.

  5. A Model for NASA-KSC's Privatization Transition

    NASA Technical Reports Server (NTRS)

    Lavelle, Jerome P.; Krumwiede, Dennis W.; Flowers, Jean

    1996-01-01

    This paper describes a model for government agencies that are considering privatization of all or part of their functions. Privatization encompasses the transitioning of government functions from government run to contractor run. The model developed in this paper is used to analyze the National Aeronautics and Space Administration's (NASA) decision to privatize space shuttle operations at the Kennedy Space Center (KSC). Several specific recommendations are given to KSC as they attempt to operationalize this privatization decision at the Center and to transition to a new relationship with their contractors.

  6. Phase transition of p-adic Ising λ-model

    SciTech Connect

    Dogan, Mutlay; Akın, Hasan; Mukhamedov, Farrukh

    2015-09-18

    We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model.

  7. Transition.

    ERIC Educational Resources Information Center

    Thompson, Sandy, Ed.; And Others

    1990-01-01

    This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition Issues for the 1990s" (William Halloran…

  8. Renewal stochastic processes with correlated events: Phase transitions along time evolution

    NASA Astrophysics Data System (ADS)

    Velázquez, Jorge; Robledo, Alberto

    2011-03-01

    We consider renewal stochastic processes generated by nonindependent events from the perspective that their basic distribution and associated generating functions obey the statistical-mechanical structure of systems with interacting degrees of freedom. Based on this fact we look briefly into the less-known case of processes that display phase transitions along time. When the density distribution ψn(t) for the occurrence of the nth event at time t is considered to be a partition function, of a “microcanonical” type for n “degrees of freedom” at fixed “energy” t, one obtains a set of four partition functions of which that for the generating function variable z and Laplace transform variable ɛ, conjugate to n and t, respectively, plays a central role. These partition functions relate to each other in the customary way and in accordance to the precepts of large deviations theory, while the entropy, or Massieu potential, derived from ψn(t) satisfies an Euler relation. We illustrate this scheme first for an ordinary renewal process of events generated by a simple exponential waiting-time distribution ψ(t). Then we examine a process modeled after the so-called Hamiltonian mean-field model that is representative of agents that perform a repeated task with an associated outcome, such as an opinion poll. When a sequence of (many) events takes place in a sufficiently short time the process exhibits clustering of the outcome, but for larger times the process resembles that of independent events. The two regimes are separated by a sharp transition, technically of the second order. Finally we point out the existence of a similar scheme for random-walk processes.

  9. Reversibility in Quantum Models of Stochastic Processes

    NASA Astrophysics Data System (ADS)

    Gier, David; Crutchfield, James; Mahoney, John; James, Ryan

    Natural phenomena such as time series of neural firing, orientation of layers in crystal stacking and successive measurements in spin-systems are inherently probabilistic. The provably minimal classical models of such stochastic processes are ɛ-machines, which consist of internal states, transition probabilities between states and output values. The topological properties of the ɛ-machine for a given process characterize the structure, memory and patterns of that process. However ɛ-machines are often not ideal because their statistical complexity (Cμ) is demonstrably greater than the excess entropy (E) of the processes they represent. Quantum models (q-machines) of the same processes can do better in that their statistical complexity (Cq) obeys the relation Cμ >= Cq >= E. q-machines can be constructed to consider longer lengths of strings, resulting in greater compression. With code-words of sufficiently long length, the statistical complexity becomes time-symmetric - a feature apparently novel to this quantum representation. This result has ramifications for compression of classical information in quantum computing and quantum communication technology.

  10. A Collaborative Process for Planning Transition Services for All Students with Disabilities.

    ERIC Educational Resources Information Center

    Aspel, Nellie; Bettis, Gail; Quinn, Pat; Test, David W.; Wood, Wendy M.

    1999-01-01

    Describes a multilevel interagency transition-planning process which includes three levels: a community-based team, school-level team, and individual-level team. Evaluation data are discussed that indicate consumer satisfaction with the Teaching All Students Skills for Employment and Life Transition planning process. Three case studies are used to…

  11. Study on the Mechanism of the Deflagration to Detonation Transition Process of Explosive

    NASA Astrophysics Data System (ADS)

    Wei, Lan; Dong, Hefei; Pan, Hao; Hu, Xiaomian; Zhu, Jianshi

    2014-10-01

    We present a numerical study of the mechanisms of the deflagration to detonation transition (DDT) process of explosives to assess its thermal stability. We treated the modeling system as a mixture of solid explosives and gaseous reaction products. We utilized a one-dimensional two-phase flow modeling approach with a space-time conservation element and solution element (CE/SE) method. Simulation results show that in the chemical reaction process a plug area of high density with relatively slow chemical reactions preceeds the new violent reactions and the consequent detonation. We found that steady detonation occurs at the regions where physical characteristics, such as pressure, density, temperature, and velocity, peak simultaneously. These simulation results agree well with high-temperature DDT tube experiments.

  12. Turbulence and transition modeling for high-speed flows

    NASA Technical Reports Server (NTRS)

    Wilcox, David C.

    1993-01-01

    Research conducted during the past three and a half years aimed at developing and testing a turbulence/transition model applicable to high-speed turbulent flows is summarized. The first two years of the project focused on fully turbulent flows, while emphasis shifted to boundary-layer development in the transition region during the final year and a half. A brief summary of research accomplished during the first three years is included and publications that describe research results in greater detail are cited. Research conducted during the final six months of the period of performance is summarized. The primary results of the last six months of the project are elimination of the k-omega model's sensitivity to the freestream value of omega and development of a method for triggering transition at a specified location, independent of the freestream turbulence level.

  13. Skin Friction and Transition Location Measurement on Supersonic Transport Models

    NASA Technical Reports Server (NTRS)

    Kennelly, Robert A., Jr.; Goodsell, Aga M.; Olsen, Lawrence E. (Technical Monitor)

    2000-01-01

    Flow visualization techniques were used to obtain both qualitative and quantitative skin friction and transition location data in wind tunnel tests performed on two supersonic transport models at Mach 2.40. Oil-film interferometry was useful for verifying boundary layer transition, but careful monitoring of model surface temperatures and systematic examination of the effects of tunnel start-up and shutdown transients will be required to achieve high levels of accuracy for skin friction measurements. A more common technique, use of a subliming solid to reveal transition location, was employed to correct drag measurements to a standard condition of all-turbulent flow on the wing. These corrected data were then analyzed to determine the additional correction required to account for the effect of the boundary layer trip devices.

  14. Coordinating the Transition Process: The Role of TransCen.

    ERIC Educational Resources Information Center

    Luecking, Richard G.

    1988-01-01

    To coordinate the planning and delivery of transition services for disabled students in Montgomery County (Maryland) Public Schools (MCPS), TransCen, Inc., a private not-for-profit corporation, was developed. TransCen's efforts concentrate on four areas: coordination with MCPS, liaison with the business community, program enhancement and technical…

  15. Transition to Community-Based Nursing Curriculum: Processes and Outcomes.

    ERIC Educational Resources Information Center

    Edwards, Joellen B.; Alley, Nancy M.

    2002-01-01

    The East Tennessee State University nursing school's transition to a community-based nursing curriculum was built on five key concepts: (1) relevance and accountability to health and social needs; (2) meeting of basic health needs through teaching and learning; (3) community experiences throughout the curriculum; (4) interdisciplinary…

  16. From Music Student to Professional: The Process of Transition

    ERIC Educational Resources Information Center

    Creech, Andrea; Papageorgi, Ioulia; Duffy, Celia; Morton, Frances; Haddon, Elizabeth; Potter, John; de Bezenac, Christophe; Whyton, Tony; Himonides, Evangelos; Welch, Graham

    2008-01-01

    This article addresses the question of whether higher education music courses adequately prepare young musicians for the critical transition from music undergraduate to professional. Thematic analyses of interviews with 27 undergraduate and portfolio career musicians representing four musical genres were compared. The evidence suggests that the…

  17. Doping induced Mott transition in the two dimensional Hubbard model

    NASA Astrophysics Data System (ADS)

    Sordi, Giovanni; Tremblay, A.-M. S.

    2010-03-01

    The description of the Mott transition by single-site dynamical mean-field theory is exact in infinite dimensions but, in two dimensions, substantial deviations from those results have been found for the interaction driven transition [1]. In addition, the experimentally relevant transition for layered systems such as the high-Tc cuprates is doping driven. We thus study this transition in the two dimensional Hubbard model on the square lattice using cluster dynamical mean-field theory with continuous-time quantum Monte Carlo in the hybridization expansion [2]. We find that the Mott transition is strongly influenced by the inclusion of short-range antiferromagnetic correlations. Doping of the Mott insulating state occurs gradually in the different momentum sectors, as found in previous studies [3], but in addition we find a first order transition between an incoherent metal and an insulator or between two incoherent metals, depending on interaction strength. Short range spin correlations create a pseudogap in a doping range that increases with interaction. [1] H. Park et al., PRL 101, 186403 (2008) [2] K. Haule, PRB 75, 155113 (2007) [3] E. Gull et al., arXiv:0909.1795 (2009)

  18. Modeling the forest transition: forest scarcity and ecosystem service hypotheses.

    PubMed

    Satake, Akiko; Rudel, Thomas K

    2007-10-01

    An historical generalization about forest cover change in which rapid deforestation gives way over time to forest restoration is called "the forest transition." Prior research on the forest transition leaves three important questions unanswered: (1) How does forest loss influence an individual landowner's incentives to reforest? (2) How does the forest recovery rate affect the likelihood of forest transition? (3) What happens after the forest transition occurs? The purpose of this paper is to develop a minimum model of the forest transition to answer these questions. We assume that deforestation caused by landowners' decisions and forest regeneration initiated by agricultural abandonment have aggregated effects that characterize entire landscapes. These effects include feedback mechanisms called the "forest scarcity" and "ecosystem service" hypotheses. In the forest scarcity hypothesis, forest losses make forest products scarcer, which increases the economic value of forests. In the ecosystem service hypothesis, the environmental degradation that accompanies the loss of forests causes the value of ecosystem services provided by forests to decline. We examined the impact of each mechanism on the likelihood of forest transition through an investigation of the equilibrium and stability of landscape dynamics. We found that the forest transition occurs only when landowners employ a low rate of future discounting. After the forest transition, regenerated forests are protected in a sustainable way if forests regenerate slowly. When forests regenerate rapidly, the forest scarcity hypothesis expects instability in which cycles of large-scale deforestation followed by forest regeneration repeatedly characterize the landscape. In contrast, the ecosystem service hypothesis predicts a catastrophic shift from a forested to an abandoned landscape when the amount of deforestation exceeds the critical level, which can lead to a resource degrading poverty trap. These findings imply

  19. Hillslopes to Hollows to Channels: Identifying Process Transitions and Domains using Characteristic Scaling Relations

    NASA Astrophysics Data System (ADS)

    Williams, K.; Locke, W. W.

    2011-12-01

    Headwater catchments are partitioned into hillslopes, unchanneled valleys (hollows), and channels. Low order (less than or equal to two) channels comprise most of the stream length in the drainage network so defining where hillslopes end and hollows begin, and where hollows end and channels begin, is important for calibration and verification of hydrologic runoff and sediment production modeling. We test the use of landscape scaling relations to detect flow regimes characteristic of diffusive, concentrated, and incisive runoff, and use these flow regimes as proxies for hillslope, hollow, and channeled landforms. We use LiDAR-derived digital elevation models (DEMs) of two pairs of headwater catchments in southwest and north-central Montana to develop scaling relations of flowpath length, total stream power, and contributing area. The catchment pairs contrast low versus high drainage density and north versus south aspect. Inflections in scaling relations of contributing area and flowpath length in a single basin (modified Hack's law) and contributing area and total stream power were used to identify hillslope and fluvial process domain transitions. In the modified Hack's law, inflections in the slope of the log-log power law are hypothesized to correspond to changes in flow regime used as proxies for hillslope, hollow, and channeled landforms. Similarly, rate of change of total stream power with contributing area is hypothesized to become constant and then decrease at the hillslope to fluvial domain transition. Power law scaling of frequency-magnitude plots of curvature and an aspect-related parameter were also tested as an indicator of the transition from scale-dependent hillslope length to the scale invariant fluvial domain. Curvature and aspect were calculated at each cell in spectrally filtered DEMs. Spectral filtering by fast Fourier and wavelet transforms enhances detection of fine-scale fluvial features by removing long wavelength topography. Using the

  20. Modeling the impact of roadway emissions in light wind, stable and transition conditions

    EPA Science Inventory

    This paper examines the processes that govern air pollution dispersion under light wind, stable and transition conditions by using a state-of-the-art dispersion model to interpret measurements from a tracer experiment conducted next to US highway 99 in Sacramento in 1981–1982 dur...

  1. Model of Transition from Laminar to Turbulent Flow

    NASA Astrophysics Data System (ADS)

    Kanda, Hidesada

    2001-11-01

    For circular pipe flows, a model of transition from laminar to turbulent flow has already been proposed and the minimum critical Reynolds number of approximately 2040 was obtained (Kanda, 1999). In order to prove the validity of the model, another verification is required. Thus, for plane Poiseuille flow, results of previous investigations were studied, focusing on experimental data on the critical Reynolds number Rc, the entrance length, and the transition length. Consequently, concerning the natural transition, it was confirmed from the experimental data that (i) the transition occurs in the entrance region, (ii) Rc increases as the contraction ratio in the inlet section increases, and (iii) the minimum Rc is obtained when the contraction ratio is the smallest or one, and there is no-bellshaped entrance or straight parallel plates. Its value exists in the neighborhood of 1300, based on the channel height and the average velocity. Although, for Hagen-Poiseuille flow, the minimum Rc is approximately 2000, based on the pipe diameter and the average velocity, there seems to be no significant difference in the transition from laminar to turbulent flow between Hagen-Poiseuille flow and plane Poiseuille flow (Kanda, 2001). Rc is determined by the shape of the inlet. Kanda, H., 1999, Proc. of ASME Fluids Engineering Division - 1999, FED-Vol. 250, pp. 197-204. Kanda, H., 2001, Proc. of ASME Fluids Engineering Division - 2001.

  2. Thermoplastic matrix composite processing model

    NASA Technical Reports Server (NTRS)

    Dara, P. H.; Loos, A. C.

    1985-01-01

    The effects the processing parameters pressure, temperature, and time have on the quality of continuous graphite fiber reinforced thermoplastic matrix composites were quantitatively accessed by defining the extent to which intimate contact and bond formation has occurred at successive ply interfaces. Two models are presented predicting the extents to which the ply interfaces have achieved intimate contact and cohesive strength. The models are based on experimental observation of compression molded laminates and neat resin conditions, respectively. Identified as the mechanism explaining the phenomenon by which the plies bond to themselves is the theory of autohesion (or self diffusion). Theoretical predictions from the Reptation Theory between autohesive strength and contact time are used to explain the effects of the processing parameters on the observed experimental strengths. The application of a time-temperature relationship for autohesive strength predictions is evaluated. A viscoelastic compression molding model of a tow was developed to explain the phenomenon by which the prepreg ply interfaces develop intimate contact.

  3. Fibrin polymerization as a phase transition wave: A mathematical model

    NASA Astrophysics Data System (ADS)

    Lobanov, A. I.

    2016-06-01

    A mathematical model of fibrin polymerization is described. The problem of the propagation of phase transition wave is reduced to a nonlinear Stefan problem. A one-dimensional discontinuity fitting difference scheme is described, and the results of one-dimensional computations are presented.

  4. Resilience-based application of state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We recommend that several conceptual modifications be incorporated into the state-and-transition model (STM) framework to: 1) explicitly link this framework to the concept of ecological resilience, 2) direct management attention away from thresholds and toward the maintenance of state resilience, an...

  5. Modeling Pedagogy for Teachers Transitioning to the Virtual Classroom

    ERIC Educational Resources Information Center

    Canuel, Michael J.; White, Beverley J.

    2014-01-01

    This study is a review of the creation and evolution of a professional development program modeled on social constructivist principles and designed for online educators in a virtual high school who transitioned from the conventional classroom to the virtual educational environment. The narrative inquiry focuses on the critical events within the…

  6. Practical guidance for developing state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State-and-transition models (STMs) are synthetic descriptions of the dynamics of vegetation and surface soils occurring within specific ecological sites. STMs consist of a diagram and narratives that describe the dynamics and its causes. STMs are developed using a broad array of evidence including h...

  7. Spatially-explicit representation of state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The broad-scale assessment of natural resource conditions (e.g., rangeland health, restoration needs) requires knowledge of their spatial distribution. We argue that creating a database that links state-and-transition models (STMs) to spatial units is a valuable management tool for structuring groun...

  8. Assessment of One- and Two-Equation Turbulence Models for Hypersonic Transitional Flows

    SciTech Connect

    ROY,CHRISTOPHER J.; BLOTTNER,FREDERICK G.

    2000-01-14

    Many Navier-Stokes codes require that the governing equations be written in conservation form with a source term. The Spalart-Allmaras one-equation model was originally developed in substantial derivative form and when rewritten in conservation form, a density gradient term appears in the source term. This density gradient term causes numerical problems and has a small influence on the numerical predictions. Further work has been performed to understand and to justify the neglect of this term. The transition trip term has been included in the one-equation eddy viscosity model of Spalart-Allmaras. Several problems with this model have been discovered when applied to high-speed flows. For the Mach 8 flat plate boundary layer flow with the standard transition method, the Baldwin-Barth and both k-{omega} models gave transition at the specified location. The Spalart-Allmaras and low Reynolds number k-{var_epsilon} models required an increase in the freestream turbulence levels in order to give transition at the desired location. All models predicted the correct skin friction levels in both the laminar and turbulent flow regions. For Mach 8 flat plate case, the transition location could not be controlled with the trip terms as given in the Spalart-Allmaras model. Several other approaches have been investigated to allow the specification of the transition location. The approach that appears most appropriate is to vary the coefficient that multiplies the turbulent production term in the governing partial differential equation for the eddy viscosity (Method 2). When this coefficient is zero, the flow remains laminar. The coefficient is increased to its normal value over a specified distance to crudely model the transition region and obtain fully turbulent flow. While this approach provides a reasonable interim solution, a separate effort should be initiated to address the proper transition procedure associated with the turbulent production term. Also, the transition process

  9. THE HANLE EFFECT OF Ly{alpha} IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Stepan, J.; Trujillo Bueno, J.; Carlsson, M.; Leenaarts, J.

    2012-10-20

    In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this end, we need to measure and model the linear polarization produced by scattering processes in strong UV lines, such as the hydrogen Ly{alpha} line. The interpretation of the observed Stokes profiles will require taking into account that the outer solar atmosphere is highly structured and dynamic, and that the height of the transition region may well vary from one place in the atmosphere to another. Here, we report on the Ly{alpha} scattering polarization signals we have calculated in a realistic model of an enhanced network region, resulting from a state-of-the-art radiation magnetohydrodynamic simulation. This model is characterized by spatially complex variations of the physical quantities at transition region heights. The results of our investigation lead us to emphasize that scattering processes in the upper solar chromosphere should indeed produce measurable linear polarization in Ly{alpha}. More importantly, we show that via the Hanle effect the model's magnetic field produces significant changes in the emergent Q/I and U/I profiles. Therefore, we argue that by measuring the polarization signals produced by scattering processes and the Hanle effect in Ly{alpha} and contrasting them with those computed in increasingly realistic atmospheric models, we should be able to decipher the magnetic, thermal, and dynamic structure of the upper chromosphere and transition region of the Sun.

  10. Apparent Transition Behavior of Widely-Used Turbulence Models

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2007-01-01

    The Spalart-Allmaras and the Menter SST k-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause non-uniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation k-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the k-omega model itself, and is not easily remedied.

  11. Apparent Transition Behavior of Widely-Used Turbulence Models

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2006-01-01

    The Spalart-Allmaras and the Menter SST kappa-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause nonuniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation kappa-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the kappa-omega model itself, and is not easily remedied.

  12. Welding process modelling and control

    NASA Technical Reports Server (NTRS)

    Romine, Peter L.; Adenwala, Jinen A.

    1993-01-01

    The research and analysis performed, and software developed, and hardware/software recommendations made during 1992 in development of the PC-based data acquisition system for support of Welding Process Modeling and Control is reported. A need was identified by the Metals Processing Branch of NASA Marshall Space Flight Center, for a mobile data aquisition and analysis system, customized for welding measurement and calibration. Several hardware configurations were evaluated and a PC-based system was chosen. The Welding Measurement System (WMS) is a dedicated instrument, strictly for the use of data aquisition and analysis. Although the WMS supports many of the functions associated with the process control, it is not the intention for this system to be used for welding process control.

  13. Incorporating spatial patterns into a state and transition model for arid grasslands and shrublands in southern New Mexico

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State and transition models synthesize and communicate information about alternative states in arid rangelands and other ecosystems but often do not adequately account for processes interacting across a range of temporal and spatial scales. Grassland to shrubland transitions have occurred as patchy ...

  14. Transition under noise in the Sznajd model on square lattice

    NASA Astrophysics Data System (ADS)

    Lima, F. W. S.

    2016-08-01

    In order to describe the formation of a consensus in human opinion dynamics, in this paper, we study the Sznajd model with probabilistic noise in two dimensions. The time evolution of this system is performed via Monte Carlo simulations. This social behavior model with noise presents a well defined second-order phase transition. For small enough noise q < 0.33 most agents end up sharing the same opinion.

  15. Meson phenomenology and phase transitions in nonlocal chiral quark models

    NASA Astrophysics Data System (ADS)

    Carlomagno, J. P.; Gomez Dumm, D.; Pagura, V.; Scoccola, N. N.

    2015-07-01

    We study the features of nonlocal chiral quark models that include wave function renormalization. Model parameters are determined from meson phenomenology, considering different nonlocal form factor shapes. In this context we analyze the characteristics of the deconfinement and chiral restoration transitions at finite temperature and chemical potential, introducing the couplings of fermions to the Polyakov loop for different Polyakov potentials. The results for various thermodynamical quantities are compared with data obtained from lattice QCD calculations.

  16. Information geometry and quantum phase transitions in the Dicke model.

    PubMed

    Dey, Anshuman; Mahapatra, Subhash; Roy, Pratim; Sarkar, Tapobrata

    2012-09-01

    We study information geometry of the Dicke model, in the thermodynamic limit. The scalar curvature R of the Riemannian metric tensor induced on the parameter space of the model is calculated. We analyze this both with and without the rotating wave approximation, and show that the parameter manifold is smooth even at the phase transition, and that the scalar curvature is continuous across the phase boundary. PMID:23030896

  17. The Dipole Model and Phase Transitions in Biological Membranes

    PubMed Central

    Almeida, Silverio P.; Bond, James D.; Ward, Thomas C.

    1971-01-01

    Assuming the dipole model for a membrane, approximate calculations are made which employ a dipole-dipole interaction energy. The calculations are based upon the assumption of cooperative coupling of membrane polar molecules and make use of the Bragg-Williams approximation. A theoretical estimate is made of the critical temperature at which phase changes might occur in certain biological membranes. Proposals are presented which explain how the dipole transition might relate to the sometimes observed thermal phase transitions in biological membranes. PMID:5134212

  18. Quasi-classical models of transition state absorption or emission

    NASA Astrophysics Data System (ADS)

    Lee, Soo-Y.; Pollard, W. Thomas; Mathies, Richard A.

    1989-11-01

    By making a short-time approximation to the correlation function in the quantum result for transition state absorption (or emission) we obtain the Lorentzian and reflection results as integrals of simple configuration space functions. These and the time-integrated quantum results are used to derive and unify the following descriptions of transition-state absorption: (a) the classical model of Bersohn and Zewail, (b) the time-dependent wave mechanical description by Agrawal, Mohan and Sathyamurthy, (c) the classical trajectory approach by Polanyi and coworkers and (d) the time-independent quantum-mechanical description by Engel, Bacic, Schinke and Shapiro.

  19. Transitioning Space Weather Models Into Operations: The Basic Building Blocks

    NASA Astrophysics Data System (ADS)

    Araujo-Pradere, Eduardo A.

    2009-10-01

    New and improved space weather models that provide real-time or near-real time operational awareness to the long list of customers that the NOAA Space Weather Prediction Center (SWPC) serves are critically needed. Recognizing this, SWPC recently established a Developmental Testbed Center (DTC [see Kumar, 2009]) at which models will be vetted for operational use. What characteristics should models have if they are to survive this transition? The difficulties around the implementation of real-time models are many. From the stability of the data input (frequently coming from third parties) to the elevated information technology (IT) security atmosphere present everywhere, scientists and developers are confronting a series of challenges in the implementation of their models. Quinn et al. [2009] noted that “the transition challenges are numerous and require ongoing interaction between model developers and users.” However, the 2006 Report of the Assessment Committee for the National Space Weather Program (NSWP; see http://www.nswp.gov/nswp_acreport0706.pdf) found that “there is an absence of suitable connection[s] for ‘academia-to-operations’ knowledge transfer and for the transition of research to operations in general.”

  20. batman: BAsic Transit Model cAlculatioN in Python

    NASA Astrophysics Data System (ADS)

    Kreidberg, Laura

    2015-11-01

    I introduce batman, a Python package for modeling exoplanet transit and eclipse light curves. The batman package supports calculation of light curves for any radially symmetric stellar limb darkening law, using a new integration algorithm for models that cannot be quickly calculated analytically. The code uses C extension modules to speed up model calculation and is parallelized with OpenMP. For a typical light curve with 100 data points in transit, batman can calculate one million quadratic limb-darkened models in 30 s with a single 1.7 GHz Intel Core i5 processor. The same calculation takes seven minutes using the four-parameter nonlinear limb darkening model (computed to 1 ppm accuracy). Maximum truncation error for integrated models is an input parameter that can be set as low as 0.001 ppm, ensuring that the community is prepared for the precise transit light curves we anticipate measuring with upcoming facilities. The batman package is open source and publicly available at https://github.com/lkreidberg/batman.

  1. Development of a One-Equation Transition/Turbulence Model

    SciTech Connect

    EDWARDS,JACK R.; ROY,CHRISTOPHER J.; BLOTTNER,FREDERICK G.; HASSAN,HASSAN A.

    2000-09-26

    This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity - transport equation for non-turbulent fluctuation growth based on that proposed by Warren and Hassan (Journal of Aircraft, Vol. 35, No. 5) is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittence function based on the work of Dhawan and Narasimha (Journal of Fluid Mechanics, Vol. 3, No. 4). The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the spatial accuracy of selected predictions is analyzed.

  2. Phase Transition Behavior in a Neutral Evolution Model

    NASA Astrophysics Data System (ADS)

    King, Dawn; Scott, Adam; Maric, Nevena; Bahar, Sonya

    2014-03-01

    The complexity of interactions among individuals and between individuals and the environment make agent based modeling ideal for studying emergent speciation. This is a dynamically complex problem that can be characterized via the critical behavior of a continuous phase transition. Concomitant with the main tenets of natural selection, we allow organisms to reproduce, mutate, and die within a neutral phenotype space. Previous work has shown phase transition behavior in an assortative mating model with variable fitness landscapes as the maximum mutation size (μ) was varied (Dees and Bahar, 2010). Similarly, this behavior was recently presented in the work of Scott et al. (2013), even on a completely neutral landscape, for bacterial-like fission as well as for assortative mating. Here we present another neutral model to investigate the `critical' phase transition behavior of three mating types - assortative, bacterial, and random - in a phenotype space as a function of the percentage of random death. Results show two types of phase transitions occurring for the parameters of the population size and the number of clusters (an analogue of species), indicating different evolutionary dynamics for system survival and clustering. This research was supported by funding from: University of Missouri Research Board and James S. McDonnell Foundation.

  3. Estimating transition probabilities among everglades wetland communities using multistate models

    USGS Publications Warehouse

    Hotaling, A.S.; Martin, J.; Kitchens, W.M.

    2009-01-01

    In this study we were able to provide the first estimates of transition probabilities of wet prairie and slough vegetative communities in Water Conservation Area 3A (WCA3A) of the Florida Everglades and to identify the hydrologic variables that determine these transitions. These estimates can be used in management models aimed at restoring proportions of wet prairie and slough habitats to historical levels in the Everglades. To determine what was driving the transitions between wet prairie and slough communities we evaluated three hypotheses: seasonality, impoundment, and wet and dry year cycles using likelihood-based multistate models to determine the main driver of wet prairie conversion in WCA3A. The most parsimonious model included the effect of wet and dry year cycles on vegetative community conversions. Several ecologists have noted wet prairie conversion in southern WCA3A but these are the first estimates of transition probabilities among these community types. In addition, to being useful for management of the Everglades we believe that our framework can be used to address management questions in other ecosystems. ?? 2009 The Society of Wetland Scientists.

  4. Animal models and conserved processes

    PubMed Central

    2012-01-01

    Background The concept of conserved processes presents unique opportunities for using nonhuman animal models in biomedical research. However, the concept must be examined in the context that humans and nonhuman animals are evolved, complex, adaptive systems. Given that nonhuman animals are examples of living systems that are differently complex from humans, what does the existence of a conserved gene or process imply for inter-species extrapolation? Methods We surveyed the literature including philosophy of science, biological complexity, conserved processes, evolutionary biology, comparative medicine, anti-neoplastic agents, inhalational anesthetics, and drug development journals in order to determine the value of nonhuman animal models when studying conserved processes. Results Evolution through natural selection has employed components and processes both to produce the same outcomes among species but also to generate different functions and traits. Many genes and processes are conserved, but new combinations of these processes or different regulation of the genes involved in these processes have resulted in unique organisms. Further, there is a hierarchy of organization in complex living systems. At some levels, the components are simple systems that can be analyzed by mathematics or the physical sciences, while at other levels the system cannot be fully analyzed by reducing it to a physical system. The study of complex living systems must alternate between focusing on the parts and examining the intact whole organism while taking into account the connections between the two. Systems biology aims for this holism. We examined the actions of inhalational anesthetic agents and anti-neoplastic agents in order to address what the characteristics of complex living systems imply for inter-species extrapolation of traits and responses related to conserved processes. Conclusion We conclude that even the presence of conserved processes is insufficient for inter

  5. Phase transition in the Sznajd model with independence

    NASA Astrophysics Data System (ADS)

    Sznajd-Weron, K.; Tabiszewski, M.; Timpanaro, A. M.

    2011-11-01

    We propose a model of opinion dynamics which describes two major types of social influence —conformity and independence. Conformity in our model is described by the so-called outflow dynamics (known as Sznajd model). According to sociologists' suggestions, we introduce also a second type of social influence, known in social psychology as independence. Various social experiments have shown that the level of conformity depends on the society. We introduce this level as a parameter of the model and show that there is a continuous phase transition between conformity and independence.

  6. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  7. Nonequilibrium Dynamics and Phase Transitions in Holographic Models.

    PubMed

    Janik, Romuald A; Jankowski, Jakub; Soltanpanahi, Hesam

    2016-08-26

    We study the poles of the retarded Green's functions of strongly coupled field theories exhibiting a variety of phase structures from a crossover up to a first order phase transition. These theories are modeled by a dual gravitational description. The poles of the holographic Green's functions appear at the frequencies of the quasinormal modes of the dual black hole background. We establish that near the transition, in all cases considered, the applicability of a hydrodynamic description breaks down already at lower momenta than in the conformal case. We establish the appearance of the spinodal region in the case of the first order phase transition at temperatures for which the speed of sound squared is negative. An estimate of the preferential scale attained by the unstable modes is also given. We additionally observe a novel diffusive regime for sound modes for a range of wavelengths. PMID:27610844

  8. Entanglement driven phase transitions in spin-orbital models

    NASA Astrophysics Data System (ADS)

    You, Wen-Long; Oleś, Andrzej M.; Horsch, Peter

    2015-08-01

    To demonstrate the role played by the von Neumann entropy (vNE) spectra in quantum phase transitions we investigate the one-dimensional anisotropic SU(2)\\otimes {XXZ} spin-orbital model with negative exchange parameter. In the case of classical Ising orbital interactions we discover an unexpected novel phase with Majumdar-Ghosh-like spin-singlet dimer correlations triggered by spin-orbital entanglement (SOE) and having k=π /2 orbital correlations, while all the other phases are disentangled. For anisotropic XXZ orbital interactions both SOE and spin-dimer correlations extend to the antiferro-spin/alternating-orbital phase. This quantum phase provides a unique example of two coupled order parameters which change the character of the phase transition from first-order to continuous. Hereby we have established the vNE spectral function as a valuable tool to identify the change of ground state degeneracies and of the SOE of elementary excitations in quantum phase transitions.

  9. The comfortable driving model revisited: traffic phases and phase transitions

    NASA Astrophysics Data System (ADS)

    Knorr, Florian; Schreckenberg, Michael

    2013-07-01

    We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast them with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner’s three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides ‘hard’ rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow to a wide moving jam often involves an intermediate transition: first from free flow to synchronized flow and then from synchronized flow to a wide moving jam. This is supported by the fact that the so-called F → S transition (from free flow to synchronized traffic) is much more likely than a direct F → J transition. The model under consideration has a functional relationship between traffic flow and traffic density. The fundamental hypothesis of the three-phase traffic theory, however, postulates that the steady states of synchronized flow occupy a two-dimensional region in the flow-density plane. Due to the obvious discrepancy between the model investigated here and the postulate of the three-phase traffic theory, the good agreement that we found could not be expected. For a more detailed analysis, we also studied vehicle dynamics at a microscopic level and provide a comparison of real detector data with simulated data of the identical highway segment.

  10. Phenomenological theory of the Potts model evaporation-condensation transition

    NASA Astrophysics Data System (ADS)

    Ibáñez-Berganza, M.

    2016-01-01

    We present a phenomenological theory describing the finite-size evaporation-condensation transition of the q-state Potts model in the microcanonical ensemble. Our arguments rely on the existence of an exponent σ, relating the surface and the volume of the condensed phase droplet. The evaporation-condensation transition temperature and energy converge to their infinite-size values with the same power, a=(1-σ)/(2-σ) , of the inverse of the system size. For the 2D Potts model we show, by means of efficient simulations up to q = 24 and 10242 sites, that the exponent a is compatible with 1/4, assuming assymptotic finite-size convergence. While this value cannot be addressed by the evaporation-condensation theory developed for the Ising model, it is obtained in the present scheme if σ=2/3 , in agreement with previous theoretical guesses. The connection with the phenomenon of metastability in the canonical ensemble is also discussed.