Science.gov

Sample records for additive mixed models

  1. Mixed additive models

    NASA Astrophysics Data System (ADS)

    Carvalho, Francisco; Covas, Ricardo

    2016-06-01

    We consider mixed models y =∑i =0 w Xiβi with V (y )=∑i =1 w θiMi Where Mi=XiXi⊤ , i = 1, . . ., w, and µ = X0β0. For these we will estimate the variance components θ1, . . ., θw, aswell estimable vectors through the decomposition of the initial model into sub-models y(h), h ∈ Γ, with V (y (h ))=γ (h )Ig (h )h ∈Γ . Moreover we will consider L extensions of these models, i.e., y˚=Ly+ɛ, where L=D (1n1, . . ., 1nw) and ɛ, independent of y, has null mean vector and variance covariance matrix θw+1Iw, where w =∑i =1 n wi .

  2. Generalized Additive Mixed-Models for Pharmacology Using Integrated Discrete Multiple Organ Co-Culture.

    PubMed

    Ingersoll, Thomas; Cole, Stephanie; Madren-Whalley, Janna; Booker, Lamont; Dorsey, Russell; Li, Albert; Salem, Harry

    2016-01-01

    Integrated Discrete Multiple Organ Co-culture (IDMOC) is emerging as an in-vitro alternative to in-vivo animal models for pharmacology studies. IDMOC allows dose-response relationships to be investigated at the tissue and organoid levels, yet, these relationships often exhibit responses that are far more complex than the binary responses often measured in whole animals. To accommodate departure from binary endpoints, IDMOC requires an expansion of analytic techniques beyond simple linear probit and logistic models familiar in toxicology. IDMOC dose-responses may be measured at continuous scales, exhibit significant non-linearity such as local maxima or minima, and may include non-independent measures. Generalized additive mixed-modeling (GAMM) provides an alternative description of dose-response that relaxes assumptions of independence and linearity. We compared GAMMs to traditional linear models for describing dose-response in IDMOC pharmacology studies. PMID:27110941

  3. Generalized Additive Mixed-Models for Pharmacology Using Integrated Discrete Multiple Organ Co-Culture

    PubMed Central

    Ingersoll, Thomas; Cole, Stephanie; Madren-Whalley, Janna; Booker, Lamont; Dorsey, Russell; Li, Albert; Salem, Harry

    2016-01-01

    Integrated Discrete Multiple Organ Co-culture (IDMOC) is emerging as an in-vitro alternative to in-vivo animal models for pharmacology studies. IDMOC allows dose-response relationships to be investigated at the tissue and organoid levels, yet, these relationships often exhibit responses that are far more complex than the binary responses often measured in whole animals. To accommodate departure from binary endpoints, IDMOC requires an expansion of analytic techniques beyond simple linear probit and logistic models familiar in toxicology. IDMOC dose-responses may be measured at continuous scales, exhibit significant non-linearity such as local maxima or minima, and may include non-independent measures. Generalized additive mixed-modeling (GAMM) provides an alternative description of dose-response that relaxes assumptions of independence and linearity. We compared GAMMs to traditional linear models for describing dose-response in IDMOC pharmacology studies. PMID:27110941

  4. Resources allocation in healthcare for cancer: a case study using generalised additive mixed models.

    PubMed

    Musio, Monica; Sauleau, Erik A; Augustin, Nicole H

    2012-11-01

    Our aim is to develop a method for helping resources re-allocation in healthcare linked to cancer, in order to replan the allocation of providers. Ageing of the population has a considerable impact on the use of health resources because aged people require more specialised medical care due notably to cancer. We propose a method useful to monitor changes of cancer incidence in space and time taking into account two age categories, according to healthcar general organisation. We use generalised additive mixed models with a Poisson response, according to the methodology presented in Wood, Generalised additive models: an introduction with R. Chapman and Hall/CRC, 2006. Besides one-dimensional smooth functions accounting for non-linear effects of covariates, the space-time interaction can be modelled using scale invariant smoothers. Incidence data collected by a general cancer registry between 1992 and 2007 in a specific area of France is studied. Our best model exhibits a strong increase of the incidence of cancer along time and an obvious spatial pattern for people more than 70 years with a higher incidence in the central band of the region. This is a strong argument for re-allocating resources for old people cancer care in this sub-region. PMID:23242683

  5. Strengthen forensic entomology in court--the need for data exploration and the validation of a generalised additive mixed model.

    PubMed

    Baqué, Michèle; Amendt, Jens

    2013-01-01

    Developmental data of juvenile blow flies (Diptera: Calliphoridae) are typically used to calculate the age of immature stages found on or around a corpse and thus to estimate a minimum post-mortem interval (PMI(min)). However, many of those data sets don't take into account that immature blow flies grow in a non-linear fashion. Linear models do not supply a sufficient reliability on age estimates and may even lead to an erroneous determination of the PMI(min). According to the Daubert standard and the need for improvements in forensic science, new statistic tools like smoothing methods and mixed models allow the modelling of non-linear relationships and expand the field of statistical analyses. The present study introduces into the background and application of these statistical techniques by analysing a model which describes the development of the forensically important blow fly Calliphora vicina at different temperatures. The comparison of three statistical methods (linear regression, generalised additive modelling and generalised additive mixed modelling) clearly demonstrates that only the latter provided regression parameters that reflect the data adequately. We focus explicitly on both the exploration of the data--to assure their quality and to show the importance of checking it carefully prior to conducting the statistical tests--and the validation of the resulting models. Hence, we present a common method for evaluating and testing forensic entomological data sets by using for the first time generalised additive mixed models. PMID:22370995

  6. Functional Generalized Additive Models.

    PubMed

    McLean, Mathew W; Hooker, Giles; Staicu, Ana-Maria; Scheipl, Fabian; Ruppert, David

    2014-01-01

    We introduce the functional generalized additive model (FGAM), a novel regression model for association studies between a scalar response and a functional predictor. We model the link-transformed mean response as the integral with respect to t of F{X(t), t} where F(·,·) is an unknown regression function and X(t) is a functional covariate. Rather than having an additive model in a finite number of principal components as in Müller and Yao (2008), our model incorporates the functional predictor directly and thus our model can be viewed as the natural functional extension of generalized additive models. We estimate F(·,·) using tensor-product B-splines with roughness penalties. A pointwise quantile transformation of the functional predictor is also considered to ensure each tensor-product B-spline has observed data on its support. The methods are evaluated using simulated data and their predictive performance is compared with other competing scalar-on-function regression alternatives. We illustrate the usefulness of our approach through an application to brain tractography, where X(t) is a signal from diffusion tensor imaging at position, t, along a tract in the brain. In one example, the response is disease-status (case or control) and in a second example, it is the score on a cognitive test. R code for performing the simulations and fitting the FGAM can be found in supplemental materials available online. PMID:24729671

  7. Progress in mix modeling

    SciTech Connect

    Harrison, A.K.

    1997-03-14

    We have identified the Cranfill multifluid turbulence model (Cranfill, 1992) as a starting point for development of subgrid models of instability, turbulent and mixing processes. We have differenced the closed system of equations in conservation form, and coded them in the object-oriented hydrodynamics code FLAG, which is to be used as a testbed for such models.

  8. Characteristics of asphalt mixes with FT additive

    NASA Astrophysics Data System (ADS)

    Štefunková, S.

    2012-03-01

    This article is focused on low-temperature asphalt mixture technologies using FT additive and RAP. The modern production and use of asphalt mixture technologies with reduced temperatures has many advantages. These advantages mainly help to save energy and the environment. Lower temperatures enable a reduction in energy consumption, a more acceptable working environment for workers, a reduction in negative environmental effects, such as greenhouse gas emissions, and an improvement in the workability of mixtures and a prolongation of their duration. This technology is currently becoming popular in many countries.

  9. Mixed Markov models

    PubMed Central

    Fridman, Arthur

    2003-01-01

    Markov random fields can encode complex probabilistic relationships involving multiple variables and admit efficient procedures for probabilistic inference. However, from a knowledge engineering point of view, these models suffer from a serious limitation. The graph of a Markov field must connect all pairs of variables that are conditionally dependent even for a single choice of values of the other variables. This makes it hard to encode interactions that occur only in a certain context and are absent in all others. Furthermore, the requirement that two variables be connected unless always conditionally independent may lead to excessively dense graphs, obscuring the independencies present among the variables and leading to computationally prohibitive inference algorithms. Mumford [Mumford, D. (1996) in ICIAM 95, eds. Kirchgassner, K., Marenholtz, O. & Mennicken, R. (Akademie Verlag, Berlin), pp. 233–256] proposed an alternative modeling framework where the graph need not be rigid and completely determined a priori. Mixed Markov models contain node-valued random variables that, when instantiated, augment the graph by a set of transient edges. A single joint probability distribution relates the values of regular and node-valued variables. In this article, we study the analytical and computational properties of mixed Markov models. In particular, we show that positive mixed models have a local Markov property that is equivalent to their global factorization. We also describe a computationally efficient procedure for answering probabilistic queries in mixed Markov models. PMID:12829802

  10. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Dimenna, R; Tamburello, D

    2011-02-14

    height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. One of the main objectives in the waste processing is to provide feed of a uniform slurry composition at a certain weight percentage (e.g. typically {approx}13 wt% at SRS) over an extended period of time. In preparation of the sludge for slurrying, several important questions have been raised with regard to sludge suspension and mixing of the solid suspension in the bulk of the tank: (1) How much time is required to prepare a slurry with a uniform solid composition? (2) How long will it take to suspend and mix the sludge for uniform composition in any particular waste tank? (3) What are good mixing indicators to answer the questions concerning sludge mixing stated above in a general fashion applicable to any waste tank/slurry pump geometry and fluid/sludge combination?

  11. The Influence of Environmental Variables on the Presence of White Sharks, Carcharodon carcharias at Two Popular Cape Town Bathing Beaches: A Generalized Additive Mixed Model

    PubMed Central

    Weltz, Kay; Kock, Alison A.; Winker, Henning; Attwood, Colin; Sikweyiya, Monwabisi

    2013-01-01

    Shark attacks on humans are high profile events which can significantly influence policies related to the coastal zone. A shark warning system in South Africa, Shark Spotters, recorded 378 white shark (Carcharodon carcharias) sightings at two popular beaches, Fish Hoek and Muizenberg, during 3690 six-hour long spotting shifts, during the months September to May 2006 to 2011. The probabilities of shark sightings were related to environmental variables using Binomial Generalized Additive Mixed Models (GAMMs). Sea surface temperature was significant, with the probability of shark sightings increasing rapidly as SST exceeded 14°C and approached a maximum at 18°C, whereafter it remains high. An 8 times (Muizenberg) and 5 times (Fish Hoek) greater likelihood of sighting a shark was predicted at 18°C than at 14°C. Lunar phase was also significant with a prediction of 1.5 times (Muizenberg) and 4 times (Fish Hoek) greater likelihood of a shark sighting at new moon than at full moon. At Fish Hoek, the probability of sighting a shark was 1.6 times higher during the afternoon shift compared to the morning shift, but no diel effect was found at Muizenberg. A significant increase in the number of shark sightings was identified over the last three years, highlighting the need for ongoing research into shark attack mitigation. These patterns will be incorporated into shark awareness and bather safety campaigns in Cape Town. PMID:23874668

  12. The influence of environmental variables on the presence of white sharks, Carcharodon carcharias at two popular Cape Town bathing beaches: a generalized additive mixed model.

    PubMed

    Weltz, Kay; Kock, Alison A; Winker, Henning; Attwood, Colin; Sikweyiya, Monwabisi

    2013-01-01

    Shark attacks on humans are high profile events which can significantly influence policies related to the coastal zone. A shark warning system in South Africa, Shark Spotters, recorded 378 white shark (Carcharodon carcharias) sightings at two popular beaches, Fish Hoek and Muizenberg, during 3690 six-hour long spotting shifts, during the months September to May 2006 to 2011. The probabilities of shark sightings were related to environmental variables using Binomial Generalized Additive Mixed Models (GAMMs). Sea surface temperature was significant, with the probability of shark sightings increasing rapidly as SST exceeded 14 °C and approached a maximum at 18 °C, whereafter it remains high. An 8 times (Muizenberg) and 5 times (Fish Hoek) greater likelihood of sighting a shark was predicted at 18 °C than at 14 °C. Lunar phase was also significant with a prediction of 1.5 times (Muizenberg) and 4 times (Fish Hoek) greater likelihood of a shark sighting at new moon than at full moon. At Fish Hoek, the probability of sighting a shark was 1.6 times higher during the afternoon shift compared to the morning shift, but no diel effect was found at Muizenberg. A significant increase in the number of shark sightings was identified over the last three years, highlighting the need for ongoing research into shark attack mitigation. These patterns will be incorporated into shark awareness and bather safety campaigns in Cape Town. PMID:23874668

  13. Using generalized additive mixed models to assess spatial, temporal, and hydrologic controls on bacteria and nitrate in a vulnerable agricultural aquifer

    NASA Astrophysics Data System (ADS)

    Mellor, Andrea F. P.; Cey, Edwin E.

    2015-11-01

    The Abbotsford-Sumas aquifer (ASA) has a history of nitrate contamination from agricultural land use and manure application to soils, yet little is known about its microbial groundwater quality. The goal of this study was to investigate the spatiotemporal distribution of pathogen indicators (Escherichia coli [E. coli] and total coliform [TC]) and nitrate in groundwater, and their potential relation to hydrologic drivers. Sampling of 46 wells over an 11-month period confirmed elevated nitrate concentrations, with more than 50% of samples exceeding 10 mg-N/L. E. coli detections in groundwater were infrequent (4 of 385 total samples) and attributed mainly to surface water-groundwater connections along Fishtrap Creek, which tested positive for E. coli in every sampling event. TC was detected frequently in groundwater (70% of samples) across the ASA. Generalized additive mixed models (GAMMs) yielded valuable insights into relationships between TC or nitrate and a range of spatial, temporal, and hydrologic explanatory variables. Increased TC values over the wetter fall and winter period were most strongly related to groundwater temperatures and levels, while precipitation and well location were weaker (but still significant) predictors. In contrast, the moderate temporal variability in nitrate concentrations was not significantly related to hydrologic forcings. TC was relatively widespread across the ASA and spatial patterns could not be attributed solely to surface water connectivity. Varying nitrate concentrations across the ASA were significantly related to both well location and depth, likely due to spatially variable nitrogen loading and localized geochemical attenuation (i.e., denitrification). Vulnerability of the ASA to bacteria was clearly linked to hydrologic conditions, and was distinct from nitrate, such that a groundwater management strategy specifically for bacterial contaminants is warranted.

  14. Using generalized additive mixed models to assess spatial, temporal, and hydrologic controls on bacteria and nitrate in a vulnerable agricultural aquifer.

    PubMed

    Mellor, Andrea F P; Cey, Edwin E

    2015-11-01

    The Abbotsford-Sumas aquifer (ASA) has a history of nitrate contamination from agricultural land use and manure application to soils, yet little is known about its microbial groundwater quality. The goal of this study was to investigate the spatiotemporal distribution of pathogen indicators (Escherichia coli [E. coli] and total coliform [TC]) and nitrate in groundwater, and their potential relation to hydrologic drivers. Sampling of 46 wells over an 11-month period confirmed elevated nitrate concentrations, with more than 50% of samples exceeding 10 mg-N/L. E. coli detections in groundwater were infrequent (4 of 385 total samples) and attributed mainly to surface water-groundwater connections along Fishtrap Creek, which tested positive for E. coli in every sampling event. TC was detected frequently in groundwater (70% of samples) across the ASA. Generalized additive mixed models (GAMMs) yielded valuable insights into relationships between TC or nitrate and a range of spatial, temporal, and hydrologic explanatory variables. Increased TC values over the wetter fall and winter period were most strongly related to groundwater temperatures and levels, while precipitation and well location were weaker (but still significant) predictors. In contrast, the moderate temporal variability in nitrate concentrations was not significantly related to hydrologic forcings. TC was relatively widespread across the ASA and spatial patterns could not be attributed solely to surface water connectivity. Varying nitrate concentrations across the ASA were significantly related to both well location and depth, likely due to spatially variable nitrogen loading and localized geochemical attenuation (i.e., denitrification). Vulnerability of the ASA to bacteria was clearly linked to hydrologic conditions, and was distinct from nitrate, such that a groundwater management strategy specifically for bacterial contaminants is warranted. PMID:26348834

  15. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Richard Dimenna, R; David Tamburello, D

    2008-11-13

    The process of recovering the waste in storage tanks at the Savannah River Site (SRS) typically requires mixing the contents of the tank with one to four dual-nozzle jet mixers located within the tank. The typical criteria to establish a mixed condition in a tank are based on the number of pumps in operation and the time duration of operation. To ensure that a mixed condition is achieved, operating times are set conservatively long. This approach results in high operational costs because of the long mixing times and high maintenance and repair costs for the same reason. A significant reduction in both of these costs might be realized by reducing the required mixing time based on calculating a reliable indicator of mixing with a suitably validated computer code. The work described in this report establishes the basis for further development of the theory leading to the identified mixing indicators, the benchmark analyses demonstrating their consistency with widely accepted correlations, and the application of those indicators to SRS waste tanks to provide a better, physically based estimate of the required mixing time. Waste storage tanks at SRS contain settled sludge which varies in height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. If shorter mixing times can be shown to support Defense Waste Processing Facility (DWPF) or other feed requirements, longer pump lifetimes can be achieved with associated operational cost and

  16. Color mixing models

    NASA Astrophysics Data System (ADS)

    Harrington, Steven J.

    1992-05-01

    In black-and-white printing the page image can be represented within a computer as an array of binary values indicating whether or not pixels should be inked. The Boolean operators of AND, OR, and EXCLUSIVE-OR are often used when adding new objects to the image array. For color printing the page may be represented as an array of continuous tone color values, and the generalization of these logic functions to gray-scale or full-color images is, in general, not defined or understood. When incrementally composing a page image new colors can replace old in an image buffer, or new colors and old can be combined according to some mixing function to form a composite color which is stored. This paper examines the properties of the Boolean operations and suggests full-color mixing functions which preserve the desired properties. These functions can be used to combine colored images, giving various transparency effects. The relationships between the mixing functions and physical models of color mixing are also discussed.

  17. Optimization of soil mixing technology through metallic iron addition.

    SciTech Connect

    Moos, L. P.

    1999-01-15

    Enhanced soil mixing is a process used to remove volatile organic compounds (VOCs) from soil. In this process, also known as soil mixing with thermally enhanced soil vapor extraction, or SM/TESVE, a soil mixing apparatus breaks up and mixes a column of soil up to 9 m (30 ft) deep; simultaneously, hot air is blown through the soil. The hot air carries the VOCs to the surface where they are collected and safely disposed of. This technology is cost effective at high VOC concentrations, but it becomes cost prohibitive at low concentrations. Argonne National Laboratory-East conducted a project to evaluate ways of improving the effectiveness of this system. The project investigated the feasibility of integrating the SM/TESVE process with three soil treatment processes--soil vapor extraction, augmented indigenous biodegradation, and zero-valent iron addition. Each of these technologies was considered a polishing treatment designed to remove the contaminants left behind by enhanced soil mixing. The experiment was designed to determine if the overall VOC removal effectiveness and cost-effectiveness of the SM/TESVE process could be improved by integrating this approach with one of the polishing treatment systems.

  18. VISUAL PLUMES MIXING ZONE MODELING SOFTWARE

    EPA Science Inventory

    The U.S. Environmental Protection Agency has a long history of both supporting plume model development and providing mixing zone modeling software. The Visual Plumes model is the most recent addition to the suite of public-domain models available through the EPA-Athens Center f...

  19. Quantifying uncertainty in stable isotope mixing models

    NASA Astrophysics Data System (ADS)

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-01

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, Stable Isotope Analysis in R (SIAR), a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods tested are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the uncertainty in calculated

  20. Quantifying uncertainty in stable isotope mixing models

    SciTech Connect

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-19

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, SIAR [Parnell et al., 2010] a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods tested are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the

  1. Quantifying uncertainty in stable isotope mixing models

    DOE PAGESBeta

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-19

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, SIAR [Parnell et al., 2010] a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods testedmore » are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the uncertainty in calculated

  2. A mixed relaxed clock model

    PubMed Central

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  3. A mixed relaxed clock model.

    PubMed

    Lartillot, Nicolas; Phillips, Matthew J; Ronquist, Fredrik

    2016-07-19

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees.This article is part of the themed issue 'Dating species divergences using rocks and clocks'. PMID:27325829

  4. Overview of Neutrino Mixing Models and Their Mixing Angle Predictions

    SciTech Connect

    Albright, Carl H.

    2009-11-01

    An overview of neutrino-mixing models is presented with emphasis on the types of horizontal flavor and vertical family symmetries that have been invoked. Distributions for the mixing angles of many models are displayed. Ways to differentiate among the models and to narrow the list of viable models are discussed.

  5. Model-Independent Bounds on Kinetic Mixing

    DOE PAGESBeta

    Hook, Anson; Izaguirre, Eder; Wacker, Jay G.

    2011-01-01

    New Abelimore » an vector bosons can kinetically mix with the hypercharge gauge boson of the Standard Model. This letter computes the model-independent limits on vector bosons with masses from 1 GeV to 1 TeV. The limits arise from the numerous e + e − experiments that have been performed in this energy range and bound the kinetic mixing by ϵ ≲ 0.03 for most of the mass range studied, regardless of any additional interactions that the new vector boson may have.« less

  6. Model Independent Bounds on Kinetic Mixing

    SciTech Connect

    Hook, Anson; Izaguirre, Eder; Wacker, Jay G.; /SLAC

    2011-08-22

    New Abelian vector bosons can kinetically mix with the hypercharge gauge boson of the Standard Model. This letter computes the model independent limits on vector bosons with masses from 1 GeV to 1 TeV. The limits arise from the numerous e{sup +}e{sup -} experiments that have been performed in this energy range and bound the kinetic mixing by {epsilon} {approx}< 0.03 for most of the mass range studied, regardless of any additional interactions that the new vector boson may have.

  7. Bayesian stable isotope mixing models

    EPA Science Inventory

    In this paper we review recent advances in Stable Isotope Mixing Models (SIMMs) and place them into an over-arching Bayesian statistical framework which allows for several useful extensions. SIMMs are used to quantify the proportional contributions of various sources to a mixtur...

  8. Inference of Mix from Experimental Data and Theoretical Mix Models

    SciTech Connect

    Welser-Sherrill, L.; Haynes, D. A.; Cooley, J. H.; Mancini, R. C.; Haan, S. W.; Golovkin, I. E.

    2007-08-02

    The mixing between fuel and shell materials in Inertial Confinement Fusion implosion cores is a topic of great interest. Mixing due to hydrodynamic instabilities can affect implosion dynamics and could also go so far as to prevent ignition. We have demonstrated that it is possible to extract information on mixing directly from experimental data using spectroscopic arguments. In order to compare this data-driven analysis to a theoretical framework, two independent mix models, Youngs' phenomenological model and the Haan saturation model, have been implemented in conjunction with a series of clean hydrodynamic simulations that model the experiments. The first tests of these methods were carried out based on a set of indirect drive implosions at the OMEGA laser. We now focus on direct drive experiments, and endeavor to approach the problem from another perspective. In the current work, we use Youngs' and Haan's mix models in conjunction with hydrodynamic simulations in order to design experimental platforms that exhibit measurably different levels of mix. Once the experiments are completed based on these designs, the results of a data-driven mix analysis will be compared to the levels of mix predicted by the simulations. In this way, we aim to increase our confidence in the methods used to extract mixing information from the experimental data, as well as to study sensitivities and the range of validity of the mix models.

  9. Enhancement of nitrate removal at the sediment-water interface by carbon addition plus vertical mixing.

    PubMed

    Chen, Xuechu; He, Shengbing; Zhang, Yueping; Huang, Xiaobo; Huang, Yingying; Chen, Danyue; Huang, Xiaochen; Tang, Jianwu

    2015-10-01

    Wetlands and ponds are frequently used to remove nitrate from effluents or runoffs. However, the efficiency of this approach is limited. Based on the assumption that introducing vertical mixing to water column plus carbon addition would benefit the diffusion across the sediment-water interface, we conducted simulation experiments to identify a method for enhancing nitrate removal. The results suggested that the sediment-water interface has a great potential for nitrate removal, and the potential can be activated after several days of acclimation. Adding additional carbon plus mixing significantly increases the nitrate removal capacity, and the removal of total nitrogen (TN) and nitrate-nitrogen (NO3(-)-N) is well fitted to a first-order reaction model. Adding Hydrilla verticillata debris as a carbon source increased nitrate removal, whereas adding Eichhornia crassipe decreased it. Adding ethanol plus mixing greatly improved the removal performance, with the removal rate of NO3(-)-N and TN reaching 15.0-16.5 g m(-2) d(-1). The feasibility of this enhancement method was further confirmed with a wetland microcosm, and the NO3(-)-N removal rate maintained at 10.0-12.0 g m(-2) d(-1) at a hydraulic loading rate of 0.5 m d(-1). PMID:25556005

  10. Use and abuse of mixing models (MixSIAR)

    EPA Science Inventory

    Background/Question/MethodsCharacterizing trophic links in food webs is a fundamental ecological question. In our efforts to quantify energy flow through food webs, ecologists have increasingly used mixing models to analyze biological tracer data, often from stable isotopes. Whil...

  11. Cascade Models of Turbulence and Mixing

    NASA Astrophysics Data System (ADS)

    Kadanoff, Leo P.

    1997-01-01

    This note describes two kinds of work on turbulence. First it describes a simplified model of turbulent energy-cascades called the GOY model. Second it mentions work on a model of mixing in fluids. In addition to a brief historical discussion, I include some mention of our own work carried on at the University of Chicago by Jane Wang, Detlef Lohse, Roberto Benzi, Norbert Schörghofer, Scott Wunsch, Tong Zhou and myself. Our own studies are in large measure the outgrowth of a paper by M. H. Jensen, G. Paladin, and A. Vulpiani [1]. I mention this connection with some sadness because I recall Paladin's recent death in a mountain accident.

  12. Toward Better Modeling of Supercritical Turbulent Mixing

    NASA Technical Reports Server (NTRS)

    Selle, Laurent; Okongo'o, Nora; Bellan, Josette; Harstad, Kenneth

    2008-01-01

    study was done as part of an effort to develop computational models representing turbulent mixing under thermodynamic supercritical (here, high pressure) conditions. The question was whether the large-eddy simulation (LES) approach, developed previously for atmospheric-pressure compressible-perfect-gas and incompressible flows, can be extended to real-gas non-ideal (including supercritical) fluid mixtures. [In LES, the governing equations are approximated such that the flow field is spatially filtered and subgrid-scale (SGS) phenomena are represented by models.] The study included analyses of results from direct numerical simulation (DNS) of several such mixing layers based on the Navier-Stokes, total-energy, and conservation- of-chemical-species governing equations. Comparison of LES and DNS results revealed the need to augment the atmospheric- pressure LES equations with additional SGS momentum and energy terms. These new terms are the direct result of high-density-gradient-magnitude regions found in the DNS and observed experimentally under fully turbulent flow conditions. A model has been derived for the new term in the momentum equation and was found to perform well at small filter size but to deteriorate with increasing filter size. Several alternative models were derived for the new SGS term in the energy equation that would need further investigations to determine if they are too computationally intensive in LES.

  13. Gray component replacement using color mixing models

    NASA Astrophysics Data System (ADS)

    Kang, Henry R.

    1994-05-01

    A new approach to the gray component replacement (GCR) has been developed. It employs the color mixing theory for modeling the spectral fit between the 3-color and 4-color prints. To achieve this goal, we first examine the accuracy of the models with respect to the experimental results by applying them to the prints made by a Canon Color Laser Copier-500 (CLC-500). An empirical halftone correction factor is used for improving the data fitting. Among the models tested, the halftone corrected Kubelka-Munk theory gives the closest fit, followed by the halftone corrected Beer-Bouguer law and the Yule-Neilsen approach. We then apply the halftone corrected BB law to GCR. The main feature of this GCR approach is based on the spectral measurements of the primary color step wedges and a software package implementing the color mixing model. The software determines the amount of the gray component to be removed, then adjusts each primary color until a good match of the peak wavelengths between the 3-color and 4-color spectra is obtained. Results indicate that the average (Delta) Eab between cmy and cmyk renditions of 64 color patches is 3.11 (Delta) Eab. Eighty-seven percent of the patches has (Delta) Eab less than 5 units. The advantage of this approach is its simplicity; there is no need for the black printer and under color addition. Because this approach is based on the spectral reproduction, it minimizes the metamerism.

  14. Computational Process Modeling for Additive Manufacturing

    NASA Technical Reports Server (NTRS)

    Bagg, Stacey; Zhang, Wei

    2014-01-01

    Computational Process and Material Modeling of Powder Bed additive manufacturing of IN 718. Optimize material build parameters with reduced time and cost through modeling. Increase understanding of build properties. Increase reliability of builds. Decrease time to adoption of process for critical hardware. Potential to decrease post-build heat treatments. Conduct single-track and coupon builds at various build parameters. Record build parameter information and QM Meltpool data. Refine Applied Optimization powder bed AM process model using data. Report thermal modeling results. Conduct metallography of build samples. Calibrate STK models using metallography findings. Run STK models using AO thermal profiles and report STK modeling results. Validate modeling with additional build. Photodiode Intensity measurements highly linear with power input. Melt Pool Intensity highly correlated to Melt Pool Size. Melt Pool size and intensity increase with power. Applied Optimization will use data to develop powder bed additive manufacturing process model.

  15. 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.

  16. Modeling populations of rotationally mixed massive stars

    NASA Astrophysics Data System (ADS)

    Brott, I.

    2011-02-01

    Massive stars can be considered as cosmic engines. With their high luminosities, strong stellar winds and violent deaths they drive the evolution of galaxies through-out the history of the universe. Despite the importance of massive stars, their evolution is still poorly understood. Two major issues have plagued evolutionary models of massive stars until today: mixing and mass loss On the main sequence, the effects of mass loss remain limited in the considered mass and metallicity range, this thesis concentrates on the role of mixing in massive stars. This thesis approaches this problem just on the cross road between observations and simulations. The main question: Do evolutionary models of single stars, accounting for the effects of rotation, reproduce the observed properties of real stars. In particular we are interested if the evolutionary models can reproduce the surface abundance changes during the main-sequence phase. To constrain our models we build a population synthesis model for the sample of the VLT-FLAMES Survey of Massive stars, for which star-formation history and rotational velocity distribution are well constrained. We consider the four main regions of the Hunter diagram. Nitrogen un-enriched slow rotators and nitrogen enriched fast rotators that are predicted by theory. Nitrogen enriched slow rotators and nitrogen unenriched fast rotators that are not predicted by our model. We conclude that currently these comparisons are not sufficient to verify the theory of rotational mixing. Physical processes in addition to rotational mixing appear necessary to explain the stars in the later two regions. The chapters of this Thesis have been published in the following Journals: Ch. 2: ``Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones'', I. Brott, S. E. de Mink, M. Cantiello, N. Langer, A. de Koter, C. J. Evans, I. Hunter, C. Trundle, J.S. Vink submitted to Astronomy & Astrop hysics Ch. 3: ``The VLT-FLAMES Survey of Massive

  17. Volatilization of ammonia from manure as affected by manure additives, temperature and mixing.

    PubMed

    Van der Stelt, B; Temminghoff, E J M; Van Vliet, P C J; Van Riemsdijk, W H

    2007-12-01

    Ammonia (NH(3)) volatilization decreases the N-nutrient value of livestock manure slurries and can lead to soil acidification and eutrophication problems. In this study the effect of three manure additives (Euro Mest-mix (Mx), Effective Micro-organisms (EM), and Agri-mest (Am)) on NH(3) volatilization at three temperatures (4, 20, and 35 degrees C) was investigated. The manufacturers claim that Mx contains absorbing clay minerals and that applying Am and EM to slurry will reduce nitrogen losses, most likely by enhancing the biodegradation of manure slurry. Furthermore, the effect of mixing slurry on NH(3) volatilization has been investigated. Ammonia volatilization increased with increasing temperature and mixing of the slurries. However, at 35 degrees C mixing of manure reduced NH(3) emissions compared to non-mixing, which is related to a reduced crust resistance to gaseous transport at higher temperatures for non-mixing. Moreover, mixing introduces oxygen into the anaerobic slurry environment which will slow down microbial activity. The use of additives did not change manure characteristics (pH, dry matter, N(total), N(mineral), C/N, and C/N(organic)) and did not result in a significant (p<0.05) decrease in NH(3) emissions, except that at 4 degrees C and no mixing a significant decrease of 34% in NH(3) volatilization was observed, when Am and EM together, were applied to slurry. PMID:17215124

  18. The effect of silane addition timing on mixing processability and properties of silica reinforced rubber compound

    NASA Astrophysics Data System (ADS)

    Jeong, Hee-Hoon; Jin, Hyun-Ho; Ha, Sung-Ho; Jang, Suk-Hee; Kang, Yong-Gu; Han, Min-Hyun

    2016-03-01

    A series of experiments were performed to determine an optimum balance between processability and performance of a highly loaded silica compound. The experiments evaluated 4 different silane injection times. All mixing related to silane addition was conducted with a scaled up "Tandem" mixer line. With exception to silane addition timing, almost all operating conditions were controlled between experimental features. It was found that when the silane addition was introduced earlier in the mixing cycle both the reaction was more complete and the bound rubber content was higher. But processability indicators such as sheet forming and Mooney plasticity were negatively impacted. On the other hand, as silane injection was delayed to later in the mixing process the filler dispersion and good sheet forming was improved. However both the bound rubber content and Silane reaction completion were decreased. With the changes in silane addition time, the processability and properties of a silica compound can be controlled.

  19. Using tank 107-AN caustic addition for confirmation of mixing scale relationship

    SciTech Connect

    Chang, S.C.

    1995-05-01

    A subscale jet mixing program was carried out in two scale tanks to extend the basis of previous subscale tests to include in-tank geometry associated with tank AN-107. The laboratory data will be correlated with the data to be collected in the upcoming tank AN-107 mixing and caustic addition test. The objective is to verify the scaling relationship used in the MWTF mixer design.

  20. Scotogenic model for co-bimaximal mixing

    NASA Astrophysics Data System (ADS)

    Ferreira, P. M.; Grimus, W.; Jurčiukonis, D.; Lavoura, L.

    2016-07-01

    We present a scotogenic model, i.e. a one-loop neutrino mass model with dark right-handed neutrino gauge singlets and one inert dark scalar gauge doublet η, which has symmetries that lead to co-bimaximal mixing, i.e. to an atmospheric mixing angle θ 23 = 45° and to a CP -violating phase δ = ±π /2, while the mixing angle θ 13 remains arbitrary. The symmetries consist of softly broken lepton numbers L α ( α = e, μ, τ ), a non-standard CP symmetry, and three Z_2 symmetries. We indicate two possibilities for extending the model to the quark sector. Since the model has, besides η, three scalar gauge doublets, we perform a thorough discussion of its scalar sector. We demonstrate that it can accommodate a Standard Model-like scalar with mass 125 GeV, with all the other charged and neutral scalars having much higher masses.

  1. Evaluation of Warm Mix Asphalt Additives for Use in Modified Asphalt Mixtures

    NASA Astrophysics Data System (ADS)

    Chamoun, Zahi

    The objective of this research effort is to evaluate the use of warm-mix additives with polymer modified and terminal blend tire rubber asphalt mixtures from Nevada and California. The research completed over two stages: first stage evaluated two different WMA technologies; Sasobit and Advera, and second stage evaluated one additional WMA technology; Evotherm. The experimental program covered the evaluation of resistance of the mixtures to moisture damage, the performance characteristics of the mixtures, and mechanistic analysis of mixtures in simulated pavements. In the both stages, the mixture resistance to moisture damage was evaluated using the indirect tensile test and the dynamic modulus at multiple freeze-thaw cycles, and the resistance of the various asphalt mixtures to permanent deformation using the Asphalt Mixture Performance Tester (AMPT). Resistance of the untreated mixes to fatigue cracking using the flexural beam fatigue was only completed for the first stage. One source of aggregates was sampled in, two different batches, three warm mix asphalt technologies (Advera, Sasobit and Evotherm) and three asphalt binder types (neat, polymer-modified, and terminal blend tire rubber modified asphalt binders) typically used in Nevada and California were evaluated in this study. This thesis presents the resistance of the first stage mixtures to permanent deformation and fatigue cracking using two warm-mix additives; Advera and Sasobit, and the resistance to moisture damage and permanent deformation of the second stage mixtures with only one warm-mix additive; Evotherm.

  2. The use of elemental powder mixes in laser-based additive manufacturing

    NASA Astrophysics Data System (ADS)

    Clayton, Rodney Michael

    This study examines the use and functionality of laser depositing alloys from mixes of elemental metallic powders. Through the use of laser-based additive manufacturing (LAM), near net-shaped 3-Dimensional metallic parts can be produced in a layer-by-layer fashion. It is customary for pre-alloyed powders to be used in this process. However, mixes of elemental powders can be used to produce alloys that are formed during the deposition process. This alternative technique requires that the elemental powders adequately mix during deposition for a homogeneous deposit to be produced. Cost savings and versatility are among several of the advantages to using elemental powder mixes in LAM. Representative alloys of 316 and 430 Stainless Steel (SS) and Ti-6Al-4V were produced with elemental powder mixes during this research. These deposits were then compared to deposits of the same material manufactured with pre-alloyed powder. Comparison between the two types of samples included; EDS analysis to examine chemical homogeneity, metallography techniques to compare microstructures, and finally hardness testing to observe mechanical properties. The enthalpy of mixing is also discussed as this can impact the resulting homogeneity of deposits produced with mixes of elemental powders. Some differences were observed between the two types of deposits for 430 SS and Ti-6Al-4V. Results indicate that deposits fabricated with mixes of elemental powders can be produced to an equivalent quality of pre-alloyed powder deposits for 316 SS. This research also proposes potential alloys that could be considered for use in an elemental powder mixing technique.

  3. Mixed Rasch Modeling of the Self-Rating Depression Scale

    ERIC Educational Resources Information Center

    Hong, Sehee; Min, Sae-Young

    2007-01-01

    In this study, mixed Rasch modeling was used on the Self-Rating Depression Scale (SDS), a widely used measure of depression, among a non-Western sample of 618 Korean college students. The results revealed three latent classes and confirmed the unidimensionality of the SDS. In addition, there was a significant effect for gender in terms of class…

  4. Learning the Structure of Mixed Graphical Models

    PubMed Central

    Lee, Jason D.; Hastie, Trevor J.

    2014-01-01

    We consider the problem of learning the structure of a pairwise graphical model over continuous and discrete variables. We present a new pairwise model for graphical models with both continuous and discrete variables that is amenable to structure learning. In previous work, authors have considered structure learning of Gaussian graphical models and structure learning of discrete models. Our approach is a natural generalization of these two lines of work to the mixed case. The penalization scheme involves a novel symmetric use of the group-lasso norm and follows naturally from a particular parametrization of the model. Supplementary materials for this paper are available online. PMID:26085782

  5. The Mixed Effects Trend Vector Model

    ERIC Educational Resources Information Center

    de Rooij, Mark; Schouteden, Martijn

    2012-01-01

    Maximum likelihood estimation of mixed effect baseline category logit models for multinomial longitudinal data can be prohibitive due to the integral dimension of the random effects distribution. We propose to use multidimensional unfolding methodology to reduce the dimensionality of the problem. As a by-product, readily interpretable graphical…

  6. Characterization studies on the additives mixed L-arginine phosphate monohydrate (LAP) crystals

    NASA Astrophysics Data System (ADS)

    Haja Hameed, A. S.; Karthikeyan, C.; Ravi, G.; Rohani, S.

    2011-04-01

    L-arginine phosphate monohydrate (LAP), potassium thiocyanate (KSCN) mixed LAP (LAP:KSCN) and sodium sulfite (Na 2SO 3) mixed LAP (LAP:Na 2SO 3) single crystals were grown by slow cooling technique. The effect of microbial contamination and coloration on the growth solutions was studied. The crystalline powders of the grown crystals were examined by X-ray diffraction and the lattice parameters of the crystals were estimated. From the FTIR spectroscopic analysis, various functional group frequencies associated with the crystals were assigned. Vickers microhardness studies were done on {1 0 0} faces for pure and additives mixed LAP crystals. From the preliminary surface second harmonic generation (SHG) results, it was found that the SHG intensity at (1 0 0) face of LAP:KSCN crystal was much stronger than that of pure LAP.

  7. Simplified models of mixed dark matter

    SciTech Connect

    Cheung, Clifford; Sanford, David E-mail: dsanford@caltech.edu

    2014-02-01

    We explore simplified models of mixed dark matter (DM), defined here to be a stable relic composed of a singlet and an electroweak charged state. Our setup describes a broad spectrum of thermal DM candidates that can naturally accommodate the observed DM abundance but are subject to substantial constraints from current and upcoming direct detection experiments. We identify ''blind spots'' at which the DM-Higgs coupling is identically zero, thus nullifying direct detection constraints on spin independent scattering. Furthermore, we characterize the fine-tuning in mixing angles, i.e. well-tempering, required for thermal freeze-out to accommodate the observed abundance. Present and projected limits from LUX and XENON1T force many thermal relic models into blind spot tuning, well-tempering, or both. This simplified model framework generalizes bino-Higgsino DM in the MSSM, singlino-Higgsino DM in the NMSSM, and scalar DM candidates that appear in models of extended Higgs sectors.

  8. Use of ready-mixed concrete plant sludge water in concrete containing an additive or admixture.

    PubMed

    Chatveera, B; Lertwattanaruk, P

    2009-04-01

    In this study, we investigated the feasibility of using sludge water from a ready-mixed concrete plant as mixing water in concrete containing either fly ash as an additive or a superplasticizer admixture based on sulfonated naphthalene-formaldehyde condensates (SNF). The chemical and physical properties of the sludge water and the dry sludge were investigated. Cement pastes were mixed using sludge water containing various levels of total solids content (0.5, 2.5, 5, 7.5, 10, 12.5, and 15%) in order to determine the optimum content in the sludge water. Increasing the total solids content beyond 5-6% tended to reduce the compressive strength and shorten the setting time. Concrete mixes were then prepared using sludge water containing 5-6% total solids content. The concrete samples were evaluated with regard to water required, setting time, slump, compressive strength, permeability, and resistance to acid attack. The use of sludge water in the concrete mix tended to reduce the effect of both fly ash and superplasticizer. Sludge water with a total solids content of less than 6% is suitable for use in the production of concrete with acceptable strength and durability. PMID:19231063

  9. Black curves and creep behaviour of crumb rubber modified binders containing warm mix asphalt additives

    NASA Astrophysics Data System (ADS)

    Gallego, Juan; Rodríguez-Alloza, Ana María; Giuliani, Felice

    2016-03-01

    Warm mix asphalt (WMA) is a new research topic in the field of road pavement materials. This technology allows lower energy consumption and greenhouse gas (GHG) emissions by reducing compaction and placement temperatures of the asphalt mixtures. However, this technology is still under study, and the influence of the WMA additives has yet to be investigated thoroughly and clearly identified, especially in the case of crumb rubber modified (CRM) binders.

  10. Multi-Length-Scale Morphologies Driven by Mixed Additives in Porphyrin-Based Organic Photovoltaics.

    PubMed

    Gao, Ke; Miao, Jingsheng; Xiao, Liangang; Deng, Wanyuan; Kan, Yuanyuan; Liang, Tianxiang; Wang, Cheng; Huang, Fei; Peng, Junbiao; Cao, Yong; Liu, Feng; Russell, Thomas P; Wu, Hongbin; Peng, Xiaobin

    2016-06-01

    A new category of deep-absorbing small molecules is developed. Optimized devices driven by mixed additives show a remarkable short-circuit current of ≈20 mA cm(-2) and a highest power conversion efficiency of 9.06%. A multi-length-scale morphology is formed, which is fully characterized by resonant soft X-ray scattering, high-angle annular dark film image transmission electron microscopy, etc. PMID:27062394

  11. Black curves and creep behaviour of crumb rubber modified binders containing warm mix asphalt additives

    NASA Astrophysics Data System (ADS)

    Gallego, Juan; Rodríguez-Alloza, Ana María; Giuliani, Felice

    2016-08-01

    Warm mix asphalt (WMA) is a new research topic in the field of road pavement materials. This technology allows lower energy consumption and greenhouse gas (GHG) emissions by reducing compaction and placement temperatures of the asphalt mixtures. However, this technology is still under study, and the influence of the WMA additives has yet to be investigated thoroughly and clearly identified, especially in the case of crumb rubber modified (CRM) binders.

  12. Linear Mixed Models: Gum and Beyond

    NASA Astrophysics Data System (ADS)

    Arendacká, Barbora; Täubner, Angelika; Eichstädt, Sascha; Bruns, Thomas; Elster, Clemens

    2014-04-01

    In Annex H.5, the Guide to the Evaluation of Uncertainty in Measurement (GUM) [1] recognizes the necessity to analyze certain types of experiments by applying random effects ANOVA models. These belong to the more general family of linear mixed models that we focus on in the current paper. Extending the short introduction provided by the GUM, our aim is to show that the more general, linear mixed models cover a wider range of situations occurring in practice and can be beneficial when employed in data analysis of long-term repeated experiments. Namely, we point out their potential as an aid in establishing an uncertainty budget and as means for gaining more insight into the measurement process. We also comment on computational issues and to make the explanations less abstract, we illustrate all the concepts with the help of a measurement campaign conducted in order to challenge the uncertainty budget in calibration of accelerometers.

  13. Mixed-Color Multiphoton Transitions as Additional Quantum Channels for Electron Photoemission

    NASA Astrophysics Data System (ADS)

    Huang, Wayne; Becker, Maria; Beck, Joshua; Batelaan, Herman

    2016-05-01

    We demonstrate mixed-color electron photoemission from tungsten nanotips. In the experiment, second-harmonic photons were introduced to modify the multiphoton emission process. A twofold increase in quantum efficiency results from the opening up of an additional three-photon quantum channel. The super-additive photoelectron signal can be controlled by input power, field polarization, and pulse overlap. The results of our study provide new prospects for quantum photonics, multiphoton microscopy, and spin-polarized electron sources. We acknowledge supports from NSF, Grant Number 1306565, 1430519. NSF Grant Number 1306565, 1430519.

  14. Stability of a general mixed additive-cubic functional equation in non-Archimedean fuzzy normed spaces

    SciTech Connect

    Xu Tianzhou; Rassias, John Michael; Xu Wanxin

    2010-09-15

    We establish some stability results concerning the general mixed additive-cubic functional equation in non-Archimedean fuzzy normed spaces. In addition, we establish some results of approximately general mixed additive-cubic mappings in non-Archimedean fuzzy normed spaces. The results improve and extend some recent results.

  15. VISUAL PLUMES MIXING ZONE MODELING SOFTWARE

    EPA Science Inventory

    The US Environmental Protection Agency has a history of developing plume models and providing technical assistance. The Visual Plumes model (VP) is a recent addition to the public-domain models available on the EPA Center for Exposure Assessment Modeling (CEAM) web page. The Wind...

  16. Multikernel linear mixed models for complex phenotype prediction.

    PubMed

    Weissbrod, Omer; Geiger, Dan; Rosset, Saharon

    2016-07-01

    Linear mixed models (LMMs) and their extensions have recently become the method of choice in phenotype prediction for complex traits. However, LMM use to date has typically been limited by assuming simple genetic architectures. Here, we present multikernel linear mixed model (MKLMM), a predictive modeling framework that extends the standard LMM using multiple-kernel machine learning approaches. MKLMM can model genetic interactions and is particularly suitable for modeling complex local interactions between nearby variants. We additionally present MKLMM-Adapt, which automatically infers interaction types across multiple genomic regions. In an analysis of eight case-control data sets from the Wellcome Trust Case Control Consortium and more than a hundred mouse phenotypes, MKLMM-Adapt consistently outperforms competing methods in phenotype prediction. MKLMM is as computationally efficient as standard LMMs and does not require storage of genotypes, thus achieving state-of-the-art predictive power without compromising computational feasibility or genomic privacy. PMID:27302636

  17. Network Reconstruction Using Nonparametric Additive ODE Models

    PubMed Central

    Henderson, James; Michailidis, George

    2014-01-01

    Network representations of biological systems are widespread and reconstructing unknown networks from data is a focal problem for computational biologists. For example, the series of biochemical reactions in a metabolic pathway can be represented as a network, with nodes corresponding to metabolites and edges linking reactants to products. In a different context, regulatory relationships among genes are commonly represented as directed networks with edges pointing from influential genes to their targets. Reconstructing such networks from data is a challenging problem receiving much attention in the literature. There is a particular need for approaches tailored to time-series data and not reliant on direct intervention experiments, as the former are often more readily available. In this paper, we introduce an approach to reconstructing directed networks based on dynamic systems models. Our approach generalizes commonly used ODE models based on linear or nonlinear dynamics by extending the functional class for the functions involved from parametric to nonparametric models. Concomitantly we limit the complexity by imposing an additive structure on the estimated slope functions. Thus the submodel associated with each node is a sum of univariate functions. These univariate component functions form the basis for a novel coupling metric that we define in order to quantify the strength of proposed relationships and hence rank potential edges. We show the utility of the method by reconstructing networks using simulated data from computational models for the glycolytic pathway of Lactocaccus Lactis and a gene network regulating the pluripotency of mouse embryonic stem cells. For purposes of comparison, we also assess reconstruction performance using gene networks from the DREAM challenges. We compare our method to those that similarly rely on dynamic systems models and use the results to attempt to disentangle the distinct roles of linearity, sparsity, and derivative

  18. Computational Process Modeling for Additive Manufacturing (OSU)

    NASA Technical Reports Server (NTRS)

    Bagg, Stacey; Zhang, Wei

    2015-01-01

    Powder-Bed Additive Manufacturing (AM) through Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM) is being used by NASA and the Aerospace industry to "print" parts that traditionally are very complex, high cost, or long schedule lead items. The process spreads a thin layer of metal powder over a build platform, then melts the powder in a series of welds in a desired shape. The next layer of powder is applied, and the process is repeated until layer-by-layer, a very complex part can be built. This reduces cost and schedule by eliminating very complex tooling and processes traditionally used in aerospace component manufacturing. To use the process to print end-use items, NASA seeks to understand SLM material well enough to develop a method of qualifying parts for space flight operation. Traditionally, a new material process takes many years and high investment to generate statistical databases and experiential knowledge, but computational modeling can truncate the schedule and cost -many experiments can be run quickly in a model, which would take years and a high material cost to run empirically. This project seeks to optimize material build parameters with reduced time and cost through modeling.

  19. CREATION OF THE MODEL ADDITIONAL PROTOCOL

    SciTech Connect

    Houck, F.; Rosenthal, M.; Wulf, N.

    2010-05-25

    In 1991, the international nuclear nonproliferation community was dismayed to discover that the implementation of safeguards by the International Atomic Energy Agency (IAEA) under its NPT INFCIRC/153 safeguards agreement with Iraq had failed to detect Iraq's nuclear weapon program. It was now clear that ensuring that states were fulfilling their obligations under the NPT would require not just detecting diversion but also the ability to detect undeclared materials and activities. To achieve this, the IAEA initiated what would turn out to be a five-year effort to reappraise the NPT safeguards system. The effort engaged the IAEA and its Member States and led to agreement in 1997 on a new safeguards agreement, the Model Protocol Additional to the Agreement(s) between States and the International Atomic Energy Agency for the Application of Safeguards. The Model Protocol makes explicit that one IAEA goal is to provide assurance of the absence of undeclared nuclear material and activities. The Model Protocol requires an expanded declaration that identifies a State's nuclear potential, empowers the IAEA to raise questions about the correctness and completeness of the State's declaration, and, if needed, allows IAEA access to locations. The information required and the locations available for access are much broader than those provided for under INFCIRC/153. The negotiation was completed in quite a short time because it started with a relatively complete draft of an agreement prepared by the IAEA Secretariat. This paper describes how the Model Protocol was constructed and reviews key decisions that were made both during the five-year period and in the actual negotiation.

  20. Detecting contaminated birthdates using generalized additive models

    PubMed Central

    2014-01-01

    Background Erroneous patient birthdates are common in health databases. Detection of these errors usually involves manual verification, which can be resource intensive and impractical. By identifying a frequent manifestation of birthdate errors, this paper presents a principled and statistically driven procedure to identify erroneous patient birthdates. Results Generalized additive models (GAM) enabled explicit incorporation of known demographic trends and birth patterns. With false positive rates controlled, the method identified birthdate contamination with high accuracy. In the health data set used, of the 58 actual incorrect birthdates manually identified by the domain expert, the GAM-based method identified 51, with 8 false positives (resulting in a positive predictive value of 86.0% (51/59) and a false negative rate of 12.0% (7/58)). These results outperformed linear time-series models. Conclusions The GAM-based method is an effective approach to identify systemic birthdate errors, a common data quality issue in both clinical and administrative databases, with high accuracy. PMID:24923281

  1. Lightning Climatology with a Generalized Additive Model

    NASA Astrophysics Data System (ADS)

    Simon, Thorsten; Mayr, Georg; Umlauf, Nikolaus; Zeileis, Achim

    2016-04-01

    This study present a lightning climatology on a 1km x 1km grid estimated via generalized additive models (GAM). GAMs provide a framework to account for non-linear effects in time and space and for non-linear spatial-temporal interaction terms simultaneously. The degrees of smoothness of the non-linear effects is selected automatically in our approach. Furthermore, the influence of topography is captured in the model by including a non-linear term. To illustrate our approach we use lightning data from the ALDIS networks and selected a region in Southeastern Austria, where complex terrain extends from 200 an 3800 m asl and summertime lightning activity is high compared to other parts of the Eastern Alps. The temporal effect in the GAM shows a rapid increase in lightning activity in early July and a slow decay in activity afterwards. The estimated spatial effect is not very smooth and requires approximately 225 effective degrees of freedom. It reveals that lightning is more likely in the Eastern and Southern part of the region of interest. This spatial effect only accounts for variability not already explained by the topography. The topography effect shows lightning to be more likely at higher altitudes. The effect describing the spatio-temporal interactions takes approximately 200 degrees of freedom, and reveals local deviations of the climatology.

  2. Logit-normal mixed model for Indian monsoon precipitation

    NASA Astrophysics Data System (ADS)

    Dietz, L. R.; Chatterjee, S.

    2014-09-01

    Describing the nature and variability of Indian monsoon precipitation is a topic of much debate in the current literature. We suggest the use of a generalized linear mixed model (GLMM), specifically, the logit-normal mixed model, to describe the underlying structure of this complex climatic event. Four GLMM algorithms are described and simulations are performed to vet these algorithms before applying them to the Indian precipitation data. The logit-normal model was applied to light, moderate, and extreme rainfall. Findings indicated that physical constructs were preserved by the models, and random effects were significant in many cases. We also found GLMM estimation methods were sensitive to tuning parameters and assumptions and therefore, recommend use of multiple methods in applications. This work provides a novel use of GLMM and promotes its addition to the gamut of tools for analysis in studying climate phenomena.

  3. Effect of Crumb Rubber and Warm Mix Additives on Asphalt Aging, Rheological, and Failure Properties

    NASA Astrophysics Data System (ADS)

    Agrawal, Prashant

    Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening.

  4. Model Selection with the Linear Mixed Model for Longitudinal Data

    ERIC Educational Resources Information Center

    Ryoo, Ji Hoon

    2011-01-01

    Model building or model selection with linear mixed models (LMMs) is complicated by the presence of both fixed effects and random effects. The fixed effects structure and random effects structure are codependent, so selection of one influences the other. Most presentations of LMM in psychology and education are based on a multilevel or…

  5. A new unsteady mixing model to predict NO(x) production during rapid mixing in a dual-stage combustor

    NASA Technical Reports Server (NTRS)

    Menon, Suresh

    1992-01-01

    An advanced gas turbine engine to power supersonic transport aircraft is currently under study. In addition to high combustion efficiency requirements, environmental concerns have placed stringent restrictions on the pollutant emissions from these engines. A combustor design with the potential for minimizing pollutants such as NO(x) emissions is undergoing experimental evaluation. A major technical issue in the design of this combustor is how to rapidly mix the hot, fuel-rich primary zone product with the secondary diluent air to obtain a fuel-lean mixture for combustion in the second stage. Numerical predictions using steady-state methods cannot account for the unsteady phenomena in the mixing region. Therefore, to evaluate the effect of unsteady mixing and combustion processes, a novel unsteady mixing model is demonstrated here. This model has been used to study multispecies mixing as well as propane-air and hydrogen-air jet nonpremixed flames, and has been used to predict NO(x) production in the mixing region. Comparison with available experimental data show good agreement, thereby providing validation of the mixing model. With this demonstration, this mixing model is ready to be implemented in conjunction with steady-state prediction methods and provide an improved engineering design analysis tool.

  6. Inference of ICF Implosion Core Mix using Experimental Data and Theoretical Mix Modeling

    SciTech Connect

    Welser-Sherrill, L; Haynes, D A; Mancini, R C; Cooley, J H; Tommasini, R; Golovkin, I E; Sherrill, M E; Haan, S W

    2008-04-30

    The mixing between fuel and shell materials in Inertial Confinement Fusion (ICF) implosion cores is a current topic of interest. The goal of this work was to design direct-drive ICF experiments which have varying levels of mix, and subsequently to extract information on mixing directly from the experimental data using spectroscopic techniques. The experimental design was accomplished using hydrodynamic simulations in conjunction with Haan's saturation model, which was used to predict the mix levels of candidate experimental configurations. These theoretical predictions were then compared to the mixing information which was extracted from the experimental data, and it was found that Haan's mix model performed well in predicting trends in the width of the mix layer. With these results, we have contributed to an assessment of the range of validity and predictive capability of the Haan saturation model, as well as increased our confidence in the methods used to extract mixing information from experimental data.

  7. Inference of ICF implosion core mix using experimental data and theoretical mix modeling

    SciTech Connect

    Sherrill, Leslie Welser; Haynes, Donald A; Cooley, James H; Sherrill, Manolo E; Mancini, Roberto C; Tommasini, Riccardo; Golovkin, Igor E; Haan, Steven W

    2009-01-01

    The mixing between fuel and shell materials in Inertial Confinement Fusion (lCF) implosion cores is a current topic of interest. The goal of this work was to design direct-drive ICF experiments which have varying levels of mix, and subsequently to extract information on mixing directly from the experimental data using spectroscopic techniques. The experimental design was accomplished using hydrodynamic simulations in conjunction with Haan's saturation model, which was used to predict the mix levels of candidate experimental configurations. These theoretical predictions were then compared to the mixing information which was extracted from the experimental data, and it was found that Haan's mix model predicted trends in the width of the mix layer as a function of initial shell thickness. These results contribute to an assessment of the range of validity and predictive capability of the Haan saturation model, as well as increasing confidence in the methods used to extract mixing information from experimental data.

  8. Reactive Additive Stabilization Process (RASP) for hazardous and mixed waste vitrification

    SciTech Connect

    Jantzen, C.M.; Pickett, J.B.; Ramsey, W.G.

    1993-07-01

    Solidification of hazardous/mixed wastes into glass is being examined at the Savannah River Site (SRS) for (1) nickel plating line (F006) sludges and (2) incinerator wastes. Vitrification of these wastes using high surface area additives, the Reactive Additive Stabilization Process (RASP), has been determined to greatly enhance the dissolution and retention of hazardous, mixed, and heavy metal species in glass. RASP lowers melt temperatures (typically 1050-- 1150{degrees}C), thereby minimizing volatility concerns during vitrification. RASP maximizes waste loading (typically 50--75 wt% on a dry oxide basis) by taking advantage of the glass forming potential of the waste. RASP vitrification thereby minimizes waste disposal volume (typically 86--97 vol. %), and maximizes cost savings. Solidification of the F006 plating line sludges containing depleted uranium has been achieved in both soda-lime-silica (SLS) and borosilicate glasses at 1150{degrees}C up to waste loadings of 75 wt%. Solidification of incinerator blowdown and mixtures of incinerator blowdown and bottom kiln ash have been achieved in SLS glass at 1150{degrees}C up to waste loadings of 50% using RASP. These waste loadings correspond to volume reductions of 86 and 94 volume %, respectively, with large associated savings in storage costs.

  9. Mixing parameterizations in ocean climate modeling

    NASA Astrophysics Data System (ADS)

    Moshonkin, S. N.; Gusev, A. V.; Zalesny, V. B.; Byshev, V. I.

    2016-03-01

    Results of numerical experiments with an eddy-permitting ocean circulation model on the simulation of the climatic variability of the North Atlantic and the Arctic Ocean are analyzed. We compare the ocean simulation quality with using different subgrid mixing parameterizations. The circulation model is found to be sensitive to a mixing parametrization. The computation of viscosity and diffusivity coefficients by an original splitting algorithm of the evolution equations for turbulence characteristics is found to be as efficient as traditional Monin-Obukhov parameterizations. At the same time, however, the variability of ocean climate characteristics is simulated more adequately. The simulation of salinity fields in the entire study region improves most significantly. Turbulent processes have a large effect on the circulation in the long-term through changes in the density fields. The velocity fields in the Gulf Stream and in the entire North Atlantic Subpolar Cyclonic Gyre are reproduced more realistically. The surface level height in the Arctic Basin is simulated more faithfully, marking the Beaufort Gyre better. The use of the Prandtl number as a function of the Richardson number improves the quality of ocean modeling.

  10. Mixing parametrizations for ocean climate modelling

    NASA Astrophysics Data System (ADS)

    Gusev, Anatoly; Moshonkin, Sergey; Diansky, Nikolay; Zalesny, Vladimir

    2016-04-01

    The algorithm is presented of splitting the total evolutionary equations for the turbulence kinetic energy (TKE) and turbulence dissipation frequency (TDF), which is used to parameterize the viscosity and diffusion coefficients in ocean circulation models. The turbulence model equations are split into the stages of transport-diffusion and generation-dissipation. For the generation-dissipation stage, the following schemes are implemented: the explicit-implicit numerical scheme, analytical solution and the asymptotic behavior of the analytical solutions. The experiments were performed with different mixing parameterizations for the modelling of Arctic and the Atlantic climate decadal variability with the eddy-permitting circulation model INMOM (Institute of Numerical Mathematics Ocean Model) using vertical grid refinement in the zone of fully developed turbulence. The proposed model with the split equations for turbulence characteristics is similar to the contemporary differential turbulence models, concerning the physical formulations. At the same time, its algorithm has high enough computational efficiency. Parameterizations with using the split turbulence model make it possible to obtain more adequate structure of temperature and salinity at decadal timescales, compared to the simpler Pacanowski-Philander (PP) turbulence parameterization. Parameterizations with using analytical solution or numerical scheme at the generation-dissipation step of the turbulence model leads to better representation of ocean climate than the faster parameterization using the asymptotic behavior of the analytical solution. At the same time, the computational efficiency left almost unchanged relative to the simple PP parameterization. Usage of PP parametrization in the circulation model leads to realistic simulation of density and circulation with violation of T,S-relationships. This error is majorly avoided with using the proposed parameterizations containing the split turbulence model

  11. A protease additive increases fermentation of alfalfa diets by mixed ruminal microorganisms in vitro.

    PubMed

    Colombatto, D; Beauchemin, K A

    2009-03-01

    In vitro experiments were conducted to examine the characteristics and mode of action of a protease that increased the ruminal fiber digestibility of alfalfa hay. A commercial source of protease (Protex 6L, Genencor Int., Rochester, NY), already characterized for its main activities, was further analyzed to determine protease activity in response to pH, molecular size by SDS-PAGE, specificity to degrade model or feed substrates, response to autoclaving, and action of specific protease inhibitors in the absence or presence of ruminal fluid. In addition, batch culture in vitro incubations in buffered ruminal fluid were conducted to compare the enzyme product with purified protease sources, and dose-response studies (0 to 10 microL/g of forage DM) were carried out using alfalfa hay as a substrate. The enzyme product was shown to be an alkaline protease (optimum pH >8.5) of approximately 30 kDa. Specificity in the absence of ruminal fluid showed that the enzyme was active against gelatin and casein to the same extent, whereas it had limited (21% of the total) activity on BSA. In the presence of ruminal fluid and with the use of feed substrates, the protease increased (P < 0.05) 22-h IVDMD (%) of alfalfa hay, fresh corn silage, dry-rolled corn, and a total mixed ration composed of the 3 ingredients (39.5 vs. 44.7; 50.3 vs. 54.5; 63.8 vs. 68.4; and 55.4 vs. 56.4 for control vs. protease for each feed, respectively). Inhibitor studies in the absence of ruminal fluid indicated that the enzyme was inhibited most by a serine protease inhibitor but not by cysteine- or metalloprotease inhibitors (10 vs. 1.9 and 0.1%, respectively). In the presence of ruminal fluid, the serine protease inhibitor reversed (P < 0.05) the increase in alfalfa IVDMD achieved by the enzyme product, such that IVDMD was similar to that of the control treatment. Comparisons among different proteases revealed that only pure subtilisin achieved increases in IVDMD that were similar to those with protease

  12. Mixed Membership Distributions with Applications to Modeling Multiple Strategy Usage

    ERIC Educational Resources Information Center

    Galyardt, April

    2012-01-01

    This dissertation examines two related questions. "How do mixed membership models work?" and "Can mixed membership be used to model how students use multiple strategies to solve problems?". Mixed membership models have been used in thousands of applications from text and image processing to genetic microarray analysis. Yet…

  13. Nitrogen oxide abatement by distributed fuel addition. [Reburning, mixing, effect of concentration of nitrogen

    SciTech Connect

    Wendt, J.O.L.; Mereb, J.B.

    1991-01-02

    Reburning experiments are presented in which the effect of the primary flame mode is examined. The application of reburning downstream of an axial diffusion primary flame without swirl is compared to reburning results in which the primary flame is premixed. The comparison is qualitative and is intended to examine reburning under more realistic conditions of utility boilers, where premixed flames are not common. Experimental results of reburning tests using nitrogen containing reburning fuels (ammonia doped natural gas and coal) are presented. The effect of reburning fuel type and nitrogen content on nitrogenous species profiles in the reburn zone are discussed. The last section is concerned with the applications of the kinetic model to predict overall reburning effectiveness from the primary NO level and to identify configuration for low total fixed nitrogen concentration. The effects of mixing in the early stage of reburning are examined and appropriate corrections are incorporated with the kinetic model to allow the prediction of nitrogenous species concentrations in the region where mixing effects are important. An empirical correlation is used to estimate the conversion of the total fixed nitrogen in the reburn zone to NO in the final stage of reburning. The kinetic model is also applied to the testing of hypothetical fuel-rich configurations to identify kinetic limits that would prevent further reductions in nitrogenous species.

  14. Effects of feed additives and mixed eimeria species infection on intestinal microbial ecology of broilers.

    PubMed

    Hume, M E; Clemente-Hernández, S; Oviedo-Rondón, E O

    2006-12-01

    Evaluation of digestive microbial ecology is necessary to understand effects of growth-promoting feed. In the current study, the dynamics of intestinal microbial communities (MC) were examined in broilers fed diets supplemented with a combination of antibiotic (bacitracin methylene disalicylate) and ionophore (Coban 60), and diets containing 1 of 2 essential oil (EO) blends, Crina Poultry (CP) and Crina Alternate (CA). Five treatments were analyzed: 1) unmedicated uninfected control; 2) unmedicated infected control; 3) feed additives monensin (bacitracin methylene disalicylate) + monensin (Coban 60; AI); 4) EO blend CP; and 5) EO blend CA. Additives were mixed into a basal feed mixture, and EO were adjusted to 100 ppm. Chicks were infected by oral gavage at 19 d of age with Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Duodenal, ileal, and cecal samples were taken from 12 birds per treatment just before and 7 d after challenge; 2 samples each were pooled to give a final number of 6 samples total; and all pooled samples were frozen until used for DNA extraction. Denaturing gradient gel electrophoresis was used to examine PCR-amplified fragments of the bacterial 16S ribosomal DNA variable region. Results are presented as percentages of similarity coefficients (SC). Dendrograms of PCR amplicon or band patterns indicated MC differences due to intestinal location, feed additives, and cocci challenge. Essential oil blends CP and CA affected MC in all gut sections. Each EO had different effects over MC, and they differed in most instances from the AI group. The cocci challenge caused drastic MC population shifts in duodenal, ileal, and cecal sections (36.7, 55.4, and 36.2% SC, respectively). Diets supplemented with CP supported higher SC between pre- and postchallenge MC (89.9, 83.3, and 76.4%) than AI (81.8., 57.4, and 60.0%). We concluded that mixed coccidia challenge caused drastic shifts in MC. These EO blends modulated MC better than AI, avoiding drastic

  15. Linkage Analysis with an Alternative Formulation for the Mixed Model of Inheritance: The Finite Polygenic Mixed Model

    PubMed Central

    Stricker, C.; Fernando, R. L.; Elston, R. C.

    1995-01-01

    This paper presents an extension of the finite polygenic mixed model of FERNANDO et al. (1994) to linkage analysis. The finite polygenic mixed model, extended for linkage analysis, leads to a likelihood that can be calculated using efficient algorithms developed for oligogenic models. For comparison, linkage analysis of 5 simulated 4021-member pedigrees was performed using the usual mixed model of inheritance, approximated by HASSTEDT (1982), and the finite polygenic mixed model extended for linkage analysis presented here. Maximum likelihood estimates of the finite polygenic mixed model could be inferred to be closer to the simulated values in these pedigrees. PMID:8601502

  16. Modeling of Low Feed-Through CD Mix Implosions

    NASA Astrophysics Data System (ADS)

    Pino, Jesse; MacLaren, Steven; Greenough, Jeff; Casey, Daniel; Dittrich, Tom; Kahn, Shahab; Kyrala, George; Ma, Tammy; Salmonson, Jay; Smalyuk, Vladimir; Tipton, Robert

    2015-11-01

    The CD Mix campaign previously demonstrated the use of nuclear diagnostics to study the mix of separated reactants in plastic capsule implosions at the National Ignition Facility. However, the previous implosions suffered from large instability growth seeded from perturbations on the outside of the capsule. Recently, the separated reactants technique has been applied to two platforms designed to minimize this feed-through and isolate local mix at the gas-ablator interface: the Two Shock (TS) and Adiabat-Shaped (AS) Platforms. Additionally, the background contamination of Deuterium in the gas has been greatly reduced, allowing for simultaneous observation of TT, DT, and DD neutrons, which respectively give information about core gas performance, gas-shell atomic mix, and heating of the shell. In this talk, we describe efforts to model these implosions using high-resolution 2D ARES simulations with both a Reynolds-Averaged Navier Stokes method and an enhanced diffusivity model. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-674867.

  17. Extended model for Richtmyer-Meshkov mix

    SciTech Connect

    Mikaelian, K O

    2009-11-18

    We examine four Richtmyer-Meshkov (RM) experiments on shock-generated turbulent mix and find them to be in good agreement with our earlier simple model in which the growth rate h of the mixing layer following a shock or reshock is constant and given by 2{alpha}A{Delta}v, independent of initial conditions h{sub 0}. Here A is the Atwood number ({rho}{sub B}-{rho}{sub A})/({rho}{sub B} + {rho}{sub A}), {rho}{sub A,B} are the densities of the two fluids, {Delta}V is the jump in velocity induced by the shock or reshock, and {alpha} is the constant measured in Rayleigh-Taylor (RT) experiments: {alpha}{sup bubble} {approx} 0.05-0.07, {alpha}{sup spike} {approx} (1.8-2.5){alpha}{sup bubble} for A {approx} 0.7-1.0. In the extended model the growth rate beings to day after a time t*, when h = h*, slowing down from h = h{sub 0} + 2{alpha}A{Delta}vt to h {approx} t{sup {theta}} behavior, with {theta}{sup bubble} {approx} 0.25 and {theta}{sup spike} {approx} 0.36 for A {approx} 0.7. They ascribe this change-over to loss of memory of the direction of the shock or reshock, signaling transition from highly directional to isotropic turbulence. In the simplest extension of the model h*/h{sub 0} is independent of {Delta}v and depends only on A. They find that h*/h{sub 0} {approx} 2.5-3.5 for A {approx} 0.7-1.0.

  18. Reduction of spalling in mixed metal oxide desulfurization sorbents by addition of a large promoter metal oxide

    DOEpatents

    Poston, James A.

    1997-01-01

    Mixed metal oxide pellets for removing hydrogen sulfide from fuel gas mixes derived from coal are stabilized for operation over repeated cycles of desulfurization and regeneration reactions by addition of a large promoter metal oxide such as lanthanum trioxide. The pellets, which may be principally made up of a mixed metal oxide such as zinc titanate, exhibit physical stability and lack of spalling or decrepitation over repeated cycles without loss of reactivity. The lanthanum oxide is mixed with pellet-forming components in an amount of 1 to 10 weight percent.

  19. Reduction of spalling in mixed metal oxide desulfurization sorbents by addition of a large promoter metal oxide

    DOEpatents

    Poston, J.A.

    1997-12-02

    Mixed metal oxide pellets for removing hydrogen sulfide from fuel gas mixes derived from coal are stabilized for operation over repeated cycles of desulfurization and regeneration reactions by addition of a large promoter metal oxide such as lanthanum trioxide. The pellets, which may be principally made up of a mixed metal oxide such as zinc titanate, exhibit physical stability and lack of spalling or decrepitation over repeated cycles without loss of reactivity. The lanthanum oxide is mixed with pellet-forming components in an amount of 1 to 10 weight percent.

  20. Effects of microscopic diffusion and rotational mixing on stellar models

    NASA Astrophysics Data System (ADS)

    Chaboyer, Brian Charles

    1993-01-01

    We have calculated evolutionary tracks for halo stars and constructed isochrones with alpha-enhanced compositions which cover the entire globular cluster metallicity range and include the effects of the diffusion of He-4. We find that including the effects of helium diffusion has a negligible effect (less than 0.5 Gyr) on the derived ages of globular clusters. Regardless of the inclusion of helium diffusion, we find a significant age spread of 5 Gyr among the globular clusters. The oldest globular cluster studied was M92 with an age of 17 +/- 2 Gyr old. The stellar models may be tested by comparing the Li-7 depletion and surface rotation rates to observations in young clusters stars. The observed Li-7 abundances clearly indicate that standard or diffusive models do not deplete enough Li-7. Instabilities induced by rotation provide an additional mixing mechanism. For this reason the stellar evolution code was modified to include the combined effects of diffusion and rotational mixing of H-1, He-4 and the trace elements He-3, Li-7 and Be-9. The calibrated solar models have a convection zone depth of 0.709-0.714 solar radius, in excellent agreement with the observed depth of (0.713 +/- 0.003) solar radius. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 50-80 percent. These models are able to reproduce the Li-7 abundances and rotation velocities observed in young cluster stars. Observations of Li-7 abundances in extremely metal poor halo stars provide another test of the stellar models. Standard models do a good job of fitting the observed Li-7 abundances and predict a primordial Li-7 abundance of log N(Li) = 2.24 +/- 0.03. Models of hot stars which include microscopic diffusion, but not rotational mixing, deplete too much Li-7. The (Fe/H) = 2.28 stellar models which include both diffusion and rotational mixing provide an excellent match to the observations, and predict a primordial Li-7

  1. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  2. MixSIAR: A Bayesian stable isotope mixing model for characterizing intrapopulation niche variation

    EPA Science Inventory

    Background/Question/Methods The science of stable isotope mixing models has tended towards the development of modeling products (e.g. IsoSource, MixSIR, SIAR), where methodological advances or syntheses of the current state of the art are published in parity with software packa...

  3. On Local Homogeneity and Stochastically Ordered Mixed Rasch Models

    ERIC Educational Resources Information Center

    Kreiner, Svend; Hansen, Mogens; Hansen, Carsten Rosenberg

    2006-01-01

    Mixed Rasch models add latent classes to conventional Rasch models, assuming that the Rasch model applies within each class and that relative difficulties of items are different in two or more latent classes. This article considers a family of stochastically ordered mixed Rasch models, with ordinal latent classes characterized by increasing total…

  4. Strategies for the use of mixed-effects models in continuous forest inventories.

    PubMed

    Westfall, James A

    2016-04-01

    Forest inventory data often consists of measurements taken on field plots as well as values predicted from statistical models, e.g., tree biomass. Many of these models only include fixed-effects parameters either because at the time the models were established, mixed-effects model theory had not yet been thoroughly developed or the use of mixed models was deemed unnecessary or too complex. Over the last two decades, considerable research has been conducted on the use of mixed models in forestry, such that mixed models and their applications are generally well understood. However, most of these assessments have focused on static validation data, and mixed model applications in the context of continuous forest inventories have not been evaluated. In comparison to fixed-effects models, the results of this study showed that mixed models can provide considerable reductions in prediction bias and variance for the population and also for subpopulations therein. However, the random effects resulting from the initial model fit deteriorated rapidly over time, such that some field data is needed to effectively recalibrate the random effects for each inventory cycle. Thus, implementation of mixed models requires ongoing maintenance to reap the benefits of improved predictive behavior. Forest inventory managers must determine if this gain in predictive power outweighs the additional effort needed to employ mixed models in a temporal framework. PMID:27010710

  5. Modeling techniques for gaining additional urban space

    NASA Astrophysics Data System (ADS)

    Thunig, Holger; Naumann, Simone; Siegmund, Alexander

    2009-09-01

    One of the major accompaniments of the globalization is the rapid growing of urban areas. Urban sprawl is the main environmental problem affecting those cities across different characteristics and continents. Various reasons for the increase in urban sprawl in the last 10 to 30 years have been proposed [1], and often depend on the socio-economic situation of cities. The quantitative reduction and the sustainable handling of land should be performed by inner urban development instead of expanding urban regions. Following the principal "spare the urban fringe, develop the inner suburbs first" requires differentiated tools allowing for quantitative and qualitative appraisals of current building potentials. Using spatial high resolution remote sensing data within an object-based approach enables the detection of potential areas while GIS-data provides information for the quantitative valuation. This paper presents techniques for modeling urban environment and opportunities of utilization of the retrieved information for urban planners and their special needs.

  6. Influence of dry mixing and distribution of conductive additives in cathodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Bauer, Werner; Nötzel, Dorit; Wenzel, Valentin; Nirschl, Hermann

    2015-08-01

    Conductive additives, like carbon black or graphite, are essential components of lithium ion batteries due to the limited electrical conductivity of most electrode materials. However, there is still a lack of knowledge about the optimized distribution of these materials within the electrode. A dry mixing process is used in order to prepare a conductive coating by depositing carbon black on the surface of Li(Ni1/3Mn1/3Co1/3)O2 (NMC) cathode particles. It is demonstrated that this - from a theoretically point of view - favorable distribution does not allow the preparation of working electrodes without taking into account the role of the binder. After adding an organic binder to the slurry, the polymer deposits on top of the carbon shell during drying and inhibits the conductive contact between the particles. This can be avoided by a fraction of distributed carbon particles which are associated with the binder phase providing conductive paths through the isolating organic material. It is shown that carbon black and graphite are principally fulfilling this task, but both materials are leading to varying processing behavior and electrode properties.

  7. A new unsteady mixing model to predict NO(x) production during rapid mixing in a dual-stage combustor

    NASA Technical Reports Server (NTRS)

    Menon, Suresh; Mcmurtry, Patrick A.; Kerstein, Alan R.; Chen, J.-Y.

    1992-01-01

    An advanced gas turbine engine to power supersonic transport aircraft is currently under study. In addition to high combustion efficiency requirements, environmental concerns have placed stringent restrictions on the pollutant emissions from these engines. A dual-stage combustor with the potential for minimizing pollutants such as NO(x) emissions is undergoing experimental evaluation. A major technical issue in the design of this combustor is how to rapidly mix the hot, fuel-rich primary stage product with the secondary diluent air to obtain a fuel-lean mixture for combustion in the secondary stage. Numerical design studies using steady-state methods cannot account for the unsteady phenomena in the mixing region. Therefore, to evaluate the effect of unsteady mixing and combustion processes, a novel unsteady mixing model is demonstrated here. This model has been used in a stand-alone mode to study mixing and combustion in hydrogen-air nonpremixed jet flames. NO(x) production in these jet flames was also predicted. Comparison of the computed results with experimental data show good agreement thereby providing validation of the mixing model.

  8. Mixed Barrier Model for the Mixed Glass Former Effect in Ion Conducting Glasses

    NASA Astrophysics Data System (ADS)

    Schuch, Michael; Müller, Christian R.; Maass, Philipp; Martin, Steve W.

    2009-04-01

    Mixing two types of glass formers in ion conducting glasses can be exploited to lower conductivity activation energy and thereby increasing the ionic conductivity, a phenomenon known as the mixed glass former effect (MGFE). We develop a model for this MGFE, where activation barriers for individual ion jumps get lowered in inhomogeneous environments containing both types of network forming units. Fits of the model to experimental data allow one to estimate the strength of the barrier reduction, and they indicate a spatial clustering of the two types of network formers. The model predicts a time-temperature superposition of conductivity spectra onto a common master curve independent of the mixing ratio.

  9. Chaos in the Mixed Even-Spin Models

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Kuo

    2014-06-01

    We consider a disordered system obtained by coupling two mixed even-spin models together. The chaos problem is concerned with the behavior of the coupled system when the external parameters in the two models, such as, temperature, disorder, or external field, are slightly different. It is conjectured that the overlap between two independently sampled spin configurations from, respectively, the Gibbs measures of the two models is essentially concentrated around a constant under the coupled Gibbs measure. Using the extended Guerra replica symmetry breaking bound together with a recent development of controlling the overlap using the Ghirlanda-Guerra identities as well as a new family of identities, we present rigorous results on chaos in temperature. In addition, chaos in disorder and in external field are addressed.

  10. Lagrangian mixed layer modeling of the western equatorial Pacific

    NASA Technical Reports Server (NTRS)

    Shinoda, Toshiaki; Lukas, Roger

    1995-01-01

    Processes that control the upper ocean thermohaline structure in the western equatorial Pacific are examined using a Lagrangian mixed layer model. The one-dimensional bulk mixed layer model of Garwood (1977) is integrated along the trajectories derived from a nonlinear 1 1/2 layer reduced gravity model forced with actual wind fields. The Global Precipitation Climatology Project (GPCP) data are used to estimate surface freshwater fluxes for the mixed layer model. The wind stress data which forced the 1 1/2 layer model are used for the mixed layer model. The model was run for the period 1987-1988. This simple model is able to simulate the isothermal layer below the mixed layer in the western Pacific warm pool and its variation. The subduction mechanism hypothesized by Lukas and Lindstrom (1991) is evident in the model results. During periods of strong South Equatorial Current, the warm and salty mixed layer waters in the central Pacific are subducted below the fresh shallow mixed layer in the western Pacific. However, this subduction mechanism is not evident when upwelling Rossby waves reach the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific due to episodes of strong wind and light precipitation associated with the El Nino-Southern Oscillation. Comparison of the results between the Lagrangian mixed layer model and a locally forced Eulerian mixed layer model indicated that horizontal advection of salty waters from the central Pacific strongly affects the upper ocean salinity variation in the western Pacific, and that this advection is necessary to maintain the upper ocean thermohaline structure in this region.

  11. Radiolysis Model Formulation for Integration with the Mixed Potential Model

    SciTech Connect

    Buck, Edgar C.; Wittman, Richard S.

    2014-07-10

    The U.S. Department of Energy Office of Nuclear Energy (DOE-NE), Office of Fuel Cycle Technology has established the Used Fuel Disposition Campaign (UFDC) to conduct the research and development activities related to storage, transportation, and disposal of used nuclear fuel (UNF) and high-level radioactive waste. Within the UFDC, the components for a general system model of the degradation and subsequent transport of UNF is being developed to analyze the performance of disposal options [Sassani et al., 2012]. Two model components of the near-field part of the problem are the ANL Mixed Potential Model and the PNNL Radiolysis Model. This report is in response to the desire to integrate the two models as outlined in [Buck, E.C, J.L. Jerden, W.L. Ebert, R.S. Wittman, (2013) “Coupling the Mixed Potential and Radiolysis Models for Used Fuel Degradation,” FCRD-UFD-2013-000290, M3FT-PN0806058

  12. Box-Cox Mixed Logit Model for Travel Behavior Analysis

    NASA Astrophysics Data System (ADS)

    Orro, Alfonso; Novales, Margarita; Benitez, Francisco G.

    2010-09-01

    To represent the behavior of travelers when they are deciding how they are going to get to their destination, discrete choice models, based on the random utility theory, have become one of the most widely used tools. The field in which these models were developed was halfway between econometrics and transport engineering, although the latter now constitutes one of their principal areas of application. In the transport field, they have mainly been applied to mode choice, but also to the selection of destination, route, and other important decisions such as the vehicle ownership. In usual practice, the most frequently employed discrete choice models implement a fixed coefficient utility function that is linear in the parameters. The principal aim of this paper is to present the viability of specifying utility functions with random coefficients that are nonlinear in the parameters, in applications of discrete choice models to transport. Nonlinear specifications in the parameters were present in discrete choice theory at its outset, although they have seldom been used in practice until recently. The specification of random coefficients, however, began with the probit and the hedonic models in the 1970s, and, after a period of apparent little practical interest, has burgeoned into a field of intense activity in recent years with the new generation of mixed logit models. In this communication, we present a Box-Cox mixed logit model, original of the authors. It includes the estimation of the Box-Cox exponents in addition to the parameters of the random coefficients distribution. Probability of choose an alternative is an integral that will be calculated by simulation. The estimation of the model is carried out by maximizing the simulated log-likelihood of a sample of observed individual choices between alternatives. The differences between the predictions yielded by models that are inconsistent with real behavior have been studied with simulation experiments.

  13. Lidar observations of mixed layer dynamics - Tests of parameterized entrainment models of mixed layer growth rate

    NASA Technical Reports Server (NTRS)

    Boers, R.; Eloranta, E. W.; Coulter, R. L.

    1984-01-01

    Ground based lidar measurements of the atmospheric mixed layer depth, the entrainment zone depth and the wind speed and wind direction were used to test various parameterized entrainment models of mixed layer growth rate. Six case studies under clear air convective conditions over flat terrain in central Illinois are presented. It is shown that surface heating alone accounts for a major portion of the rise of the mixed layer on all days. A new set of entrainment model constants was determined which optimized height predictions for the dataset. Under convective conditions, the shape of the mixed layer height prediction curves closely resembled the observed shapes. Under conditions when significant wind shear was present, the shape of the height prediction curve departed from the data suggesting deficiencies in the parameterization of shear production. Development of small cumulus clouds on top of the layer is shown to affect mixed layer depths in the afternoon growth phase.

  14. The transport exponent in percolation models with additional loops

    NASA Astrophysics Data System (ADS)

    Babalievski, F.

    1994-10-01

    Several percolation models with additional loops were studied. The transport exponents for these models were estimated numerically by means of a transfer-matrix approach. It was found that the transport exponent has a drastically changed value for some of the models. This result supports some previous numerical studies on the vibrational properties of similar models (with additional loops).

  15. Effects of Microscopic Diffusion and Rotational Mixing on Stellar Models

    NASA Astrophysics Data System (ADS)

    Chaboyer, Brian

    1994-02-01

    Evolutionary tracks and isochrones were calculated with alpha-enhanced compositions which cover the entire globular cluster metallicity range and include the effects of the diffusion of ^4He. Including the effects of helium diffusion has a negligible effect (< 0.5 Gyr) on the derived ages of globular clusters. Regardless of the inclusion of helium diffusion, a significant age spread of ~5$ Gyr exists among the globular clusters. The oldest globular cluster studied was M92 with an age of 17 +/- 2 Gyr old. The stellar models may be tested by comparing the Li depletion and surface rotation rates to observations in young clusters stars. The observed Li abundances clearly indicate that standard or diffusive models do not deplete enough Li. Instabilities induced by rotation provide an additional mixing mechanism. For this reason the stellar evolution code was modified to include the combined effects of diffusion and rotational mixing on ^1H, ^4He and the trace elements ^3He, ^6Li, ^7Li, and ^9Be. The calibrated solar models have a convection zone depth of 0.709 - 0.714~R_odot, in excellent agreement with the observed depth of (0.713 +/- 0.003)~R_odot. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 30 - 50%. The combined models are able to simultaneously match the Li abundances observed in the Pleiades, UMaG, Hyades, NGC 752 and M67. They also match the observed rotation periods in the Hyades. However, these models are unable to explain the presence of the rapidly rotating G and K stars in the Pleiades. Observations of Li abundances in extremely metal poor halo stars provide another test of the stellar models. All models which use Kurucz (1992) model atmospheres to determine the surface boundary conditions are unable to match the observed Li depletion in cool halo stars. Models which use the gray atmosphere approximation provide a much better fit to the data. Standard models do a good job

  16. Models of neutrino mass, mixing and CP violation

    NASA Astrophysics Data System (ADS)

    King, Stephen F.

    2015-12-01

    In this topical review we argue that neutrino mass and mixing data motivates extending the Standard Model (SM) to include a non-Abelian discrete flavour symmetry in order to accurately predict the large leptonic mixing angles and {C}{P} violation. We begin with an overview of the SM puzzles, followed by a description of some classic lepton mixing patterns. Lepton mixing may be regarded as a deviation from tri-bimaximal mixing, with charged lepton corrections leading to solar mixing sum rules, or tri-maximal lepton mixing leading to atmospheric mixing rules. We survey neutrino mass models, using a roadmap based on the open questions in neutrino physics. We then focus on the seesaw mechanism with right-handed neutrinos, where sequential dominance (SD) can account for large lepton mixing angles and {C}{P} violation, with precise predictions emerging from constrained SD (CSD). We define the flavour problem and discuss progress towards a theory of favour using GUTs and discrete family symmetry. We classify models as direct, semidirect or indirect, according to the relation between the Klein symmetry of the mass matrices and the discrete family symmetry, in all cases focussing on spontaneous {C}{P} violation. Finally we give two examples of realistic and highly predictive indirect models with CSD, namely an A to Z of flavour with Pati-Salam and a fairly complete A 4 × SU(5) SUSY GUT of flavour, where both models have interesting implications for leptogenesis.

  17. Linear mixing model applied to coarse resolution satellite data

    NASA Technical Reports Server (NTRS)

    Holben, Brent N.; Shimabukuro, Yosio E.

    1992-01-01

    A linear mixing model typically applied to high resolution data such as Airborne Visible/Infrared Imaging Spectrometer, Thematic Mapper, and Multispectral Scanner System is applied to the NOAA Advanced Very High Resolution Radiometer coarse resolution satellite data. The reflective portion extracted from the middle IR channel 3 (3.55 - 3.93 microns) is used with channels 1 (0.58 - 0.68 microns) and 2 (0.725 - 1.1 microns) to run the Constrained Least Squares model to generate fraction images for an area in the west central region of Brazil. The derived fraction images are compared with an unsupervised classification and the fraction images derived from Landsat TM data acquired in the same day. In addition, the relationship betweeen these fraction images and the well known NDVI images are presented. The results show the great potential of the unmixing techniques for applying to coarse resolution data for global studies.

  18. Mixed inflaton and spectator field models: CMB constraints and μ distortion

    NASA Astrophysics Data System (ADS)

    Enqvist, Kari; Sekiguchi, Toyokazu; Takahashi, Tomo

    2016-04-01

    We discuss mixed inflaton and spectator field models where both the fields are responsible for the observed density fluctuations. We combine the angular power spectrum of the CMB temperature anisotropy from the Planck 2013 result and other ground-based CMB observations in order to constrain both the general mixed model as well as some specific representative scenarios. Based on the Markov Chain Monte Carlo method, in addition to constraints on model parameters, we obtain the predictive posterior distributions of the CMB spectral μ distortion for those models. We demonstrate that the standard single-field inflaton model typically predicts μ ~ 10-8 with a relatively narrow distribution, whereas for the mixed models, the distribution turns out to be much broader, and μ could be larger by almost an order of magnitude. Hence future experiments of μ distortion could provide a tool for the critical testing of the mixed source models of the primordial perturbation.

  19. A multifluid mix model with material strength effects

    SciTech Connect

    Chang, C. H.; Scannapieco, A. J.

    2012-04-23

    We present a new multifluid mix model. Its features include material strength effects and pressure and temperature nonequilibrium between mixing materials. It is applicable to both interpenetration and demixing of immiscible fluids and diffusion of miscible fluids. The presented model exhibits the appropriate smooth transition in mathematical form as the mixture evolves from multiphase to molecular mixing, extending its applicability to the intermediate stages in which both types of mixing are present. Virtual mass force and momentum exchange have been generalized for heterogeneous multimaterial mixtures. The compression work has been extended so that the resulting species energy equations are consistent with the pressure force and material strength.

  20. A New Model for Mix It Up

    ERIC Educational Resources Information Center

    Holladay, Jennifer

    2009-01-01

    Since 2002, Teaching Tolerance's Mix It Up at Lunch Day program has helped millions of students cross social boundaries and create more inclusive school communities. Its goal is to create a safe, purposeful opportunity for students to break down the patterns of social self-segregation that too often plague schools. Research conducted in 2006 by…

  1. Liposome-based liquid handling platform featuring addition, mixing, and aliquoting of femtoliter volumes.

    PubMed

    Shiomi, Hideaki; Tsuda, Soichiro; Suzuki, Hiroaki; Yomo, Tetsuya

    2014-01-01

    This paper describes the utilization of giant unilamellar vesicles (GUVs) as a platform for handling chemical and biochemical reagents. GUVs with diameters of 5 to 10 µm and containing chemical/biochemical reagents together with inert polymers were fused with electric pulses (electrofusion). After reagent mixing, the fused GUVs spontaneously deformed to a budding shape, separating the mixed solution into sub-volumes. We utilized a microfluidic channel and optical tweezers to select GUVs of interest, bring them into contact, and fuse them together to mix and aliquot the reaction product. We also show that, by lowering the ambient temperature close to the phase transition temperature Tm of the lipid used, daughter GUVs completely detached (fission). This process performs all the liquid-handing features used in bench-top biochemistry using the GUV, which could be advantageous for the membrane-related biochemical assays. PMID:24991878

  2. Estimating anatomical trajectories with Bayesian mixed-effects modeling

    PubMed Central

    Ziegler, G.; Penny, W.D.; Ridgway, G.R.; Ourselin, S.; Friston, K.J.

    2015-01-01

    We introduce a mass-univariate framework for the analysis of whole-brain structural trajectories using longitudinal Voxel-Based Morphometry data and Bayesian inference. Our approach to developmental and aging longitudinal studies characterizes heterogeneous structural growth/decline between and within groups. In particular, we propose a probabilistic generative model that parameterizes individual and ensemble average changes in brain structure using linear mixed-effects models of age and subject-specific covariates. Model inversion uses Expectation Maximization (EM), while voxelwise (empirical) priors on the size of individual differences are estimated from the data. Bayesian inference on individual and group trajectories is realized using Posterior Probability Maps (PPM). In addition to parameter inference, the framework affords comparisons of models with varying combinations of model order for fixed and random effects using model evidence. We validate the model in simulations and real MRI data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) project. We further demonstrate how subject specific characteristics contribute to individual differences in longitudinal volume changes in healthy subjects, Mild Cognitive Impairment (MCI), and Alzheimer's Disease (AD). PMID:26190405

  3. Estimating anatomical trajectories with Bayesian mixed-effects modeling.

    PubMed

    Ziegler, G; Penny, W D; Ridgway, G R; Ourselin, S; Friston, K J

    2015-11-01

    We introduce a mass-univariate framework for the analysis of whole-brain structural trajectories using longitudinal Voxel-Based Morphometry data and Bayesian inference. Our approach to developmental and aging longitudinal studies characterizes heterogeneous structural growth/decline between and within groups. In particular, we propose a probabilistic generative model that parameterizes individual and ensemble average changes in brain structure using linear mixed-effects models of age and subject-specific covariates. Model inversion uses Expectation Maximization (EM), while voxelwise (empirical) priors on the size of individual differences are estimated from the data. Bayesian inference on individual and group trajectories is realized using Posterior Probability Maps (PPM). In addition to parameter inference, the framework affords comparisons of models with varying combinations of model order for fixed and random effects using model evidence. We validate the model in simulations and real MRI data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) project. We further demonstrate how subject specific characteristics contribute to individual differences in longitudinal volume changes in healthy subjects, Mild Cognitive Impairment (MCI), and Alzheimer's Disease (AD). PMID:26190405

  4. Analysis and modeling of subgrid scalar mixing using numerical data

    NASA Technical Reports Server (NTRS)

    Girimaji, Sharath S.; Zhou, YE

    1995-01-01

    Direct numerical simulations (DNS) of passive scalar mixing in isotropic turbulence is used to study, analyze and, subsequently, model the role of small (subgrid) scales in the mixing process. In particular, we attempt to model the dissipation of the large scale (supergrid) scalar fluctuations caused by the subgrid scales by decomposing it into two parts: (1) the effect due to the interaction among the subgrid scales; and (2) the effect due to interaction between the supergrid and the subgrid scales. Model comparisons with DNS data show good agreement. This model is expected to be useful in the large eddy simulations of scalar mixing and reaction.

  5. Parameter recovery and model selection in mixed Rasch models.

    PubMed

    Preinerstorfer, David; Formann, Anton K

    2012-05-01

    This study examines the precision of conditional maximum likelihood estimates and the quality of model selection methods based on information criteria (AIC and BIC) in mixed Rasch models. The design of the Monte Carlo simulation study included four test lengths (10, 15, 25, 40), three sample sizes (500, 1000, 2500), two simulated mixture conditions (one and two groups), and population homogeneity (equally sized subgroups) or heterogeneity (one subgroup three times larger than the other). The results show that both increasing sample size and increasing number of items lead to higher accuracy; medium-range parameters were estimated more precisely than extreme ones; and the accuracy was higher in homogeneous populations. The minimum-BIC method leads to almost perfect results and is more reliable than AIC-based model selection. The results are compared to findings by Li, Cohen, Kim, and Cho (2009) and practical guidelines are provided. PMID:21675964

  6. An Investigation of Item Fit Statistics for Mixed IRT Models

    ERIC Educational Resources Information Center

    Chon, Kyong Hee

    2009-01-01

    The purpose of this study was to investigate procedures for assessing model fit of IRT models for mixed format data. In this study, various IRT model combinations were fitted to data containing both dichotomous and polytomous item responses, and the suitability of the chosen model mixtures was evaluated based on a number of model fit procedures.…

  7. On the coalescence-dispersion modeling of turbulent molecular mixing

    NASA Technical Reports Server (NTRS)

    Givi, Peyman; Kosaly, George

    1987-01-01

    The general coalescence-dispersion (C/D) closure provides phenomenological modeling of turbulent molecular mixing. The models of Curl and Dopazo and O'Brien appear as two limiting C/D models that bracket the range of results one can obtain by various models. This finding is used to investigate the sensitivtiy of the results to the choice of the model. Inert scalar mixing is found to be less model-sensitive than mixing accompanied by chemical reaction. Infinitely fast chemistry approximation is used to relate the C/D approach to Toor's earlier results. Pure mixing and infinite rate chemistry calculations are compared to study further a recent result of Hsieh and O'Brien who found that higher concentration moments are not sensitive to chemistry.

  8. Computer modeling of jet mixing in INEL waste tanks

    SciTech Connect

    Meyer, P.A.

    1994-01-01

    The objective of this study is to examine the feasibility of using submerged jet mixing pumps to mobilize and suspend settled sludge materials in INEL High Level Radioactive Waste Tanks. Scenarios include removing the heel (a shallow liquid and sludge layer remaining after tank emptying processes) and mobilizing and suspending solids in full or partially full tanks. The approach used was to (1) briefly review jet mixing theory, (2) review erosion literature in order to identify and estimate important sludge characterization parameters (3) perform computer modeling of submerged liquid mixing jets in INEL tank geometries, (4) develop analytical models from which pump operating conditions and mixing times can be estimated, and (5) analyze model results to determine overall feasibility of using jet mixing pumps and make design recommendations.

  9. Diagnostic tools for mixing models of stream water chemistry

    USGS Publications Warehouse

    Hooper, R.P.

    2003-01-01

    Mixing models provide a useful null hypothesis against which to evaluate processes controlling stream water chemical data. Because conservative mixing of end-members with constant concentration is a linear process, a number of simple mathematical and multivariate statistical methods can be applied to this problem. Although mixing models have been most typically used in the context of mixing soil and groundwater end-members, an extension of the mathematics of mixing models is presented that assesses the "fit" of a multivariate data set to a lower dimensional mixing subspace without the need for explicitly identified end-members. Diagnostic tools are developed to determine the approximate rank of the data set and to assess lack of fit of the data. This permits identification of processes that violate the assumptions of the mixing model and can suggest the dominant processes controlling stream water chemical variation. These same diagnostic tools can be used to assess the fit of the chemistry of one site into the mixing subspace of a different site, thereby permitting an assessment of the consistency of controlling end-members across sites. This technique is applied to a number of sites at the Panola Mountain Research Watershed located near Atlanta, Georgia.

  10. Development of a Medicaid Behavioral Health Case-Mix Model

    ERIC Educational Resources Information Center

    Robst, John

    2009-01-01

    Many Medicaid programs have either fully or partially carved out mental health services. The evaluation of carve-out plans requires a case-mix model that accounts for differing health status across Medicaid managed care plans. This article develops a diagnosis-based case-mix adjustment system specific to Medicaid behavioral health care. Several…

  11. Kinetic mixing effect in the 3 -3 -1 -1 model

    NASA Astrophysics Data System (ADS)

    Dong, P. V.; Si, D. T.

    2016-06-01

    We show that the mixing effect of the neutral gauge bosons in the 3 -3 -1 -1 model comes from two sources. The first one is due to the 3 -3 -1 -1 gauge symmetry breaking as usual, whereas the second one results from the kinetic mixing between the gauge bosons of U (1 )X and U (1 )N groups, which are used to determine the electric charge and baryon minus lepton numbers, respectively. Such mixings modify the ρ -parameter and the known couplings of Z with fermions. The constraints that arise from flavor-changing neutral currents due to the gauge boson mixings and nonuniversal fermion generations are also given.

  12. The Toxic Effects of Cigarette Additives. Philip Morris' Project Mix Reconsidered: An Analysis of Documents Released through Litigation

    PubMed Central

    Wertz, Marcia S.; Kyriss, Thomas; Paranjape, Suman; Glantz, Stanton A.

    2011-01-01

    Background In 2009, the promulgation of US Food and Drug Administration (FDA) tobacco regulation focused attention on cigarette flavor additives. The tobacco industry had prepared for this eventuality by initiating a research program focusing on additive toxicity. The objective of this study was to analyze Philip Morris' Project MIX as a case study of tobacco industry scientific research being positioned strategically to prevent anticipated tobacco control regulations. Methods and Findings We analyzed previously secret tobacco industry documents to identify internal strategies for research on cigarette additives and reanalyzed tobacco industry peer-reviewed published results of this research. We focused on the key group of studies conducted by Phillip Morris in a coordinated effort known as “Project MIX.” Documents showed that Project MIX subsumed the study of various combinations of 333 cigarette additives. In addition to multiple internal reports, this work also led to four peer-reviewed publications (published in 2001). These papers concluded that there was no evidence of substantial toxicity attributable to the cigarette additives studied. Internal documents revealed post hoc changes in analytical protocols after initial statistical findings indicated an additive-associated increase in cigarette toxicity as well as increased total particulate matter (TPM) concentrations in additive-modified cigarette smoke. By expressing the data adjusted by TPM concentration, the published papers obscured this underlying toxicity and particulate increase. The animal toxicology results were based on a small number of rats in each experiment, raising the possibility that the failure to detect statistically significant changes in the end points was due to underpowering the experiments rather than lack of a real effect. Conclusion The case study of Project MIX shows tobacco industry scientific research on the use of cigarette additives cannot be taken at face value. The

  13. Trends in stratospheric ozone profiles using functional mixed models

    NASA Astrophysics Data System (ADS)

    Park, A. Y.; Guillas, S.; Petropavlovskikh, I.

    2013-05-01

    This paper is devoted to the modeling of altitude-dependent patterns of ozone variations over time. Umkher ozone profiles (quarter of Umkehr layer) from 1978 to 2011 are investigated at two locations: Boulder (USA) and Arosa (Switzerland). The study consists of two statistical stages. First we approximate ozone profiles employing an appropriate basis. To capture primary modes of ozone variations without losing essential information, a functional principal component analysis is performed as it penalizes roughness of the function and smooths excessive variations in the shape of the ozone profiles. As a result, data driven basis functions are obtained. Secondly we estimate the effects of covariates - month, year (trend), quasi biennial oscillation, the Solar cycle, arctic oscillation and the El Niño/Southern Oscillation cycle - on the principal component scores of ozone profiles over time using generalized additive models. The effects are smooth functions of the covariates, and are represented by knot-based regression cubic splines. Finally we employ generalized additive mixed effects models incorporating a more complex error structure that reflects the observed seasonality in the data. The analysis provides more accurate estimates of influences and trends, together with enhanced uncertainty quantification. We are able to capture fine variations in the time evolution of the profiles such as the semi-annual oscillation. We conclude by showing the trends by altitude over Boulder. The strongly declining trends over 2003-2011 for altitudes of 32-64 hPa show that stratospheric ozone is not yet fully recovering.

  14. Criteria for deviation from predictions by the concentration addition model.

    PubMed

    Takeshita, Jun-Ichi; Seki, Masanori; Kamo, Masashi

    2016-07-01

    Loewe's additivity (concentration addition) is a well-known model for predicting the toxic effects of chemical mixtures under the additivity assumption of toxicity. However, from the perspective of chemical risk assessment and/or management, it is important to identify chemicals whose toxicities are additive when present concurrently, that is, it should be established whether there are chemical mixtures to which the concentration addition predictive model can be applied. The objective of the present study was to develop criteria for judging test results that deviated from the predictions by the concentration addition chemical mixture model. These criteria were based on the confidence interval of the concentration addition model's prediction and on estimation of errors of the predicted concentration-effect curves by toxicity tests after exposure to single chemicals. A log-logit model with 2 parameters was assumed for the concentration-effect curve of each individual chemical. These parameters were determined by the maximum-likelihood method, and the criteria were defined using the variances and the covariance of the parameters. In addition, the criteria were applied to a toxicity test of a binary mixture of p-n-nonylphenol and p-n-octylphenol using the Japanese killifish, medaka (Oryzias latipes). Consequently, the concentration addition model using confidence interval was capable of predicting the test results at any level, and no reason for rejecting the concentration addition was found. Environ Toxicol Chem 2016;35:1806-1814. © 2015 SETAC. PMID:26660330

  15. Mixed waste treatment model: Basis and analysis

    SciTech Connect

    Palmer, B.A.

    1995-09-01

    The Department of Energy`s Programmatic Environmental Impact Statement (PEIS) required treatment system capacities for risk and cost calculation. Los Alamos was tasked with providing these capacities to the PEIS team. This involved understanding the Department of Energy (DOE) Complex waste, making the necessary changes to correct for problems, categorizing the waste for treatment, and determining the treatment system requirements. The treatment system requirements depended on the incoming waste, which varied for each PEIS case. The treatment system requirements also depended on the type of treatment that was desired. Because different groups contributing to the PEIS needed specific types of results, we provided the treatment system requirements in a variety of forms. In total, some 40 data files were created for the TRU cases, and for the MLLW case, there were 105 separate data files. Each data file represents one treatment case consisting of the selected waste from various sites, a selected treatment system, and the reporting requirements for such a case. The treatment system requirements in their most basic form are the treatment process rates for unit operations in the desired treatment system, based on a 10-year working life and 20-year accumulation of the waste. These results were reported in cubic meters and for the MLLW case, in kilograms as well. The treatment system model consisted of unit operations that are linked together. Each unit operation`s function depended on the input waste streams, waste matrix, and contaminants. Each unit operation outputs one or more waste streams whose matrix, contaminants, and volume/mass may have changed as a result of the treatment. These output streams are then routed to the appropriate unit operation for additional treatment until the output waste stream meets the treatment requirements for disposal. The total waste for each unit operation was calculated as well as the waste for each matrix treated by the unit.

  16. Shell model of optimal passive-scalar mixing

    NASA Astrophysics Data System (ADS)

    Miles, Christopher; Doering, Charles

    2015-11-01

    Optimal mixing is significant to process engineering within industries such as food, chemical, pharmaceutical, and petrochemical. An important question in this field is ``How should one stir to create a homogeneous mixture while being energetically efficient?'' To answer this question, we consider an initially unmixed scalar field representing some concentration within a fluid on a periodic domain. This passive-scalar field is advected by the velocity field, our control variable, constrained by a physical quantity such as energy or enstrophy. We consider two objectives: local-in-time (LIT) optimization (what will maximize the mixing rate now?) and global-in-time (GIT) optimization (what will maximize mixing at the end time?). Throughout this work we use the H-1 mix-norm to measure mixing. To gain a better understanding, we provide a simplified mixing model by using a shell model of passive-scalar advection. LIT optimization in this shell model gives perfect mixing in finite time for the energy-constrained case and exponential decay to the perfect-mixed state for the enstrophy-constrained case. Although we only enforce that the time-average energy (or enstrophy) equals a chosen value in GIT optimization, interestingly, the optimal control keeps this value constant over time.

  17. The effects of mixing on stratospheric Age of Air in global models

    NASA Astrophysics Data System (ADS)

    Garny, Hella; Birner, Thomas; Bönisch, Harald

    2014-05-01

    The stratospheric Brewer-Dobson circulation is often quantified by the integrated transport measure stratospheric age of air (AoA). AoA is influenced both by mean transport along the residual circulation and by two-way mixing. Therefore, AoA is a good measure of the overall capabilities of a global model to simulate stratospheric transport. Currently, a large spread in the simulation of AoA by global models is found. In this study we use a method that allows us to quantify the effect of mixing on AoA from global model data. AoA is contrasted with a hypothetical age - the age air would have if it was only transported by the residual circulation, the residual circulation transit time (RCTT). The difference of AoA and RCTT is interpreted as the additional aging by mixing. Mixing causes air to be older almost in the entire lower stratosphere (AoA > RCTT). This increase in AoA by mixing is largely due to mixing between the tropics and extratropics, that leads to recirculation of air through the stratosphere. A "mixing efficiency" is defined as the ratio of the two-way mixing mass flux across the subtropical barrier to the net (residual) mass flux. This mixing efficiency controls the ratio of tropical mean AoA to RCTT, and thus the relative increase in AoA by mixing. These diagnostics are applied to a set of global model simulations to examine the causes for the spread in the simulation of AoA in different models. It is found that both differences in the residual circulation strength and in mixing contribute to the spread in simulated AoA. The mixing efficiency varies strongly between models - leading to differences in AoA between models even if the residual circulation strength did not differ. Possible causes for the differences in the mixing efficiency might be found in the model dynamics (e.g. the wave spectrum) and/or numerics (e.g. the advection scheme used). The different mixing efficiencies in models also modulate the response of AoA to long-term changes in the

  18. Radiological, physical, and chemical characterization of additional alpha contaminated and mixed low-level waste for treatment at the advanced mixed waste treatment project

    SciTech Connect

    Hutchinson, D.P.

    1995-07-01

    This document provides physical, chemical, and radiological descriptive information for a portion of mixed waste that is potentially available for private sector treatment. The format and contents are designed to provide treatment vendors with preliminary information on the characteristics and properties for additional candidate portions of the Idaho National Engineering Laboratory (INEL) and offsite mixed wastes not covered in the two previous characterization reports for the INEL-stored low-level alpha-contaminated and transuranic wastes. This report defines the waste, provides background information, briefly reviews the requirements of the Federal Facility Compliance Act (P.L. 102-386), and relates the Site Treatment Plans developed under the Federal Facility Compliance Act to the waste streams described herein. Each waste is summarized in a Waste Profile Sheet with text, charts, and tables of waste descriptive information for a particular waste stream. A discussion of the availability and uncertainty of data for these waste streams precedes the characterization descriptions.

  19. Agility and mixed-model furniture production

    NASA Astrophysics Data System (ADS)

    Yao, Andrew C.

    2000-10-01

    The manufacture of upholstered furniture provides an excellent opportunity to analyze the effect of a comprehensive communication system on classical production management functions. The objective of the research is to study the scheduling heuristics that embrace the concepts inherent in MRP, JIT and TQM while recognizing the need for agility in a somewhat complex and demanding environment. An on-line, real-time data capture system provides the status and location of production lots, components, subassemblies for schedule control. Current inventory status of raw material and purchased items are required in order to develop and adhere to schedules. For the large variety of styles and fabrics customers may order, the communication system must provide timely, accurate and comprehensive information for intelligent decisions with respect to the product mix and production resources.

  20. Systematic Classification of Mixed-Lineage Leukemia Fusion Partners Predicts Additional Cancer Pathways

    PubMed Central

    2016-01-01

    Chromosomal translocations of the human mixed-lineage leukemia (MLL) gene have been analyzed for more than 20 yr at the molecular level. So far, we have collected about 80 direct MLL fusions (MLL-X alleles) and about 120 reciprocal MLL fusions (X-MLL alleles). The reason for the higher amount of reciprocal MLL fusions is that the excess is caused by 3-way translocations with known direct fusion partners. This review is aiming to propose a solution for an obvious problem, namely why so many and completely different MLL fusion alleles are always leading to the same leukemia phenotypes (ALL, AML, or MLL). This review is aiming to explain the molecular consequences of MLL translocations, and secondly, the contribution of the different fusion partners. A new hypothesis will be posed that can be used for future research, aiming to find new avenues for the treatment of this particular leukemia entity. PMID:26709255

  1. A Bayesian Semiparametric Latent Variable Model for Mixed Responses

    ERIC Educational Resources Information Center

    Fahrmeir, Ludwig; Raach, Alexander

    2007-01-01

    In this paper we introduce a latent variable model (LVM) for mixed ordinal and continuous responses, where covariate effects on the continuous latent variables are modelled through a flexible semiparametric Gaussian regression model. We extend existing LVMs with the usual linear covariate effects by including nonparametric components for nonlinear…

  2. A Comparison of Item Fit Statistics for Mixed IRT Models

    ERIC Educational Resources Information Center

    Chon, Kyong Hee; Lee, Won-Chan; Dunbar, Stephen B.

    2010-01-01

    In this study we examined procedures for assessing model-data fit of item response theory (IRT) models for mixed format data. The model fit indices used in this study include PARSCALE's G[superscript 2], Orlando and Thissen's S-X[superscript 2] and S-G[superscript 2], and Stone's chi[superscript 2*] and G[superscript 2*]. To investigate the…

  3. Weakly nonlinear models for turbulent mixing in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Liou, William W.; Morris, Philip J.

    1992-01-01

    New closure models for turbulent free shear flows are presented in this paper. They are based on a weakly nonlinear theory with a description of the dominant large-scale structures as instability waves. Two models are presented that describe the evolution of the free shear flows in terms of the time-averaged mean flow and the dominant large-scale turbulent structure. The local characteristics of the large-scale motions are described using linear theory. Their amplitude is determined from an energy integral analysis. The models have been applied to the study of an incompressible mixing layer. For both models, predictions of the mean flow developed are made. In the second model, predictions of the time-dependent motion of the large-scale structures in the mixing layer are made. The predictions show good agreement with experimental observations.

  4. Alteration of belowground carbon dynamics by nitrogen addition in southern California mixed conifer forests

    SciTech Connect

    Nowinski, Nicole S.; Trumbore, Susan E.; Jimenez, Gloria; Fenn, Mark E.

    2009-04-01

    Nitrogen deposition rates in southern California are the highest in North America and have had substantial effects on ecosystem functioning. We document changes in the belowground C cycle near ponderosa pine trees experiencing experimental nitrogen (N) addition (50 and 150 kg N ha 1 a 1 as slow release urea since 1997) at two end member sites along a pollution gradient in the San Bernardino Mountains, California. Despite considerable differences in N deposition between the two sites, we observed parallel changes in microbial substrate use and soil enzyme activity with N addition. 14C measurements indicate that the mean age of C respired by the Oa horizon declined 10 15 years with N addition at both sites. N addition caused an increase in cellulolytic enzyme activity at the polluted site and a decrease in ligninolytic enzyme activity at the unpolluted site. Given the likely differences in lignin and cellulose ages, this could explain the difference in the age of microbial respiration with N addition. Measurements of fractionated soil organic matter did not show the same magnitude of changes in response to N addition as were observed for respired C. This lesser response was likely because the soils are mostly composed of C having turnover times of decades to centuries, and 9 years of N amendment were not enough to affect this material. Consequently, 14C of respired CO2 provided a more sensitive indicator of the effects of N addition than other methods. Results suggest that enhanced N deposition alone may not result in increased soil C storage in xeric ecosystems.

  5. Alteration of belowground carbon dynamics by nitrogen addition in southern California mixed conifer forests

    NASA Astrophysics Data System (ADS)

    Nowinski, Nicole S.; Trumbore, Susan E.; Jimenez, Gloria; Fenn, Mark E.

    2009-06-01

    Nitrogen deposition rates in southern California are the highest in North America and have had substantial effects on ecosystem functioning. We document changes in the belowground C cycle near ponderosa pine trees experiencing experimental nitrogen (N) addition (50 and 150 kg N ha-1 a-1 as slow release urea since 1997) at two end-member sites along a pollution gradient in the San Bernardino Mountains, California. Despite considerable differences in N deposition between the two sites, we observed parallel changes in microbial substrate use and soil enzyme activity with N addition. Δ14C measurements indicate that the mean age of C respired by the Oa horizon declined 10-15 years with N addition at both sites. N addition caused an increase in cellulolytic enzyme activity at the polluted site and a decrease in ligninolytic enzyme activity at the unpolluted site. Given the likely differences in lignin and cellulose ages, this could explain the difference in the age of microbial respiration with N addition. Measurements of fractionated soil organic matter did not show the same magnitude of changes in response to N addition as were observed for respired C. This lesser response was likely because the soils are mostly composed of C having turnover times of decades to centuries, and 9 years of N amendment were not enough to affect this material. Consequently, Δ14C of respired CO2 provided a more sensitive indicator of the effects of N addition than other methods. Results suggest that enhanced N deposition alone may not result in increased soil C storage in xeric ecosystems.

  6. LIDAR OBSERVATIONS OF MIXED LAYER DYNAMICS: TESTS OF PARAMETERIZED ENTRAINMENT MODELS OF MIXED LAYER GROWTH RATE

    EPA Science Inventory

    Lidar measurements of the atmospheric boundary layer height, the entrainment zone, wind speed and direction, ancillary temperature profiles and surface flux data were used to test current parameterized entrainment models of mixed layer growth rate. Six case studies under clear ai...

  7. Complex Modelling Scheme Of An Additive Manufacturing Centre

    NASA Astrophysics Data System (ADS)

    Popescu, Liliana Georgeta

    2015-09-01

    This paper presents a modelling scheme sustaining the development of an additive manufacturing research centre model and its processes. This modelling is performed using IDEF0, the resulting model process representing the basic processes required in developing such a centre in any university. While the activities presented in this study are those recommended in general, changes may occur in specific existing situations in a research centre.

  8. Mixing by barotropic instability in a nonlinear model

    NASA Technical Reports Server (NTRS)

    Bowman, Kenneth P.; Chen, Ping

    1994-01-01

    A global, nonlinear, equivalent barotropic model is used to study the isentropic mixing of passive tracers by barotropic instability. Basic states are analytical zonal-mean jets representative of the zonal-mean flow in the upper stratosphere, where the observed 4-day wave is thought to be a result of barotropic, and possibly baroclinic, instability. As is known from previous studies, the phase speed and growth rate of the unstable waves is fairly sensitive to the shape of the zonal-mean jet; and the dominant wave mode at saturation is not necessarily the fastest growing mode; but the unstable modes share many features of the observed 4-day wave. Lagrangian trajectories computed from model winds are used to characterize the mixing by the flow. For profiles with both midlatitude and polar modes, mixing is stronger in midlatitude than inside the vortex; but there is little exchange of air across the vortex boundary. There is a minimum in the Lyapunov exponents of the flow and the particle dispersion at the jet maximum. For profiles with only polar unstable modes, there is weak mixing inside the vortex, no mixing outside the vortex, and no exchange of air across the vortex boundary. These results support the theoretical arguments that, whether wave disturbances are generated by local instability or propagate from other regions, the mixing properties of the total flow are determined by the locations of the wave critical lines and that strong gradients of potential vorticity are very resistant to mixing.

  9. New mixing angles in the left-right symmetric model

    NASA Astrophysics Data System (ADS)

    Kokado, Akira; Saito, Takesi

    2015-12-01

    In the left-right symmetric model neutral gauge fields are characterized by three mixing angles θ12,θ23,θ13 between three gauge fields Bμ,WLμ 3,WRμ 3, which produce mass eigenstates Aμ,Zμ,Zμ', when G =S U (2 )L×S U (2 )R×U (1 )B-L×D is spontaneously broken down until U (1 )em . We find a new mixing angle θ', which corresponds to the Weinberg angle θW in the standard model with the S U (2 )L×U (1 )Y gauge symmetry, from these mixing angles. It is then shown that any mixing angle θi j can be expressed by ɛ and θ', where ɛ =gL/gR is a ratio of running left-right gauge coupling strengths. We observe that light gauge bosons are described by θ' only, whereas heavy gauge bosons are described by two parameters ɛ and θ'.

  10. Ecotoxicity of arsenic contaminated sludge after mixing with soils and addition into composting and vermicomposting processes.

    PubMed

    Vašíčková, Jana; Maňáková, Blanka; Šudoma, Marek; Hofman, Jakub

    2016-11-01

    Sludge coming from remediation of groundwater contaminated by industry is usually managed as hazardous waste despite it might be considered for further processing as a source of nutrients. The ecotoxicity of phosphorus rich sludge contaminated with arsenic was evaluated after mixing with soil and cultivation with Sinapis alba, and supplementation into composting and vermicomposting processes. The Enchytraeus crypticus and Folsomia candida reproduction tests and the Lactuca sativa root growth test were used. Invertebrate bioassays reacted sensitively to arsenic presence in soil-sludge mixtures. The root elongation of L. sativa was not sensitive and showed variable results. In general, the relationship between invertebrate tests results and arsenic mobile concentration was indicated in majority endpoints. Nevertheless, significant portion of the results still cannot be satisfactorily explained by As chemistry data. Composted and vermicomposted sludge mixtures showed surprisingly high toxicity on all three tested organisms despite the decrease in arsenic mobility, probably due to toxic metabolites of bacteria and earthworms produced during these processes. The results from the study indicated the inability of chemical methods to predict the effects of complex mixtures on living organisms with respect to ecotoxicity bioassays. PMID:27348256

  11. Real Longitudinal Data Analysis for Real People: Building a Good Enough Mixed Model

    PubMed Central

    Cheng, Jing; Edwards, Lloyd J.; Maldonado-Molina, Mildred M.; Komro, Kelli A.; Muller, Keith E.

    2009-01-01

    Summary Mixed effect models have become very popular, especially for the analysis of longitudinal data. One challenge is how to build a good enough mixed effects model. In this paper, we suggest a systematic strategy for addressing this challenge and introduce easily implemented practical advice to build mixed effect models. A general discussion of scientific strategies motivates the recommended five step procedure for model fitting. The need to model both the mean structure (the fixed effects) and the covariance structure (the random effects and residual error) creates the fundamental flexibility and complexity. Some very practical recommendations help conquer the complexity. Centering, scaling, and full-rank coding all predictor variables radically improves the chances of convergence, computing speed, and numerical accuracy. Applying computational and assumption diagnostics from univariate linear models to mixed model data greatly helps detect and solve related computational problems. Applying computational and assumption diagnostics from univariate linear models to mixed model data can radically improve the chances of convergence, computing speed, and numerical accuracy. The approach helps fit more general covariance models, a crucial step in selecting a credible covariance model needed for defensible inference. A detailed demonstration of the recommended strategy is based on data from a published study of a randomized trial of a multicomponent intervention to prevent young adolescents' alcohol use. The discussion highlights a need for additional covariance and inference tools for mixed models. The discussion also highlights the need for improving how scientists and statisticians teach and review the process of finding a good enough mixed model. PMID:20013937

  12. Simplified renormalizable T' model for tribimaximal mixing and Cabibbo angle

    NASA Astrophysics Data System (ADS)

    Frampton, Paul H.; Kephart, Thomas W.; Matsuzaki, Shinya

    2008-10-01

    In a simplified renormalizable model where the neutrinos have Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixings tan⁡2θ12=(1)/(2), θ13=0, θ23=π/4 and with flavor symmetry T' there is a corresponding prediction where the quarks have Cabibbo-Kobayashi-Maskawa (CKM) mixings tan⁡2Θ12=(2)/(3), Θ13=0, Θ23=0.

  13. Comprehensive European dietary exposure model (CEDEM) for food additives.

    PubMed

    Tennant, David R

    2016-05-01

    European methods for assessing dietary exposures to nutrients, additives and other substances in food are limited by the availability of detailed food consumption data for all member states. A proposed comprehensive European dietary exposure model (CEDEM) applies summary data published by the European Food Safety Authority (EFSA) in a deterministic model based on an algorithm from the EFSA intake method for food additives. The proposed approach can predict estimates of food additive exposure provided in previous EFSA scientific opinions that were based on the full European food consumption database. PMID:26987377

  14. A Mixed Effects Randomized Item Response Model

    ERIC Educational Resources Information Center

    Fox, J.-P.; Wyrick, Cheryl

    2008-01-01

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

  15. Generalized Dynamic Factor Models for Mixed-Measurement Time Series

    PubMed Central

    Cui, Kai; Dunson, David B.

    2013-01-01

    In this article, we propose generalized Bayesian dynamic factor models for jointly modeling mixed-measurement time series. The framework allows mixed-scale measurements associated with each time series, with different measurements having different distributions in the exponential family conditionally on time-varying latent factor(s). Efficient Bayesian computational algorithms are developed for posterior inference on both the latent factors and model parameters, based on a Metropolis Hastings algorithm with adaptive proposals. The algorithm relies on a Greedy Density Kernel Approximation (GDKA) and parameter expansion with latent factor normalization. We tested the framework and algorithms in simulated studies and applied them to the analysis of intertwined credit and recovery risk for Moody’s rated firms from 1982–2008, illustrating the importance of jointly modeling mixed-measurement time series. The article has supplemental materials available online. PMID:24791133

  16. Generalized Dynamic Factor Models for Mixed-Measurement Time Series.

    PubMed

    Cui, Kai; Dunson, David B

    2014-02-12

    In this article, we propose generalized Bayesian dynamic factor models for jointly modeling mixed-measurement time series. The framework allows mixed-scale measurements associated with each time series, with different measurements having different distributions in the exponential family conditionally on time-varying latent factor(s). Efficient Bayesian computational algorithms are developed for posterior inference on both the latent factors and model parameters, based on a Metropolis Hastings algorithm with adaptive proposals. The algorithm relies on a Greedy Density Kernel Approximation (GDKA) and parameter expansion with latent factor normalization. We tested the framework and algorithms in simulated studies and applied them to the analysis of intertwined credit and recovery risk for Moody's rated firms from 1982-2008, illustrating the importance of jointly modeling mixed-measurement time series. The article has supplemental materials available online. PMID:24791133

  17. Validation of hydrogen gas stratification and mixing models

    DOE PAGESBeta

    Wu, Hsingtzu; Zhao, Haihua

    2015-05-26

    Two validation benchmarks confirm that the BMIX++ code is capable of simulating unintended hydrogen release scenarios efficiently. The BMIX++ (UC Berkeley mechanistic MIXing code in C++) code has been developed to accurately and efficiently predict the fluid mixture distribution and heat transfer in large stratified enclosures for accident analyses and design optimizations. The BMIX++ code uses a scaling based one-dimensional method to achieve large reduction in computational effort compared to a 3-D computational fluid dynamics (CFD) simulation. Two BMIX++ benchmark models have been developed. One is for a single buoyant jet in an open space and another is for amore » large sealed enclosure with both a jet source and a vent near the floor. Both of them have been validated by comparisons with experimental data. Excellent agreements are observed. The entrainment coefficients of 0.09 and 0.08 are found to fit the experimental data for hydrogen leaks with the Froude number of 99 and 268 best, respectively. In addition, the BIX++ simulation results of the average helium concentration for an enclosure with a vent and a single jet agree with the experimental data within a margin of about 10% for jet flow rates ranging from 1.21 × 10⁻⁴ to 3.29 × 10⁻⁴ m³/s. In conclusion, computing time for each BMIX++ model with a normal desktop computer is less than 5 min.« less

  18. Validation of hydrogen gas stratification and mixing models

    SciTech Connect

    Wu, Hsingtzu; Zhao, Haihua

    2015-05-26

    Two validation benchmarks confirm that the BMIX++ code is capable of simulating unintended hydrogen release scenarios efficiently. The BMIX++ (UC Berkeley mechanistic MIXing code in C++) code has been developed to accurately and efficiently predict the fluid mixture distribution and heat transfer in large stratified enclosures for accident analyses and design optimizations. The BMIX++ code uses a scaling based one-dimensional method to achieve large reduction in computational effort compared to a 3-D computational fluid dynamics (CFD) simulation. Two BMIX++ benchmark models have been developed. One is for a single buoyant jet in an open space and another is for a large sealed enclosure with both a jet source and a vent near the floor. Both of them have been validated by comparisons with experimental data. Excellent agreements are observed. The entrainment coefficients of 0.09 and 0.08 are found to fit the experimental data for hydrogen leaks with the Froude number of 99 and 268 best, respectively. In addition, the BIX++ simulation results of the average helium concentration for an enclosure with a vent and a single jet agree with the experimental data within a margin of about 10% for jet flow rates ranging from 1.21 × 10⁻⁴ to 3.29 × 10⁻⁴ m³/s. In conclusion, computing time for each BMIX++ model with a normal desktop computer is less than 5 min.

  19. Validation of hydrogen gas stratification and mixing models

    SciTech Connect

    Wu, Hsingtzu; Zhao, Haihua

    2015-11-01

    Two validation benchmarks confirm that the BMIX++ code is capable of simulating unintended hydrogen release scenarios efficiently. The BMIX++ (UC Berkeley mechanistic MIXing code in C++) code has been developed to accurately and efficiently predict the fluid mixture distribution and heat transfer in large stratified enclosures for accident analyses and design optimizations. The BMIX++ code uses a scaling based one-dimensional method to achieve large reduction in computational effort compared to a 3-D computational fluid dynamics (CFD) simulation. Two BMIX++ benchmark models have been developed. One is for a single buoyant jet in an open space and another is for a large sealed enclosure with both a jet source and a vent near the floor. Both of them have been validated by comparisons with experimental data. Excellent agreements are observed. The entrainment coefficients of 0.09 and 0.08 are found to fit the experimental data for hydrogen leaks with the Froude number of 99 and 268 best, respectively. In addition, the BIX++ simulation results of the average helium concentration for an enclosure with a vent and a single jet agree with the experimental data within a margin of about 10% for jet flow rates ranging from 1.21 × 10⁻⁴ to 3.29 × 10⁻⁴ m³/s. Computing time for each BMIX++ model with a normal desktop computer is less than 5 min.

  20. Mapping eQTL Networks with Mixed Graphical Markov Models

    PubMed Central

    Tur, Inma; Roverato, Alberto; Castelo, Robert

    2014-01-01

    Expression quantitative trait loci (eQTL) mapping constitutes a challenging problem due to, among other reasons, the high-dimensional multivariate nature of gene-expression traits. Next to the expression heterogeneity produced by confounding factors and other sources of unwanted variation, indirect effects spread throughout genes as a result of genetic, molecular, and environmental perturbations. From a multivariate perspective one would like to adjust for the effect of all of these factors to end up with a network of direct associations connecting the path from genotype to phenotype. In this article we approach this challenge with mixed graphical Markov models, higher-order conditional independences, and q-order correlation graphs. These models show that additive genetic effects propagate through the network as function of gene–gene correlations. Our estimation of the eQTL network underlying a well-studied yeast data set leads to a sparse structure with more direct genetic and regulatory associations that enable a straightforward comparison of the genetic control of gene expression across chromosomes. Interestingly, it also reveals that eQTLs explain most of the expression variability of network hub genes. PMID:25271303

  1. Analyzing Mixed-Dyadic Data Using Structural Equation Models

    ERIC Educational Resources Information Center

    Peugh, James L.; DiLillo, David; Panuzio, Jillian

    2013-01-01

    Mixed-dyadic data, collected from distinguishable (nonexchangeable) or indistinguishable (exchangeable) dyads, require statistical analysis techniques that model the variation within dyads and between dyads appropriately. The purpose of this article is to provide a tutorial for performing structural equation modeling analyses of cross-sectional…

  2. Teaching Service Modelling to a Mixed Class: An Integrated Approach

    ERIC Educational Resources Information Center

    Deng, Jeremiah D.; Purvis, Martin K.

    2015-01-01

    Service modelling has become an increasingly important area in today's telecommunications and information systems practice. We have adapted a Network Design course in order to teach service modelling to a mixed class of both the telecommunication engineering and information systems backgrounds. An integrated approach engaging mathematics teaching…

  3. MULTIVARIATE LINEAR MIXED MODELS FOR MULTIPLE OUTCOMES. (R824757)

    EPA Science Inventory

    We propose a multivariate linear mixed (MLMM) for the analysis of multiple outcomes, which generalizes the latent variable model of Sammel and Ryan. The proposed model assumes a flexible correlation structure among the multiple outcomes, and allows a global test of the impact of ...

  4. Generation Mixing in the Sakata-Nagoya Model

    NASA Astrophysics Data System (ADS)

    Nishijima, K.

    The Sakata model as combined with the SU(3) symmetry served in introducing the idea of the fundamental triplet in particle physics. In the Nagoya model the correspondence between baryons and leptons was emphasized and was exploited later in forming the concept of generation and generation-mixing.

  5. Additive-multiplicative rates model for recurrent events.

    PubMed

    Liu, Yanyan; Wu, Yuanshan; Cai, Jianwen; Zhou, Haibo

    2010-07-01

    Recurrent events are frequently encountered in biomedical studies. Evaluating the covariates effects on the marginal recurrent event rate is of practical interest. There are mainly two types of rate models for the recurrent event data: the multiplicative rates model and the additive rates model. We consider a more flexible additive-multiplicative rates model for analysis of recurrent event data, wherein some covariate effects are additive while others are multiplicative. We formulate estimating equations for estimating the regression parameters. The estimators for these regression parameters are shown to be consistent and asymptotically normally distributed under appropriate regularity conditions. Moreover, the estimator of the baseline mean function is proposed and its large sample properties are investigated. We also conduct simulation studies to evaluate the finite sample behavior of the proposed estimators. A medical study of patients with cystic fibrosis suffered from recurrent pulmonary exacerbations is provided for illustration of the proposed method. PMID:20229314

  6. Model for compound formation during ion-beam mixing

    SciTech Connect

    Desimoni, J.; Traverse, A. )

    1993-11-01

    We propose an ion-beam-mixing model that accounts for compound formation at a boundary between two materials during ion irradiation. It is based on Fick's law together with a chemical driving force in order to simulate the chemical reaction at the boundary. The behavior of the squared thickness of the mixed layer, [ital X][sup 2], with the irradiation fluence, [Phi], has been found in several mixing experiments to be either quadratic ([ital X][sup 2][alpha][Phi][sup 2]) or linear ([ital X][sup 2][alpha][Phi]), a result which is qualitatively reproduced. Depending on the fluence range, compound formation or diffusion is the limiting process of mixing kinetics. A criterion is established in terms of the ratio of the diffusion coefficient [ital D] due to irradiation to the chemical reaction rate squared which allows us to predict quadratic or linear behavior. When diffusion is the limiting process, [ital D] is enhanced by a factor which accounts for the formation of a compound in the mixed layer. Good agreement is found between the calculated mixing rates and the data taken from mixing experiments in metal/Si bilayers.

  7. Modeling the iron cycling in the mixed layer

    NASA Astrophysics Data System (ADS)

    Weber, L.; Voelker, C.; Schartau, M.; Wolf-Gladrow, D.

    2003-04-01

    We present a comprehensive model of the iron cycling within the mixed layer of the ocean, which predicts the time course of iron concentration and speciation. The speciation of iron within the mixed layer is heavily influenced by photochemistry, organic complexation, colloid formation and aggregation, as well as uptake and release by marine biota. The model is driven by mixed layer dynamics, dust deposition and insolation, as well as coupled to a simple ecosystem model (based on Schartau at al.2001: Deep-Sea Res.II.48,1769-1800) and applied to the site of the Bermuda Atlantic Time-series Study (BATS). Parameters in the model were chosen to reproduce the small number of available speciation measurements resolving a daily cycle. The model clearly reproduces the available Fe concentration at the BATS station but the annual balance of Fe fluxes at BATS is less constrained, due to uncertainties in the model parameters. Hence we discuss the model's sensitivity to parameter uncertainties and which observations might help to better constrain the relevant model parameters. Futher we discuss how the most important model parameters are constrained by the data. The mixed layer cycle in the model strongly influences seasonality of primary production as well as light dependency of photoreductive processes and therefore controlls iron speciation. Futhermore short events within a day (e.g. heavy rain, change of irradiance, intense dust deposition and temporary deepening of the mixed layer) may push processes like colloidal aggregation. For this reason we compare two versions of the model: The first one is forced by monthly averaged climatological variables, the second one by daily climatological variabilities.

  8. A 3D Bubble Merger Model for RTI Mixing

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian

    2015-11-01

    In this work we present a model for the merger processes of bubbles at the edge of an unstable acceleration driven mixing layer. Steady acceleration defines a self-similar mixing process, with a time-dependent inverse cascade of structures of increasing size. The time evolution is itself a renormalization group evolution. The model predicts the growth rate of a Rayleigh-Taylor chaotic fluid-mixing layer. The 3-D model differs from the 2-D merger model in several important ways. Beyond the extension of the model to three dimensions, the model contains one phenomenological parameter, the variance of the bubble radii at fixed time. The model also predicts several experimental numbers: the bubble mixing rate, the mean bubble radius, and the bubble height separation at the time of merger. From these we also obtain the bubble height to the radius aspect ratio, which is in good agreement with experiments. Applications to recent NIF and Omega experiments will be discussed. This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

  9. Modeling and Analysis of Mixed Synchronous/Asynchronous Systems

    NASA Technical Reports Server (NTRS)

    Driscoll, Kevin R.; Madl. Gabor; Hall, Brendan

    2012-01-01

    Practical safety-critical distributed systems must integrate safety critical and non-critical data in a common platform. Safety critical systems almost always consist of isochronous components that have synchronous or asynchronous interface with other components. Many of these systems also support a mix of synchronous and asynchronous interfaces. This report presents a study on the modeling and analysis of asynchronous, synchronous, and mixed synchronous/asynchronous systems. We build on the SAE Architecture Analysis and Design Language (AADL) to capture architectures for analysis. We present preliminary work targeted to capture mixed low- and high-criticality data, as well as real-time properties in a common Model of Computation (MoC). An abstract, but representative, test specimen system was created as the system to be modeled.

  10. Fermion masses and mixing in Δ (27 ) flavor model

    NASA Astrophysics Data System (ADS)

    Abbas, Mohammed; Khalil, Shaaban

    2015-03-01

    An extension of the Standard Model (SM) based on the non-Abelian discrete group Δ (27 ) is considered. The Δ (27 ) flavor symmetry is spontaneously broken only by gauge singlet scalar fields, therefore our model is free from any flavor changing neutral current (FCNC). We show that the model accounts simultaneously for the observed quark and lepton masses and their mixing. In the quark sector, we find that the up-quark mass matrix is flavor diagonal and the Cabbibo-Kobayashi-Maskawa (CKM) mixing matrix arises from down quarks. In the lepton sector, we show that the charged lepton mass matrix is almost diagonal. We also adopt type-I seesaw mechanism to generate neutrino masses. A deviated mixing matrix from tri-bimaximal Maki-Nakagawa-Sakata (MNS), with a correlation between sin θ13 and sin2θ23 are illustrated.

  11. Selection and estimation for mixed graphical models

    PubMed Central

    Chen, Shizhe; Witten, Daniela M.; shojaie, Ali

    2016-01-01

    Summary We consider the problem of estimating the parameters in a pairwise graphical model in which the distribution of each node, conditioned on the others, may have a different exponential family form. We identify restrictions on the parameter space required for the existence of a well-defined joint density, and establish the consistency of the neighbourhood selection approach for graph reconstruction in high dimensions when the true underlying graph is sparse. Motivated by our theoretical results, we investigate the selection of edges between nodes whose conditional distributions take different parametric forms, and show that efficiency can be gained if edge estimates obtained from the regressions of particular nodes are used to reconstruct the graph. These results are illustrated with examples of Gaussian, Bernoulli, Poisson and exponential distributions. Our theoretical findings are corroborated by evidence from simulation studies.

  12. Accelerated Nucleation Due to Trace Additives: A Fluctuating Coverage Model.

    PubMed

    Poon, Geoffrey G; Peters, Baron

    2016-03-01

    We develop a theory to account for variable coverage of trace additives that lower the interfacial free energy for nucleation. The free energy landscape is based on classical nucleation theory and a statistical mechanical model for Langmuir adsorption. Dynamics are modeled by diffusion-controlled attachment and detachment of solutes and adsorbing additives. We compare the mechanism and kinetics from a mean-field model, a projection of the dynamics and free energy surface onto nucleus size, and a full two-dimensional calculation using Kramers-Langer-Berezhkovskii-Szabo theory. The fluctuating coverage model predicts rates more accurately than mean-field models of the same process primarily because it more accurately estimates the potential of mean force along the size coordinate. PMID:26485064

  13. Computer modeling of ORNL storage tank sludge mobilization and mixing

    SciTech Connect

    Terrones, G.; Eyler, L.L.

    1993-09-01

    This report presents and analyzes the results of the computer modeling of mixing and mobilization of sludge in horizontal, cylindrical storage tanks using submerged liquid jets. The computer modeling uses the TEMPEST computational fluid dynamics computer program. The horizontal, cylindrical storage tank configuration is similar to the Melton Valley Storage Tanks (MVST) at Oak Ridge National (ORNL). The MVST tank contents exhibit non-homogeneous, non-Newtonian rheology characteristics. The eventual goals of the simulations are to determine under what conditions sludge mobilization using submerged liquid jets is feasible in tanks of this configuration, and to estimate mixing times required to approach homogeneity of the contents of the tanks.

  14. Photoionized Mixing Layer Models of the Diffuse Ionized Gas

    NASA Astrophysics Data System (ADS)

    Binette, Luc; Flores-Fajardo, Nahiely; Raga, Alejandro C.; Drissen, Laurent; Morisset, Christophe

    2009-04-01

    It is generally believed that O stars, confined near the galactic midplane, are somehow able to photoionize a significant fraction of what is termed the "diffuse ionized gas" (DIG) of spiral galaxies, which can extend up to 1-2 kpc above the galactic midplane. The heating of the DIG remains poorly understood, however, as simple photoionization models do not reproduce the observed line ratio correlations well or the DIG temperature. We present turbulent mixing layer (TML) models in which warm photoionized condensations are immersed in a hot supersonic wind. Turbulent dissipation and mixing generate an intermediate region where the gas is accelerated, heated, and mixed. The emission spectrum of such layers is compared with observations of Rand of the DIG in the edge-on spiral NGC 891. We generate two sequence of models that fit the line ratio correlations between [S II]/Hα, [O I]/Hα, [N II]/[S II], and [O III]/Hβ reasonably well. In one sequence of models, the hot wind velocity increases, while in the other, the ionization parameter and layer opacity increase. Despite the success of the mixing layer models, the overall efficiency in reprocessing the stellar UV is much too low, much less than 1%, which compels us to reject the TML model in its present form.

  15. Sensitivity of fine sediment source apportionment to mixing model assumptions

    NASA Astrophysics Data System (ADS)

    Cooper, Richard; Krueger, Tobias; Hiscock, Kevin; Rawlins, Barry

    2015-04-01

    Mixing models have become increasingly common tools for quantifying fine sediment redistribution in river catchments. The associated uncertainties may be modelled coherently and flexibly within a Bayesian statistical framework (Cooper et al., 2015). However, there is more than one way to represent these uncertainties because the modeller has considerable leeway in making error assumptions and model structural choices. In this presentation, we demonstrate how different mixing model setups can impact upon fine sediment source apportionment estimates via a one-factor-at-a-time (OFAT) sensitivity analysis. We formulate 13 versions of a mixing model, each with different error assumptions and model structural choices, and apply them to sediment geochemistry data from the River Blackwater, Norfolk, UK, to apportion suspended particulate matter (SPM) contributions from three sources (arable topsoils, road verges and subsurface material) under base flow conditions between August 2012 and August 2013 (Cooper et al., 2014). Whilst all 13 models estimate subsurface sources to be the largest contributor of SPM (median ~76%), comparison of apportionment estimates reveals varying degrees of sensitivity to changing prior parameter distributions, inclusion of covariance terms, incorporation of time-variant distributions and methods of proportion characterisation. We also demonstrate differences in apportionment results between a full and an empirical Bayesian setup and between a Bayesian and a popular Least Squares optimisation approach. Our OFAT sensitivity analysis reveals that mixing model structural choices and error assumptions can significantly impact upon fine sediment source apportionment results, with estimated median contributions in this study varying by up to 21% between model versions. Users of mixing models are therefore strongly advised to carefully consider and justify their choice of model setup prior to conducting fine sediment source apportionment investigations

  16. Modeling Errors in Daily Precipitation Measurements: Additive or Multiplicative?

    NASA Technical Reports Server (NTRS)

    Tian, Yudong; Huffman, George J.; Adler, Robert F.; Tang, Ling; Sapiano, Matthew; Maggioni, Viviana; Wu, Huan

    2013-01-01

    The definition and quantification of uncertainty depend on the error model used. For uncertainties in precipitation measurements, two types of error models have been widely adopted: the additive error model and the multiplicative error model. This leads to incompatible specifications of uncertainties and impedes intercomparison and application.In this letter, we assess the suitability of both models for satellite-based daily precipitation measurements in an effort to clarify the uncertainty representation. Three criteria were employed to evaluate the applicability of either model: (1) better separation of the systematic and random errors; (2) applicability to the large range of variability in daily precipitation; and (3) better predictive skills. It is found that the multiplicative error model is a much better choice under all three criteria. It extracted the systematic errors more cleanly, was more consistent with the large variability of precipitation measurements, and produced superior predictions of the error characteristics. The additive error model had several weaknesses, such as non constant variance resulting from systematic errors leaking into random errors, and the lack of prediction capability. Therefore, the multiplicative error model is a better choice.

  17. Modelling the behaviour of additives in gun barrels

    NASA Astrophysics Data System (ADS)

    Rhodes, N.; Ludwig, J. C.

    1986-01-01

    A mathematical model which predicts the flow and heat transfer in a gun barrel is described. The model is transient, two-dimensional and equations are solved for velocities and enthalpies of a gas phase, which arises from the combustion of propellant and cartridge case, for particle additives which are released from the case; volume fractions of the gas and particles. Closure of the equations is obtained using a two-equation turbulence model. Preliminary calculations are described in which the proportions of particle additives in the cartridge case was altered. The model gives a good prediction of the ballistic performance and the gas to wall heat transfer. However, the expected magnitude of reduction in heat transfer when particles are present is not predicted. The predictions of gas flow invalidate some of the assumptions made regarding case and propellant behavior during combustion and further work is required to investigate these effects and other possible interactions, both chemical and physical, between gas and particles.

  18. Modelling spherical explosions with turbulent mixing and post-detonation

    NASA Astrophysics Data System (ADS)

    Saurel, Richard; Huber, Gregory; Jourdan, Georges; Lapébie, Emmanuel; Munier, Laurent

    2012-11-01

    This paper addresses post detonation modelling in spherical explosions. One of the challenges is thus related to compressible turbulent mixing layers modelling. A one-dimensional flow model is derived consisting in a reduced two-phase compressible flow model with velocity drift. To reduce the number of model parameters, the stiff velocity relaxation limit is considered. A semi-discrete analysis is used resulting in a specific artificial viscosity formulation embedded in the diffuse interface model of Kapila et al. [Phys. Fluids 13(10), 3002-3024 (2001)], 10.1063/1.1398042. Thanks to the velocity non-equilibrium model and semi discrete formulation, the model fulfils the second law of thermodynamics in the global sense and uses a single parameter. Multidimensional mixing layer effects occurring at gas-gas unstable interfaces are thus summarized as artificial viscosity effects. Model's predictions are compared against experimental measurements of mixing layer growth in shock tubes at moderate initial pressure ratios as well as fireball radius evolutions in air explosions at high initial pressure ratios. Also, pressure signals recorded at various stations are compared, showing excellent agreement for the leading shock wave as well as the secondary one. With the help of various experiments in the low and high initial pressure ratios bounds, estimates for the interpenetration parameter are given.

  19. Modeling of three-dimensional mixing and reacting ducted flows

    NASA Technical Reports Server (NTRS)

    Zelazny, S. W.; Baker, A. J.; Rushmore, W. L.

    1976-01-01

    A computer code, based upon a finite element solution algorithm, was developed to solve the governing equations for three-dimensional, reacting boundary region, and constant area ducted flow fields. Effective diffusion coefficients are employed to allow analyses of turbulent, transitional or laminar flows. The code was used to investigate mixing and reacting hydrogen jets injected from multiple orifices, transverse and parallel to a supersonic air stream. Computational results provide a three-dimensional description of velocity, temperature, and species-concentration fields downstream of injection. Experimental data for eight cases covering different injection conditions and geometries were modeled using mixing length theory (MLT). These results were used as a baseline for examining the relative merits of other mixing models. Calculations were made using a two-equation turbulence model (k+d) and comparisons were made between experiment and mixing length theory predictions. The k+d model shows only a slight improvement in predictive capability over MLT. Results of an examination of the effect of tensorial transport coefficients on mass and momentum field distribution are also presented. Solutions demonstrating the ability of the code to model ducted flows and parallel strut injection are presented and discussed.

  20. Identifying genetically driven clinical phenotypes using linear mixed models.

    PubMed

    Mosley, Jonathan D; Witte, John S; Larkin, Emma K; Bastarache, Lisa; Shaffer, Christian M; Karnes, Jason H; Stein, C Michael; Phillips, Elizabeth; Hebbring, Scott J; Brilliant, Murray H; Mayer, John; Ye, Zhan; Roden, Dan M; Denny, Joshua C

    2016-01-01

    We hypothesized that generalized linear mixed models (GLMMs), which estimate the additive genetic variance underlying phenotype variability, would facilitate rapid characterization of clinical phenotypes from an electronic health record. We evaluated 1,288 phenotypes in 29,349 subjects of European ancestry with single-nucleotide polymorphism (SNP) genotyping on the Illumina Exome Beadchip. We show that genetic liability estimates are primarily driven by SNPs identified by prior genome-wide association studies and SNPs within the human leukocyte antigen (HLA) region. We identify 44 (false discovery rate q<0.05) phenotypes associated with HLA SNP variation and show that hypothyroidism is genetically correlated with Type I diabetes (rG=0.31, s.e. 0.12, P=0.003). We also report novel SNP associations for hypothyroidism near HLA-DQA1/HLA-DQB1 at rs6906021 (combined odds ratio (OR)=1.2 (95% confidence interval (CI): 1.1-1.2), P=9.8 × 10(-11)) and for polymyalgia rheumatica near C6orf10 at rs6910071 (OR=1.5 (95% CI: 1.3-1.6), P=1.3 × 10(-10)). Phenome-wide application of GLMMs identifies phenotypes with important genetic drivers, and focusing on these phenotypes can identify novel genetic associations. PMID:27109359

  1. Identifying genetically driven clinical phenotypes using linear mixed models

    PubMed Central

    Mosley, Jonathan D.; Witte, John S.; Larkin, Emma K.; Bastarache, Lisa; Shaffer, Christian M.; Karnes, Jason H.; Stein, C. Michael; Phillips, Elizabeth; Hebbring, Scott J.; Brilliant, Murray H.; Mayer, John; Ye, Zhan; Roden, Dan M.; Denny, Joshua C.

    2016-01-01

    We hypothesized that generalized linear mixed models (GLMMs), which estimate the additive genetic variance underlying phenotype variability, would facilitate rapid characterization of clinical phenotypes from an electronic health record. We evaluated 1,288 phenotypes in 29,349 subjects of European ancestry with single-nucleotide polymorphism (SNP) genotyping on the Illumina Exome Beadchip. We show that genetic liability estimates are primarily driven by SNPs identified by prior genome-wide association studies and SNPs within the human leukocyte antigen (HLA) region. We identify 44 (false discovery rate q<0.05) phenotypes associated with HLA SNP variation and show that hypothyroidism is genetically correlated with Type I diabetes (rG=0.31, s.e. 0.12, P=0.003). We also report novel SNP associations for hypothyroidism near HLA-DQA1/HLA-DQB1 at rs6906021 (combined odds ratio (OR)=1.2 (95% confidence interval (CI): 1.1–1.2), P=9.8 × 10−11) and for polymyalgia rheumatica near C6orf10 at rs6910071 (OR=1.5 (95% CI: 1.3–1.6), P=1.3 × 10−10). Phenome-wide application of GLMMs identifies phenotypes with important genetic drivers, and focusing on these phenotypes can identify novel genetic associations. PMID:27109359

  2. Observing and Modelling Upper Ocean Mixing by Near-Inertial Oscillations

    NASA Astrophysics Data System (ADS)

    Pillar, Helen; Jochum, Markus; Nuterman, Roman; Bentsen, Mats

    2016-04-01

    Near-inertial oscillations (NIOs) have been observed to drive substantial ocean mixing during the passage of atmospheric storms. This mixing is poorly resolved in climate models due to coarse spatial and temporal resolution of the atmospheric forcing and missing ocean physics. A new parameterisation is developed in the Norwegian Earth System Model (NorESM) to account for enhancement of both mixed layer turbulent kinetic energy and interior diapycnal diffusivity by locally forced NIOs. This parameterisation is based on the inclusion of a simple slab model in the NorESM coupler, receiving high frequency wind forcing and generating near-inertial current distributions consistent with available observations from surface drifters. Our results suggest that NIOs are unimportant for mixing at depth, but act to deepen the ocean mixed layer and significantly impact air-sea buoyancy fluxes, contributing to the reduction of large model biases in tropical SST. Additional analysis of mooring data from the PIRATA observational array reveals that a large fraction of the near-inertial energy injected at the surface is realised through a few extreme storms rather than a continuum of events. Further improvements to the ocean mixing parameterisation may thus require the resolution dependence of the simulated storm activity to be explored in more detail.

  3. An Additional Symmetry in the Weinberg-Salam Model

    SciTech Connect

    Bakker, B.L.G.; Veselov, A.I.; Zubkov, M.A.

    2005-06-01

    An additional Z{sub 6} symmetry hidden in the fermion and Higgs sectors of the Standard Model has been found recently. It has a singular nature and is connected to the centers of the SU(3) and SU(2) subgroups of the gauge group. A lattice regularization of the Standard Model was constructed that possesses this symmetry. In this paper, we report our results on the numerical simulation of its electroweak sector.

  4. Modeling uranium transport in acidic contaminated groundwater with base addition

    SciTech Connect

    Zhang, Fan; Luo, Wensui; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip; Gu, Baohua

    2011-01-01

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  5. Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova

    SciTech Connect

    Glimm, James

    2008-06-24

    The three year plan for this project is to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (both Direct Numerical Simulation and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We will model 2D and 3D perturbations of planar interfaces. We will compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we will develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. We will conduct analytic studies of mix, in support of these objectives. Advanced issues, including multiple layers and reshock, will be considered.

  6. Using Set Model for Learning Addition of Integers

    ERIC Educational Resources Information Center

    Lestari, Umi Puji; Putri, Ratu Ilma Indra; Hartono, Yusuf

    2015-01-01

    This study aims to investigate how set model can help students' understanding of addition of integers in fourth grade. The study has been carried out to 23 students and a teacher of IVC SD Iba Palembang in January 2015. This study is a design research that also promotes PMRI as the underlying design context and activity. Results showed that the…

  7. Stabilization of inorganic mixed waste to pass the TCLP and STLC tests using clay and pH-insensitive additives

    SciTech Connect

    Bowers, J.S.; Anson, S.M.; Painter, S.M.

    1995-09-01

    Stabilization is a best demonstrated available technology, or BDAT, as defined by the U.S. Environmental Protection Agency (EPA) in Title 40, part 268, of the Code of Federal Regulations (40 CFR 268). This technology traps toxic contaminants (usually both chemically and physically) in a matrix so that they do not. leach into the environment. Typical contaminants that are trapped by stabilization are metals (mostly transition metals) that exhibit the characteristic of toxicity as defined by 40 CFR part 261. The stabilization process routinely uses pozzolanic materials. Portland cement, fly ash-lime mixes, gypsum cements, and clays are some of the most common materials. They are inexpensive, easy to use, and effective for wastes containing low concentrations of toxic materials. At the Lawrence Livermore National Laboratory (LLNL), additives such as dithiocarbamates and thiocarbonates, which are pH-insensitive and provide resistance to ligand formation are used in the waste stabilization process. Attapulgite, montmorillonite, and sepiolite clays are used because they are forgiving (recipe can be adjusted before the matrix hardens) when formulating a stabilization matrix, and they have a neutral pH. By using these clays and additives, LLNL`s highly concentrated wastewater treatment sludges have passed the TCLP and STLC tests. The most frequently used stabilization process consists of a customized recipe involving waste sludge, clay and dithiocarbamate salt, mixed with a double planetary mixer into a pasty consistency. TCLP and STLC data on this waste matrix have shown that the process matrix meets land disposal requirements.

  8. The effect of mixed-enzyme addition in anaerobic digestion on methane yield of dairy cattle manure.

    PubMed

    Sutaryo, Sutaryo; Ward, Alastair James; Møller, Henrik Bjarne

    2014-01-01

    This study investigates the effect of applying a mixture of enzymes (ME) to dairy cattle manure (DCM) as substrate in anaerobic digestion (AD). The aims of this study were to evaluate different methods of ME application to DCM at different temperatures and to investigate the effect of adding ME during the pre-treatment of the solid fractions of dairy cattle manure (SFDCM). The results showed that there was no positive effect of direct ME addition to substrate at either mesophilic (35 degrees C) or thermophilic (50 degrees C) process temperatures, but there was a significant 4.44% increase in methane yield when DCM, which had been incubated with ME addition at 50 degrees C for three days, was fed to a digester when compared to a control digester operating at the same retention time. Methane production was detected during the pre-treatment incubation, and the total sum methane yield during pre-treatment and digestion was found to be 8.33% higher than in the control. The addition of ME to the SFDCM in a pre-incubation stage of 20 h at 35 degrees C gave a significant increase in methane yield by 4.15% in a digester treating a mixed substrate (30% liquid fractions DCM and 70% enzyme-treated SFDCM) when compared with the control digester treating a similar mixed substrate with inactivated enzyme addition. The results indicate that direct physical contact of enzyme molecules and organic material in DCM prior to AD, without the intervention of extracellular enzymes from the indigenous microorganism population, was needed in order to increase methane yields. PMID:25145202

  9. Are mixed explicit/implicit solvation models reliable for studying phosphate hydrolysis? A comparative study of continuum, explicit and mixed solvation models.

    SciTech Connect

    Kamerlin, Shina C. L.; Haranczyk, Maciej; Warshel, Arieh

    2009-05-01

    Phosphate hydrolysis is ubiquitous in biology. However, despite intensive research on this class of reactions, the precise nature of the reaction mechanism remains controversial. In this work, we have examined the hydrolysis of three homologous phosphate diesters. The solvation free energy was simulated by means of either an implicit solvation model (COSMO), hybrid quantum mechanical / molecular mechanical free energy perturbation (QM/MM-FEP) or a mixed solvation model in which N water molecules were explicitly included in the ab initio description of the reacting system (where N=1-3), with the remainder of the solvent being implicitly modelled as a continuum. Here, both COSMO and QM/MM-FEP reproduce Delta Gobs within an error of about 2kcal/mol. However, we demonstrate that in order to obtain any form of reliable results from a mixed model, it is essential to carefully select the explicit water molecules from short QM/MM runs that act as a model for the true infinite system. Additionally, the mixed models tend to be increasingly inaccurate the more explicit water molecules are placed into the system. Thus, our analysis indicates that this approach provides an unreliable way for modelling phosphate hydrolysis in solution.

  10. INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS

    EPA Science Inventory

    Stable isotopes are frequently used to quantify the contributions of multiple sources to a mixture; e.g., C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source linear mixing model ass...

  11. The Worm Process for the Ising Model is Rapidly Mixing

    NASA Astrophysics Data System (ADS)

    Collevecchio, Andrea; Garoni, Timothy M.; Hyndman, Timothy; Tokarev, Daniel

    2016-07-01

    We prove rapid mixing of the worm process for the zero-field ferromagnetic Ising model, on all finite connected graphs, and at all temperatures. As a corollary, we obtain a fully-polynomial randomized approximation scheme for the Ising susceptibility, and for a certain restriction of the two-point correlation function.

  12. A Nonlinear Mixed Effects Model for Latent Variables

    ERIC Educational Resources Information Center

    Harring, Jeffrey R.

    2009-01-01

    The nonlinear mixed effects model for continuous repeated measures data has become an increasingly popular and versatile tool for investigating nonlinear longitudinal change in observed variables. In practice, for each individual subject, multiple measurements are obtained on a single response variable over time or condition. This structure can be…

  13. COMBINING SOURCES IN STABLE ISOTOPE MIXING MODELS: ALTERNATIVE METHODS

    EPA Science Inventory

    Stable isotope mixing models are often used to quantify source contributions to a mixture. Examples include pollution source identification; trophic web studies; analysis of water sources for soils, plants, or water bodies; and many others. A common problem is having too many s...

  14. Sensitivity Analysis of Mixed Models for Incomplete Longitudinal Data

    ERIC Educational Resources Information Center

    Xu, Shu; Blozis, Shelley A.

    2011-01-01

    Mixed models are used for the analysis of data measured over time to study population-level change and individual differences in change characteristics. Linear and nonlinear functions may be used to describe a longitudinal response, individuals need not be observed at the same time points, and missing data, assumed to be missing at random (MAR),…

  15. Historical development of stable isotope mixing models in ecology

    EPA Science Inventory

    More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

  16. Development of stable isotope mixing models in ecology - Dublin

    EPA Science Inventory

    More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

  17. Development of stable isotope mixing models in ecology - Fremantle

    EPA Science Inventory

    More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

  18. Development of stable isotope mixing models in ecology - Sydney

    EPA Science Inventory

    More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

  19. Confidence Intervals for Assessing Heterogeneity in Generalized Linear Mixed Models

    ERIC Educational Resources Information Center

    Wagler, Amy E.

    2014-01-01

    Generalized linear mixed models are frequently applied to data with clustered categorical outcomes. The effect of clustering on the response is often difficult to practically assess partly because it is reported on a scale on which comparisons with regression parameters are difficult to make. This article proposes confidence intervals for…

  20. Development of stable isotope mixing models in ecology - Perth

    EPA Science Inventory

    More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

  1. The Worm Process for the Ising Model is Rapidly Mixing

    NASA Astrophysics Data System (ADS)

    Collevecchio, Andrea; Garoni, Timothy M.; Hyndman, Timothy; Tokarev, Daniel

    2016-09-01

    We prove rapid mixing of the worm process for the zero-field ferromagnetic Ising model, on all finite connected graphs, and at all temperatures. As a corollary, we obtain a fully-polynomial randomized approximation scheme for the Ising susceptibility, and for a certain restriction of the two-point correlation function.

  2. An epidemic model to evaluate the homogeneous mixing assumption

    NASA Astrophysics Data System (ADS)

    Turnes, P. P.; Monteiro, L. H. A.

    2014-11-01

    Many epidemic models are written in terms of ordinary differential equations (ODE). This approach relies on the homogeneous mixing assumption; that is, the topological structure of the contact network established by the individuals of the host population is not relevant to predict the spread of a pathogen in this population. Here, we propose an epidemic model based on ODE to study the propagation of contagious diseases conferring no immunity. The state variables of this model are the percentages of susceptible individuals, infectious individuals and empty space. We show that this dynamical system can experience transcritical and Hopf bifurcations. Then, we employ this model to evaluate the validity of the homogeneous mixing assumption by using real data related to the transmission of gonorrhea, hepatitis C virus, human immunodeficiency virus, and obesity.

  3. Mixed inflaton and spectator field models after Planck

    SciTech Connect

    Enqvist, Kari; Takahashi, Tomo E-mail: tomot@cc.saga-u.ac.jp

    2013-10-01

    We investigate the possibility that the primordial perturbation has two sources: the inflaton and a spectator field, which is not dynamically important during inflation but which after inflation can contribute to the curvature perturbation. We derive the constraints on the model by using recent Planck results on the spectral index, tensor-to-scalar ratio and nonlinearity parameters f{sub NL} and τ{sub NL} for the cases with and without specifying the inflation and spectator models. If one chooses the spectator to be the curvaton with a quadratic potential, non-Gaussianities can be computed and imply restrictions on possible values of the ratio of the spectator-to-inflaton power R. We also consider a mixed curvaton and chaotic inflation model and show that even quartic chaotic inflation is still feasible in the context of mixed models even with Planck data.

  4. Analytical and numerical modeling of non-collinear shear wave mixing at an imperfect interface.

    PubMed

    Zhang, Ziyin; Nagy, Peter B; Hassan, Waled

    2016-02-01

    Non-collinear shear wave mixing at an imperfect interface between two solids can be exploited for nonlinear ultrasonic assessment of bond quality. In this study we developed two analytical models for nonlinear imperfect interfaces. The first model uses a finite nonlinear interfacial stiffness representation of an imperfect interface of vanishing thickness, while the second model relies on a thin nonlinear interphase layer to represent an imperfect interface region. The second model is actually a derivative of the first model obtained by calculating the equivalent interfacial stiffness of a thin isotropic nonlinear interphase layer in the quasi-static approximation. The predictions of both analytical models were numerically verified by comparison to COMSOL finite element simulations. These models can accurately predict the additional nonlinearity caused by interface imperfections based on the strength of the reflected and transmitted mixed longitudinal waves produced by them under non-collinear shear wave interrogation. PMID:26482394

  5. Quasi 1D Modeling of Mixed Compression Supersonic Inlets

    NASA Technical Reports Server (NTRS)

    Kopasakis, George; Connolly, Joseph W.; Paxson, Daniel E.; Woolwine, Kyle J.

    2012-01-01

    The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.

  6. Improving Bayesian isotope mixing models: a response to Jackson et al. (2009).

    PubMed

    Semmens, Brice X; Moore, Jonathan W; Ward, Eric J

    2009-03-01

    We recently described a Bayesian framework for stable isotope mixing models and provided a software tool, MixSIR, for conducting such analyses (Ecol. Lett., 2008; 11:470). Jackson et al. (Ecol. Lett., 2009; 12:E1) criticized the performance of our software based on tests using simulated data. However, their simulation data were flawed, rendering claims of erroneous behaviour inaccurate. A re-evaluation of the MixSIR source code did, however, uncover two minor coding errors, which we have fixed. When data are correctly simulated according to eqns (1)-(4) in Jackson et al. (2009), MixSIR consistently and accurately estimated the proportional contribution of prey to a predator diet, and was surprisingly robust to additional unquantified error. Jackson et al. (2009) also suggested we use a Dirichlet prior on the source proportion parameters, which we agree with. Finally, Jackson et al. (2009) propose adding additional error parameters to our mixing model framework. We caution that such increases in model complexity should be evaluated based on data support. PMID:19245585

  7. Modelling of externally mixed particles in the atmosphere

    NASA Astrophysics Data System (ADS)

    ZHU, Shupeng; Sartelet, Karine; Seigneur, Christian

    2014-05-01

    Particles present in the atmosphere have significant impacts on climate as well as on human health. Thus, it is important to accurately simulate and forecast their concentrations. Most commonly used air quality models assume that particles are internally mixed, largely for computational reasons. However, this assumption is disproved by measurements, especially close to sources. In fact, the externally-mixed properties of particles are important for aerosol source identification, radiative effects and particle evolution. In this study, a new size-composition resolved aerosol model is developed. It can solve the aerosol dynamic evolution for external mixtures taking into account the processes of coagulation, condensation and nucleation. Both the size of particles and the mass fraction of each chemical compound are discretized. For a given particle size, particles of different chemical composition may co-exist. Aerosol dynamics is solved in each grid cell by splitting coagulation and condensation/evaporation-nucleation processes. For the condensation/evaporation, surface equilibrium between gas and aerosol is calculated based on ISORROPIA and the newly developed H2O (Hydrophilic/Hydrophobic Organic) Model. Because size and chemical composition sections evolve during condensation/evaporation, concentrations need to be redistributed on fixed sections after condensation/evaporation to be able to use the model in 3 dimensions. This is done based on the numerical scheme HEMEN, which was initially developed for size redistribution. Chemical components can be grouped into several aggregates to reduce computational cost. The 0D model is validated by comparison to results obtained for internally mixed particles and the effect of mixing is investigated for up to 31 species and 4 aggregates. The model will be integrated into the air quality modeling platform POLYPHEMUS to investigate its performance in modeling air quality by comparing with observations during the MEGAPOLI

  8. Application of large eddy interaction model to a mixing layer

    NASA Technical Reports Server (NTRS)

    Murthy, S. N. B.

    1989-01-01

    The large eddy interaction model (LEIM) is a statistical model of turbulence based on the interaction of selected eddies with the mean flow and all of the eddies in a turbulent shear flow. It can be utilized as the starting point for obtaining physical structures in the flow. The possible application of the LEIM to a mixing layer formed between two parallel, incompressible flows with a small temperature difference is developed by invoking a detailed similarity between the spectra of velocity and temperature.

  9. Estimating soil water retention using soil component additivity model

    NASA Astrophysics Data System (ADS)

    Zeiliger, A.; Ermolaeva, O.; Semenov, V.

    2009-04-01

    Soil water retention is a major soil hydraulic property that governs soil functioning in ecosystems and greatly affects soil management. Data on soil water retention are used in research and applications in hydrology, agronomy, meteorology, ecology, environmental protection, and many other soil-related fields. Soil organic matter content and composition affect both soil structure and adsorption properties; therefore water retention may be affected by changes in soil organic matter that occur because of both climate change and modifications of management practices. Thus, effects of organic matter on soil water retention should be understood and quantified. Measurement of soil water retention is relatively time-consuming, and become impractical when soil hydrologic estimates are needed for large areas. One approach to soil water retention estimation from readily available data is based on the hypothesis that soil water retention may be estimated as an additive function obtained by summing up water retention of pore subspaces associated with soil textural and/or structural components and organic matter. The additivity model and was tested with 550 soil samples from the international database UNSODA and 2667 soil samples from the European database HYPRES containing all textural soil classes after USDA soil texture classification. The root mean square errors (RMSEs) of the volumetric water content estimates for UNSODA vary from 0.021 m3m-3 for coarse sandy loam to 0.075 m3m-3 for sandy clay. Obtained RMSEs are at the lower end of the RMSE range for regression-based water retention estimates found in literature. Including retention estimates of organic matter significantly improved RMSEs. The attained accuracy warrants testing the 'additivity' model with additional soil data and improving this model to accommodate various types of soil structure. Keywords: soil water retention, soil components, additive model, soil texture, organic matter.

  10. Dynamic behaviours of mix-game model and its application

    NASA Astrophysics Data System (ADS)

    Gou, Cheng-Ling

    2006-06-01

    In this paper a minority game (MG) is modified by adding into it some agents who play a majority game. Such a game is referred to as a mix-game. The highlight of this model is that the two groups of agents in the mix-game have different bounded abilities to deal with historical information and to count their own performance. Through simulations, it is found that the local volatilities change a lot by adding some agents who play the majority game into the MG and the change of local volatilities greatly depends on different combinations of historical memories of the two groups. Furthermore, the analyses of the underlying mechanisms for this finding are made. The applications of mix-game mode are also given as an example.

  11. New models for hyperspectral anomaly detection and un-mixing

    NASA Astrophysics Data System (ADS)

    Bernhardt, M.; Heather, J. P.; Smith, M. I.

    2005-06-01

    It is now established that hyperspectral images of many natural backgrounds have statistics with fat-tails. In spite of this, many of the algorithms that are used to process them appeal to the multivariate Gaussian model. In this paper we consider biologically motivated generative models that might explain observed mixtures of vegetation in natural backgrounds. The degree to which these models match the observed fat-tailed distributions is investigated. Having shown how fat-tailed statistics arise naturally from the generative process, the models are put to work in new anomaly detection and un-mixing algorithms. The performance of these algorithms is compared with more traditional approaches.

  12. A New Mixed Model Based on the Velocity Structure Function

    NASA Astrophysics Data System (ADS)

    Brun, Christophe; Friedrich, Rainer; Da Silva, Carlos B.; Métais, Olivier

    We propose a new mixed model for Large Eddy-Simulation based on the 3D spatial velocity increment. This approach blends the non-linear properties of the Increment model (Brun & Friedrich (2001)) with the eddy viscosity characteristics of the Structure Function model (Métais & Lesieur (1992)). The behaviour of this subgrid scale model is studied both via a priori tests of a plane jet at ReH=3000 and Large Eddy-Simulation of a round jet at ReD=25000. This approach allows to describe both forward and backward energy transfer encountered in transitional shear flows.

  13. Logit-normal mixed model for Indian Monsoon rainfall extremes

    NASA Astrophysics Data System (ADS)

    Dietz, L. R.; Chatterjee, S.

    2014-03-01

    Describing the nature and variability of Indian monsoon rainfall extremes is a topic of much debate in the current literature. We suggest the use of a generalized linear mixed model (GLMM), specifically, the logit-normal mixed model, to describe the underlying structure of this complex climatic event. Several GLMM algorithms are described and simulations are performed to vet these algorithms before applying them to the Indian precipitation data procured from the National Climatic Data Center. The logit-normal model was applied with fixed covariates of latitude, longitude, elevation, daily minimum and maximum temperatures with a random intercept by weather station. In general, the estimation methods concurred in their suggestion of a relationship between the El Niño Southern Oscillation (ENSO) and extreme rainfall variability estimates. This work provides a valuable starting point for extending GLMM to incorporate the intricate dependencies in extreme climate events.

  14. Linear mixing model applied to AVHRR LAC data

    NASA Technical Reports Server (NTRS)

    Holben, Brent N.; Shimabukuro, Yosio E.

    1993-01-01

    A linear mixing model was applied to coarse spatial resolution data from the NOAA Advanced Very High Resolution Radiometer. The reflective component of the 3.55 - 3.93 microns channel was extracted and used with the two reflective channels 0.58 - 0.68 microns and 0.725 - 1.1 microns to run a Constraine Least Squares model to generate vegetation, soil, and shade fraction images for an area in the Western region of Brazil. The Landsat Thematic Mapper data covering the Emas National park region was used for estimating the spectral response of the mixture components and for evaluating the mixing model results. The fraction images were compared with an unsupervised classification derived from Landsat TM data acquired on the same day. The relationship between the fraction images and normalized difference vegetation index images show the potential of the unmixing techniques when using coarse resolution data for global studies.

  15. Combining sources in stable isotope mixing models: alternative methods.

    PubMed

    Phillips, Donald L; Newsome, Seth D; Gregg, Jillian W

    2005-08-01

    Stable isotope mixing models are often used to quantify source contributions to a mixture. Examples include pollution source identification; trophic web studies; analysis of water sources for soils, plants; or water bodies, and many others. A common problem is having too many sources to allow a unique solution. We discuss two alternative procedures for addressing this problem. One option is a priori to combine sources with similar signatures so the number of sources is small enough to provide a unique solution. Aggregation should be considered only when isotopic signatures of clustered sources are not significantly different, and sources are related so the combined source group has some functional significance. For example, in a food web analysis, lumping several species within a trophic guild allows more interpretable results than lumping disparate food sources, even if they have similar isotopic signatures. One result of combining mixing model sources is increased uncertainty of the combined end-member isotopic signatures and consequently the source contribution estimates; this effect can be quantified using the IsoError model (http://www.epa.gov/wed/pages/models/isotopes/isoerror1_04.htm). As an alternative to lumping sources before a mixing analysis, the IsoSource mixing model (http://www.epa.gov/wed/pages/models/isosource/isosource.htm) can be used to find all feasible solutions of source contributions consistent with isotopic mass balance. While ranges of feasible contributions for each individual source can often be quite broad, contributions from functionally related groups of sources can be summed a posteriori, producing a range of solutions for the aggregate source that may be considerably narrower. A paleo-human dietary analysis example illustrates this method, which involves a terrestrial meat food source, a combination of three terrestrial plant foods, and a combination of three marine foods. In this case, a posteriori aggregation of sources allowed

  16. Additions to Mars Global Reference Atmospheric Model (Mars-GRAM)

    NASA Technical Reports Server (NTRS)

    Justus, C. G.

    1991-01-01

    Three major additions or modifications were made to the Mars Global Reference Atmospheric Model (Mars-GRAM): (1) in addition to the interactive version, a new batch version is available, which uses NAMELIST input, and is completely modular, so that the main driver program can easily be replaced by any calling program, such as a trajectory simulation program; (2) both the interactive and batch versions now have an option for treating local-scale dust storm effects, rather than just the global-scale dust storms in the original Mars-GRAM; and (3) the Zurek wave perturbation model was added, to simulate the effects of tidal perturbations, in addition to the random (mountain wave) perturbation model of the original Mars-GRAM. A minor modification has also been made which allows heights to go below local terrain height and return realistic pressure, density, and temperature (not the surface values) as returned by the original Mars-GRAM. This feature will allow simulations of Mars rover paths which might go into local valley areas which lie below the average height of the present, rather coarse-resolution, terrain height data used by Mars-GRAM. Sample input and output of both the interactive and batch version of Mars-GRAM are presented.

  17. Additions to Mars Global Reference Atmospheric Model (MARS-GRAM)

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; James, Bonnie

    1992-01-01

    Three major additions or modifications were made to the Mars Global Reference Atmospheric Model (Mars-GRAM): (1) in addition to the interactive version, a new batch version is available, which uses NAMELIST input, and is completely modular, so that the main driver program can easily be replaced by any calling program, such as a trajectory simulation program; (2) both the interactive and batch versions now have an option for treating local-scale dust storm effects, rather than just the global-scale dust storms in the original Mars-GRAM; and (3) the Zurek wave perturbation model was added, to simulate the effects of tidal perturbations, in addition to the random (mountain wave) perturbation model of the original Mars-GRAM. A minor modification was also made which allows heights to go 'below' local terrain height and return 'realistic' pressure, density, and temperature, and not the surface values, as returned by the original Mars-GRAM. This feature will allow simulations of Mars rover paths which might go into local 'valley' areas which lie below the average height of the present, rather coarse-resolution, terrain height data used by Mars-GRAM. Sample input and output of both the interactive and batch versions of Mars-GRAM are presented.

  18. Rapid estimation of lives of deficient superpave mixes and laboratory-based accelerated mix testing models

    NASA Astrophysics Data System (ADS)

    Manandhar, Chandra Bahadur

    The engineers from the Kansas Department of Transportation (KDOT) often have to decide whether or not to accept non-conforming Superpave mixtures during construction. The first part of this study focused on estimating lives of deficient Superpave pavements incorporating nonconforming Superpave mixtures. These criteria were based on the Hamburg Wheel-Tracking Device (HWTD) test results and analysis. The second part of this study focused on developing accelerated mix testing models to considerably reduce test duration. To accomplish the first objective, nine fine-graded Superpave mixes of 12.5-mm nominal maximum aggregate size (NMAS) with asphalt grade PG 64-22 from six administrative districts of KDOT were selected. Specimens were prepared at three different target air void levels Ndesign gyrations and four target simulated in-place density levels with the Superpave gyratory compactor. Average number of wheel passes to 20-mm rut depth, creep slope, stripping slope, and stripping inflection point in HWTD tests were recorded and then used in the statistical analysis. Results showed that, in general, higher simulated in-place density up to a certain limit of 91% to 93%, results in a higher number of wheel passes until 20-mm rut depth in HWTD tests. A Superpave mixture with very low air voids Ndesign (2%) level performed very poorly in the HWTD test. HWTD tests were also performed on six 12.5-mm NMAS mixtures with air voids Ndesign of 4% for six projects, simulated in-place density of 93%, two temperature levels and five load levels with binder grades of PG 64-22, PG 64-28, and PG 70-22. Field cores of 150-mm in diameter from three projects in three KDOT districts with 12.5-mm NMAS and asphalt grade of PG 64-22 were also obtained and tested in HWTD for model evaluation. HWTD test results indicated as expected. Statistical analysis was performed and accelerated mix testing models were developed to determine the effect of increased temperature and load on the duration of

  19. Uncertainty in mixing models: a blessing in disguise?

    NASA Astrophysics Data System (ADS)

    Delsman, J. R.; Oude Essink, G. H. P.

    2012-04-01

    Despite the abundance of tracer-based studies in catchment hydrology over the past decades, relatively few studies have addressed the uncertainty associated with these studies in much detail. This uncertainty stems from analytical error, spatial and temporal variance in end-member composition, and from not incorporating all relevant processes in the necessarily simplistic mixing models. Instead of applying standard EMMA methodology, we used end-member mixing model analysis within a Monte Carlo framework to quantify the uncertainty surrounding our analysis. Borrowing from the well-known GLUE methodology, we discarded mixing models that could not satisfactorily explain sample concentrations and analyzed the posterior parameter set. This use of environmental tracers aided in disentangling hydrological pathways in a Dutch polder catchment. This 10 km2 agricultural catchment is situated in the coastal region of the Netherlands. Brackish groundwater seepage, originating from Holocene marine transgressions, adversely affects water quality in this catchment. Current water management practice is aimed at improving water quality by flushing the catchment with fresh water from the river Rhine. Climate change is projected to decrease future fresh water availability, signifying the need for a more sustainable water management practice and a better understanding of the functioning of the catchment. The end-member mixing analysis increased our understanding of the hydrology of the studied catchment. The use of a GLUE-like framework for applying the end-member mixing analysis not only quantified the uncertainty associated with the analysis, the analysis of the posterior parameter set also identified the existence of catchment processes otherwise overlooked.

  20. Hematological parameters in Polish mixed breed rabbits with addition of meat breed blood in the annual cycle.

    PubMed

    Tokarz-Deptuła, B; Niedźwiedzka-Rystwej, P; Adamiak, M; Hukowska-Szematowicz, B; Trzeciak-Ryczek, A; Deptuła, W

    2015-01-01

    In the paper we studied haematologic values, such as haemoglobin concentration, haematocrit value, thrombocytes, leucocytes: lymphocytes, neutrophils, basophils, eosinophils and monocytes in the pheral blood in Polish mixed-breeds with addition of meat breed blood in order to obtain the reference values which are until now not available for this animals. In studying this indices we took into consideration the impact of the season (spring, summer, autumn, winter), and sex of the animals. The studies have shown a high impact of the season of the year on those rabbits, but only in spring and summer. Moreover we observed that the sex has mean impact on the studied values of haematological parameters in those rabbits. According to our knowledge, this is the first paper on haematologic values in this widely used group of rabbits, so they may serve as reference values. PMID:26812808

  1. Soil microbial responses to forest floor litter manipulation and nitrogen addition in a mixed-wood forest of northern China.

    PubMed

    Sun, Xiao-Lu; Zhao, Jing; You, Ye-Ming; Jianxin Sun, Osbert

    2016-01-01

    Changes in litterfall dynamics and soil properties due to anthropogenic or natural perturbations have important implications to soil carbon (C) and nutrient cycling via microbial pathway. Here we determine soil microbial responses to contrasting types of litter inputs (leaf vs. fine woody litter) and nitrogen (N) deposition by conducting a multi-year litter manipulation and N addition experiment in a mixed-wood forest. We found significantly higher soil organic C, total N, microbial biomass C (MBC) and N (MBN), microbial activity (MR), and activities of four soil extracellular enzymes, including β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), phenol oxidase (PO), and peroxidase (PER), as well as greater total bacteria biomass and relative abundance of gram-negative bacteria (G-) community, in top soils of plots with presence of leaf litter than of those without litter or with presence of only fine woody litter. No apparent additive or interactive effects of N addition were observed in this study. The occurrence of more labile leaf litter stimulated G-, which may facilitate microbial community growth and soil C stabilization as inferred by findings in literature. A continued treatment with contrasting types of litter inputs is likely to result in divergence in soil microbial community structure and function. PMID:26762490

  2. Soil microbial responses to forest floor litter manipulation and nitrogen addition in a mixed-wood forest of northern China

    PubMed Central

    Sun, Xiao-Lu; Zhao, Jing; You, Ye-Ming; Jianxin Sun, Osbert

    2016-01-01

    Changes in litterfall dynamics and soil properties due to anthropogenic or natural perturbations have important implications to soil carbon (C) and nutrient cycling via microbial pathway. Here we determine soil microbial responses to contrasting types of litter inputs (leaf vs. fine woody litter) and nitrogen (N) deposition by conducting a multi-year litter manipulation and N addition experiment in a mixed-wood forest. We found significantly higher soil organic C, total N, microbial biomass C (MBC) and N (MBN), microbial activity (MR), and activities of four soil extracellular enzymes, including β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), phenol oxidase (PO), and peroxidase (PER), as well as greater total bacteria biomass and relative abundance of gram-negative bacteria (G-) community, in top soils of plots with presence of leaf litter than of those without litter or with presence of only fine woody litter. No apparent additive or interactive effects of N addition were observed in this study. The occurrence of more labile leaf litter stimulated G-, which may facilitate microbial community growth and soil C stabilization as inferred by findings in literature. A continued treatment with contrasting types of litter inputs is likely to result in divergence in soil microbial community structure and function. PMID:26762490

  3. Understanding Rasch Measurement: The Rasch Model, Additive Conjoint Measurement, and New Models of Probabilistic Measurement Theory.

    ERIC Educational Resources Information Center

    Karabatsos, George

    2001-01-01

    Describes similarities and differences between additive conjoint measurement and the Rasch model, and formalizes some new nonparametric item response models that are, in a sense, probabilistic measurement theory models. Applies these new models to published and simulated data. (SLD)

  4. Improvement on the storage performance of LiMn2O4 with the mixed additives of ethanolamine and heptamethyldisilazane

    NASA Astrophysics Data System (ADS)

    Wu, Xianwen; Li, Xinhai; Wang, Zhixing; Guo, Huajun; Yue, Peng; Zhang, Yunhe

    2013-03-01

    The commercial LiMn2O4 are added into the LiPF6-based electrolyte without or with the mixed additives of ethanolamine and heptamethyldisilazane to be exposed in air at 60 °C for 2-6 h, and the effect of different electrolytes on the storage behavior of LiMn2O4 materials and LiMn2O4/Li cells at elevated temperature is investigated comparatively for the first time by FTIR, SEM, TEM, XRD and charge-discharge measurements. The results show that the electrochemical performances of LiMn2O4 exposed in the LiPF6-based electrolyte become worse gradually with the storage time increasing. However, when the mixture of ethanolamine and heptamethyldisilazane as electrolyte additives is added into the LiPF6-based electrolyte, it can stabilize the original morphology and spinel structure of LiMn2O4 greatly and improve the storage performance of the material and LiMn2O4/Li cells effectively. As the commercial LiMn2O4 is exposed in the LiPF6-based electrolyte with additives for 4 h at 60 °C, the initial discharge capacity of 97.7 mA h g-1 at 0.1 C and the capacity retention of 89.14% at 1 C rate after 150 cycles are much better than that LiMn2O4 exposed in the LiPF6-based electrolyte under the same conditions. Furthermore, the LiMn2O4/Li cells using the LiPF6-based electrolyte with additives exhibit higher initial discharge capacity before storage and higher capacity retention after storage at 60 °C for a week compared to the cells without additives in the LiPF6-based electrolyte.

  5. Stabilization of inorganic mixed waste to pass the TCLP and STLC tests using clay and pH-insensitive additives

    SciTech Connect

    Bowers, J.S.; Anson, J.R.; Painter, S.M.

    1995-12-31

    Stabilization is a best demonstrated available technology, or BDAT. This technology traps toxic contaminants in a matrix so that they do not leach into the environment. The stabilization process routinely uses pozzolanic materials. Portland cement, fly ash-lime mixes, gypsum cements, and clays are some of the most common materials. In many instances, materials that can pass the Toxicity Characteristic Leaching Procedure (TCLP the federal leach test) or the Soluble Threshold Leachate Concentration (STLC the California leach test) must have high concentrations of lime or other caustic material because of the low pH of the leaching media. Both leaching media, California`s and EPA`s, have a pH of 5.0. California uses citric acid and sodium citrate while EPA uses acetic acid and sodium acetate. The concentration in the leachate is approximately ten times higher for the STLC procedure than the TCLP. These media can form ligands that provide excellent metal leaching. Because of the aggressive nature of the leaching medium, stabilized wastes in many cases will not pass the leaching tests. At the Lawrence Livermore National Laboratory (LLNL), additives such as dithiocarbamates and thiocarbonates, which are pH-insensitive and provide resistance to ligand formation, are used in the waste stabilization process. Attapulgite, montmorillonite, and sepiolite clays are used because they are forgiving (recipe can be adjusted before the matrix hardens) when formulating a stabilization matrix, and they have a neutral pH. By using these clays and additives, LLNL`s highly concentrated wastewater treatment sludges have passed the TCLP and STLC tests. The most frequently used stabilization process consists of a customized recipe involving waste sludge, clay and dithiocarbamate salt, mixed with a double planetary mixer into a pasty consistency. TCLP and STLC data on this waste matrix have shown that the process matrix meets land disposal requirements.

  6. Backbone additivity in the transfer model of protein solvation

    PubMed Central

    Hu, Char Y; Kokubo, Hironori; Lynch, Gillian C; Bolen, D Wayne; Pettitt, B Montgomery

    2010-01-01

    The transfer model implying additivity of the peptide backbone free energy of transfer is computationally tested. Molecular dynamics simulations are used to determine the extent of change in transfer free energy (ΔGtr) with increase in chain length of oligoglycine with capped end groups. Solvation free energies of oligoglycine models of varying lengths in pure water and in the osmolyte solutions, 2M urea and 2M trimethylamine N-oxide (TMAO), were calculated from simulations of all atom models, and ΔGtr values for peptide backbone transfer from water to the osmolyte solutions were determined. The results show that the transfer free energies change linearly with increasing chain length, demonstrating the principle of additivity, and provide values in reasonable agreement with experiment. The peptide backbone transfer free energy contributions arise from van der Waals interactions in the case of transfer to urea, but from electrostatics on transfer to TMAO solution. The simulations used here allow for the calculation of the solvation and transfer free energy of longer oligoglycine models to be evaluated than is currently possible through experiment. The peptide backbone unit computed transfer free energy of −54 cal/mol/M compares quite favorably with −43 cal/mol/M determined experimentally. PMID:20306490

  7. Backbone Additivity in the Transfer Model of Protein Solvation

    SciTech Connect

    Hu, Char Y.; Kokubo, Hironori; Lynch, Gillian C.; Bolen, D Wayne; Pettitt, Bernard M.

    2010-05-01

    The transfer model implying additivity of the peptide backbone free energy of transfer is computationally tested. Molecular dynamics simulations are used to determine the extent of change in transfer free energy (ΔGtr) with increase in chain length of oligoglycine with capped end groups. Solvation free energies of oligoglycine models of varying lengths in pure water and in the osmolyte solutions, 2M urea and 2M trimethylamine N-oxide (TMAO), were calculated from simulations of all atom models, and ΔGtr values for peptide backbone transfer from water to the osmolyte solutions were determined. The results show that the transfer free energies change linearly with increasing chain length, demonstrating the principle of additivity, and provide values in reasonable agreement with experiment. The peptide backbone transfer free energy contributions arise from van der Waals interactions in the case of transfer to urea, but from electrostatics on transfer to TMAO solution. The simulations used here allow for the calculation of the solvation and transfer free energy of longer oligoglycine models to be evaluated than is currently possible through experiment. The peptide backbone unit computed transfer free energy of –54 cal/mol/Mcompares quite favorably with –43 cal/mol/M determined experimentally.

  8. A Adaptive Mixing Depth Model for AN Industrialized Shoreline Area.

    NASA Astrophysics Data System (ADS)

    Dunk, Richard H.

    1993-01-01

    Internal boundary layer characteristics are often overlooked in atmospheric diffusion modeling applications but are essential for accurate air quality assessment. This study focuses on a unique air pollution problem that is partially resolved by representative internal boundary layer description and prediction. Emissions from a secondary non-ferrous smelter located adjacent to a large waterway, which is situated near a major coastal zone, became suspect in causing adverse air quality. In an effort to prove or disprove this allegation, "accepted" air quality modeling was performed. Predicted downwind concentrations indicated that the smelter plume was not responsible for causing regulatory standards to be exceeded. However, chronic community complaints continued to be directed toward the smelter facility. Further investigation into the problem revealed that complaint occurrences coincided with onshore southeasterly flows. Internal boundary layer development during onshore flow was assumed to produce a mixing depth conducive to plume trapping or fumigation. The preceding premise led to the utilization of estimated internal boundary layer depths for dispersion model input in an attempt to improve prediction accuracy. Monitored downwind ambient air concentrations showed that model predictions were still substantially lower than actual values. After analyzing the monitored values and comparing them with actual plume observations conducted during several onshore flow occurrences, the author hypothesized that the waterway could cause a damping effect on internal boundary layer development. This effective decrease in mixing depths would explain the abnormally high ambient air concentrations experienced during onshore flows. Therefore, a full-scale field study was designed and implemented to study the waterway's influence on mixing depth characteristics. The resultant data were compiled and formulated into an area-specific mixing depth model that can be adapted to

  9. Fermion masses and mixing in general warped extra dimensional models

    NASA Astrophysics Data System (ADS)

    Frank, Mariana; Hamzaoui, Cherif; Pourtolami, Nima; Toharia, Manuel

    2015-06-01

    We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave functions to small flavor breaking effects yield hierarchical masses and mixing as it is usual in warped models with fermions in the bulk. In the neutrino sector, the exponential wave-function factors can be flavor blind and thus insensitive to the small flavor symmetry breaking effects, directly linking their masses and mixing angles to the flavor symmetric structure of the five-dimensional neutrino Yukawa couplings. The Higgs must be localized in the bulk and the model is more successful in generalized warped scenarios where the metric background solution is different than five-dimensional anti-de Sitter (AdS5 ). We study these features in two simple frameworks, flavor complimentarity and flavor democracy, which provide specific predictions and correlations between quarks and leptons, testable as more precise data in the neutrino sector becomes available.

  10. Extension of the stochastic mixing model to cumulonimbus clouds

    SciTech Connect

    Raymond, D.J.; Blyth, A.M. )

    1992-11-01

    The stochastic mixing model of cumulus clouds is extended to the case in which ice and precipitation form. A simple cloud microphysical model is adopted in which ice crystals and aggregates are carried along with the updraft, whereas raindrops, graupel, and hail are assumed to immediately fall out. The model is then applied to the 2 August 1984 case study of convection over the Magdalena Mountains of central New Mexico, with excellent results. The formation of ice and precipitation can explain the transition of this system from a cumulus congestus cloud to thunderstorm. 28 refs.

  11. A Mixed-Culture Biofilm Model with Cross-Diffusion.

    PubMed

    Rahman, Kazi A; Sudarsan, Rangarajan; Eberl, Hermann J

    2015-11-01

    We propose a deterministic continuum model for mixed-culture biofilms. A crucial aspect is that movement of one species is affected by the presence of the other. This leads to a degenerate cross-diffusion system that generalizes an earlier single-species biofilm model. Two derivations of this new model are given. One, like cellular automata biofilm models, starts from a discrete in space lattice differential equation where the spatial interaction is described by microscopic rules. The other one starts from the same continuous mass balances that are the basis of other deterministic biofilm models, but it gives up a simplifying assumption of these models that has recently been criticized as being too restrictive in terms of ecological structure. We show that both model derivations lead to the same PDE model, if corresponding closure assumptions are introduced. To investigate the role of cross-diffusion, we conduct numerical simulations of three biofilm systems: competition, allelopathy and a mixed system formed by an aerobic and an anaerobic species. In all cases, we find that accounting for cross-diffusion affects local distribution of biomass, but it does not affect overall lumped quantities such as the total amount of biomass in the system. PMID:26582360

  12. Structural and rate studies of the 1,2-additions of lithium phenylacetylide to lithiated quinazolinones: influence of mixed aggregates on the reaction mechanism.

    PubMed

    Briggs, Timothy F; Winemiller, Mark D; Collum, David B; Parsons, Rodney L; Davulcu, Akin H; Harris, Gregory D; Fortunak, Joseph M; Confalone, Pat N

    2004-05-01

    The 1,2-addition of lithium phenylacetylide (PhCCLi) to quinazolinones was investigated using a combination of structural and rate studies. (6)Li, (13)C, and (19)F NMR spectroscopies show that deprotonation of quinazolinones and phenylacetylene in THF/pentane solutions with lithium hexamethyldisilazide affords a mixture of lithium quinazolinide/PhCCLi mixed dimer and mixed tetramer along with PhCCLi dimer. Although the mixed tetramer dominates at high mixed aggregate concentrations and low temperatures used for the structural studies, the mixed dimer is the dominant form at the low total mixed aggregate concentrations, high THF concentrations, and ambient temperatures used to investigate the 1,2-addition. Monitoring the reaction rates using (19)F NMR spectroscopy revealed a first-order dependence on mixed dimer, a zeroth-order dependence on THF, and a half-order dependence on the PhCCLi concentration. The rate law is consistent with the addition of a disolvated PhCCLi monomer to the mixed dimer. Investigation of the 1,2-addition of PhCCLi to an O-protected quinazolinone implicates reaction via trisolvated PhCCLi monomers. PMID:15113214

  13. Multiscale and Multiphysics Modeling of Additive Manufacturing of Advanced Materials

    NASA Technical Reports Server (NTRS)

    Liou, Frank; Newkirk, Joseph; Fan, Zhiqiang; Sparks, Todd; Chen, Xueyang; Fletcher, Kenneth; Zhang, Jingwei; Zhang, Yunlu; Kumar, Kannan Suresh; Karnati, Sreekar

    2015-01-01

    The objective of this proposed project is to research and develop a prediction tool for advanced additive manufacturing (AAM) processes for advanced materials and develop experimental methods to provide fundamental properties and establish validation data. Aircraft structures and engines demand materials that are stronger, useable at much higher temperatures, provide less acoustic transmission, and enable more aeroelastic tailoring than those currently used. Significant improvements in properties can only be achieved by processing the materials under nonequilibrium conditions, such as AAM processes. AAM processes encompass a class of processes that use a focused heat source to create a melt pool on a substrate. Examples include Electron Beam Freeform Fabrication and Direct Metal Deposition. These types of additive processes enable fabrication of parts directly from CAD drawings. To achieve the desired material properties and geometries of the final structure, assessing the impact of process parameters and predicting optimized conditions with numerical modeling as an effective prediction tool is necessary. The targets for the processing are multiple and at different spatial scales, and the physical phenomena associated occur in multiphysics and multiscale. In this project, the research work has been developed to model AAM processes in a multiscale and multiphysics approach. A macroscale model was developed to investigate the residual stresses and distortion in AAM processes. A sequentially coupled, thermomechanical, finite element model was developed and validated experimentally. The results showed the temperature distribution, residual stress, and deformation within the formed deposits and substrates. A mesoscale model was developed to include heat transfer, phase change with mushy zone, incompressible free surface flow, solute redistribution, and surface tension. Because of excessive computing time needed, a parallel computing approach was also tested. In addition

  14. Trending in Probability of Collision Measurements via a Bayesian Zero-Inflated Beta Mixed Model

    NASA Technical Reports Server (NTRS)

    Vallejo, Jonathon; Hejduk, Matt; Stamey, James

    2015-01-01

    We investigate the performance of a generalized linear mixed model in predicting the Probabilities of Collision (Pc) for conjunction events. Specifically, we apply this model to the log(sub 10) transformation of these probabilities and argue that this transformation yields values that can be considered bounded in practice. Additionally, this bounded random variable, after scaling, is zero-inflated. Consequently, we model these values using the zero-inflated Beta distribution, and utilize the Bayesian paradigm and the mixed model framework to borrow information from past and current events. This provides a natural way to model the data and provides a basis for answering questions of interest, such as what is the likelihood of observing a probability of collision equal to the effective value of zero on a subsequent observation.

  15. Shell Model Depiction of Isospin Mixing in sd Shell

    SciTech Connect

    Lam, Yi Hua; Smirnova, Nadya A.; Caurier, Etienne

    2011-11-30

    We constructed a new empirical isospin-symmetry breaking (ISB) Hamiltonian in the sd(1s{sub 1/2}, 0d{sub 5/2} and 0d{sub 3/2}) shell-model space. In this contribution, we present its application to two important case studies: (i){beta}-delayed proton emission from {sup 22}Al and (ii) isospin-mixing correction to superallowed 0{sup +}{yields}0{sup +}{beta}-decay ft-values.

  16. Pricing turbo warrants under mixed-exponential jump diffusion model

    NASA Astrophysics Data System (ADS)

    Yu, Jianfeng; Xu, Weidong

    2016-06-01

    Turbo warrant is a special type of barrier options in which the rebate is calculated as another exotic option. In this paper, using Laplace transforms we obtain the valuation of turbo warrant under the mixed-exponential jump diffusion model, which is able to approximate any jump size distribution. The numerical Laplace inversion examples verify that the analytical solutions are accurate. The results of simulation confirm the argument that jump risk should not be ignored in the valuation of turbo warrants.

  17. Modeling oxygen dissolution and biological uptake during pulse oxygen additions in oenological fermentations.

    PubMed

    Saa, Pedro A; Moenne, M Isabel; Pérez-Correa, J Ricardo; Agosin, Eduardo

    2012-09-01

    Discrete oxygen additions during oenological fermentations can have beneficial effects both on yeast performance and on the resulting wine quality. However, the amount and time of the additions must be carefully chosen to avoid detrimental effects. So far, most oxygen additions are carried out empirically, since the oxygen dynamics in the fermenting must are not completely understood. To efficiently manage oxygen dosage, we developed a mass balance model of the kinetics of oxygen dissolution and biological uptake during wine fermentation on a laboratory scale. Model calibration was carried out employing a novel dynamic desorption-absorption cycle based on two optical sensors able to generate enough experimental data for the precise determination of oxygen uptake and volumetric mass transfer coefficients. A useful system for estimating the oxygen solubility in defined medium and musts was also developed and incorporated into the mass balance model. Results indicated that several factors, such as the fermentation phase, wine composition, mixing and carbon dioxide concentration, must be considered when performing oxygen addition during oenological fermentations. The present model will help develop better oxygen addition policies in wine fermentations on an industrial scale. PMID:22349928

  18. Estimating Preferential Flow in Karstic Aquifers Using Statistical Mixed Models

    PubMed Central

    Anaya, Angel A.; Padilla, Ingrid; Macchiavelli, Raul; Vesper, Dorothy J.; Meeker, John D.; Alshawabkeh, Akram N.

    2013-01-01

    Karst aquifers are highly productive groundwater systems often associated with conduit flow. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure to humans and ecosystems. This work develops statistical models to spatially characterize flow and transport patterns in karstified limestone and determines the effect of aquifer flow rates on these patterns. A laboratory-scale Geo-HydroBed model is used to simulate flow and transport processes in a karstic limestone unit. The model consists of stainless-steel tanks containing a karstified limestone block collected from a karst aquifer formation in northern Puerto Rico. Experimental work involves making a series of flow and tracer injections, while monitoring hydraulic and tracer response spatially and temporally. Statistical mixed models are applied to hydraulic data to determine likely pathways of preferential flow in the limestone units. The models indicate a highly heterogeneous system with dominant, flow-dependent preferential flow regions. Results indicate that regions of preferential flow tend to expand at higher groundwater flow rates, suggesting a greater volume of the system being flushed by flowing water at higher rates. Spatial and temporal distribution of tracer concentrations indicates the presence of conduit-like and diffuse flow transport in the system, supporting the notion of both combined transport mechanisms in the limestone unit. The temporal response of tracer concentrations at different locations in the model coincide with, and confirms the preferential flow distribution generated with the statistical mixed models used in the study. PMID:23802921

  19. Modeling and diagnosing interface mix in layered ICF implosions

    NASA Astrophysics Data System (ADS)

    Weber, C. R.; Berzak Hopkins, L. F.; Clark, D. S.; Haan, S. W.; Ho, D. D.; Meezan, N. B.; Milovich, J. L.; Robey, H. F.; Smalyuk, V. A.; Thomas, C. A.

    2015-11-01

    Mixing at the fuel-ablator interface of an inertial confinement fusion (ICF) implosion can arise from an unfavorable in-flight Atwood number between the cryogenic DT fuel and the ablator. High-Z dopant is typically added to the ablator to control the Atwood number, but recent high-density carbon (HDC) capsules have been shot at the National Ignition Facility (NIF) without this added dopant. Highly resolved post-shot modeling of these implosions shows that there was significant mixing of ablator material into the dense DT fuel. This mix lowers the fuel density and results in less overall compression, helping to explain the measured ratio of down scattered-to-primary neutrons. Future experimental designs will seek to improve this issue through adding dopant and changing the x-ray spectra with a different hohlraum wall material. To test these changes, we are designing an experimental platform to look at the growth of this mixing layer. This technique uses side-on radiography to measure the spatial extent of an embedded high-Z tracer layer near the interface. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  20. Effects of mixing in threshold models of social behavior

    NASA Astrophysics Data System (ADS)

    Akhmetzhanov, Andrei R.; Worden, Lee; Dushoff, Jonathan

    2013-07-01

    We consider the dynamics of an extension of the influential Granovetter model of social behavior, where individuals are affected by their personal preferences and observation of the neighbors’ behavior. Individuals are arranged in a network (usually the square lattice), and each has a state and a fixed threshold for behavior changes. We simulate the system asynchronously by picking a random individual and we either update its state or exchange it with another randomly chosen individual (mixing). We describe the dynamics analytically in the fast-mixing limit by using the mean-field approximation and investigate it mainly numerically in the case of finite mixing. We show that the dynamics converge to a manifold in state space, which determines the possible equilibria, and show how to estimate the projection of this manifold by using simulated trajectories, emitted from different initial points. We show that the effects of considering the network can be decomposed into finite-neighborhood effects, and finite-mixing-rate effects, which have qualitatively similar effects. Both of these effects increase the tendency of the system to move from a less-desired equilibrium to the “ground state.” Our findings can be used to probe shifts in behavioral norms and have implications for the role of information flow in determining when social norms that have become unpopular in particular communities (such as foot binding or female genital cutting) persist or vanish.

  1. Mixing during intravertebral arterial infusions in an in vitro model.

    PubMed

    Lutz, Robert J; Warren, Kathy; Balis, Frank; Patronas, Nicholas; Dedrick, Robert L

    2002-06-01

    Regional delivery of drugs can offer a pharmacokinetic advantage in the treatment of localized tumors. One method of regional delivery is by intra-arterial infusion into the basilar/vertebral artery network that provides local access to infratentorial tumors, which are frequent locations of childhood brain cancers. Proper delivery of drug by infused solutions requires adequate mixing of the infusate at the site of infusion within the artery lumen. Our mixing studies with an in vitro model of the vertebral artery network indicate that streaming of drug solution is likely to occur at low, steady infusion rates of 2 ml/min. Streaming leads to maldistribution of drug to distal perfused brain regions and may result in toxic levels in some regions while concurrently yielding subtherapeutic levels in adjacent regions. According to our model findings, distribution to both brain hemispheres is not likely following infusion into a single vertebral artery even if the infusate is well-mixed at the infusion site. This outcome results from the unique fluid flow properties of two converging channels, which are represented by the left and right vertebral branches converging into the basilar. Fluid in the model remains stratified on the side of the basilar artery served by the infused vertebral artery. Careful thought and planning of the methods of intravertebral drug infusions for treating posterior fossa tumors are required to assure proper distribution of the drug to the desired tissue regions. Improper delivery may be responsible for some noted toxicities or for failure of the treatments. PMID:12164691

  2. Beyond simple linear mixing models: process-based isotope partitioning of ecological processes.

    PubMed

    Ogle, Kiona; Tucker, Colin; Cable, Jessica M

    2014-01-01

    Stable isotopes are valuable tools for partitioning the components contributing to ecological processes of interest, such as animal diets and trophic interactions, plant resource use, ecosystem gas fluxes, streamflow, and many more. Stable isotope data are often analyzed with simple linear mixing (SLM) models to partition the contributions of different sources, but SLM models cannot incorporate a mechanistic understanding of the underlying processes and do not accommodate additional data associated with these processes (e.g., environmental covariates, flux data, gut contents). Thus, SLM models lack predictive ability. We describe a process-based mixing (PBM) model approach for integrating stable isotopes, other data sources, and process models to partition different sources or process components. This is accomplished via a hierarchical Bayesian framework that quantifies multiple sources of uncertainty and enables the incorporation of process models and prior information to help constrain the source-specific proportional contributions, thereby potentially avoiding identifiability issues that plague SLM models applied to "too many" sources. We discuss the application of the PBM model framework to three diverse examples: temporal and spatial partitioning of streamflow, estimation of plant rooting profiles and water uptake profiles (or water sources) with extension to partitioning soil and ecosystem CO2 fluxes, and reconstructing animal diets. These examples illustrate the advantages of the PBM modeling approach, which facilitates incorporation of ecological theory and diverse sources of information into the mixing model framework, thus enabling one to partition key process components across time and space. PMID:24640543

  3. Addition Table of Colours: Additive and Subtractive Mixtures Described Using a Single Reasoning Model

    ERIC Educational Resources Information Center

    Mota, A. R.; Lopes dos Santos, J. M. B.

    2014-01-01

    Students' misconceptions concerning colour phenomena and the apparent complexity of the underlying concepts--due to the different domains of knowledge involved--make its teaching very difficult. We have developed and tested a teaching device, the addition table of colours (ATC), that encompasses additive and subtractive mixtures in a single…

  4. Sensitivity analysis of geometric errors in additive manufacturing medical models.

    PubMed

    Pinto, Jose Miguel; Arrieta, Cristobal; Andia, Marcelo E; Uribe, Sergio; Ramos-Grez, Jorge; Vargas, Alex; Irarrazaval, Pablo; Tejos, Cristian

    2015-03-01

    Additive manufacturing (AM) models are used in medical applications for surgical planning, prosthesis design and teaching. For these applications, the accuracy of the AM models is essential. Unfortunately, this accuracy is compromised due to errors introduced by each of the building steps: image acquisition, segmentation, triangulation, printing and infiltration. However, the contribution of each step to the final error remains unclear. We performed a sensitivity analysis comparing errors obtained from a reference with those obtained modifying parameters of each building step. Our analysis considered global indexes to evaluate the overall error, and local indexes to show how this error is distributed along the surface of the AM models. Our results show that the standard building process tends to overestimate the AM models, i.e. models are larger than the original structures. They also show that the triangulation resolution and the segmentation threshold are critical factors, and that the errors are concentrated at regions with high curvatures. Errors could be reduced choosing better triangulation and printing resolutions, but there is an important need for modifying some of the standard building processes, particularly the segmentation algorithms. PMID:25649961

  5. Additive Manufacturing of Medical Models--Applications in Rhinology.

    PubMed

    Raos, Pero; Klapan, Ivica; Galeta, Tomislav

    2015-09-01

    In the paper we are introducing guidelines and suggestions for use of 3D image processing SW in head pathology diagnostic and procedures for obtaining physical medical model by additive manufacturing/rapid prototyping techniques, bearing in mind the improvement of surgery performance, its maximum security and faster postoperative recovery of patients. This approach has been verified in two case reports. In the treatment we used intelligent classifier-schemes for abnormal patterns using computer-based system for 3D-virtual and endoscopic assistance in rhinology, with appropriate visualization of anatomy and pathology within the nose, paranasal sinuses, and scull base area. PMID:26898064

  6. Variable selection for semiparametric mixed models in longitudinal studies.

    PubMed

    Ni, Xiao; Zhang, Daowen; Zhang, Hao Helen

    2010-03-01

    We propose a double-penalized likelihood approach for simultaneous model selection and estimation in semiparametric mixed models for longitudinal data. Two types of penalties are jointly imposed on the ordinary log-likelihood: the roughness penalty on the nonparametric baseline function and a nonconcave shrinkage penalty on linear coefficients to achieve model sparsity. Compared to existing estimation equation based approaches, our procedure provides valid inference for data with missing at random, and will be more efficient if the specified model is correct. Another advantage of the new procedure is its easy computation for both regression components and variance parameters. We show that the double-penalized problem can be conveniently reformulated into a linear mixed model framework, so that existing software can be directly used to implement our method. For the purpose of model inference, we derive both frequentist and Bayesian variance estimation for estimated parametric and nonparametric components. Simulation is used to evaluate and compare the performance of our method to the existing ones. We then apply the new method to a real data set from a lactation study. PMID:19397585

  7. Further considerations on modeling the sea breeze with a mixed-layer model

    NASA Technical Reports Server (NTRS)

    Anthes, R. A.; Keyser, D.; Deardorff, J. W.

    1982-01-01

    Mixed-layer models have been used to simulate low-level flows under a variety of situations, including flow over complex terrain and in the vicinity of coastal zones. The advantage of mixed-layer models compared to multilevel models is their simplicity and minimal computational requirements. A disadvantage is that the atmosphere above the mixed layer is not modeled explicitly and approximations pertaining to this layer become necessary. This paper examines five approximations for treating this upper layer for a simple sea-breeze circulation. Approximating the flow immediately above the mixed-layer height h by the mixed-layer velocity and using this velocity to advect potential temperature above h gives a better simulation of the sea breeze than the approximation used by Anthes et al. (1980), which neglected horizontal advection at this level.

  8. Multiscale Modeling of Powder Bed–Based Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Markl, Matthias; Körner, Carolin

    2016-07-01

    Powder bed fusion processes are additive manufacturing technologies that are expected to induce the third industrial revolution. Components are built up layer by layer in a powder bed by selectively melting confined areas, according to sliced 3D model data. This technique allows for manufacturing of highly complex geometries hardly machinable with conventional technologies. However, the underlying physical phenomena are sparsely understood and difficult to observe during processing. Therefore, an intensive and expensive trial-and-error principle is applied to produce components with the desired dimensional accuracy, material characteristics, and mechanical properties. This review presents numerical modeling approaches on multiple length scales and timescales to describe different aspects of powder bed fusion processes. In combination with tailored experiments, the numerical results enlarge the process understanding of the underlying physical mechanisms and support the development of suitable process strategies and component topologies.

  9. Stabilization of inorganic mixed waste to pass the TCLP and STLC tests using clay and pH-insensitive additives

    SciTech Connect

    Bowers, J.S.; Anson, J.R.; Painter, S.M.; Maitino, R.E.

    1995-03-01

    Stabilization traps toxic contaminants (usually both chemically and physically) in a matrix so that they do not leach into the environment. Typical contaminants are metals (mostly transition metals) that exhibit the characteristic of toxicity. The stabilization process routinely uses pozzolanic materials. Portland cement, fly ash-lime mixes, gypsum cements, and clays are some of the most common materials. In many instances, materials that can pass the Toxicity Characteristic Leaching Procedure (TCLP-the federal leach test) or the Soluble Threshold Leachate Concentration (STLC-the California leach test) must have high concentrations of lime or other caustic material because of the low pH of the leaching media. Both leaching media, California`s and EPA`s, have a pH of 5.0. California uses citric acid and sodium citrate while EPA uses acetic acid and sodium acetate. These media can form ligands that provide excellent metal leaching. Because of the aggressive nature of the leaching medium, stabilized wastes in many cases will not pass the leaching tests. At the Lawrence Livermore National Laboratory, additives such as dithiocarbamates and thiocarbonates, which are pH-insensitive and provide resistance to ligand formation, are used in the waste stabilization process. Attapulgite, montmorillonite, and sepiolite clays are used because they are forgiving (recipe can be adjusted before the matrix hardens). The most frequently used stabilization process consists of a customized recipe involving waste sludge, clay and dithiocarbamate salt, mixed with a double planetary mixer into a pasty consistency. TCLP and STLC data on this waste matrix have shown that the process matrix meets land disposal requirements.

  10. Development of consistent equivalent models by mixed-model search

    NASA Technical Reports Server (NTRS)

    Guo, X.; Stoica, A.; Zebulum, R.; Keymeulen, D.

    2003-01-01

    This paper introduces a new approach to the development of equivalent models. Models of various accuracy and simulation speed may be needed in different contexts of design and analysis, or within different simulators.

  11. Thermodynamic modeling of protein retention in mixed-mode chromatography: An extended model for isocratic and dual gradient elution chromatography.

    PubMed

    Lee, Yi Feng; Graalfs, Heiner; Frech, Christian

    2016-09-16

    An extended model is developed to describe protein retention in mixed-mode chromatography based on thermodynamic principles. Special features are the incorporation of pH dependence of the ionic interaction on a mixed-mode resin and the addition of a water term into the model which enables one to describe the total number of water molecules released at the hydrophobic interfaces upon protein-ligand binding. Examples are presented on how to determine the model parameters using isocratic elution chromatography. Four mixed-mode anion-exchanger prototype resins with different surface chemistries and ligand densities were tested using isocratic elution of two monoclonal antibodies at different pH values (7-10) and encompassed a wide range of NaCl concentrations (0-5M). U-shape mixed-mode retention curves were observed for all four resins. By taking into account of the deprotonation and protonation of the weak cationic functional groups in these mixed-mode anion-exchanger prototype resins, conditions which favor protein-ligand binding via mixed-mode strong cationic ligands as well as conditions which favor protein-ligand binding via both mixed-mode strong cationic ligands and non-hydrophobic weak cationic ligands were identified. The changes in the retention curves with pH, salt, protein, and ligand can be described very well by the extended model using meaningful thermodynamic parameters like Gibbs energy, number of ionic and hydrophobic interactions, total number of released water molecules as well as modulator interaction constant. Furthermore, the fitted model parameters based on isocratic elution data can also be used to predict protein retention in dual salt-pH gradient elution chromatography. PMID:27554024

  12. A mixed system modeling two-directional pedestrian flows.

    PubMed

    Goatin, Paola; Mimault, Matthias

    2015-04-01

    In this article, we present a simplified model to describe the dynamics of two groups of pedestrians moving in opposite directions in a corridor. The model consists of a 2 x 2 system of conservation laws of mixed hyperbolic-elliptic type. We study the basic properties of the system to understand why and how bounded oscillations in numerical simulations arise. We show that Lax-Friedrichs scheme ensures the invariance of the domain and we investigate the existence of measure-valued solutions as limit of a subsequence of approximate solutions. PMID:25811441

  13. Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova

    SciTech Connect

    James Glimm

    2009-06-04

    The three year plan for this project was to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (Direct Numerical Simulation (DNS), Large Eddy Simulations (LES), full two fluid simulations and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We model 2D and 3D perturbations of planar or circular interfaces. We compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. Multiple layers and reshock are considered here.

  14. Simple model for the turbulent mixing width at an ablating surface

    NASA Astrophysics Data System (ADS)

    Cherfils, Catherine; Mikaelian, Karnig O.

    1996-02-01

    A diffusion model is applied to calculate the turbulent mixing width at an ablating surface. It is proposed that the general model be tested first on well-determined and easily accessible stabilizing mechanisms such as surface tension, viscosity, density gradient, or finite thickness. In this model the turbulent mixing width h is directly correlated with the growth rate γ of the perturbations in the presence of stabilizing mechanisms: h/hclass=(γ/γclass)1/2, where hclass=0.07 Agτ2 and γclass=√Agk (where A is the Atwood number, g is the acceleration, τ is the time, and k =2π/λ =2π/(ωhclass), ω being a dimensionless constant in the model). The method is illustrated with several examples for hablation, each based on a different γablation. Direct numerical simulations are presented comparing h with and without density gradients. In addition to mixing due to the Rayleigh-Taylor instability, the diffusion model is applied to the Kelvin-Helmholtz and the Richtmyer-Meshkov mixing layers.

  15. Photonic states mixing beyond the plasmon hybridization model

    NASA Astrophysics Data System (ADS)

    Suryadharma, Radius N. S.; Iskandar, Alexander A.; Tjia, May-On

    2016-07-01

    A study is performed on a photonic-state mixing-pattern in an insulator-metal-insulator cylindrical silver nanoshell and its rich variations induced by changes in the geometry and dielectric media of the system, representing the combined influences of plasmon coupling strength and cavity effects. This study is performed in terms of the photonic local density of states (LDOS) calculated using the Green tensor method, in order to elucidate those combined effects. The energy profiles of LDOS inside the dielectric core are shown to exhibit consistently growing number of redshifted photonic states due to an enhanced plasmon coupling induced state mixing arising from decreased shell thickness, increased cavity size effect, and larger symmetry breaking effect induced by increased permittivity difference between the core and the background media. Further, an increase in cavity size leads to increased additional peaks that spread out toward the lower energy regime. A systematic analysis of those variations for a silver nanoshell with a fixed inner radius in vacuum background reveals a certain pattern of those growing number of redshifted states with an analytic expression for the corresponding energy downshifts, signifying a photonic state mixing scheme beyond the commonly adopted plasmon hybridization scheme. Finally, a remarkable correlation is demonstrated between the LDOS energy profiles outside the shell and the corresponding scattering efficiencies.

  16. Intercomparison of garnet barometers and implications for garnet mixing models

    SciTech Connect

    Anovitz, L.M.; Essene, E.J.

    1985-01-01

    Several well-calibrated barometers are available in the system Ca-Fe-Ti-Al-Si-O, including: Alm+3Ru-3Ilm+Sil+2Qtz (GRAIL), 2Alm+Grreverse arrow6Ru=6Ilm+3An+3Qtz (GRIPS); 2Alm+Gr=3Fa+3An (FAG); 3AnGr+Ky+Qtz (GASP); 2Fs-Fa+Qtz (FFQ); and Gr+Qtz=An+2Wo (WAGS). GRIPS, GRAIL and GASP form a linearly dependent set such that any two should yield the third given an a/X model for the grossular/almandine solid-solution. Application to barometry of garnet granulite assemblages from the Grenville in Ontario yields average pressures 0.1 kb lower for GRIPS and 0.4 kb higher for FAGS using our mixing model. Results from Parry Island, Ontario, yield 8.7 kb from GRAIL as opposed to 9.1 kb using Ganguly and Saxena's model. For GASP, Parry Island assemblages yield 8.4 kb with the authors calibration. Ganguly and Saxena's model gives 5.4 kb using Gasparik's reversals and 8.1 kb using the position of GASP calculated from GRIPS and GRAIL. These corrections allow GRIPS, GRAIL, GASP and FAGS to yield consistent pressures to +/- 0.5 kb in regional metamorphic terranes. Application of their mixing model outside of the fitted range 700-1000 K is not encouraged as extrapolation may yield erroneous results.

  17. Nonlinear spectral mixing theory to model multispectral signatures

    SciTech Connect

    Borel, C.C.

    1996-02-01

    Nonlinear spectral mixing occurs due to multiple reflections and transmissions between discrete surfaces, e.g. leaves or facets of a rough surface. The radiosity method is an energy conserving computational method used in thermal engineering and it models nonlinear spectral mixing realistically and accurately. In contrast to the radiative transfer method the radiosity method takes into account the discreteness of the scattering surfaces (e.g. exact location, orientation and shape) such as leaves and includes mutual shading between them. An analytic radiosity-based scattering model for vegetation was developed and used to compute vegetation indices for various configurations. The leaf reflectance and transmittance was modeled using the PROSPECT model for various amounts of water, chlorophyll and variable leaf structure. The soil background was modeled using SOILSPEC with a linear mixture of reflectances of sand, clay and peat. A neural network and a geometry based retrieval scheme were used to retrieve leaf area index and chlorophyll concentration for dense canopies. Only simulated canopy reflectances in the 6 visible through short wave IR Landsat TM channels were used. The authors used an empirical function to compute the signal-to-noise ratio of a retrieved quantity.

  18. Mixing characteristics of sludge simulant in a model anaerobic digester.

    PubMed

    Low, Siew Cheng; Eshtiaghi, Nicky; Slatter, Paul; Baudez, Jean-Christophe; Parthasarathy, Rajarathinam

    2016-03-01

    This study aims to investigate the mixing characteristics of a transparent sludge simulant in a mechanically agitated model digester using flow visualisation technique. Video images of the flow patterns were obtained by recording the progress of an acid-base reaction and analysed to determine the active and inactive volumes as a function of time. The doughnut-shaped inactive region formed above and below the impeller in low concentration simulant decreases in size with time and disappears finally. The 'cavern' shaped active mixing region formed around the impeller in simulant solutions with higher concentrations increases with increasing agitation time and reaches a steady state equilibrium size, which is a function of specific power input. These results indicate that the active volume is jointly determined by simulant rheology and specific power input. A mathematical correlation is proposed to estimate the active volume as a function of simulant concentration in terms of yield Reynolds number. PMID:26739143

  19. An open source Bayesian Monte Carlo isotope mixing model with applications in Earth surface processes

    NASA Astrophysics Data System (ADS)

    Arendt, Carli A.; Aciego, Sarah M.; Hetland, Eric A.

    2015-05-01

    The implementation of isotopic tracers as constraints on source contributions has become increasingly relevant to understanding Earth surface processes. Interpretation of these isotopic tracers has become more accessible with the development of Bayesian Monte Carlo (BMC) mixing models, which allow uncertainty in mixing end-members and provide methodology for systems with multicomponent mixing. This study presents an open source multiple isotope BMC mixing model that is applicable to Earth surface environments with sources exhibiting distinct end-member isotopic signatures. Our model is first applied to new δ18O and δD measurements from the Athabasca Glacier, which showed expected seasonal melt evolution trends and vigorously assessed the statistical relevance of the resulting fraction estimations. To highlight the broad applicability of our model to a variety of Earth surface environments and relevant isotopic systems, we expand our model to two additional case studies: deriving melt sources from δ18O, δD, and 222Rn measurements of Greenland Ice Sheet bulk water samples and assessing nutrient sources from ɛNd and 87Sr/86Sr measurements of Hawaiian soil cores. The model produces results for the Greenland Ice Sheet and Hawaiian soil data sets that are consistent with the originally published fractional contribution estimates. The advantage of this method is that it quantifies the error induced by variability in the end-member compositions, unrealized by the models previously applied to the above case studies. Results from all three case studies demonstrate the broad applicability of this statistical BMC isotopic mixing model for estimating source contribution fractions in a variety of Earth surface systems.

  20. Mixing in age-structured population models of infectious diseases.

    PubMed

    Glasser, John; Feng, Zhilan; Moylan, Andrew; Del Valle, Sara; Castillo-Chavez, Carlos

    2012-01-01

    Infectious diseases are controlled by reducing pathogen replication within or transmission between hosts. Models can reliably evaluate alternative strategies for curtailing transmission, but only if interpersonal mixing is represented realistically. Compartmental modelers commonly use convex combinations of contacts within and among groups of similarly aged individuals, respectively termed preferential and proportionate mixing. Recently published face-to-face conversation and time-use studies suggest that parents and children and co-workers also mix preferentially. As indirect effects arise from the off-diagonal elements of mixing matrices, these observations are exceedingly important. Accordingly, we refined the formula published by Jacquez et al. [19] to account for these newly-observed patterns and estimated age-specific fractions of contacts with each preferred group. As the ages of contemporaries need not be identical nor those of parents and children to differ by exactly the generation time, we also estimated the variances of the Gaussian distributions with which we replaced the Kronecker delta commonly used in theoretical studies. Our formulae reproduce observed patterns and can be used, given contacts, to estimate probabilities of infection on contact, infection rates, and reproduction numbers. As examples, we illustrate these calculations for influenza based on "attack rates" from a prospective household study during the 1957 pandemic and for varicella based on cumulative incidence estimated from a cross-sectional serological survey conducted from 1988-94, together with contact rates from the several face-to-face conversation and time-use studies. Susceptibility to infection on contact generally declines with age, but may be elevated among adolescents and adults with young children. PMID:22037144

  1. Mixing behavior of a model cellulosic biomass slurry during settling and resuspension

    DOE PAGESBeta

    Crawford, Nathan C.; Sprague, Michael A.; Stickel, Jonathan J.

    2016-01-29

    Thorough mixing during biochemical deconstruction of biomass is crucial for achieving maximum process yields and economic success. However, due to the complex morphology and surface chemistry of biomass particles, biomass mixing is challenging and currently it is not well understood. This study investigates the bulk rheology of negatively buoyant, non-Brownian α-cellulose particles during settling and resuspension. The torque signal of a vane mixer across two distinct experimental setups (vane-in-cup and vane-in-beaker) was used to understand how mixing conditions affect the distribution of biomass particles. During experimentation, a bifurcated torque response as a function of vane speed was observed, indicating thatmore » the slurry transitions from a “settling-dominant” regime to a “suspension-dominant” regime. The torque response of well-characterized fluids (i.e., DI water) were then used to empirically identify when sufficient mixing turbulence was established in each experimental setup. The predicted critical mixing speeds were in agreement with measured values, suggesting that secondary flows are required in order to keep the cellulose particles fully suspended. In addition, a simple scaling relationship was developed to model the entire torque signal of the slurry throughout settling and resuspension. Furthermore, qualitative and semi-quantitative agreement between the model and experimental results was observed.« less

  2. Modeling of Transient Flow Mixing of Streams Injected into a Mixing Chamber

    NASA Technical Reports Server (NTRS)

    Voytovych, Dmytro M.; Merkle, Charles L.; Lucht, Robert P.; Hulka, James R.; Jones, Gregg W.

    2006-01-01

    Ignition is recognized as one the critical drivers in the reliability of multiple-start rocket engines. Residual combustion products from previous engine operation can condense on valves and related structures thereby creating difficulties for subsequent starting procedures. Alternative ignition methods that require fewer valves can mitigate the valve reliability problem, but require improved understanding of the spatial and temporal propellant distribution in the pre-ignition chamber. Current design tools based mainly on one-dimensional analysis and empirical models cannot predict local details of the injection and ignition processes. The goal of this work is to evaluate the capability of the modern computational fluid dynamics (CFD) tools in predicting the transient flow mixing in pre-ignition environment by comparing the results with the experimental data. This study is a part of a program to improve analytical methods and methodologies to analyze reliability and durability of combustion devices. In the present paper we describe a series of detailed computational simulations of the unsteady mixing events as the cold propellants are first introduced into the chamber as a first step in providing this necessary environmental description. The present computational modeling represents a complement to parallel experimental simulations' and includes comparisons with experimental results from that effort. A large number of rocket engine ignition studies has been previously reported. Here we limit our discussion to the work discussed in Refs. 2, 3 and 4 which is both similar to and different from the present approach. The similarities arise from the fact that both efforts involve detailed experimental/computational simulations of the ignition problem. The differences arise from the underlying philosophy of the two endeavors. The approach in Refs. 2 to 4 is a classical ignition study in which the focus is on the response of a propellant mixture to an ignition source, with

  3. A Bayesian nonlinear mixed-effects disease progression model

    PubMed Central

    Kim, Seongho; Jang, Hyejeong; Wu, Dongfeng; Abrams, Judith

    2016-01-01

    A nonlinear mixed-effects approach is developed for disease progression models that incorporate variation in age in a Bayesian framework. We further generalize the probability model for sensitivity to depend on age at diagnosis, time spent in the preclinical state and sojourn time. The developed models are then applied to the Johns Hopkins Lung Project data and the Health Insurance Plan for Greater New York data using Bayesian Markov chain Monte Carlo and are compared with the estimation method that does not consider random-effects from age. Using the developed models, we obtain not only age-specific individual-level distributions, but also population-level distributions of sensitivity, sojourn time and transition probability. PMID:26798562

  4. Mixing and shocks in geophysical shallow water models

    NASA Astrophysics Data System (ADS)

    Jacobson, Tivon

    In the first section, a reduced two-layer shallow water model for fluid mixing is described. The model is a nonlinear hyperbolic quasilinear system of partial differential equations, derived by taking the limit as the upper layer becomes infinitely deep. It resembles the shallow water equations, but with an active buoyancy. Fluid entrainment is supposed to occur from the upper layer to the lower. Several physically motivated closures are proposed, including a robust closure based on maximizing a mixing entropy (also defined and derived) at shocks. The structure of shock solutions is examined. The Riemann problem is solved by setting the shock speed to maximize the production of mixing entropy. Shock-resolving finite-volume numerical models are presented with and without topographic forcing. Explicit shock tracking is required for strong shocks. The constraint that turbulent energy production be positive is considered. The model has geophysical applications in studying the dynamics of dense sill overflows in the ocean. The second section discusses stationary shocks of the shallow water equations in a reentrant rotating channel with wind stress and topography. Asymptotic predictions for the shock location, strength, and associated energy dissipation are developed by taking the topographic perturbation to be small. The scaling arguments for the asymptotics are developed by demanding integrated energy and momentum balance, with the result that the free surface perturbation is of the order of the square root of the topographic perturbation. Shock formation requires that linear waves be nondispersive, which sets a solvability condition on the mean flow and which leads to a class of generalized Kelvin waves. Two-dimensional shock-resolving numerical simulations validate the asymptotic expressions and demonstrate the presence of stationary separated flow shocks in some cases. Geophysical applications are considered. Overview sections on shock-resolving numerical methods

  5. Subgrid models for mass and thermal diffusion in turbulent mixing

    SciTech Connect

    Sharp, David H; Lim, Hyunkyung; Li, Xiao - Lin; Gilmm, James G

    2008-01-01

    We are concerned with the chaotic flow fields of turbulent mixing. Chaotic flow is found in an extreme form in multiply shocked Richtmyer-Meshkov unstable flows. The goal of a converged simulation for this problem is twofold: to obtain converged solutions for macro solution features, such as the trajectories of the principal shock waves, mixing zone edges, and mean densities and velocities within each phase, and also for such micro solution features as the joint probability distributions of the temperature and species concentration. We introduce parameterized subgrid models of mass and thermal diffusion, to define large eddy simulations (LES) that replicate the micro features observed in the direct numerical simulation (DNS). The Schmidt numbers and Prandtl numbers are chosen to represent typical liquid, gas and plasma parameter values. Our main result is to explore the variation of the Schmidt, Prandtl and Reynolds numbers by three orders of magnitude, and the mesh by a factor of 8 per linear dimension (up to 3200 cells per dimension), to allow exploration of both DNS and LES regimes and verification of the simulations for both macro and micro observables. We find mesh convergence for key properties describing the molecular level of mixing, including chemical reaction rates between the distinct fluid species. We find results nearly independent of Reynolds number for Re 300, 6000, 600K . Methodologically, the results are also new. In common with the shock capturing community, we allow and maintain sharp solution gradients, and we enhance these gradients through use of front tracking. In common with the turbulence modeling community, we include subgrid scale models with no adjustable parameters for LES. To the authors' knowledge, these two methodologies have not been previously combined. In contrast to both of these methodologies, our use of Front Tracking, with DNS or LES resolution of the momentum equation at or near the Kolmogorov scale, but without resolving the

  6. MIXING MODELING ANALYSIS FOR SRS SALT WASTE DISPOSITION

    SciTech Connect

    Lee, S.

    2011-01-18

    Nuclear waste at Savannah River Site (SRS) waste tanks consists of three different types of waste forms. They are the lighter salt solutions referred to as supernate, the precipitated salts as salt cake, and heavier fine solids as sludge. The sludge is settled on the tank floor. About half of the residual waste radioactivity is contained in the sludge, which is only about 8 percentage of the total waste volume. Mixing study to be evaluated here for the Salt Disposition Integration (SDI) project focuses on supernate preparations in waste tanks prior to transfer to the Salt Waste Processing Facility (SWPF) feed tank. The methods to mix and blend the contents of the SRS blend tanks were evalutaed to ensure that the contents are properly blended before they are transferred from the blend tank such as Tank 50H to the SWPF feed tank. The work consists of two principal objectives to investigate two different pumps. One objective is to identify a suitable pumping arrangement that will adequately blend/mix two miscible liquids to obtain a uniform composition in the tank with a minimum level of sludge solid particulate in suspension. The other is to estimate the elevation in the tank at which the transfer pump inlet should be located where the solid concentration of the entrained fluid remains below the acceptance criterion (0.09 wt% or 1200 mg/liter) during transfer operation to the SWPF. Tank 50H is a Waste Tank that will be used to prepare batches of salt feed for SWPF. The salt feed must be a homogeneous solution satisfying the acceptance criterion of the solids entrainment during transfer operation. The work described here consists of two modeling areas. They are the mixing modeling analysis during miscible liquid blending operation, and the flow pattern analysis during transfer operation of the blended liquid. The modeling results will provide quantitative design and operation information during the mixing/blending process and the transfer operation of the blended

  7. Marginally specified generalized linear mixed models: a robust approach.

    PubMed

    Mills, J E; Field, C A; Dupuis, D J

    2002-12-01

    Longitudinal data modeling is complicated by the necessity to deal appropriately with the correlation between observations made on the same individual. Building on an earlier nonrobust version proposed by Heagerty (1999, Biometrics 55, 688-698), our robust marginally specified generalized linear mixed model (ROBMS-GLMM) provides an effective method for dealing with such data. This model is one of the first to allow both population-averaged and individual-specific inference. As well, it adopts the flexibility and interpretability of generalized linear mixed models for introducing dependence but builds a regression structure for the marginal mean, allowing valid application with time-dependent (exogenous) and time-independent covariates. These new estimators are obtained as solutions of a robustified likelihood equation involving Huber's least favorable distribution and a collection of weights. Huber's least favorable distribution produces estimates that are resistant to certain deviations from the random effects distributional assumptions. Innovative weighting strategies enable the ROBMS-GLMM to perform well when faced with outlying observations both in the response and covariates. We illustrate the methodology with an analysis of a prospective longitudinal study of laryngoscopic endotracheal intubation, a skill that numerous health-care professionals are expected to acquire. The principal goal of our research is to achieve robust inference in longitudinal analyses. PMID:12495126

  8. Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

    NASA Astrophysics Data System (ADS)

    Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

    2016-04-01

    A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

  9. [Critical of the additive model of the randomized controlled trial].

    PubMed

    Boussageon, Rémy; Gueyffier, François; Bejan-Angoulvant, Theodora; Felden-Dominiak, Géraldine

    2008-01-01

    Randomized, double-blind, placebo-controlled clinical trials are currently the best way to demonstrate the clinical effectiveness of drugs. Its methodology relies on the method of difference (John Stuart Mill), through which the observed difference between two groups (drug vs placebo) can be attributed to the pharmacological effect of the drug being tested. However, this additive model can be questioned in the event of statistical interactions between the pharmacological and the placebo effects. Evidence in different domains has shown that the placebo effect can influence the effect of the active principle. This article evaluates the methodological, clinical and epistemological consequences of this phenomenon. Topics treated include extrapolating results, accounting for heterogeneous results, demonstrating the existence of several factors in the placebo effect, the necessity to take these factors into account for given symptoms or pathologies, as well as the problem of the "specific" effect. PMID:18387273

  10. Model of Mixing Layer With Multicomponent Evaporating Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2004-01-01

    A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The study is motivated by the fact that typical real petroleum fuels contain hundreds of chemical species. Previously, for the sake of computational efficiency, spray studies were performed using either models based on a single representative species or models based on surrogate fuels of at most 15 species. The present multicomponent model makes it possible to perform more realistic simulations by accounting for hundreds of chemical species in a computationally efficient manner. The model is used to perform Direct Numerical Simulations in continuing studies directed toward understanding the behavior of liquid petroleum fuel sprays. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and the drops, respectively. This representation is consistent with the expected volumetrically small loading of the drops in gas (of the order of 10 3), although the mass loading can be substantial because of the high ratio (of the order of 103) between the densities of liquid and gas. The drops are treated as point sources of mass, momentum, and energy; this representation is consistent with the drop size being smaller than the Kolmogorov scale. Unsteady drag, added-mass effects, Basset history forces, and collisions between the drops are neglected, and the gas is assumed calorically perfect. The model incorporates the concept of continuous thermodynamics, according to which the chemical composition of a fuel is described probabilistically, by use of a distribution function. Distribution functions generally depend on many parameters. However, for mixtures of homologous species, the distribution can be approximated with acceptable accuracy as a sole function of the molecular weight. The mixing layer is initially laden with drops in its lower stream, and the drops are colder than the gas

  11. Stochastic Mixing Model with Power Law Decay of Variance

    NASA Technical Reports Server (NTRS)

    Fedotov, S.; Ihme, M.; Pitsch, H.

    2003-01-01

    Here we present a simple stochastic mixing model based on the law of large numbers (LLN). The reason why the LLN is involved in our formulation of the mixing problem is that the random conserved scalar c = c(t,x(t)) appears to behave as a sample mean. It converges to the mean value mu, while the variance sigma(sup 2)(sub c) (t) decays approximately as t(exp -1). Since the variance of the scalar decays faster than a sample mean (typically is greater than unity), we will introduce some non-linear modifications into the corresponding pdf-equation. The main idea is to develop a robust model which is independent from restrictive assumptions about the shape of the pdf. The remainder of this paper is organized as follows. In Section 2 we derive the integral equation from a stochastic difference equation describing the evolution of the pdf of a passive scalar in time. The stochastic difference equation introduces an exchange rate gamma(sub n) which we model in a first step as a deterministic function. In a second step, we generalize gamma(sub n) as a stochastic variable taking fluctuations in the inhomogeneous environment into account. In Section 3 we solve the non-linear integral equation numerically and analyze the influence of the different parameters on the decay rate. The paper finishes with a conclusion.

  12. Analysis on sheet cyclic plastic deformation using mixed hardening model

    NASA Astrophysics Data System (ADS)

    Li, Qun; Jin, Miao; Yuxin, Zhu

    2013-05-01

    Treating the cyclic deformation problem of sheet flowing through drawbead as the object of the research, using HILL anisotropy yield criterion and mixed hardening model, the cyclic plastic deformation mechanism of sheet was studied, the deformation characteristics of sheet subjected to cyclic loads were revealed, and the influence of Bauschinger effect on stress-strain circulating relationship and the influence of bending neutral layer migration on the stress of sheet's intermediate integral point were analyzed as well. The effectiveness of the model was verified by experiments. The results of analysis were showed that the stress values influenced by Bauschinger effect were different at the yield point of reverse loading and the point of unloading during the cyclic deformation. The stress rate at the yield point of reverse loading and the point of unloading in different loading branches was also different. The stress-strain circulating relationship in different loading branches can be approximately treated as bilinear. The tangent modulus of each loading branch showed a significant downward trend as the times of the reverse loading increased. The tangent modulus calculated by the mixed hardening model after the second loading branch reduced to less than 21% of the first loading tangent modulus. Effected by the neutral layer migration, the stress-strain curve of integral point of sheet's intermediate layer showed alternating transition phenomenon of the tensile stress and compressive stress.

  13. Molybdenum-based additives to mixed-metal oxides for use in hot gas cleanup sorbents for the catalytic decomposition of ammonia in coal gases

    DOEpatents

    Ayala, Raul E.

    1993-01-01

    This invention relates to additives to mixed-metal oxides that act simultaneously as sorbents and catalysts in cleanup systems for hot coal gases. Such additives of this type, generally, act as a sorbent to remove sulfur from the coal gases while substantially simultaneously, catalytically decomposing appreciable amounts of ammonia from the coal gases.

  14. Non-Additive Effects on Decomposition from Mixing Litter of the Invasive Mikania micrantha H.B.K. with Native Plants

    PubMed Central

    Chen, Bao-Ming; Peng, Shao-Lin; D’Antonio, Carla M.; Li, Dai-Jiang; Ren, Wen-Tao

    2013-01-01

    A common hypothesis to explain the effect of litter mixing is based on the difference in litter N content between mixed species. Although many studies have shown that litter of invasive non-native plants typically has higher N content than that of native plants in the communities they invade, there has been surprisingly little study of mixing effects during plant invasions. We address this question in south China where Mikania micrantha H.B.K., a non-native vine, with high litter N content, has invaded many forested ecosystems. We were specifically interested in whether this invader accelerated decomposition and how the strength of the litter mixing effect changes with the degree of invasion and over time during litter decomposition. Using litterbags, we evaluated the effect of mixing litter of M. micrantha with the litter of 7 native resident plants, at 3 ratios: M1 (1∶4, = exotic:native litter), M2 (1∶1) and M3 (4∶1, = exotic:native litter) over three incubation periods. We compared mixed litter with unmixed litter of the native species to identify if a non-additive effect of mixing litter existed. We found that there were positive significant non-additive effects of litter mixing on both mass loss and nutrient release. These effects changed with native species identity, mixture ratio and decay times. Overall the greatest accelerations of mixture decay and N release tended to be in the highest degree of invasion (mix ratio M3) and during the middle and final measured stages of decomposition. Contrary to expectations, the initial difference in litter N did not explain species differences in the effect of mixing but overall it appears that invasion by M. micrantha is accelerating the decomposition of native species litter. This effect on a fundamental ecosystem process could contribute to higher rates of nutrient turnover in invaded ecosystems. PMID:23840435

  15. A continuous mixing model for pdf simulations and its applications to combusting shear flows

    NASA Technical Reports Server (NTRS)

    Hsu, A. T.; Chen, J.-Y.

    1991-01-01

    The problem of time discontinuity (or jump condition) in the coalescence/dispersion (C/D) mixing model is addressed in this work. A C/D mixing model continuous in time is introduced. With the continuous mixing model, the process of chemical reaction can be fully coupled with mixing. In the case of homogeneous turbulence decay, the new model predicts a pdf very close to a Gaussian distribution, with finite higher moments also close to that of a Gaussian distribution. Results from the continuous mixing model are compared with both experimental data and numerical results from conventional C/D models.

  16. Fermion flavor mixing in models with dynamical mass generation

    SciTech Connect

    Benes, Petr

    2010-03-15

    We present a model-independent method of dealing with fermion flavor mixing in the case when instead of constant, momentum-independent mass matrices one has rather momentum-dependent self-energies. This situation is typical for strongly coupled models of dynamical fermion mass generation. We demonstrate our approach on the example of quark mixing. We show that quark self-energies with a generic momentum dependence lead to an effective Cabibbo-Kobayashi-Maskawa matrix, which turns out to be in general nonunitary, in accordance with previous claims of other authors, and to nontrivial flavor changing electromagnetic and neutral currents. We also discuss some conceptual consequences of the momentum-dependent self-energies and show that in such a case the interaction basis and the mass basis are not related by a unitary transformation. In fact, we argue that the latter is merely an effective concept, in a specified sense. While focusing mainly on the fermionic self-energies, we also study the effects of momentum-dependent radiative corrections to the gauge bosons and to the proper vertices. Our approach is based on an application of the Lehmann-Symanzik-Zimmermann reduction formula and for the special case of constant self-energies it gives the same results as the standard approach based on the diagonalization of mass matrices.

  17. System dynamics of behaviour-evolutionary mix-game models

    NASA Astrophysics Data System (ADS)

    Gou, Cheng-Ling; Gao, Jie-Ping; Chen, Fang

    2010-11-01

    In real financial markets there are two kinds of traders: one is fundamentalist, and the other is a trend-follower. The mix-game model is proposed to mimic such phenomena. In a mix-game model there are two groups of agents: Group 1 plays the majority game and Group 2 plays the minority game. In this paper, we investigate such a case that some traders in real financial markets could change their investment behaviours by assigning the evolutionary abilities to agents: if the winning rates of agents are smaller than a threshold, they will join the other group; and agents will repeat such an evolution at certain time intervals. Through the simulations, we obtain the following findings: (i) the volatilities of systems increase with the increase of the number of agents in Group 1 and the times of behavioural changes of all agents; (ii) the performances of agents in both groups and the stabilities of systems become better if all agents take more time to observe their new investment behaviours; (iii) there are two-phase zones of market and non-market and two-phase zones of evolution and non-evolution; (iv) parameter configurations located within the cross areas between the zones of markets and the zones of evolution are suited for simulating the financial markets.

  18. Functional Nonlinear Mixed Effects Models For Longitudinal Image Data

    PubMed Central

    Luo, Xinchao; Zhu, Lixing; Kong, Linglong; Zhu, Hongtu

    2015-01-01

    Motivated by studying large-scale longitudinal image data, we propose a novel functional nonlinear mixed effects modeling (FN-MEM) framework to model the nonlinear spatial-temporal growth patterns of brain structure and function and their association with covariates of interest (e.g., time or diagnostic status). Our FNMEM explicitly quantifies a random nonlinear association map of individual trajectories. We develop an efficient estimation method to estimate the nonlinear growth function and the covariance operator of the spatial-temporal process. We propose a global test and a simultaneous confidence band for some specific growth patterns. We conduct Monte Carlo simulation to examine the finite-sample performance of the proposed procedures. We apply FNMEM to investigate the spatial-temporal dynamics of white-matter fiber skeletons in a national database for autism research. Our FNMEM may provide a valuable tool for charting the developmental trajectories of various neuropsychiatric and neurodegenerative disorders. PMID:26213453

  19. A mixing evolution model for bidirectional microblog user networks

    NASA Astrophysics Data System (ADS)

    Yuan, Wei-Guo; Liu, Yun

    2015-08-01

    Microblogs have been widely used as a new form of online social networking. Based on the user profile data collected from Sina Weibo, we find that the number of microblog user bidirectional friends approximately corresponds with the lognormal distribution. We then build two microblog user networks with real bidirectional relationships, both of which have not only small-world and scale-free but also some special properties, such as double power-law degree distribution, disassortative network, hierarchical and rich-club structure. Moreover, by detecting the community structures of the two real networks, we find both of their community scales follow an exponential distribution. Based on the empirical analysis, we present a novel evolution network model with mixed connection rules, including lognormal fitness preferential and random attachment, nearest neighbor interconnected in the same community, and global random associations in different communities. The simulation results show that our model is consistent with real network in many topology features.

  20. A Mixed Approach for Modeling Blood Flow in Brain Microcirculation

    NASA Astrophysics Data System (ADS)

    Lorthois, Sylvie; Peyrounette, Myriam; Davit, Yohan; Quintard, Michel; Groupe d'Etude sur les Milieux Poreux Team

    2015-11-01

    Consistent with its distribution and exchange functions, the vascular system of the human brain cortex is a superposition of two components. At small-scale, a homogeneous and space-filling mesh-like capillary network. At large scale, quasi-fractal branched veins and arteries. From a modeling perspective, this is the superposition of: (a) a continuum model resulting from the homogenization of slow transport in the small-scale capillary network; and (b) a discrete network approach describing fast transport in the arteries and veins, which cannot be homogenized because of their fractal nature. This problematic is analogous to fast conducting wells embedded in a reservoir rock in petroleum engineering. An efficient method to reduce the computational cost is to use relatively large grid blocks for the continuum model. This makes it difficult to accurately couple both components. We solve this issue by adapting the ``well model'' concept used in petroleum engineering to brain specific 3D situations. We obtain a unique linear system describing the discrete network, the continuum and the well model. Results are presented for realistic arterial and venous geometries. The mixed approach is compared with full network models including various idealized capillary networks of known permeability. ERC BrainMicroFlow GA615102.

  1. Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

    SciTech Connect

    Xu, Songchen; Manna, Kuntal; Ellern, Arkady; Sadow, Aaron D

    2014-12-08

    In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(η4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(η4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(η4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(η4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(μ-Cl)(η2-C8H14)2]2 (M = Rh, Ir) provide {κ4-PhB(OxMe2)2ImMes'CH2}Rh(μ-H)(μ-Cl)Rh(η2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(η3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {κ4-PhB(OxMe2)2ImMes'CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis

  2. Application of Hierarchical Linear Models/Linear Mixed-Effects Models in School Effectiveness Research

    ERIC Educational Resources Information Center

    Ker, H. W.

    2014-01-01

    Multilevel data are very common in educational research. Hierarchical linear models/linear mixed-effects models (HLMs/LMEs) are often utilized to analyze multilevel data nowadays. This paper discusses the problems of utilizing ordinary regressions for modeling multilevel educational data, compare the data analytic results from three regression…

  3. Mesoscale Modeling During Mixed-Phase Arctic Cloud Experiment

    SciTech Connect

    Avramov, A.; Harringston, J.Y.; Verlinde, J.

    2005-03-18

    Mixed-phase arctic stratus clouds are the predominant cloud type in the Arctic (Curry et al. 2000) and through various feedback mechanisms exert a strong influence on the Arctic climate. Perhaps one of the most intriguing of their features is that they tend to have liquid tops that precipitate ice. Despite the fact that this situation is colloidally unstable, these cloud systems are quite long lived - from a few days to over a couple of weeks. It has been hypothesized that mixed-phase clouds are maintained through a balance between liquid water condensation resulting from the cloud-top radiative cooling and ice removal by precipitation (Pinto 1998; Harrington et al. 1999). In their modeling study Harrington et al. (1999) found that the maintenance of this balance depends strongly on the ambient concentration of ice forming nucleus (IFN). In a follow-up study, Jiang et al. (2002), using only 30% of IFN concentration predicted by Meyers et al. (1992) IFN parameterization were able to obtain results similar to the observations reported by Pinto (1998). The IFN concentration measurements collected during the Mixed-Phase Arctic Cloud Experiment (M-PACE), conducted in October 2004 over the North Slope of Alaska and the Beaufort Sea (Verlinde et al. 2005), also showed much lower values then those predicted (Prenne, pers. comm.) by currently accepted ice nucleation parameterizations (e.g. Meyers et al. 1992). The goal of this study is to use the extensive IFN data taken during M-PACE to examine what effects low IFN concentrations have on mesoscale cloud structure and coastal dynamics.

  4. THE USE OF DI WATER TO MITIGATE DUSTING FOR ADDITION OF DWPF FRIT TO THE SLURRY MIX EVAPORATOR

    SciTech Connect

    Hansen, E.

    2010-07-21

    The Defense Waste Processing Facility (DPWF) presently is in the process to determine means to reduce water utilization in the Slurry Mix Evaporator (SME) process, thus reducing effluent and processing times. The frit slurry addition system mixes the dry frit with water, yielding approximately a 50 weight percent slurry containing frit and the other fraction water. This slurry is discharged into the SME and excess water is removed via boiling. To reduce this water load to the SME, DWPF has proposed using a pneumatic system in conveying the frit to the SME, in essence a dry delivery system. The problem associated with utilizing a dry delivery system with the existing frit is the generation of dust when discharged into the SME. The use of water has been shown to be effective in the mining industry as well in the DOE complex to mitigate dusting. The method employed by SRNL to determine the quantity of water to mitigate dusting in dry powders was effective, between a lab and bench scale tests. In those tests, it was shown that as high as five weight percent (wt%) of water addition was required to mitigate dust from batches of glass forming minerals used by the Waste Treatment Plant at Hanford, Washington. The same method used to determine the quantity of water to mitigate dusting was used in this task to determine the quantity of water to mitigate this dusting using as-received frit. The ability for water to mitigate dusting is due to its adhesive properties as shown in Figure 1-1. Wetting the frit particles allows for the smaller frit particles (including dust) to adhere to the larger frit particles or to agglomerate into large particles. Fluids other than water can also be used, but their adhesive properties are different than water and the quantity required to mitigate dusting is different, as was observed in reference 1. Excessive water, a few weight percentages greater than that required to mitigate dusting can cause the resulting material not to flow. The primary

  5. Tactical application of an atmospheric mixed-layer model

    NASA Astrophysics Data System (ADS)

    Graves, R. M.

    1982-12-01

    Modern Naval weapon and sensor systems are strongly influenced by the marine environment. Foremost among the atmospheric effects is ducting of electromagnetic energy by refractive layers in the atmosphere. To assess the effect of ducting on electromagnetic emissions, the Navy developed the Integrated Refractive Effects Prediction System (IREPS). Research at Naval Postgraduate School (NPS) has led to development of a state-of-the-art model which can be used to predict changes to the refractive profile of the lower atmosphere. The model uses radiosonde data and surface meteorological observations to predict changes in refractive conditions and low level cloud/fog formation over 18 to 30 hour periods. The model shows some skill in forecasting duct regions when subsidence rates can be specified to within +/-.0015 m/s. This thesis shows the applicability of the NPS marine atmospheric mixed layer model to fleet tactics. Atmospheric refractive effects on specific emitters can be predicted when model predictions are used in conjunction with IREPS.

  6. Percolation model with an additional source of disorder.

    PubMed

    Kundu, Sumanta; Manna, S S

    2016-06-01

    The ranges of transmission of the mobiles in a mobile ad hoc network are not uniform in reality. They are affected by the temperature fluctuation in air, obstruction due to the solid objects, even the humidity difference in the environment, etc. How the varying range of transmission of the individual active elements affects the global connectivity in the network may be an important practical question to ask. Here a model of percolation phenomena, with an additional source of disorder, is introduced for a theoretical understanding of this problem. As in ordinary percolation, sites of a square lattice are occupied randomly with probability p. Each occupied site is then assigned a circular disk of random value R for its radius. A bond is defined to be occupied if and only if the radii R_{1} and R_{2} of the disks centered at the ends satisfy a certain predefined condition. In a very general formulation, one divides the R_{1}-R_{2} plane into two regions by an arbitrary closed curve. One defines a point within one region as representing an occupied bond; otherwise it is a vacant bond. The study of three different rules under this general formulation indicates that the percolation threshold always varies continuously. This threshold has two limiting values, one is p_{c}(sq), the percolation threshold for the ordinary site percolation on the square lattice, and the other is unity. The approach of the percolation threshold to its limiting values are characterized by two exponents. In a special case, all lattice sites are occupied by disks of random radii R∈{0,R_{0}} and a percolation transition is observed with R_{0} as the control variable, similar to the site occupation probability. PMID:27415234

  7. Percolation model with an additional source of disorder

    NASA Astrophysics Data System (ADS)

    Kundu, Sumanta; Manna, S. S.

    2016-06-01

    The ranges of transmission of the mobiles in a mobile ad hoc network are not uniform in reality. They are affected by the temperature fluctuation in air, obstruction due to the solid objects, even the humidity difference in the environment, etc. How the varying range of transmission of the individual active elements affects the global connectivity in the network may be an important practical question to ask. Here a model of percolation phenomena, with an additional source of disorder, is introduced for a theoretical understanding of this problem. As in ordinary percolation, sites of a square lattice are occupied randomly with probability p . Each occupied site is then assigned a circular disk of random value R for its radius. A bond is defined to be occupied if and only if the radii R1 and R2 of the disks centered at the ends satisfy a certain predefined condition. In a very general formulation, one divides the R1-R2 plane into two regions by an arbitrary closed curve. One defines a point within one region as representing an occupied bond; otherwise it is a vacant bond. The study of three different rules under this general formulation indicates that the percolation threshold always varies continuously. This threshold has two limiting values, one is pc(sq) , the percolation threshold for the ordinary site percolation on the square lattice, and the other is unity. The approach of the percolation threshold to its limiting values are characterized by two exponents. In a special case, all lattice sites are occupied by disks of random radii R ∈{0 ,R0} and a percolation transition is observed with R0 as the control variable, similar to the site occupation probability.

  8. Efficient material flow in mixed model assembly lines.

    PubMed

    Alnahhal, Mohammed; Noche, Bernd

    2013-01-01

    In this study, material flow from decentralized supermarkets to stations in mixed model assembly lines using tow (tugger) trains is investigated. Train routing, scheduling, and loading problems are investigated in parallel to minimize the number of trains, variability in loading and in routes lengths, and line-side inventory holding costs. The general framework for solving these problems in parallel contains analytical equations, Dynamic Programming (DP), and Mixed Integer Programming (MIP). Matlab in conjunction with LP-solve software was used to formulate the problem. An example was presented to explain the idea. Results which were obtained in very short CPU time showed the effect of using time buffer among routes on the feasible space and on the optimal solution. Results also showed the effect of the objective, concerning reducing the variability in loading, on the results of routing, scheduling, and loading. Moreover, results showed the importance of considering the maximum line-side inventory beside the capacity of the train in the same time in finding the optimal solution. PMID:24024101

  9. Robust, Adaptive Functional Regression in Functional Mixed Model Framework

    PubMed Central

    Zhu, Hongxiao; Brown, Philip J.; Morris, Jeffrey S.

    2012-01-01

    Functional data are increasingly encountered in scientific studies, and their high dimensionality and complexity lead to many analytical challenges. Various methods for functional data analysis have been developed, including functional response regression methods that involve regression of a functional response on univariate/multivariate predictors with nonparametrically represented functional coefficients. In existing methods, however, the functional regression can be sensitive to outlying curves and outlying regions of curves, so is not robust. In this paper, we introduce a new Bayesian method, robust functional mixed models (R-FMM), for performing robust functional regression within the general functional mixed model framework, which includes multiple continuous or categorical predictors and random effect functions accommodating potential between-function correlation induced by the experimental design. The underlying model involves a hierarchical scale mixture model for the fixed effects, random effect and residual error functions. These modeling assumptions across curves result in robust nonparametric estimators of the fixed and random effect functions which down-weight outlying curves and regions of curves, and produce statistics that can be used to flag global and local outliers. These assumptions also lead to distributions across wavelet coefficients that have outstanding sparsity and adaptive shrinkage properties, with great flexibility for the data to determine the sparsity and the heaviness of the tails. Together with the down-weighting of outliers, these within-curve properties lead to fixed and random effect function estimates that appear in our simulations to be remarkably adaptive in their ability to remove spurious features yet retain true features of the functions. We have developed general code to implement this fully Bayesian method that is automatic, requiring the user to only provide the functional data and design matrices. It is efficient

  10. Effect of SiO2 and Al2O3 addition on the density, Tg and CTE of mixed alkali - alkaline earth borate glass

    NASA Astrophysics Data System (ADS)

    Deshpande, A. M.; Deshpande, V. K.

    2009-07-01

    Mixed alkali — alkaline earth borate glasses, with the addition of silica and alumina, have been studied for their density, Tg and CTE with a view of exploring the applicability of these glasses in glass to metal sealing applications. It has been observed that silica addition results in an increase in density and Tg while the alumina addition decreases the density and Tg. The variation in CTE exhibits minima with the addition of both, silica and alumina. An attempt is made here to explain the observed variations in the properties on the basis of different mass of the additives, number of non bridging oxygens (NBOs) and other changes in the glass network.

  11. Nonlinear resonances and mixing in a simple shallow lake model

    NASA Astrophysics Data System (ADS)

    Sandor, Balazs

    2013-04-01

    Large-scale transport in environmental flows is often dominantly determined by the velocity field of the flow. Diffusion of certain quantities, like pollutants and temperature, can be neglected with respect to advective transport. Understanding the topological features of the velocity field is thus very important for the qualitative analysis of the large-scale mixing properties of these passive scalars in water bodies. Large horizontal circulating zones (often called gyres) are prevalent structures of wind induced shallow lake flows. In this presentation we analyse the currents generated by wind in a square shaped shallow lake. In case of a steady flow field, induced by a time-independent wind stress field, the typical flow pattern consists of two counter-rotating gyres. When applying periodic disturbances in the wind stress field, mixing regions of different widths develop between the gyres. This region is filled with coherent structures, strongly increasing advective transport in the lake. Meanwhile, the inner regions of the gyres remain stable; their outer periodic orbits serve as transport barriers. Our statement is that the width of the mixing region reaches its maximum at a certain scale of wind disturbation frequencies. This characteristic frequency scale corresponds to the typical circulation frequencies of the gyres. Our flow model consists of a two dimensional, depth-averaged flow field of the volume preserving water body with wind surface stress. The flow has a stream function that satisfies the linearised shallow-water vorticity transport equation. This corresponds to a Hamiltonian system, where the stream function plays the role of the Hamiltonian In the steady state the gyres consist of periodic orbits, so this is an (one degree of freedom) integrable mechanical system, like the undamped pendulum. In the periodically disturbed case the system remains Hamiltonian with a topological similarity to the phase portrait of the forced pendulum. Thus we can

  12. Mixed-Effects Modeling with Crossed Random Effects for Subjects and Items

    ERIC Educational Resources Information Center

    Baayen, R. H.; Davidson, D. J.; Bates, D. M.

    2008-01-01

    This paper provides an introduction to mixed-effects models for the analysis of repeated measurement data with subjects and items as crossed random effects. A worked-out example of how to use recent software for mixed-effects modeling is provided. Simulation studies illustrate the advantages offered by mixed-effects analyses compared to…

  13. COMPUTATIONAL FLUID DYNAMICS MODELING OF SCALED HANFORD DOUBLE SHELL TANK MIXING - CFD MODELING SENSITIVITY STUDY RESULTS

    SciTech Connect

    JACKSON VL

    2011-08-31

    The primary purpose of the tank mixing and sampling demonstration program is to mitigate the technical risks associated with the ability of the Hanford tank farm delivery and celtification systems to measure and deliver a uniformly mixed high-level waste (HLW) feed to the Waste Treatment and Immobilization Plant (WTP) Uniform feed to the WTP is a requirement of 24590-WTP-ICD-MG-01-019, ICD-19 - Interface Control Document for Waste Feed, although the exact definition of uniform is evolving in this context. Computational Fluid Dynamics (CFD) modeling has been used to assist in evaluating scaleup issues, study operational parameters, and predict mixing performance at full-scale.

  14. Sensitivity of fluvial sediment source apportionment to mixing model assumptions: A Bayesian model comparison

    NASA Astrophysics Data System (ADS)

    Cooper, Richard J.; Krueger, Tobias; Hiscock, Kevin M.; Rawlins, Barry G.

    2014-11-01

    Mixing models have become increasingly common tools for apportioning fluvial sediment load to various sediment sources across catchments using a wide variety of Bayesian and frequentist modeling approaches. In this study, we demonstrate how different model setups can impact upon resulting source apportionment estimates in a Bayesian framework via a one-factor-at-a-time (OFAT) sensitivity analysis. We formulate 13 versions of a mixing model, each with different error assumptions and model structural choices, and apply them to sediment geochemistry data from the River Blackwater, Norfolk, UK, to apportion suspended particulate matter (SPM) contributions from three sources (arable topsoils, road verges, and subsurface material) under base flow conditions between August 2012 and August 2013. Whilst all 13 models estimate subsurface sources to be the largest contributor of SPM (median ˜76%), comparison of apportionment estimates reveal varying degrees of sensitivity to changing priors, inclusion of covariance terms, incorporation of time-variant distributions, and methods of proportion characterization. We also demonstrate differences in apportionment results between a full and an empirical Bayesian setup, and between a Bayesian and a frequentist optimization approach. This OFAT sensitivity analysis reveals that mixing model structural choices and error assumptions can significantly impact upon sediment source apportionment results, with estimated median contributions in this study varying by up to 21% between model versions. Users of mixing models are therefore strongly advised to carefully consider and justify their choice of model structure prior to conducting sediment source apportionment investigations.

  15. Multilevel Latent Class Models with Dirichlet Mixing Distribution

    PubMed Central

    Di, Chong-Zhi; Bandeen-Roche, Karen

    2010-01-01

    Summary Latent class analysis (LCA) and latent class regression (LCR) are widely used for modeling multivariate categorical outcomes in social science and biomedical studies. Standard analyses assume data of different respondents to be mutually independent, excluding application of the methods to familial and other designs in which participants are clustered. In this paper, we consider multilevel latent class models, in which subpopulation mixing probabilities are treated as random effects that vary among clusters according to a common Dirichlet distribution. We apply the Expectation-Maximization (EM) algorithm for model fitting by maximum likelihood (ML). This approach works well, but is computationally intensive when either the number of classes or the cluster size is large. We propose a maximum pairwise likelihood (MPL) approach via a modified EM algorithm for this case. We also show that a simple latent class analysis, combined with robust standard errors, provides another consistent, robust, but less efficient inferential procedure. Simulation studies suggest that the three methods work well in finite samples, and that the MPL estimates often enjoy comparable precision as the ML estimates. We apply our methods to the analysis of comorbid symptoms in the Obsessive Compulsive Disorder study. Our models' random effects structure has more straightforward interpretation than those of competing methods, thus should usefully augment tools available for latent class analysis of multilevel data. PMID:20560936

  16. Bayesian Gaussian Copula Factor Models for Mixed Data

    PubMed Central

    Murray, Jared S.; Dunson, David B.; Carin, Lawrence; Lucas, Joseph E.

    2013-01-01

    Gaussian factor models have proven widely useful for parsimoniously characterizing dependence in multivariate data. There is a rich literature on their extension to mixed categorical and continuous variables, using latent Gaussian variables or through generalized latent trait models acommodating measurements in the exponential family. However, when generalizing to non-Gaussian measured variables the latent variables typically influence both the dependence structure and the form of the marginal distributions, complicating interpretation and introducing artifacts. To address this problem we propose a novel class of Bayesian Gaussian copula factor models which decouple the latent factors from the marginal distributions. A semiparametric specification for the marginals based on the extended rank likelihood yields straightforward implementation and substantial computational gains. We provide new theoretical and empirical justifications for using this likelihood in Bayesian inference. We propose new default priors for the factor loadings and develop efficient parameter-expanded Gibbs sampling for posterior computation. The methods are evaluated through simulations and applied to a dataset in political science. The models in this paper are implemented in the R package bfa.1 PMID:23990691

  17. Subgrid models for mass and thermal diffusion in turbulent mixing

    NASA Astrophysics Data System (ADS)

    Lim, H.; Yu, Y.; Glimm, J.; Li, X.-L.; Sharp, D. H.

    2010-12-01

    We propose a new method for the large eddy simulation (LES) of turbulent mixing flows. The method yields convergent probability distribution functions (PDFs) for temperature and concentration and a chemical reaction rate when applied to reshocked Richtmyer-Meshkov (RM) unstable flows. Because such a mesh convergence is an unusual and perhaps original capability for LES of RM flows, we review previous validation studies of the principal components of the algorithm. The components are (i) a front tracking code, FronTier, to control numerical mass diffusion and (ii) dynamic subgrid scale (SGS) models to compensate for unresolved scales in the LES. We also review the relevant code comparison studies. We compare our results to a simple model based on 1D diffusion, taking place in the geometry defined statistically by the interface (the 50% isoconcentration surface between the two fluids). Several conclusions important to physics could be drawn from our study. We model chemical reactions with no closure approximations beyond those in the LES of the fluid variables itself, and as with dynamic SGS models, these closures contain no adjustable parameters. The chemical reaction rate is specified by the joint PDF for temperature and concentration. We observe a bimodal distribution for the PDF and we observe significant dependence on fluid transport parameters.

  18. Computation of Supersonic Jet Mixing Noise Using PARC Code With a kappa-epsilon Turbulence Model

    NASA Technical Reports Server (NTRS)

    Khavaran, A.; Kim, C. M.

    1999-01-01

    A number of modifications have been proposed in order to improve the jet noise prediction capabilities of the MGB code. This code which was developed at General Electric, employees the concept of acoustic analogy for the prediction of turbulent mixing noise. The source convection and also refraction of sound due to the shrouding effect of the mean flow are accounted for by incorporating the high frequency solution to Lilley's equation for cylindrical jets (Balsa and Mani). The broadband shock-associated noise is estimated using Harper-Bourne and Fisher's shock noise theory. The proposed modifications are aimed at improving the aerodynamic predictions (source/spectrum computations) and allowing for the non- axisymmetric effects in the jet plume and nozzle geometry (sound/flow interaction). In addition, recent advances in shock noise prediction as proposed by Tam can be employed to predict the shock-associated noise as an addition to the jet mixing noise when the flow is not perfectly expanded. Here we concentrate on the aerodynamic predictions using the PARC code with a k-E turbulence model and the ensuing turbulent mixing noise. The geometry under consideration is an axisymmetric convergent-divergent nozzle at its design operating conditions. Aerodynamic and acoustic computations are compared with data as well as predictions due to the original MGB model using Reichardt's aerodynamic theory.

  19. An efficient hierarchical generalized linear mixed model for pathway analysis of genome-wide association studies

    PubMed Central

    Wang, Lily; Jia, Peilin; Wolfinger, Russell D.; Chen, Xi; Grayson, Britney L.; Aune, Thomas M.; Zhao, Zhongming

    2011-01-01

    Motivation: In genome-wide association studies (GWAS) of complex diseases, genetic variants having real but weak associations often fail to be detected at the stringent genome-wide significance level. Pathway analysis, which tests disease association with combined association signals from a group of variants in the same pathway, has become increasingly popular. However, because of the complexities in genetic data and the large sample sizes in typical GWAS, pathway analysis remains to be challenging. We propose a new statistical model for pathway analysis of GWAS. This model includes a fixed effects component that models mean disease association for a group of genes, and a random effects component that models how each gene's association with disease varies about the gene group mean, thus belongs to the class of mixed effects models. Results: The proposed model is computationally efficient and uses only summary statistics. In addition, it corrects for the presence of overlapping genes and linkage disequilibrium (LD). Via simulated and real GWAS data, we showed our model improved power over currently available pathway analysis methods while preserving type I error rate. Furthermore, using the WTCCC Type 1 Diabetes (T1D) dataset, we demonstrated mixed model analysis identified meaningful biological processes that agreed well with previous reports on T1D. Therefore, the proposed methodology provides an efficient statistical modeling framework for systems analysis of GWAS. Availability: The software code for mixed models analysis is freely available at http://biostat.mc.vanderbilt.edu/LilyWang. Contact: lily.wang@vanderbilt.edu; zhongming.zhao@vanderbilt.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:21266443

  20. Chemical geothermometers and mixing models for geothermal systems

    USGS Publications Warehouse

    Fournier, R.O.

    1977-01-01

    Qualitative chemical geothermometers utilize anomalous concentrations of various "indicator" elements in groundwaters, streams, soils, and soil gases to outline favorable places to explore for geothermal energy. Some of the qualitative methods, such as the delineation of mercury and helium anomalies in soil gases, do not require the presence of hot springs or fumaroles. However, these techniques may also outline fossil thermal areas that are now cold. Quantitative chemical geothermometers and mixing models can provide information about present probable minimum subsurface temperatures. Interpretation is easiest where several hot or warm springs are present in a given area. At this time the most widely used quantitative chemical geothermometers are silica, Na/K, and Na-K-Ca. ?? 1976.

  1. Neutrino mixing in a left-right model

    NASA Astrophysics Data System (ADS)

    Martins Simões, J. A.; Ponciano, J. A.

    We study the mixing among different generations of massive neutrino fields in a model can accommodate a consistent pattern for neutral fermion masses as well as neutrino oscillations. The left and right sectors can be connected by a new neutral current. PACS: 12.60.-i, 14.60.St, 14.60.Pq

  2. Wave–turbulence interaction-induced vertical mixing and its effects in ocean and climate models

    PubMed Central

    Qiao, Fangli; Yuan, Yeli; Deng, Jia; Dai, Dejun; Song, Zhenya

    2016-01-01

    Heated from above, the oceans are stably stratified. Therefore, the performance of general ocean circulation models and climate studies through coupled atmosphere–ocean models depends critically on vertical mixing of energy and momentum in the water column. Many of the traditional general circulation models are based on total kinetic energy (TKE), in which the roles of waves are averaged out. Although theoretical calculations suggest that waves could greatly enhance coexisting turbulence, no field measurements on turbulence have ever validated this mechanism directly. To address this problem, a specially designed field experiment has been conducted. The experimental results indicate that the wave–turbulence interaction-induced enhancement of the background turbulence is indeed the predominant mechanism for turbulence generation and enhancement. Based on this understanding, we propose a new parametrization for vertical mixing as an additive part to the traditional TKE approach. This new result reconfirmed the past theoretical model that had been tested and validated in numerical model experiments and field observations. It firmly establishes the critical role of wave–turbulence interaction effects in both general ocean circulation models and atmosphere–ocean coupled models, which could greatly improve the understanding of the sea surface temperature and water column properties distributions, and hence model-based climate forecasting capability. PMID:26953182

  3. Wave-turbulence interaction-induced vertical mixing and its effects in ocean and climate models.

    PubMed

    Qiao, Fangli; Yuan, Yeli; Deng, Jia; Dai, Dejun; Song, Zhenya

    2016-04-13

    Heated from above, the oceans are stably stratified. Therefore, the performance of general ocean circulation models and climate studies through coupled atmosphere-ocean models depends critically on vertical mixing of energy and momentum in the water column. Many of the traditional general circulation models are based on total kinetic energy (TKE), in which the roles of waves are averaged out. Although theoretical calculations suggest that waves could greatly enhance coexisting turbulence, no field measurements on turbulence have ever validated this mechanism directly. To address this problem, a specially designed field experiment has been conducted. The experimental results indicate that the wave-turbulence interaction-induced enhancement of the background turbulence is indeed the predominant mechanism for turbulence generation and enhancement. Based on this understanding, we propose a new parametrization for vertical mixing as an additive part to the traditional TKE approach. This new result reconfirmed the past theoretical model that had been tested and validated in numerical model experiments and field observations. It firmly establishes the critical role of wave-turbulence interaction effects in both general ocean circulation models and atmosphere-ocean coupled models, which could greatly improve the understanding of the sea surface temperature and water column properties distributions, and hence model-based climate forecasting capability. PMID:26953182

  4. Calibrating the Updated Overshoot Mixing Model on Eclipsing Binary Stars: HY Vir, YZ Cas, χ2 Hya, and VV Crv

    NASA Astrophysics Data System (ADS)

    Meng, Y.; Zhang, Q. S.

    2014-06-01

    Detached eclipsing binary stars with convective cores provide a good tool to investigate convective core overshoot. It has been performed on some binary stars to restrict the classical overshoot model which simply extends the boundary of the fully mixed region. However, the classical overshoot model is physically unreasonable and inconsistent with helioseismic investigations. An updated model of overshoot mixing was established recently. There is a key parameter in the model. In this paper, we use observations of four eclipsing binary stars, i.e., HY Vir, YZ Cas, χ2 Hya, and VV Crv, to investigate a suitable value for the parameter. It is found that the value suggested by calibrations on eclipsing binary stars is the same as the value recommended by other methods. In addition, we have studied the effects of the updated overshoot model on the stellar structure. The diffusion coefficient of convective/overshoot mixing is very high in the convection zone, then quickly decreases near the convective boundary, and exponentially decreases in the overshoot region. The low value of the diffusion coefficient in the overshoot region leads to weak mixing and a partially mixed overshoot region. Semi-convection, which appears in the standard stellar models of low-mass stars with convective cores, is removed by partial overshoot mixing.

  5. Sensitivity of fluvial sediment source apportionment to mixing model assumptions: A Bayesian model comparison

    PubMed Central

    Cooper, Richard J; Krueger, Tobias; Hiscock, Kevin M; Rawlins, Barry G

    2014-01-01

    Mixing models have become increasingly common tools for apportioning fluvial sediment load to various sediment sources across catchments using a wide variety of Bayesian and frequentist modeling approaches. In this study, we demonstrate how different model setups can impact upon resulting source apportionment estimates in a Bayesian framework via a one-factor-at-a-time (OFAT) sensitivity analysis. We formulate 13 versions of a mixing model, each with different error assumptions and model structural choices, and apply them to sediment geochemistry data from the River Blackwater, Norfolk, UK, to apportion suspended particulate matter (SPM) contributions from three sources (arable topsoils, road verges, and subsurface material) under base flow conditions between August 2012 and August 2013. Whilst all 13 models estimate subsurface sources to be the largest contributor of SPM (median ∼76%), comparison of apportionment estimates reveal varying degrees of sensitivity to changing priors, inclusion of covariance terms, incorporation of time-variant distributions, and methods of proportion characterization. We also demonstrate differences in apportionment results between a full and an empirical Bayesian setup, and between a Bayesian and a frequentist optimization approach. This OFAT sensitivity analysis reveals that mixing model structural choices and error assumptions can significantly impact upon sediment source apportionment results, with estimated median contributions in this study varying by up to 21% between model versions. Users of mixing models are therefore strongly advised to carefully consider and justify their choice of model structure prior to conducting sediment source apportionment investigations. Key Points An OFAT sensitivity analysis of sediment fingerprinting mixing models is conducted Bayesian models display high sensitivity to error assumptions and structural choices Source apportionment results differ between Bayesian and frequentist approaches PMID

  6. An optimization of protocol for mixed chimerism induction in mice model.

    PubMed

    Baśkiewicz-Masiuk, M; Grymuła, K; Pius, E; Hałasa, M; Dziedziejko, V; Schmidt, Ch; Walczak, M; Machaliński, B

    2009-01-01

    Studies on mixed chimerism are currently focused primarily on obtaining less toxic conditioning protocols. With these issues in mind, we have undertaken the attempt to optimize the procedure of mixed chimerism induction in mice. In order to reduce toxicity, we used decreasing doses of total body irradiation (TBI) together with combination of blocking antibodies. We also tried to eliminate immunosuppression (cyclophosphamide - CP) treatment after bone marrow transplantation. B6.SJL-PtprcaPep3b mice were injected with 20-30 x 106 bone marrow cells from Balb C mice. Mice were treated with TBI (3 - 1.5 - 0 Gy) on "-1" day of the experiment and blocking antibodies against CD40L ("0", and "4" days) and additionally anti-CD8 ("-2" day) and/or anti-NK1.1 ("-3" day). Mice in certain groups also received CP (175 mg/kg) on "2" day. Presence of mixed chimerism was assessed in peripheral blood cells by flow cytometry on the 1st, 2nd, 3rd, 4th, 6th and 8th weeks of the experiment by detecting of CD45.1 (characteristic for B6.SJL-PtprcaPep3b strain) and CD45.2 (characteristic for Balb C strain) antigens expression. We also analyzed the percentage of peripheral blood CD8 T-cells (CD3e/CD8a) and NK cells (Ly-49D/NK1.1). We found that reduction of TBI dose and elimination of CP decrease the rate of mixed chimerism formation. The highest percentage of donor cells was obtained in the group of animals treated with 3 Gy of TBI, CP and combination of anti-CD40L, anti-CD8, and anti-NK1.1 antibodies. The 3 Gy TBI was necessary to induce stable mixed chimerism, but it could be obtained without the CP use. The percentage of CD3e/CD8a and Ly-49D/NK1.1 cells was significantly lower in the groups of mice treated by corresponding antibodies. Moreover, we observed the lowest number of peripheral blood Ly-49D/NK1.1 cells in the group of animals with highest mixed chimerism. Our experiments in mice model can help in better understanding of mixed chimerism phenomenon and in selecting the method of

  7. Recycle of mixed automotive plastics: A model study

    NASA Astrophysics Data System (ADS)

    Woramongconchai, Somsak

    decreased with increased twin-screw extrusion temperature. The flexural modulus of the recycled mixed automotive plastics expected in 2003 was higher than the 1980s and 1990 recycle. Flexural strength effects were not large enough for serious consideration, but were more dominant when compared to those in the 1980s and 1990s. Impact strengths at 20-30 J/m were the lowest value compared to the 1980s and 1990s mixed automotive recycle. Torque rheometry, dynamic mechanical analysis and optical and electron microscopy agreed with each other on the characterization of the processability and morphology of the blends. LLDPE and HDPE were miscible while PP was partially miscible with polyethylene. ABS and nylon-6 were immiscible with the polyolefins, but partially miscible with each other. As expected, the polyurethane foam was immiscible with the other components. The minor components of the model recycle of mixed automotive materials were probably partially miscible with ABS/nylon-6, but there were multiple and unresolved phases in the major blends.

  8. Research on mixed network architecture collaborative application model

    NASA Astrophysics Data System (ADS)

    Jing, Changfeng; Zhao, Xi'an; Liang, Song

    2009-10-01

    When facing complex requirements of city development, ever-growing spatial data, rapid development of geographical business and increasing business complexity, collaboration between multiple users and departments is needed urgently, however conventional GIS software (such as Client/Server model or Browser/Server model) are not support this well. Collaborative application is one of the good resolutions. Collaborative application has four main problems to resolve: consistency and co-edit conflict, real-time responsiveness, unconstrained operation, spatial data recoverability. In paper, application model called AMCM is put forward based on agent and multi-level cache. AMCM can be used in mixed network structure and supports distributed collaborative. Agent is an autonomous, interactive, initiative and reactive computing entity in a distributed environment. Agent has been used in many fields such as compute science and automation. Agent brings new methods for cooperation and the access for spatial data. Multi-level cache is a part of full data. It reduces the network load and improves the access and handle of spatial data, especially, in editing the spatial data. With agent technology, we make full use of its characteristics of intelligent for managing the cache and cooperative editing that brings a new method for distributed cooperation and improves the efficiency.

  9. Using Bayesian Stable Isotope Mixing Models to Enhance Marine Ecosystem Models

    EPA Science Inventory

    The use of stable isotopes in food web studies has proven to be a valuable tool for ecologists. We investigated the use of Bayesian stable isotope mixing models as constraints for an ecosystem model of a temperate seagrass system on the Atlantic coast of France. δ13C and δ15N i...

  10. Covariate-Adjusted Linear Mixed Effects Model with an Application to Longitudinal Data

    PubMed Central

    Nguyen, Danh V.; Şentürk, Damla; Carroll, Raymond J.

    2009-01-01

    Linear mixed effects (LME) models are useful for longitudinal data/repeated measurements. We propose a new class of covariate-adjusted LME models for longitudinal data that nonparametrically adjusts for a normalizing covariate. The proposed approach involves fitting a parametric LME model to the data after adjusting for the nonparametric effects of a baseline confounding covariate. In particular, the effect of the observable covariate on the response and predictors of the LME model is modeled nonparametrically via smooth unknown functions. In addition to covariate-adjusted estimation of fixed/population parameters and random effects, an estimation procedure for the variance components is also developed. Numerical properties of the proposed estimators are investigated with simulation studies. The consistency and convergence rates of the proposed estimators are also established. An application to a longitudinal data set on calcium absorption, accounting for baseline distortion from body mass index, illustrates the proposed methodology. PMID:19266053

  11. Mixing in mantle convection models with self-consistent plate tectonics and melting and crustal production: Application to mixing in the early Earth

    NASA Astrophysics Data System (ADS)

    Tackley, Paul

    2016-04-01

    It is generally thought that the early Earth's mantle was hotter than today, which using conventional convective scalings should have led to vigorous convection and mixing. Geochemical observations, however, suggest that mixing was not as rapid as would be expected, leading to the suggestion that early Earth had stagnant lid convection (Debaille et al., EPSL 2013). Additionally, the mantle's thermal evolution is difficult to explain using conventional scalings because early heat loss would have been too rapid, which has led to the hypothesis that plate tectonics convection does not follow the conventional convective scalings (Korenaga, GRL 2003). One physical process that could be important in this context is partial melting leading to crustal production, which has been shown to have the major effects of buffering mantle temperature and carrying a significant fraction of the heat from hot mantle (Nakagawa and Tackley, EPSL 2012), making plate tectonics easier (Lourenco et al., submitted), and causing compositional differentiation of the mantle that can buffer core heat loss (Nakagawa and Tackley, GCubed 2010). Here, the influence of this process on mantle mixing is examined, using secular thermo-chemical models that simulate Earth's evolution over 4.5 billion years. Mixing is quantified both in terms of how rapidly stretching occurs, and in terms of dispersion: how rapidly initially close heterogeneities are dispersed horizontally and vertically through the mantle. These measures are quantified as a function of time through Earth's evolution. The results will then be related to geochemically-inferred mixing rates.

  12. Cruise observation and numerical modeling of turbulent mixing in the Pearl River estuary in summer

    NASA Astrophysics Data System (ADS)

    Pan, Jiayi; Gu, Yanzhen

    2016-06-01

    The turbulent mixing in the Pearl River estuary and plume area is analyzed by using cruise data and simulation results of the Regional Ocean Model System (ROMS). The cruise observations reveal that strong mixing appeared in the bottom layer on larger ebb in the estuary. Modeling simulations are consistent with the observation results, and suggest that inside the estuary and in the near-shore water, the mixing is stronger on ebb than on flood. The mixing generation mechanism analysis based on modeling data reveals that bottom stress is responsible for the generation of turbulence in the estuary, for the re-circulating plume area, internal shear instability plays an important role in the mixing, and wind may induce the surface mixing in the plume far-field. The estuary mixing is controlled by the tidal strength, and in the re-circulating plume bulge, the wind stirring may reinforce the internal shear instability mixing.

  13. Mixed axion/neutralino cold dark matter in supersymmetric models

    SciTech Connect

    Baer, Howard; Lessa, Andre; Rajagopalan, Shibi; Sreethawong, Warintorn E-mail: lessa@nhn.ou.edu E-mail: wstan@nhn.ou.edu

    2011-06-01

    We consider supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/axino supermultiplet. We examine R-parity conserving models where the neutralino is the lightest SUSY particle, so that a mixture of neutralinos and axions serve as cold dark matter (a Z-tilde {sub 1} CDM). The mixed a Z-tilde {sub 1} CDM scenario can match the measured dark matter abundance for SUSY models which typically give too low a value of the usual thermal neutralino abundance, such as models with wino-like or higgsino-like dark matter. The usual thermal neutralino abundance can be greatly enhanced by the decay of thermally-produced axinos (ã) to neutralinos, followed by neutralino re-annihilation at temperatures much lower than freeze-out. In this case, the relic density is usually neutralino dominated, and goes as ∼ (f{sub a}/N)/m{sub ã}{sup 3/2}. If axino decay occurs before neutralino freeze-out, then instead the neutralino abundance can be augmented by relic axions to match the measured abundance. Entropy production from late-time axino decays can diminish the axion abundance, but ultimately not the neutralino abundance. In a Z-tilde {sub 1} CDM models, it may be possible to detect both a WIMP and an axion as dark matter relics. We also discuss possible modifications of our results due to production and decay of saxions. In the appendices, we present expressions for the Hubble expansion rate and the axion and neutralino relic densities in radiation, matter and decaying-particle dominated universes.

  14. Low Frequency Variability in a Stochastic Atmosphere - Ocean Mixed Layer Model

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.

    2015-12-01

    The climate system exhibits low-frequency variability in characteristic spatial structures, but the mechanisms for this variability have remained unclear partly due to observational limitations and partly due to difficulties in analyzing simulations from nonlinear, chaotic models. In addition, recent studies have questioned the necessity of ocean circulations to generate such low-frequency variability. Our research is intended to clarify mechanisms of low-frequency climate variability that can occur purely from atmospheric dynamics coupled to an ocean mixed-layer model. For this purpose, we have built a new stochastic model based on the linearized primitive equations for the atmosphere, a slab mixed-layer model for the ocean, a gray radiation scheme for radiative effects, and a diffusive scheme for vertical turbulent eddy fluxes. Temperature is randomly excited in midlatitudes, and all variables except surface pressure are damped artificially with a 1-day time scale. The atmospheric model alone is shown to produce realistic seasonal mean eddy variances and fluxes in midlatitudes, despite the absence of moisture, clouds, moist convection, topography, and zonal asymmetries in the back- ground state. Because the atmospheric eddy statistics are realistic, it is argued that coupling these eddies to a mixed-layer model will produce more realistic low-frequency variability than the traditional Hasselmann model in which the atmospheric stochastic forcing is imposed by fiat. We have shown that such coupling does indeed generate peaks in the low-frequency power spectrum that otherwise would not occur in the absence of coupling. Now, we are trying to comprehensively analyze the mechanism for these low-frequency peaks, exploiting the fact that the model is purely linear. We further aim to analyze simulations from a comprehensive nonlinear aquaplanet GCM. The results from nonlinear simulations will serve as a baseline for theoretical statistical studies in low frequency

  15. Mixed-Effects Logistic Regression Models for Indirectly Observed Discrete Outcome Variables

    ERIC Educational Resources Information Center

    Vermunt, Jeroen K.

    2005-01-01

    A well-established approach to modeling clustered data introduces random effects in the model of interest. Mixed-effects logistic regression models can be used to predict discrete outcome variables when observations are correlated. An extension of the mixed-effects logistic regression model is presented in which the dependent variable is a latent…

  16. Extended Mixed-Efects Item Response Models with the MH-RM Algorithm

    ERIC Educational Resources Information Center

    Chalmers, R. Philip

    2015-01-01

    A mixed-effects item response theory (IRT) model is presented as a logical extension of the generalized linear mixed-effects modeling approach to formulating explanatory IRT models. Fixed and random coefficients in the extended model are estimated using a Metropolis-Hastings Robbins-Monro (MH-RM) stochastic imputation algorithm to accommodate for…

  17. Chandra Observations and Models of the Mixed Morphology Supernova Remnant W44: Global Trends

    NASA Technical Reports Server (NTRS)

    Shelton, R. L.; Kuntz, K. D.; Petre, R.

    2004-01-01

    We report on the Chandra observations of the archetypical mixed morphology (or thermal composite) supernova remnant, W44. As with other mixed morphology remnants, W44's projected center is bright in thermal X-rays. It has an obvious radio shell, but no discernable X-ray shell. In addition, X-ray bright knots dot W44's image. The spectral analysis of the Chandra data show that the remnant s hot, bright projected center is metal-rich and that the bright knots are regions of comparatively elevated elemental abundances. Neon is among the affected elements, suggesting that ejecta contributes to the abundance trends. Furthermore, some of the emitting iron atoms appear to be underionized with respect to the other ions, providing the first potential X-ray evidence for dust destruction in a supernova remnant. We use the Chandra data to test the following explanations for W44's X-ray bright center: 1.) entropy mixing due to bulk mixing or thermal conduction, 2.) evaporation of swept up clouds, and 3.) a metallicity gradient, possibly due to dust destruction and ejecta enrichment. In these tests, we assume that the remnant has evolved beyond the adiabatic evolutionary stage, which explains the X-ray dimness of the shell. The entropy mixed model spectrum was tested against the Chandra spectrum for the remnant's projected center and found to be a good match. The evaporating clouds model was constrained by the finding that the ionization parameters of the bright knots are similar to those of the surrounding regions. While both the entropy mixed and the evaporating clouds models are known to predict centrally bright X-ray morphologies, their predictions fall short of the observed brightness gradient. The resulting brightness gap can be largely filled in by emission from the extra metals in and near the remnant's projected center. The preponderance of evidence (including that drawn from other studies) suggests that W44's remarkable morphology can be attributed to dust destruction

  18. Using Generalized Additive Models to Analyze Single-Case Designs

    ERIC Educational Resources Information Center

    Shadish, William; Sullivan, Kristynn

    2013-01-01

    Many analyses for single-case designs (SCDs)--including nearly all the effect size indicators-- currently assume no trend in the data. Regression and multilevel models allow for trend, but usually test only linear trend and have no principled way of knowing if higher order trends should be represented in the model. This paper shows how Generalized…

  19. Interfacial Pressures and Shocks in a Multiphase Flow mix Model

    SciTech Connect

    Klem, D E

    2004-10-01

    Multiphase flow models have been proposed for use in situations which have combined Rayleigh-Taylor (RTI) and Richtmyer-Meshkov (RMI) instabilities [2, 3]. Such an approach works poorly for the case of a heavy to light shock incidence on a developed interface. I suggest that this difficulty can be overcome by adding an additional source to the turbulence kinetic energy equation. A variety of constraints on such a source are considered. In this context it is observed that a new constraint on closures arises. This occurs because of the discontinuity within the shock responsible for the RMI. The proposed model (Shock Scattering) is shown to give useful results.

  20. Mixed dark matter in left-right symmetric models

    NASA Astrophysics Data System (ADS)

    Berlin, Asher; Fox, Patrick J.; Hooper, Dan; Mohlabeng, Gopolang

    2016-06-01

    Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions of parameter space for TeV-scale thermal dark matter. Decays of the heavy charged W' boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when fixed to the rate of the Run 1 excesses, moving towards the theoretically attractive scenario, gR = gL. This region of parameter space may be probed by future collider searches for new Higgs bosons or electroweak fermions.

  1. Coolant mixing and distribution in a transparent reactor model

    SciTech Connect

    Fanning, M.W.; Haury, G.; Pflug, L.; Rothe, P.H.

    1983-11-01

    Following a small break loss-of-coolant accident in a pressurized water reactor, coolant water may be injected at high pressure to help cool the core. This paper reports the results of tests which determined the mixing and distribution of the coolant in a 1/5-scale transparent model of the reactor. The model components included the reactor vessel, cold leg pipe, pump, and loop seal with steam generator and hot leg simulators completing the flow loop. Tests were conducted for a no-refill condition with constant liquid inventory in the facility and zero flow of the primary water. Salt water, dyed red was used for the coolant water to create prototypical density differences in this atmospheric facility. Steady state fluid distribution was determined from flow and density measurements and complete mass balances. Interpretation of the quantitative results was aided by extensive flow visualization studies which include still photographs and motion picture films for all tests. The test parameters included the fluid density ratio, the flow rate of coolant water, and the flow rate of primary water injected in the vessel downcomer to simulate a natural circulation flow through vent valves between the reactor core and the downcomer. Four locations of the small break were tested.

  2. Mixed dark matter in left-right symmetric models

    DOE PAGESBeta

    Berlin, Asher; Fox, Patrick J.; Hooper, Dan; Mohlabeng, Gopolang

    2016-06-08

    Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions of parameter space for TeV-scale thermal darkmore » matter. Decays of the heavy charged W(') boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when fixed to the rate of the Run 1 excesses, moving towards the theoretically attractive scenario, gR = gL. Furthermore, this region of parameter space may be probed by future collider searches for new Higgs bosons or electroweak fermions.« less

  3. How much additional model complexity do the use of catchment hydrological signatures, additional data and expert knowledge warrant?

    NASA Astrophysics Data System (ADS)

    Hrachowitz, M.; Fovet, O.; RUIZ, L.; Gascuel-odoux, C.; Savenije, H.

    2013-12-01

    In the frequent absence of sufficient suitable data to constrain hydrological models, it is not uncommon to represent catchments at a range of scales by lumped model set-ups. Although process heterogeneity can average out on the catchment scale to generate simple catchment integrated responses whose general flow features can frequently be reproduced by lumped models, these models often fail to get details of the flow pattern as well as catchment internal dynamics, such as groundwater level changes, right to a sufficient degree, resulting in considerable predictive uncertainty. Traditionally, models are constrained by only one or two objectives functions, which does not warrant more than a handful of parameters to avoid elevated predictive uncertainty, thereby preventing more complex model set-ups accounting for increased process heterogeneity. In this study it was tested how much additional process heterogeneity is warranted in models when optimizing the model calibration strategy, using additional data and expert knowledge. Long-term timeseries of flow and groundwater levels for small nested experimental catchments in French Brittany with considerable differences in geology, topography and flow regime were used in this study to test which degree of model process heterogeneity is warranted with increased availability of information. In a first step, as a benchmark, the system was treated as one lumped entity and the model was trained based only on its ability to reproduce the hydrograph. Although it was found that the overall modelled flow generally reflects the observed flow response quite well, the internal system dynamics could not be reproduced. In further steps the complexity of this model was gradually increased, first by adding a separate riparian reservoir to the lumped set-up and then by a semi-distributed set-up, allowing for independent, parallel model structures, representing the contrasting nested catchments. Although calibration performance increased

  4. Additive Manufacturing of Anatomical Models from Computed Tomography Scan Data.

    PubMed

    Gür, Y

    2014-12-01

    The purpose of the study presented here was to investigate the manufacturability of human anatomical models from Computed Tomography (CT) scan data via a 3D desktop printer which uses fused deposition modelling (FDM) technology. First, Digital Imaging and Communications in Medicine (DICOM) CT scan data were converted to 3D Standard Triangle Language (STL) format by using In Vaselius digital imaging program. Once this STL file is obtained, a 3D physical version of the anatomical model can be fabricated by a desktop 3D FDM printer. As a case study, a patient's skull CT scan data was considered, and a tangible version of the skull was manufactured by a 3D FDM desktop printer. During the 3D printing process, the skull was built using acrylonitrile-butadiene-styrene (ABS) co-polymer plastic. The printed model showed that the 3D FDM printing technology is able to fabricate anatomical models with high accuracy. As a result, the skull model can be used for preoperative surgical planning, medical training activities, implant design and simulation to show the potential of the FDM technology in medical field. It will also improve communication between medical stuff and patients. Current result indicates that a 3D desktop printer which uses FDM technology can be used to obtain accurate anatomical models. PMID:26336695

  5. Addition of Diffusion Model to MELCOR and Comparison with Data

    SciTech Connect

    Brad Merrill; Richard Moore; Chang Oh

    2004-06-01

    A chemical diffusion model was incorporated into the thermal-hydraulics package of the MELCOR Severe Accident code (Reference 1) for analyzing air ingress events for a very high temperature gas-cooled reactor.

  6. Modelling dissimilarity: generalizing ultrametric and additive tree representations.

    PubMed

    Hubert, L; Arabie, P; Meulman, J

    2001-05-01

    Methods for the hierarchical clustering of an object set produce a sequence of nested partitions such that object classes within each successive partition are constructed from the union of object classes present at the previous level. Any such sequence of nested partitions can in turn be characterized by an ultrametric. An approach to generalizing an (ultrametric) representation is proposed in which the nested character of the partition sequence is relaxed and replaced by the weaker requirement that the classes within each partition contain objects consecutive with respect to a fixed ordering of the objects. A method for fitting such a structure to a given proximity matrix is discussed, along with several alternative strategies for graphical representation. Using this same ultrametric extension, additive tree representations can also be generalized by replacing the ultrametric component in the decomposition of an additive tree (into an ultrametric and a centroid metric). A common numerical illustration is developed and maintained throughout the paper. PMID:11393895

  7. 1,4-Addition of Lithium Diisopropylamide to Unsaturated Esters: Role of Rate-Limiting Deaggregation, Autocatalysis, Lithium Chloride Catalysis and Other Mixed Aggregation Effects

    PubMed Central

    Ma, Yun; Hoepker, Alexander C.; Gupta, Lekha; Faggin, Marc F.; Collum, David B.

    2010-01-01

    Lithium diisopropylamide (LDA) in tetrahydrofuran at −78 °C undergoes 1,4-addition to an unsaturated ester via a rate-limiting deaggregation of LDA dimer followed by a post-rate-limiting reaction with the substrate. Muted autocatalysis is traced to a lithium enolate-mediated deaggregation of the LDA dimer and the intervention of LDA-lithium enolate mixed aggregates displaying higher reactivities than LDA. Striking accelerations are elicited by <1.0 mol % LiCl. Rate and mechanistic studies reveal that the uncatalyzed and catalyzed pathways funnel through a common monosolvated-monomer-based intermediate. Four distinct classes of mixed aggregation effects are discussed. PMID:20961095

  8. Analysis and Modeling of soil hydrology under different soil additives in artificial runoff plots

    NASA Astrophysics Data System (ADS)

    Ruidisch, M.; Arnhold, S.; Kettering, J.; Huwe, B.; Kuzyakov, Y.; Ok, Y.; Tenhunen, J. D.

    2009-12-01

    The impact of monsoon events during June and July in the Korean project region Haean Basin, which is located in the northeastern part of South Korea plays a key role for erosion, leaching and groundwater pollution risk by agrochemicals. Therefore, the project investigates the main hydrological processes in agricultural soils under field and laboratory conditions on different scales (plot, hillslope and catchment). Soil hydrological parameters were analysed depending on different soil additives, which are known for prevention of soil erosion and nutrient loss as well as increasing of water infiltration, aggregate stability and soil fertility. Hence, synthetic water-soluble Polyacrylamides (PAM), Biochar (Black Carbon mixed with organic fertilizer), both PAM and Biochar were applied in runoff plots at three agricultural field sites. Additionally, as control a subplot was set up without any additives. The field sites were selected in areas with similar hillslope gradients and with emphasis on the dominant land management form of dryland farming in Haean, which is characterised by row planting and row covering by foil. Hydrological parameters like satured water conductivity, matrix potential and water content were analysed by infiltration experiments, continuous tensiometer measurements, time domain reflectometry as well as pressure plates to indentify characteristic water retention curves of each horizon. Weather data were observed by three weather stations next to the runoff plots. Measured data also provide the input data for modeling water transport in the unsatured zone in runoff plots with HYDRUS 1D/2D/3D and SWAT (Soil & Water Assessment Tool).

  9. Guarana provides additional stimulation over caffeine alone in the planarian model.

    PubMed

    Moustakas, Dimitrios; Mezzio, Michael; Rodriguez, Branden R; Constable, Mic Andre; Mulligan, Margaret E; Voura, Evelyn B

    2015-01-01

    The stimulant effect of energy drinks is primarily attributed to the caffeine they contain. Many energy drinks also contain other ingredients that might enhance the tonic effects of these caffeinated beverages. One of these additives is guarana. Guarana is a climbing plant native to the Amazon whose seeds contain approximately four times the amount of caffeine found in coffee beans. The mix of other natural chemicals contained in guarana seeds is thought to heighten the stimulant effects of guarana over caffeine alone. Yet, despite the growing use of guarana as an additive in energy drinks, and a burgeoning market for it as a nutritional supplement, the science examining guarana and how it affects other dietary ingredients is lacking. To appreciate the stimulant effects of guarana and other natural products, a straightforward model to investigate their physiological properties is needed. The planarian provides such a system. The locomotor activity and convulsive response of planarians with substance exposure has been shown to provide an excellent system to measure the effects of drug stimulation, addiction and withdrawal. To gauge the stimulant effects of guarana we studied how it altered the locomotor activity of the planarian species Dugesia tigrina. We report evidence that guarana seeds provide additional stimulation over caffeine alone, and document the changes to this stimulation in the context of both caffeine and glucose. PMID:25880065

  10. Guarana Provides Additional Stimulation over Caffeine Alone in the Planarian Model

    PubMed Central

    Moustakas, Dimitrios; Mezzio, Michael; Rodriguez, Branden R.; Constable, Mic Andre; Mulligan, Margaret E.; Voura, Evelyn B.

    2015-01-01

    The stimulant effect of energy drinks is primarily attributed to the caffeine they contain. Many energy drinks also contain other ingredients that might enhance the tonic effects of these caffeinated beverages. One of these additives is guarana. Guarana is a climbing plant native to the Amazon whose seeds contain approximately four times the amount of caffeine found in coffee beans. The mix of other natural chemicals contained in guarana seeds is thought to heighten the stimulant effects of guarana over caffeine alone. Yet, despite the growing use of guarana as an additive in energy drinks, and a burgeoning market for it as a nutritional supplement, the science examining guarana and how it affects other dietary ingredients is lacking. To appreciate the stimulant effects of guarana and other natural products, a straightforward model to investigate their physiological properties is needed. The planarian provides such a system. The locomotor activity and convulsive response of planarians with substance exposure has been shown to provide an excellent system to measure the effects of drug stimulation, addiction and withdrawal. To gauge the stimulant effects of guarana we studied how it altered the locomotor activity of the planarian species Dugesia tigrina. We report evidence that guarana seeds provide additional stimulation over caffeine alone, and document the changes to this stimulation in the context of both caffeine and glucose. PMID:25880065

  11. Additional Research Needs to Support the GENII Biosphere Models

    SciTech Connect

    Napier, Bruce A.; Snyder, Sandra F.; Arimescu, Carmen

    2013-11-30

    In the course of evaluating the current parameter needs for the GENII Version 2 code (Snyder et al. 2013), areas of possible improvement for both the data and the underlying models have been identified. As the data review was implemented, PNNL staff identified areas where the models can be improved both to accommodate the locally significant pathways identified and also to incorporate newer models. The areas are general data needs for the existing models and improved formulations for the pathway models. It is recommended that priorities be set by NRC staff to guide selection of the most useful improvements in a cost-effective manner. Suggestions are made based on relatively easy and inexpensive changes, and longer-term more costly studies. In the short term, there are several improved model formulations that could be applied to the GENII suite of codes to make them more generally useful. • Implementation of the separation of the translocation and weathering processes • Implementation of an improved model for carbon-14 from non-atmospheric sources • Implementation of radon exposure pathways models • Development of a KML processor for the output report generator module data that are calculated on a grid that could be superimposed upon digital maps for easier presentation and display • Implementation of marine mammal models (manatees, seals, walrus, whales, etc.). Data needs in the longer term require extensive (and potentially expensive) research. Before picking any one radionuclide or food type, NRC staff should perform an in-house review of current and anticipated environmental analyses to select “dominant” radionuclides of interest to allow setting of cost-effective priorities for radionuclide- and pathway-specific research. These include • soil-to-plant uptake studies for oranges and other citrus fruits, and • Development of models for evaluation of radionuclide concentration in highly-processed foods such as oils and sugars. Finally, renewed

  12. Creep damage in a localized load sharing fibre bundle model with additional ageing

    NASA Astrophysics Data System (ADS)

    Lennartz-Sassinek, Sabine; Danku, Zsuzsa; Main, Ian; Kun, Ferenc

    2013-04-01

    Many fields of science are interested in the damage growth in earth materials. Often the damage propagates not in big avalanches like the crack growth measured by acoustic emissions. Also "silent" damage may occur whose emissions are either to small to be detected or mix with back ground noise. These silent emissions may carry the majority of the over all damage in a system until failure. One famous model for damage growth is the fibre bundle model. Here we consider an extended version of a localized load sharing fibre bundle model which incorporates additional time dependent ageing of each fibre motivated by a chemically active environment. We present the non-trivial time dependent damage growth in this model in the low load limit representing creep damage far away from failure. We show both numerical simulations and analytical equations describing the damage rate of silent events and the corresponding amount of triggered "acoustic" damage. The analytical description is in agreement with the numerical results.

  13. Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

    NASA Astrophysics Data System (ADS)

    Saber, Mostafa

    and alpha → gamma phase transformation in Fe-Ni-Zr alloys. In addition to the experimental study of thermal stabilization of nanocrystalline Fe-Cr-Zr or Fe-Ni-Zr alloys, the thesis presented here developed a new predictive model, applicable to strongly segregating solutes, for thermodynamic stabilization of binary alloys. This model can serve as a benchmark for selecting solute and evaluating the possible contribution of stabilization. Following a regular solution model, both the chemical and elastic strain energy contributions are combined to obtain the mixing enthalpy. The total Gibbs free energy of mixing is then minimized with respect to simultaneous variations in the grain boundary volume fraction and the solute concentration in the grain boundary and the grain interior. The Lagrange multiplier method was used to obtained numerical solutions. Application are given for the temperature dependence of the grain size and the grain boundary solute excess for selected binary system where experimental results imply that thermodynamic stabilization could be operative. This thesis also extends the binary model to a new model for thermodynamic stabilization of ternary nanocrystalline alloys. It is applicable to strongly segregating size-misfit solutes and uses input data available in the literature. In a same manner as the binary model, this model is based on a regular solution approach such that the chemical and elastic strain energy contributions are incorporated into the mixing enthalpy DeltaHmix, and the mixing entropy DeltaSmix is obtained using the ideal solution approximation. The Gibbs mixing free energy Delta Gmix is then minimized with respect to simultaneous variations in grain growth and solute segregation parameters. The Lagrange multiplier method is similarly used to obtain numerical solutions for the minimum Delta Gmix. The temperature dependence of the nanocrystalline grain size and interfacial solute excess can be obtained for selected ternary systems. As

  14. Benchmark studies of thermal jet mixing in SFRs using a two-jet model

    SciTech Connect

    Omotowa, O. A.; Skifton, R.; Tokuhiro, A.

    2012-07-01

    To guide the modeling, simulations and design of Sodium Fast Reactors (SFRs), we explore and compare the predictive capabilities of two numerical solvers COMSOL and OpenFOAM in the thermal jet mixing of two buoyant jets typical of the outlet flow from a SFR tube bundle. This process will help optimize on-going experimental efforts at obtaining high resolution data for V and V of CFD codes as anticipated in next generation nuclear systems. Using the k-{epsilon} turbulence models of both codes as reference, their ability to simulate the turbulence behavior in similar environments was first validated for single jet experimental data reported in literature. This study investigates the thermal mixing of two parallel jets having a temperature difference (hot-to-cold) {Delta}T{sub hc}= 5 deg. C, 10 deg. C and velocity ratios U{sub c}/U{sub h} = 0.5, 1. Results of the computed turbulent quantities due to convective mixing and the variations in flow field along the axial position are presented. In addition, this study also evaluates the effect of spacing ratio between jets in predicting the flow field and jet behavior in near and far fields. (authors)

  15. Modeling BOD removal in constructed wetlands with mixing cell method

    SciTech Connect

    Chen, S.; Wang, G.T.; Xue, S.K.

    1999-01-01

    A new concept, transport detention time, is proposed in this paper to describe solute-transport processes. Using this concept, a new mathematical model was developed to describe biochemical oxygen demand removal in constructed wetlands. By treating a constructed wetland as a series of continuous stir tank reactors, an nth-order ordinary differential equation was derived based on the principle of mass balance and convective-dispersive equation and by introducing transfer function and Laplace transform. The number of continuous stir tank reactors of a particular wetland was determined by the parameters, such as dispersion coefficient and flow velocity, occurring in the wetland. Two examples were presented to illustrate the applications of the model. Moment method and a combination of moment and optimization methods were used to estimate the model parameters from tracer experiment data. A comparison between the model presented in this paper and the currently used plug-flow-constructed wetland model indicated that the former was more accurate. Additionally, this model can be applied to transient conditions, is theoretically sound, and represents a theoretical advance in constructed wetland research.

  16. Concentration Addition, Independent Action and Generalized Concentration Addition Models for Mixture Effect Prediction of Sex Hormone Synthesis In Vitro

    PubMed Central

    Hadrup, Niels; Taxvig, Camilla; Pedersen, Mikael; Nellemann, Christine; Hass, Ulla; Vinggaard, Anne Marie

    2013-01-01

    Humans are concomitantly exposed to numerous chemicals. An infinite number of combinations and doses thereof can be imagined. For toxicological risk assessment the mathematical prediction of mixture effects, using knowledge on single chemicals, is therefore desirable. We investigated pros and cons of the concentration addition (CA), independent action (IA) and generalized concentration addition (GCA) models. First we measured effects of single chemicals and mixtures thereof on steroid synthesis in H295R cells. Then single chemical data were applied to the models; predictions of mixture effects were calculated and compared to the experimental mixture data. Mixture 1 contained environmental chemicals adjusted in ratio according to human exposure levels. Mixture 2 was a potency adjusted mixture containing five pesticides. Prediction of testosterone effects coincided with the experimental Mixture 1 data. In contrast, antagonism was observed for effects of Mixture 2 on this hormone. The mixtures contained chemicals exerting only limited maximal effects. This hampered prediction by the CA and IA models, whereas the GCA model could be used to predict a full dose response curve. Regarding effects on progesterone and estradiol, some chemicals were having stimulatory effects whereas others had inhibitory effects. The three models were not applicable in this situation and no predictions could be performed. Finally, the expected contributions of single chemicals to the mixture effects were calculated. Prochloraz was the predominant but not sole driver of the mixtures, suggesting that one chemical alone was not responsible for the mixture effects. In conclusion, the GCA model seemed to be superior to the CA and IA models for the prediction of testosterone effects. A situation with chemicals exerting opposing effects, for which the models could not be applied, was identified. In addition, the data indicate that in non-potency adjusted mixtures the effects cannot always be

  17. A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Jonsson, Lage Tord Ingemar; Tilliander, Anders; Cheng, Guoguang; Jönsson, Pär Göran

    2015-02-01

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD + WSD, KMD + KV, and KMD + WSD + KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i.e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace

  18. A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Jonsson, Lage Tord Ingemar; Tilliander, Anders; Cheng, Guoguang; Jönsson, Pär Göran

    2014-09-01

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD + WSD, KMD + KV, and KMD + WSD + KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i.e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace

  19. Modeling of CO2 solubility in single and mixed electrolyte solutions using statistical associating fluid theory

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Panagiotopoulos, Athanassios Z.; Economou, Ioannis G.

    2016-03-01

    Statistical associating fluid theory (SAFT) is used to model CO2 solubilities in single and mixed electrolyte solutions. The proposed SAFT model implements an improved mean spherical approximation in the primitive model to represent the electrostatic interactions between ions, using a parameter K to correct the excess energies ("KMSA" for short). With the KMSA formalism, the proposed model is able to describe accurately mean ionic activity coefficients and liquid densities of electrolyte solutions including Na+, K+, Ca2+, Mg2+, Cl-, Br- and SO42- from 298.15 K to 473.15 K using mostly temperature independent parameters, with sole exception being the volume of anions. CO2 is modeled as a non-associating molecule, and temperature-dependent CO2-H2O and CO2-ion cross interactions are used to obtain CO2 solubilities in H2O and in single ion electrolyte solutions. Without any additional fitting parameters, CO2 solubilities in mixed electrolyte solutions and synthetic brines are predicted, in good agreement with experimental measurements.

  20. An improved mixing model providing joint statistics of scalar and scalar dissipation

    SciTech Connect

    Meyer, Daniel W.; Jenny, Patrick

    2008-11-15

    For the calculation of nonpremixed turbulent flames with thin reaction zones the joint probability density function (PDF) of the mixture fraction and its dissipation rate plays an important role. The corresponding PDF transport equation involves a mixing model for the closure of the molecular mixing term. Here, the parameterized scalar profile (PSP) mixing model is extended to provide the required joint statistics. Model predictions are validated using direct numerical simulation (DNS) data of a passive scalar mixing in a statistically homogeneous turbulent flow. Comparisons between the DNS and the model predictions are provided, which involve different initial scalar-field lengthscales. (author)

  1. Genomic Heritability of Bovine Growth Using a Mixed Model

    PubMed Central

    Ryu, Jihye; Lee, Chaeyoung

    2014-01-01

    This study investigated heritability for bovine growth estimated with genomewide single nucleotide polymorphism (SNP) information obtained from a DNA microarray chip. Three hundred sixty seven Korean cattle were genotyped with the Illumina BovineSNP50 BeadChip, and 39,112 SNPs of 364 animals filtered by quality assurance were analyzed to estimate heritability of body weights at 6, 9, 12, 15, 18, 21, and 24 months of age. Restricted maximum likelihood estimate of heritability was obtained using covariance structure of genomic relationships among animals in a mixed model framework. Heritability estimates ranged from 0.58 to 0.76 for body weights at different ages. The heritability estimates using genomic information in this study were larger than those which had been estimated previously using pedigree information. The results revealed a trend that the heritability for body weight increased at a younger age (6 months). This suggests an early genetic evaluation for bovine growth using genomic information to increase genetic merits of animals. PMID:25358309

  2. The addition of algebraic turbulence modeling to program LAURA

    NASA Technical Reports Server (NTRS)

    Cheatwood, F. Mcneil; Thompson, R. A.

    1993-01-01

    The Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) is modified to allow the calculation of turbulent flows. This is accomplished using the Cebeci-Smith and Baldwin-Lomax eddy-viscosity models in conjunction with the thin-layer Navier-Stokes options of the program. Turbulent calculations can be performed for both perfect-gas and equilibrium flows. However, a requirement of the models is that the flow be attached. It is seen that for slender bodies, adequate resolution of the boundary-layer gradients may require more cells in the normal direction than a laminar solution, even when grid stretching is employed. Results for axisymmetric and three-dimensional flows are presented. Comparison with experimental data and other numerical results reveal generally good agreement, except in the regions of detached flow.

  3. Estimation of trends in rainfall extremes with mixed effects models

    NASA Astrophysics Data System (ADS)

    Kamruzzaman, M.; Beecham, S.; Metcalfe, A. V.

    2016-02-01

    Estimates of seasonal rainfall maxima at durations as short as 6 min are needed for many applications including the design and analysis of urban drainage systems. It is also important to investigate whether or not there is evidence of changes in these extremes, both as an indicator of the sensitivity of rainfall to anthropogenic and natural climate change and as an aid to the calibration of future scenarios. Estimation of trends in extreme values in a region needs to be based on all the available data if precision is to be achieved. However, extremes at different periods of accumulation at neighbouring sites are not independent because there are temporal and spatial correlations, respectively. A linear mixed effects (lme) model allows for this correlation structure, and can be fitted to unequal record lengths at different sites. The modelling technique is demonstrated with an analysis of monthly maximum rainfall, at nine aggregations between 6 min and 24 h, from six sites, with record lengths between 10 and 25 years, from a region in South Australia. In terms of mean value, there is no evidence of a trend or change in the seasonal distribution of the monthly extreme rainfall. However, there is a strong evidence of an increase in variability of monthly extreme rainfall, estimated as a 58% increase in absolute value of deviation from the mean over a 25 year period. Rainfall records are often only available as a daily accumulation. A formula for the ratio of the monthly maxima at durations shorter than 24 h, down to 6 min, to the 24 h monthly maximum, in terms of: duration, month of the year, and a site specific adjustment is estimated. There is a clear seasonal variation in the ratios and there is evidence of a difference between rainfall stations.

  4. Mixed-effects models for GAW18 longitudinal blood pressure data.

    PubMed

    Chung, Wonil; Zou, Fei

    2014-01-01

    In this paper, we propose two mixed-effects models for Genetic Analysis Workshop 18 (GAW18) longitudinal blood pressure data. The first method extends EMMA, an efficient mixed-model association-mapping algorithm. EMMA corrects for population structure and genetic relatedness using a kinship similarity matrix. We replace the kinship similarity matrix in EMMA with an estimated correlation matrix for modeling the dependence structure of repeated measurements. Our second approach is a Bayesian multiple association-mapping algorithm based on a mixed-effects model with a built-in variable selection feature. It models multiple single-nucleotide polymorphisms (SNPs) simultaneously and allows for SNP-SNP interactions and SNP-environment interactions. We applied these two methods to the longitudinal systolic blood pressure (SBP) and diastolic blood pressure (DBP) data from GAW18. The extended EMMA method identified a single SNP on Chr5:75506197 (p-value = 4.67 × 10(-7)) for SBP and three SNPs on Chr3:23715851 (p-value = 9.00 × 10(-8)), Chr 17:54834217 (p-value = 1.98 × 10(-7)), and Chr21:18744081 (p-value = 4.95 × 10(-7)) for DBP. The Bayesian method identified several additional SNPs on Chr1:17876090 (Bayes factor [BF] = 102), Chr3:197469358 (BF = 69), Chr15:87675666 (BF = 43), and Chr19:41642807 (BF = 33) for SBP. Furthermore, for SBP, we found a single SNP on Chr3:197469358 (BF = 69) that has a strong interaction with age. We further evaluated the performances of the proposed methods by simulations. PMID:25519345

  5. The Development of Mathematical Prediction Model to Predict Resilient Modulus for Natural Soil Stabilized by Pofa-Opc Additive for the Use in Unpaved Road Design

    NASA Astrophysics Data System (ADS)

    Gamil, Y. M. R.; Bakar, I. H.

    2016-07-01

    Resilient Modulus (Mr) is considered one of the most important parameters in the design of road structure. This paper describes the development of the mathematical model to predict resilient modulus of organic soil stabilized by the mix of Palm Oil Fuel Ash - Ordinary Portland Cement (POFA-OPC) soil stabilization additives. It aims to optimize the use of the use of POFA in soil stabilization. The optimization models enable to eliminate the arbitrary selection and its associated disadvantages in determination of the optimum additive proportion. The model was developed based on Scheffe regression theory. The mix proportions of the samples in the experiment were adopted from similar studies reported in the literature Twenty five samples were designed, prepared and then characterized for each mix proportion based on the MR in 28 days curing. The results are used to develop the mathematical prediction model. The model was statistically analyzed and verified for its adequacy and validity using F-test.

  6. Modeling of mixing processes: Fluids, particulates, and powders

    SciTech Connect

    Ottino, J.M.; Hansen, S.

    1995-12-31

    Work under this grant involves two main areas: (1) Mixing of Viscous Liquids, this first area comprising aggregation, fragmentation and dispersion, and (2) Mixing of Powders. In order to produce a coherent self-contained picture, we report primarily on results obtained under (1), and within this area, mostly on computational studies of particle aggregation in regular and chaotic flows. Numerical simulations show that the average cluster size of compact clusters grows algebraically, while the average cluster size of fractal clusters grows exponentially; companion mathematical arguments are used to describe the initial growth of average cluster size and polydispersity. It is found that when the system is well mixed and the capture radius independent of mass, the polydispersity is constant for long-times and the cluster size distribution is self-similar. Furthermore, our simulations indicate that the fractal nature of the clusters is dependent upon the mixing.

  7. Computer modeling of forced mixing in waste storage tanks

    SciTech Connect

    Eyler, L.L.; Michener, T.E.

    1992-04-01

    Numerical simulation results of fluid dynamic and physical processes in radioactive waste storage tanks are presented. Investigations include simulation of jet mixing pump induced flows intended to mix and maintain particulate material uniformly distributed throughout the liquid volume. Physical effects of solids are included in the code. These are particle size through a settling velocity and mixture properties through density and viscosity. Calculations have been accomplished for a centrally located, rotationally-oscillating, horizontally-directed jet mixing pump for two cases. One case is with low jet velocity and high settling velocity. It results in nonuniform distribution. The other case is with high jet velocity and low settling velocity. It results in uniform conditions. Results are being used to aid in experiment design and to understand mixing in the waste tanks. These results are to be used in conjunction with scaled experiments to define limits of pump operation to maintain uniformity of the mixture in the storage tanks during waste retrieval operations.

  8. Software reliability: Additional investigations into modeling with replicated experiments

    NASA Technical Reports Server (NTRS)

    Nagel, P. M.; Schotz, F. M.; Skirvan, J. A.

    1984-01-01

    The effects of programmer experience level, different program usage distributions, and programming languages are explored. All these factors affect performance, and some tentative relational hypotheses are presented. An analytic framework for replicated and non-replicated (traditional) software experiments is presented. A method of obtaining an upper bound on the error rate of the next error is proposed. The method was validated empirically by comparing forecasts with actual data. In all 14 cases the bound exceeded the observed parameter, albeit somewhat conservatively. Two other forecasting methods are proposed and compared to observed results. Although demonstrated relative to this framework that stages are neither independent nor exponentially distributed, empirical estimates show that the exponential assumption is nearly valid for all but the extreme tails of the distribution. Except for the dependence in the stage probabilities, Cox's model approximates to a degree what is being observed.

  9. Mixed model approaches for the identification of QTLs within a maize hybrid breeding program.

    PubMed

    van Eeuwijk, Fred A; Boer, Martin; Totir, L Radu; Bink, Marco; Wright, Deanne; Winkler, Christopher R; Podlich, Dean; Boldman, Keith; Baumgarten, Andy; Smalley, Matt; Arbelbide, Martin; ter Braak, Cajo J F; Cooper, Mark

    2010-01-01

    Two outlines for mixed model based approaches to quantitative trait locus (QTL) mapping in existing maize hybrid selection programs are presented: a restricted maximum likelihood (REML) and a Bayesian Markov Chain Monte Carlo (MCMC) approach. The methods use the in-silico-mapping procedure developed by Parisseaux and Bernardo (2004) as a starting point. The original single-point approach is extended to a multi-point approach that facilitates interval mapping procedures. For computational and conceptual reasons, we partition the full set of relationships from founders to parents of hybrids into two types of relations by defining so-called intermediate founders. QTL effects are defined in terms of those intermediate founders. Marker based identity by descent relationships between intermediate founders define structuring matrices for the QTL effects that change along the genome. The dimension of the vector of QTL effects is reduced by the fact that there are fewer intermediate founders than parents. Furthermore, additional reduction in the number of QTL effects follows from the identification of founder groups by various algorithms. As a result, we obtain a powerful mixed model based statistical framework to identify QTLs in genetic backgrounds relevant to the elite germplasm of a commercial breeding program. The identification of such QTLs will provide the foundation for effective marker assisted and genome wide selection strategies. Analyses of an example data set show that QTLs are primarily identified in different heterotic groups and point to complementation of additive QTL effects as an important factor in hybrid performance. PMID:19921142

  10. Fermion masses and mixings from heterotic orbifold models

    SciTech Connect

    Park, Jae-hyeon

    2005-12-02

    We search for a possibility of getting realistic fermion mass ratios and mixing angles from renormalizable couplings on the Z6-I heterotic orbifold with one pair of Higgs doublets. In the quark sector, we find cases with reasonable results if we ignore the first family. In the lepton sector, we can fit the charged lepton mass ratios, the neutrino mass squared difference ratio, and the lepton mixing angles, considering all three families00.

  11. Three-dimensional modeling of the mixing state of particles over Greater Paris

    NASA Astrophysics Data System (ADS)

    Zhu, Shupeng; Sartelet, Karine; Zhang, Yang; Nenes, Athanasios

    2016-05-01

    A size-composition resolved aerosol model (SCRAM) is coupled to the Polyphemus air quality platform and evaluated over Greater Paris. SCRAM simulates the particle mixing state and solves the aerosol dynamic evolution taking into account the processes of coagulation, condensation/evaporation, and nucleation. Both the size and mass fractions of chemical components of particles are discretized. The performance of SCRAM to model air quality over Greater Paris is evaluated by comparison to PM2.5, PM10, and Aerosol Optical Depth (AOD) measurements. Because air quality models usually assume that particles are internally mixed, the impact of the mixing state on aerosols formation, composition, optical properties, and their ability to be activated as cloud condensation nuclei (CCN) is investigated. The simulation results show that more than half (up to 80% during rush hours) of black carbon particles are barely mixed at the urban site of Paris, while they are more mixed with organic species at a rural site. The comparisons between the internal-mixing simulation and the mixing state-resolved simulation show that the internal-mixing assumption leads to lower nitrate and higher ammonium concentrations in the particulate phase. Moreover, the internal-mixing assumption leads to lower single scattering albedo, and the difference of aerosol optical depth caused by the mixing state assumption can be as high as 72.5%. Furthermore, the internal-mixing assumption leads to lower CCN activation percentage at low supersaturation, but higher CCN activation percentage at high supersaturation.

  12. A model of the holographic principle: Randomness and additional dimension

    NASA Astrophysics Data System (ADS)

    Boyarsky, Abraham; Góra, Paweł; Proppe, Harald

    2010-01-01

    In recent years an idea has emerged that a system in a 3-dimensional space can be described from an information point of view by a system on its 2-dimensional boundary. This mysterious correspondence is called the Holographic Principle and has had profound effects in string theory and our perception of space-time. In this note we describe a purely mathematical model of the Holographic Principle using ideas from nonlinear dynamical systems theory. We show that a random map on the surface S of a 3-dimensional open ball B has a natural counterpart in B, and the two maps acting in different dimensional spaces have the same entropy. We can reverse this construction if we start with a special 3-dimensional map in B called a skew product. The key idea is to use the randomness, as imbedded in the parameter of the 2-dimensional random map, to define a third dimension. The main result shows that if we start with an arbitrary dynamical system in B with entropy E we can construct a random map on S whose entropy is arbitrarily close to E.

  13. Additional Developments in Atmosphere Revitalization Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Coker, Robert F.; Knox, James C.; Cummings, Ramona; Brooks, Thomas; Schunk, Richard G.

    2013-01-01

    NASA's Advanced Exploration Systems (AES) program is developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit. These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by evaluating structured sorbents, seeking more robust pelletized sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach. This paper describes the continuing development of atmosphere revitalization models and simulations in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM)

  14. Additional Developments in Atmosphere Revitalization Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Coker, Robert F.; Knox, James C.; Cummings, Ramona; Brooks, Thomas; Schunk, Richard G.; Gomez, Carlos

    2013-01-01

    NASA's Advanced Exploration Systems (AES) program is developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit. These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by evaluating structured sorbents, seeking more robust pelletized sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach. This paper describes the continuing development of atmosphere revitalization models and simulations in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project within the AES program.

  15. Modelling Coral Biomineralization: Mixed Kinetic/Equilibrium Trace Element Coprecipitation Models Reveal new Complexity

    NASA Astrophysics Data System (ADS)

    Sinclair, D. J.; Risk, M.

    2004-12-01

    A mixed kinetic/equilibrium steady state model of trace-element co-precipitation in coral skeleton is presented, and tested against high spatial resolution observations of coral trace-element composition made previously by LA-ICP-MS. The model is implemented in PHREEQC, and simulates physicochemical precipitation from a small pocket of seawater which is isolated by the coral, and modified by enzyme exchange of 2 H+ for Ca2+. The model assumes that all aqueous trace-element species in the calcifying fluid are in full equilibrium and that selected trace element species compete kinetically for precipitation with the major aqueous species (Ca2+ for cation substituents and CO32- for anion substituents). No equilibrium is assumed for the CaCO3 skeleton. Carbon is supplied to the system by diffusion of CO2 into the high-pH calcifying fluid, and trace elements are continuously replenished through the addition of fresh seawater. The rate at which the coral operates the enzyme pump, and the rate at which it replenishes the seawater component are independent variables, and the steady state trace-element composition of the skeleton/calcifying fluid are evaluated over a 2D grid of variables spanning realistic rates of pumping and seawater influx. It is assumed that variations in the trace element composition of the coral skeleton are the result of shifts in the steady-state caused by changes to these variables. The results indicate an unexpected complexity in the response of the trace elements. First order predictions suggest that increasing the rate of calcification by increasing the enzyme pumping should result in a mutual dilution of most trace element species by pumped Ca2+ and diffused CO2. However, for high rates of pumping and low seawater replenishment, the model predicts a change in the trace-element response of the system as high CO32- concentrations drive calcification and deplete Ca2+. This added complexity makes rationalizing observations with models more difficult.

  16. The Vineyard Yeast Microbiome, a Mixed Model Microbial Map

    PubMed Central

    Setati, Mathabatha Evodia; Jacobson, Daniel; Andong, Ursula-Claire; Bauer, Florian

    2012-01-01

    Vineyards harbour a wide variety of microorganisms that play a pivotal role in pre- and post-harvest grape quality and will contribute significantly to the final aromatic properties of wine. The aim of the current study was to investigate the spatial distribution of microbial communities within and between individual vineyard management units. For the first time in such a study, we applied the Theory of Sampling (TOS) to sample gapes from adjacent and well established commercial vineyards within the same terroir unit and from several sampling points within each individual vineyard. Cultivation-based and molecular data sets were generated to capture the spatial heterogeneity in microbial populations within and between vineyards and analysed with novel mixed-model networks, which combine sample correlations and microbial community distribution probabilities. The data demonstrate that farming systems have a significant impact on fungal diversity but more importantly that there is significant species heterogeneity between samples in the same vineyard. Cultivation-based methods confirmed that while the same oxidative yeast species dominated in all vineyards, the least treated vineyard displayed significantly higher species richness, including many yeasts with biocontrol potential. The cultivatable yeast population was not fully representative of the more complex populations seen with molecular methods, and only the molecular data allowed discrimination amongst farming practices with multivariate and network analysis methods. Importantly, yeast species distribution is subject to significant intra-vineyard spatial fluctuations and the frequently reported heterogeneity of tank samples of grapes harvested from single vineyards at the same stage of ripeness might therefore, at least in part, be due to the differing microbiota in different sections of the vineyard. PMID:23300721

  17. An uncertainty inclusive un-mixing model to identify tracer non-conservativeness

    NASA Astrophysics Data System (ADS)

    Sherriff, Sophie; Rowan, John; Franks, Stewart; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

    2015-04-01

    Sediment fingerprinting is being increasingly recognised as an essential tool for catchment soil and water management. Selected physico-chemical properties (tracers) of soils and river sediments are used in a statistically-based 'un-mixing' model to apportion sediment delivered to the catchment outlet (target) to its upstream sediment sources. Development of uncertainty-inclusive approaches, taking into account uncertainties in the sampling, measurement and statistical un-mixing, are improving the robustness of results. However, methodological challenges remain including issues of particle size and organic matter selectivity and non-conservative behaviour of tracers - relating to biogeochemical transformations along the transport pathway. This study builds on our earlier uncertainty-inclusive approach (FR2000) to detect and assess the impact of tracer non-conservativeness using synthetic data before applying these lessons to new field data from Ireland. Un-mixing was conducted on 'pristine' and 'corrupted' synthetic datasets containing three to fifty tracers (in the corrupted dataset one target tracer value was manually corrupted to replicate non-conservative behaviour). Additionally, a smaller corrupted dataset was un-mixed using a permutation version of the algorithm. Field data was collected in an 11 km2 river catchment in Ireland. Source samples were collected from topsoils, subsoils, channel banks, open field drains, damaged road verges and farm tracks. Target samples were collected using time integrated suspended sediment samplers at the catchment outlet at 6-12 week intervals from July 2012 to June 2013. Samples were dried (<40°C), sieved (125 µm) and analysed for mineral magnetic susceptibility, anhysteretic remanence and iso-thermal remanence, and geochemical elements Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn (following microwave-assisted acid digestion). Discriminant analysis was used to reduce the number of tracer numbers before un-mixing. Tracer non

  18. Modeling Scalar variance from Direct Numerical Simulations of a turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Ravinel, Baptiste; Blanquart, Guillaume

    2010-11-01

    Many studies have focused on analyzing and predicting the mixing of a scalar such as fuel concentration in turbulent flows. However, the subfilter scalar variance in Large Eddy Simulations (LES) still requires additional considerations. The present work aims at obtaining results for the turbulent mixture of a scalar in configurations relevant to reactive flows, i.e. in the presence of mean velocity/scalar gradients. A Direct Numerical Simulation (DNS) of a turbulent mixing layer has been performed by initially combining two boundary layers. The high order conservative finite difference low Mach number NGA code was used together with the BQuick scheme for the transport of mixture fraction. The self-similar nature of the flow and energy spectra have been considered to analyze the turbulent flow field. High order velocity schemes (4th order) were found to play an important role in capturing accurately the mixing of fuel and air. The scalar variance has been calculated by filtering the solution and has been compared to various models usually used in LES. Following an earlier study by Balarac et al. [Phys. Fluids 20 (2008)], the concept of optimal estimators has been considered to identify the set of parameters most suitable to express the subfilter variance. Finally, the quality of the standard dynamic approach has been assessed.

  19. A Proposed Model of Retransformed Qualitative Data within a Mixed Methods Research Design

    ERIC Educational Resources Information Center

    Palladino, John M.

    2009-01-01

    Most models of mixed methods research design provide equal emphasis of qualitative and quantitative data analyses and interpretation. Other models stress one method more than the other. The present article is a discourse about the investigator's decision to employ a mixed method design to examine special education teachers' advocacy and…

  20. CONVERTING ISOTOPE RATIOS TO DIET COMPOSITION - THE USE OF MIXING MODELS

    EPA Science Inventory

    Investigations of wildlife foraging ecology with stable isotope analysis are increasing. Converting isotope values to proportions of different foods in a consumer's diet requires the use of mixing models. Simple mixing models based on mass balance equations have been used for d...

  1. Best practices for use of stable isotope mixing models in food-web studies

    EPA Science Inventory

    Stable isotope mixing models are increasingly used to quantify contributions of resources to consumers. While potentially powerful tools, these mixing models have the potential to be misused, abused, and misinterpreted. Here we draw on our collective experiences to address the qu...

  2. Item Purification in Differential Item Functioning Using Generalized Linear Mixed Models

    ERIC Educational Resources Information Center

    Liu, Qian

    2011-01-01

    For this dissertation, four item purification procedures were implemented onto the generalized linear mixed model for differential item functioning (DIF) analysis, and the performance of these item purification procedures was investigated through a series of simulations. Among the four procedures, forward and generalized linear mixed model (GLMM)…

  3. Transferability of regional permafrost disturbance susceptibility modelling using generalized linear and generalized additive models

    NASA Astrophysics Data System (ADS)

    Rudy, Ashley C. A.; Lamoureux, Scott F.; Treitz, Paul; van Ewijk, Karin Y.

    2016-07-01

    To effectively assess and mitigate risk of permafrost disturbance, disturbance-prone areas can be predicted through the application of susceptibility models. In this study we developed regional susceptibility models for permafrost disturbances using a field disturbance inventory to test the transferability of the model to a broader region in the Canadian High Arctic. Resulting maps of susceptibility were then used to explore the effect of terrain variables on the occurrence of disturbances within this region. To account for a large range of landscape characteristics, the model was calibrated using two locations: Sabine Peninsula, Melville Island, NU, and Fosheim Peninsula, Ellesmere Island, NU. Spatial patterns of disturbance were predicted with a generalized linear model (GLM) and generalized additive model (GAM), each calibrated using disturbed and randomized undisturbed locations from both locations and GIS-derived terrain predictor variables including slope, potential incoming solar radiation, wetness index, topographic position index, elevation, and distance to water. Each model was validated for the Sabine and Fosheim Peninsulas using independent data sets while the transferability of the model to an independent site was assessed at Cape Bounty, Melville Island, NU. The regional GLM and GAM validated well for both calibration sites (Sabine and Fosheim) with the area under the receiver operating curves (AUROC) > 0.79. Both models were applied directly to Cape Bounty without calibration and validated equally with AUROC's of 0.76; however, each model predicted disturbed and undisturbed samples differently. Additionally, the sensitivity of the transferred model was assessed using data sets with different sample sizes. Results indicated that models based on larger sample sizes transferred more consistently and captured the variability within the terrain attributes in the respective study areas. Terrain attributes associated with the initiation of disturbances were

  4. Deviations from tribimaximal mixing due to the vacuum expectation value misalignment in A{sub 4} models

    SciTech Connect

    Barry, James; Rodejohann, Werner

    2010-05-01

    The addition of an A{sub 4} family symmetry and extended Higgs sector to the standard model can generate the tribimaximal mixing pattern for leptons, assuming the correct vacuum expectation value alignment of the Higgs scalars. Deviating this alignment affects the predictions for the neutrino oscillation and neutrino mass observables. An attempt is made to classify the plethora of models in the literature, with respect to the chosen A{sub 4} particle assignments. Of these models, two particularly popular examples have been analyzed for deviations from tribimaximal mixing by perturbing the vacuum expectation value alignments. The effect of perturbations on the mixing angle observables is studied. However, it is only investigation of the mass-related observables (the effective mass for neutrinoless double beta decay and the sum of masses from cosmology) that can lead to the exclusion of particular models by constraints from future data, which indicates the importance of neutrino mass in disentangling models. The models have also been tested for fine-tuning of the parameters. Furthermore, a well-known seesaw model is generalized to include additional scalars, which transform as representations of A{sub 4} not included in the original model.

  5. Inverse modeling of the global CO cycle, 1. Inversion of CO mixing ratios

    NASA Astrophysics Data System (ADS)

    Bergamaschi, Peter; Hein, Ralf; Heimann, Martin; Crutzen, Paul J.

    2000-01-01

    A three-dimensional modeling study on atmospheric carbon monoxide is presented, based on the TM2 model. A Bayesian inverse technique is applied to optimize the agreement between model and observational data, including a priori source information as regularization term. Using the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory data set for CO mixing ratios at 31 globally distributed sites, a posteriori CO budgets can be derived, which allow the model to reproduce the observations at most sites within two standard deviations of monthly mean values. Use of different spatiotemporal emission distributions for terpenes (Global Emissions Inventory Activity, ˜80% of emissions in the tropics; Hough [1991], ˜70% of emissions in the extratropical Northern Hemisphere) showed a large impact on calculated a posteriori source strengths and on the modeled partitioning among individual CO sources. In order to reproduce the interhemispheric gradient of observed CO mixing ratios, a ratio between total sources in the Northern Hemisphere and those in the Southern Hemisphere of ˜1.8 is required. While it is obvious that this asymmetry is mainly due to CO emissions from technological sources, the inversion results suggest that either (1) the global technological CO source strength is higher (˜800 Tg CO/yr) than present inventory based estimates or (2) CO from terpenes or vegetation (or additional sources with dominant emissions in the Northern Hemisphere) have a significant impact on the northern hemispheric mixing ratios. Further sensitivity studies showed that a posteriori results slightly depend on biomass burning seasonality (shifted by 1 month), but they are virtually identical for the two different OH fields (CH4-nonmethanehydrocarbons chemistry vs. CH4-Only chemistry). Inversion results, however, were sensitive to model wind fields used (based on meteorological observations of 1987 and 1986, respectively), mainly due to stations

  6. Application of mixing-controlled combustion models to gas turbine combustors

    NASA Technical Reports Server (NTRS)

    Nguyen, Hung Lee

    1990-01-01

    Gas emissions were studied from a staged Rich Burn/Quick-Quench Mix/Lean Burn combustor were studied under test conditions encountered in High Speed Research engines. The combustor was modeled at conditions corresponding to different engine power settings, and the effect of primary dilution airflow split on emissions, flow field, flame size and shape, and combustion intensity, as well as mixing, was investigated. A mathematical model was developed from a two-equation model of turbulence, a quasi-global kinetics mechanism for the oxidation of propane, and the Zeldovich mechanism for nitric oxide formation. A mixing-controlled combustion model was used to account for turbulent mixing effects on the chemical reaction rate. This model assumes that the chemical reaction rate is much faster than the turbulent mixing rate.

  7. A time-dependent Mixing Model for PDF Methods in Heterogeneous Aquifers

    NASA Astrophysics Data System (ADS)

    Schüler, Lennart; Suciu, Nicolae; Knabner, Peter; Attinger, Sabine

    2016-04-01

    Predicting the transport of groundwater contaminations remains a demanding task, especially with respect to the heterogeneity of the subsurface and the large measurement uncertainties. A risk analysis also includes the quantification of the uncertainty in order to evaluate how accurate the predictions are. Probability density function (PDF) methods are a promising alternative to predicting the transport of solutes in groundwater under uncertainty. They make it possible to derive the evolution equations of the mean concentration and the concentration variance, which can be used as a first measure of uncertainty. A mixing model, also known as a dissipation model, is essential for both methods. Finding a satisfactory mixing model is still an open question and due to the rather elaborate PDF methods, a difficult undertaking. Both the PDF equation and the concentration variance equation depend on the same mixing model. This connection is used to find and test an improved mixing model for the much easier to handle concentration variance. Subsequently, this mixing model is transferred to the PDF equation and tested. The newly proposed mixing model yields significantly improved results for both variance modelling and PDF modelling. The implications of the new mixing model for different kinds of flow conditions are discussed and some comments are made on efficiently handling spatially resolved higher moments.

  8. Multiple jet mixing flowfields in an isothermal model combustor

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Schulz, R. J.; Giel, T. V., Jr.

    1986-01-01

    The purpose of the present experimental investigation of confined, multiple turbulent jet-mixing with recirculation, in an axisymmetric duct that simulated a combustor, was the examination of flow fields that employ injector plates for the mixing of fuels and oxidizers. Quantitative descriptions of the velocity and turbulence fields were obtained with a vectorized, two-component laser Doppler velocimeter. The results obtained indicate that the annular slit injector jet generates a two-dimensional combustor flow that is in accord with theoretical studies, although rings of discrete injector jets create very complex, fully three-dimensional combustor flow fields.

  9. Quantum theory of multiwave mixing - Squeezed-vacuum model

    NASA Astrophysics Data System (ADS)

    An, Sunghyuck; Sargent, Murray, III

    1989-12-01

    The present paper combines a Langevin quantum-regression method with a denisty-operator approach to derive the master equation for the quantum theory of multiwave mixing in a very efficient way. The approach is quite general and is particularly valuable for analyzing complicated media such as semiconductors. It is used in the present paper to derive the quantum multiwave-mixing equations in a squeezed vacuum. Improved formulas are found for resonance fluorescence in a squeezed vacuum as well as the squeezing coefficients in a squeezed vacuum. Comparing squeezing spectra in squeezed and ordinary vacuums, significantly enhanced squeezing for the appropriate pump-vacuum relative phase is found.

  10. Probabilistic performance-assessment modeling of the mixed waste landfill at Sandia National Laboratories.

    SciTech Connect

    Peace, Gerald L.; Goering, Timothy James; Miller, Mark Laverne; Ho, Clifford Kuofei

    2007-01-01

    A probabilistic performance assessment has been conducted to evaluate the fate and transport of radionuclides (americium-241, cesium-137, cobalt-60, plutonium-238, plutonium-239, radium-226, radon-222, strontium-90, thorium-232, tritium, uranium-238), heavy metals (lead and cadmium), and volatile organic compounds (VOCs) at the Mixed Waste Landfill (MWL). Probabilistic analyses were performed to quantify uncertainties inherent in the system and models for a 1,000-year period, and sensitivity analyses were performed to identify parameters and processes that were most important to the simulated performance metrics. Comparisons between simulated results and measured values at the MWL were made to gain confidence in the models and perform calibrations when data were available. In addition, long-term monitoring requirements and triggers were recommended based on the results of the quantified uncertainty and sensitivity analyses.

  11. Prediction of microbial growth in mixed culture with a competition model.

    PubMed

    Fujikawa, Hiroshi; Sakha, Mohammad Z

    2014-01-01

    Prediction of microbial growth in mixed culture was studied with a competition model that we had developed recently. The model, which is composed of the new logistic model and the Lotka-Volterra model, is shown to successfully describe the microbial growth of two species in mixed culture using Staphylococcus aureus, Escherichia coli, and Salmonella. With the parameter values of the model obtained from the experimental data on monoculture and mixed culture with two species, it then succeeded in predicting the simultaneous growth of the three species in mixed culture inoculated with various cell concentrations. To our knowledge, it is the first time for a prediction model for multiple (three) microbial species to be reported. The model, which is not built on any premise for specific microorganisms, may become a basic competition model for microorganisms in food and food materials. PMID:24975413

  12. Mixed boundary conditions versus coupling with an energy-moisture balance model for a zonally averaged ocean climate model

    SciTech Connect

    Bjornsson, H.; Mysak, L.A.; Schmidt, G.A.

    1997-10-01

    The Wright and Stocker oceanic thermohaline circulation model is coupled to a recently developed zonally averaged energy moisture balance model for the atmosphere. The results obtained with this coupled model are compared with those from an ocean-only model that employs mixed boundary conditions. The ocean model geometry uses either one zonally averaged interhemispheric basin (the {open_quotes}Atlantic{close_quotes}) or two zonally averaged basins (roughly approximating the Atlantic and the Pacific Oceans) connected by a parameterized Antarctic Circumpolar Current. The differences in the steady states and their linear stability are examined over a wide range of parameters. The presence of additional feedbacks between the ocean circulation and the atmosphere and hydrological cycle in the coupled model produces significant differences between the latter and the ocean-only model, in both the one-basin and two-basin geometries. The authors conclude that due to the effects produced by the feedbacks in the coupled model, they must have serious reservations about the results concerning long-term climate variability obtained from ocean-only models. Thus, to investigate long-term climatic variability a coupled model is necessary. 31 refs., 15 figs., 7 tabs.

  13. Taxonomy Of Magma Mixing I: Magma Mixing Metrics And The Thermochemistry Of Magma Hybridization Illuminated With A Toy Model

    NASA Astrophysics Data System (ADS)

    Spera, F. J.; Bohrson, W. A.; Schmidt, J.

    2013-12-01

    The rock record preserves abundant evidence of magma mixing in the form of mafic enclaves and mixed pumice in volcanic eruptions, syn-plutonic mafic or silicic dikes and intrusive complexes, replenishment events recorded in cumulates from layered intrusions, and crystal scale heterogeneity in phenocrysts and cumulate minerals. These evidently show that magma mixing in conjunction with crystallization (perfect fractional or incremental batch) is a first-order petrogenetic process. Magma mixing (sensu lato) occurs across a spectrum of mixed states from magma mingling to complete blending. The degree of mixing is quantified (Oldenburg et al, 1989) using two measures: the statistics of the segregation length scales (scale of segregation, L*) and the spatial contrast in composition (C) relative to the mean C (intensity of segregation, I). Mingling of dissimilar magmas produces a heterogeneous mixture containing discrete regions of end member melts and populations of crystals with L* = finite and I > 0. When L*→∞ and I→0 , the mixing magmas become hybridized and can be studied thermodynamically. Such hybrid magma is a multiphase equilibrium mixture of homogeneous melt, unzoned crystals and possible bubbles of a supercritical fluid. Here, we use a toy model to elucidate the principles of magma hybridization in a binary system (components A and B with pure crystals of α or β phase) with simple thermodynamics to build an outcome taxonomy. This binary system is not unlike the system Anorthite-Diopside, the classic low-pressure model basalt system. In the toy model, there are seven parameters describing the phase equilibria (eutectic T and X, specific heat, melting T and fusion enthalpies of α and β crystals) and five variables describing the magma mixing conditions: end member bulk compositions, temperatures and fraction of resident magma (M) that blends with recharge (R) magma to form a single equilibrium hybrid magma. There are 24 possible initial states when M

  14. Mixed model of repeated measures versus slope models in Alzheimer's disease clinical trials.

    PubMed

    Donohue, M C; Aisen, P S

    2012-04-01

    Randomized clinical trials of Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI) typically assess intervention efficacy with measures of cognitive or functional assessments repeated every six months for one to two years. The Mixed Model of Repeated Measures (MMRM), which assumes an "unstructured mean" by treating time as categorical, is attractive because it makes no assumptions about the shape of the mean trajectory of the outcome over time. However, categorical time models may be over-parameterized and inefficient in detecting treatment effects relative to continuous time models of, say, the linear trend of the outcome over time. Mixed effects models can also be extended to model quadratic time effects, although it is questionable whether the duration and interval of observations in AD and MCI studies is sufficient to support such models. Furthermore, it is unknown which of these models are most robust to missing data, which plagues AD and MCI studies. We review the literature and compare estimates of treatment effects from four potential models fit to data from five AD Cooperative Study (ADCS) trials in MCI and AD. PMID:22499459

  15. Comparative analysis of some models of gene regulation in mixed-substrate microbial growth.

    PubMed

    Narang, Atul

    2006-09-21

    Mixed-substrate microbial growth is of fundamental interest in microbiology and bioengineering. Several mathematical models have been developed to account for the genetic regulation of such systems, especially those resulting in diauxic growth. In this work, we compare the dynamics of three such models (Narang, 1998a. The dynamical analogy between microbial growth on mixtures of substrates and population growth of competing species. Biotechnol. Bioeng. 59, 116-121; Thattai and Shraiman, 2003. Metabolic switching in the sugar phosphotransferase system of Escherichia coli. Biophys. J. 85(2), 744-754; Brandt et al., 2004. Modelling microbial adaptation to changing availability of substrates. Water Res. 38, 1004-1013). We show that these models are dynamically similar--the initial motion of the inducible enzymes in all the models is described by the Lotka-Volterra equations for competing species. In particular, the prediction of diauxic growth corresponds to "extinction" of one of the enzymes during the first few hours of growth. The dynamic similarity occurs because in all the models, the inducible enzymes possess properties characteristic of competing species: they are required for their own synthesis, and they inhibit each other. Despite this dynamic similarity, the models vary with respect to the range of dynamics captured. The Brandt et al. model always predicts the diauxic growth pattern, whereas the remaining two models exhibit both diauxic and non-diauxic growth patterns. The models also differ with respect to the mechanisms that generate the mutual inhibition between the enzymes. In the Narang model, mutual inhibition occurs because the enzymes for each substrate enhance the dilution of the enzymes for the other substrate. The Brandt et al. model superimposes upon this dilution effect an additional mechanism of mutual inhibition. In the Thattai and Shraiman model, the mutual inhibition is entirely due to competition for the phosphoryl groups. For quantitative

  16. Estimating water quality using linear mixed models with stream discharge and turbidity

    NASA Astrophysics Data System (ADS)

    Lessels, J. S.; Bishop, T. F. A.

    2013-08-01

    Most water quality monitoring schemes rely on estimation methods as it is often far too expensive to monitor water quality properties continuously. Estimations are used to evaluate management strategies and long term trends. It is critical that the estimation methods provide accurate estimations and an accurate estimate of the associated uncertainty. Currently the most common estimation methods assume observations are sampled using a probabilistic sampling scheme, however this assumption is often not met. This paper evaluated the ability of a linear mixed model to estimate water quality concentration values based on observations collected using non-probabilistic sampling. The linear mixed models were used to predict total phosphorus and total nitrogen observations from two catchments in south east Australia. A comparison between stream discharge and turbidity as predictors is made to investigate the effectiveness of turbidity to estimate water quality. In addition to stream discharge and turbidity, several covariates were derived from stream discharge in an attempt to account for hydrological processes. To compare models and their covariates leave one out event cross validation was performed. Event cross validation evaluated predictions during periods of high stream discharge. The inclusion of temporal auto-correlation component improved the accuracy of all models for total phosphorus and total nitrogen. For both catchments the use of turbidity instead of stream discharge increased the accuracy of predictions by at least 15% for total phosphorus and total nitrogen. However, event based cross validation indicated that a combination of both turbidity and stream discharge based variables provided more accurate predictions, decreasing the event RMSE by 18% for total phosphorus and 24% for total nitrogen. In catchments characterised by long periods of base-flow and short rainfall events the addition of turbidity measurements provide more accurate predictions during base

  17. Modeling the cardiovascular system using a nonlinear additive autoregressive model with exogenous input

    NASA Astrophysics Data System (ADS)

    Riedl, M.; Suhrbier, A.; Malberg, H.; Penzel, T.; Bretthauer, G.; Kurths, J.; Wessel, N.

    2008-07-01

    The parameters of heart rate variability and blood pressure variability have proved to be useful analytical tools in cardiovascular physics and medicine. Model-based analysis of these variabilities additionally leads to new prognostic information about mechanisms behind regulations in the cardiovascular system. In this paper, we analyze the complex interaction between heart rate, systolic blood pressure, and respiration by nonparametric fitted nonlinear additive autoregressive models with external inputs. Therefore, we consider measurements of healthy persons and patients suffering from obstructive sleep apnea syndrome (OSAS), with and without hypertension. It is shown that the proposed nonlinear models are capable of describing short-term fluctuations in heart rate as well as systolic blood pressure significantly better than similar linear ones, which confirms the assumption of nonlinear controlled heart rate and blood pressure. Furthermore, the comparison of the nonlinear and linear approaches reveals that the heart rate and blood pressure variability in healthy subjects is caused by a higher level of noise as well as nonlinearity than in patients suffering from OSAS. The residue analysis points at a further source of heart rate and blood pressure variability in healthy subjects, in addition to heart rate, systolic blood pressure, and respiration. Comparison of the nonlinear models within and among the different groups of subjects suggests the ability to discriminate the cohorts that could lead to a stratification of hypertension risk in OSAS patients.

  18. MEASUREMENTS AND MODELS FOR HAZARDOUS CHEMICAL AND MIXED WASTES

    EPA Science Inventory

    Mixed hazardous and low-level radioactive wastes are in storage at DOE sites around the United States, awaiting treatment and disposal. These hazardous chemical wastes contain many components in multiple phases, presenting very difficult handling and treatment problems. These was...

  19. Segregation parameters and pair-exchange mixing models for turbulent nonpremixed flames

    NASA Technical Reports Server (NTRS)

    Chen, J.-Y.; Kollman, W.

    1991-01-01

    The progress of chemical reactions in nonpremixed turbulent flows depends on the coexistence of reactants, which are brought together by mixing. The degree of mixing can strongly influence the chemical reactions and it can be quantified by segregation parameters. In this paper, the relevance of segregation parameters to turbulent mixing and chemical reactions is explored. An analysis of the pair-exchange mixing models is performed and an explanation is given for the peculiar behavior of such models in homogeneous turbulence. The nature of segregation parameters in a H2/Ar-air nonpremixed jet flame is investigated. The results show that Monte Carlo simulation with the modified Curl's mixing model predicts segregation parameters in close agreement with the experimental values, providing an indirect validation for the theoretical model.

  20. Mixing in the Extratropical Stratosphere: Model-measurements Comparisons using MLM Diagnostics

    NASA Technical Reports Server (NTRS)

    Ma, Jun; Waugh, Darryn W.; Douglass, Anne R.; Kawa, Stephan R.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    We evaluate transport processes in the extratropical lower stratosphere for both models and measurements with the help of equivalent length diagnostic from the modified Lagrangian-mean (MLM) analysis. This diagnostic is used to compare measurements of long-lived tracers made by the Cryogenic Limb Array Etalon Spectrometer (CLAES) on the Upper Atmosphere Research Satellite (UARS) with simulated tracers. Simulations are produced in Chemical and Transport Models (CTMs), in which meteorological fields are taken from the Goddard Earth Observing System Data Assimilation System (GEOS DAS), the Middle Atmosphere Community Climate Model (MACCM2), and the Geophysical Fluid Dynamics Laboratory (GFDL) "SKYHI" model, respectively. Time series of isentropic equivalent length show that these models are able to capture major mixing and transport properties observed by CLAES, such as the formation and destruction of polar barriers, the presence of surf zones in both hemispheres. Differences between each model simulation and the observation are examined in light of model performance. Among these differences, only the simulation driven by GEOS DAS shows one case of the "top-down" destruction of the Antarctic polar vortex, as observed in the CLAES data. Additional experiments of isentropic advection of artificial tracer by GEOS DAS winds suggest that diabatic movement might have considerable contribution to the equivalent length field in the 3D CTM diagnostics.

  1. Modeling Temporal Behavior in Large Networks: A Dynamic Mixed-Membership Model

    SciTech Connect

    Rossi, R; Gallagher, B; Neville, J; Henderson, K

    2011-11-11

    Given a large time-evolving network, how can we model and characterize the temporal behaviors of individual nodes (and network states)? How can we model the behavioral transition patterns of nodes? We propose a temporal behavior model that captures the 'roles' of nodes in the graph and how they evolve over time. The proposed dynamic behavioral mixed-membership model (DBMM) is scalable, fully automatic (no user-defined parameters), non-parametric/data-driven (no specific functional form or parameterization), interpretable (identifies explainable patterns), and flexible (applicable to dynamic and streaming networks). Moreover, the interpretable behavioral roles are generalizable, computationally efficient, and natively supports attributes. We applied our model for (a) identifying patterns and trends of nodes and network states based on the temporal behavior, (b) predicting future structural changes, and (c) detecting unusual temporal behavior transitions. We use eight large real-world datasets from different time-evolving settings (dynamic and streaming). In particular, we model the evolving mixed-memberships and the corresponding behavioral transitions of Twitter, Facebook, IP-Traces, Email (University), Internet AS, Enron, Reality, and IMDB. The experiments demonstrate the scalability, flexibility, and effectiveness of our model for identifying interesting patterns, detecting unusual structural transitions, and predicting the future structural changes of the network and individual nodes.

  2. Biases in modeled surface snow BC mixing ratios in prescribed-aerosol climate model runs

    NASA Astrophysics Data System (ADS)

    Doherty, S. J.; Bitz, C. M.; Flanner, M. G.

    2014-11-01

    Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, leading to positive radiative forcing, climate warming and earlier snowmelt. A series of recent studies have used prescribed-aerosol deposition flux fields in climate model runs to assess the forcing by black carbon in snow. In these studies, the prescribed mass deposition flux of BC to surface snow is decoupled from the mass deposition flux of snow water to the surface. Here we compare prognostic- and prescribed-aerosol runs and use a series of offline calculations to show that the prescribed-aerosol approach results, on average, in a factor of about 1.5-2.5 high bias in annual-mean surface snow BC mixing ratios in three key regions for snow albedo forcing by BC: Greenland, Eurasia and North America. These biases will propagate directly to positive biases in snow and surface albedo reduction by BC. The bias is shown be due to coupling snowfall that varies on meteorological timescales (daily or shorter) with prescribed BC mass deposition fluxes that are more temporally and spatially smooth. The result is physically non-realistic mixing ratios of BC in surface snow. We suggest that an alternative approach would be to prescribe BC mass mixing ratios in snowfall, rather than BC mass fluxes, and we show that this produces more physically realistic BC mixing ratios in snowfall and in the surface snow layer.

  3. Eating and drinking activity of newly weaned piglets: effects of individual characteristics, social mixing, and addition of extra zinc to the feed.

    PubMed

    Dybkjaer, L; Jacobsen, A P; Tøgersen, F A; Poulsen, H D

    2006-03-01

    In production systems, piglets usually fast for a period after weaning, thereby increasing the risk of diarrhea and a reduction in growth. The low level of eating may relate to insufficient drinking activity, as solid feed intake must be accompanied by water intake. Mixing of newly weaned piglets is a well-known stressor and a common procedure in pig production. The effect of mixing on the temporal development of eating and drinking activity in newly weaned piglets has not been elucidated. High concentrations of zinc (Zn) in the feed improve the health and performance of piglets after weaning, but the underlying mechanisms are still obscure. One possibility is that Zn affects eating and drinking behavior. The effects of mixing 4 littermates from each of 2 litters and adding zinc oxide (ZnO; 2,500 ppm of Zn) to the feed were studied in a 2 x 2 factorial experiment using 123 piglets weaned at 27 d of age. Individual eating and drinking times during the initial 48 h after weaning were analyzed on 2 levels of aggregation, day and hour. The piglets spent less time eating on the first day after weaning compared with the second day (20 +/- 5 vs. 98 +/- 10 min, respectively; P < 0.001), whereas they spent more time drinking on the first day compared with the second day (13 +/- 1 vs. 9 +/- 0.5 min, respectively; P < 0.001). Eating and drinking times were positively associated (P < 0.001). Females ate for longer than males (61 +/- 8 vs. 44 +/- 7 min/24 h, respectively, P = 0.002), whereas sex did not affect drinking time. Drinking time increased (P = 0.003) and eating time decreased (P = 0.001) with increasing preweaning growth rate and weaning weight. Neither mixing nor addition of ZnO affected the daily eating time. However, nonmixed piglets given 2,500 ppm of Zn as ZnO in the feed spent more time drinking per day (12 +/- 1 min) than did nonmixed piglets offered 100 ppm of Zn as ZnO (10 +/- 1 min; P = 0.002). Mixing also affected the hourly distribution of the drinking

  4. Model analysis of influences of aerosol mixing state upon its optical properties in East Asia

    NASA Astrophysics Data System (ADS)

    Han, Xiao; Zhang, Meigen; Zhu, Lingyun; Xu, Liren

    2013-07-01

    The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach ±5 W m-2. The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect.

  5. A weighted dictionary learning model for denoising images corrupted by mixed noise.

    PubMed

    Liu, Jun; Tai, Xue-Cheng; Huang, Haiyang; Huan, Zhongdan

    2013-03-01

    This paper proposes a general weighted l(2)-l(0) norms energy minimization model to remove mixed noise such as Gaussian-Gaussian mixture, impulse noise, and Gaussian-impulse noise from the images. The approach is built upon maximum likelihood estimation framework and sparse representations over a trained dictionary. Rather than optimizing the likelihood functional derived from a mixture distribution, we present a new weighting data fidelity function, which has the same minimizer as the original likelihood functional but is much easier to optimize. The weighting function in the model can be determined by the algorithm itself, and it plays a role of noise detection in terms of the different estimated noise parameters. By incorporating the sparse regularization of small image patches, the proposed method can efficiently remove a variety of mixed or single noise while preserving the image textures well. In addition, a modified K-SVD algorithm is designed to address the weighted rank-one approximation. The experimental results demonstrate its better performance compared with some existing methods. PMID:23193456

  6. Mixed model analysis of censored longitudinal data with flexible random-effects density

    PubMed Central

    Vock, David M.; Davidian, Marie; Tsiatis, Anastasios A.; Muir, Andrew J.

    2012-01-01

    Mixed models are commonly used to represent longitudinal or repeated measures data. An additional complication arises when the response is censored, for example, due to limits of quantification of the assay used. While Gaussian random effects are routinely assumed, little work has characterized the consequences of misspecifying the random-effects distribution nor has a more flexible distribution been studied for censored longitudinal data. We show that, in general, maximum likelihood estimators will not be consistent when the random-effects density is misspecified, and the effect of misspecification is likely to be greatest when the true random-effects density deviates substantially from normality and the number of noncensored observations on each subject is small. We develop a mixed model framework for censored longitudinal data in which the random effects are represented by the flexible seminonparametric density and show how to obtain estimates in SAS procedure NLMIXED. Simulations show that this approach can lead to reduction in bias and increase in efficiency relative to assuming Gaussian random effects. The methods are demonstrated on data from a study of hepatitis C virus. PMID:21914727

  7. Mixed Effects Modeling Using Stochastic Differential Equations: Illustrated by Pharmacokinetic Data of Nicotinic Acid in Obese Zucker Rats.

    PubMed

    Leander, Jacob; Almquist, Joachim; Ahlström, Christine; Gabrielsson, Johan; Jirstrand, Mats

    2015-05-01

    Inclusion of stochastic differential equations in mixed effects models provides means to quantify and distinguish three sources of variability in data. In addition to the two commonly encountered sources, measurement error and interindividual variability, we also consider uncertainty in the dynamical model itself. To this end, we extend the ordinary differential equation setting used in nonlinear mixed effects models to include stochastic differential equations. The approximate population likelihood is derived using the first-order conditional estimation with interaction method and extended Kalman filtering. To illustrate the application of the stochastic differential mixed effects model, two pharmacokinetic models are considered. First, we use a stochastic one-compartmental model with first-order input and nonlinear elimination to generate synthetic data in a simulated study. We show that by using the proposed method, the three sources of variability can be successfully separated. If the stochastic part is neglected, the parameter estimates become biased, and the measurement error variance is significantly overestimated. Second, we consider an extension to a stochastic pharmacokinetic model in a preclinical study of nicotinic acid kinetics in obese Zucker rats. The parameter estimates are compared between a deterministic and a stochastic NiAc disposition model, respectively. Discrepancies between model predictions and observations, previously described as measurement noise only, are now separated into a comparatively lower level of measurement noise and a significant uncertainty in model dynamics. These examples demonstrate that stochastic differential mixed effects models are useful tools for identifying incomplete or inaccurate model dynamics and for reducing potential bias in parameter estimates due to such model deficiencies. PMID:25693487

  8. A novel modeling framework to obtain new insights into the controls of catchment mixing processes

    NASA Astrophysics Data System (ADS)

    Neubauer, Markus; Musolff, Andreas; de Rooij, Gerrit; Fleckenstein, Jan H.

    2015-04-01

    Understanding the dominant controls and time-invariant behavior of travel times of water and solutes at the scale of catchments is of great scientific interest as it can provide means to quantify catchment-scale solute fluxes. Recent studies, such as, van der Velde et al. (2012) and Botter et al. (2011) have proposed conceptual frameworks for catchment-scale mixing processes by relating travel time distributions for evapotranspiration, discharge and storage to each other in order to derive the Storage Outflow Probability (STOP) functions and the Age functions of water leaving the catchment. However, there is a lack of methodology to directly measure or derive time-variant travel time distributions in the discharge as well as in the evapotranspiration flux. As an alternative, numerical models of water flow are can be used to study major controls of catchment mixing and water age within storage, evapotranspiration and discharge. We propose a novel modeling framework, which is capable of obtaining transient travel time distributions based on a coupled three dimensional surface-subsurface numerical model, external particle tracking routines and subsequent statistical evaluation. We tested our approach on the hydrological well-studied Schäfertal catchment in Central Germany as a base case scenario. Additionally, we aimed to systematically study the shift of the travel time distributions in discharge, evapotranspiration and storage by varying the potential controls, such as: bedrock morphology, catchment slopes, soil properties and temporal dynamics of climatic input in numerical experiments. Furthermore, the travel time distribution results, obtained by our particle tracking approach, were used to calculate the STOP and Age functions for each modeled scenario. Our results provide new insights into the controls of catchment mixing processes, and the transient behavior of age distributions in response to time-variant precipitation and evapotranspiration. References Van

  9. Narrowing the Search for Sources of Fecal Indicator Bacteria with a Simple Salinity Mixing Model

    NASA Astrophysics Data System (ADS)

    McLaughlin, K.; Ahn, J.; Litton, R.; Grant, S. B.

    2006-12-01

    Newport Bay, the second largest estuarine embayment in Southern California, provides critical natural habitat for terrestrial and aquatic species and is a regionally important recreational area. Unfortunately, the beneficial uses of Newport Bay are threatened by numerous sources of pollutant loading, either through direct discharge into the bay or through its tributaries. Fecal indicator bacteria (FIB) are associated with human pathogens and are present in high concentrations in sewage and urban runoff. Standardized and inexpensive assays used for the detection of FIB have allowed their concentrations to be used as a common test of water quality. In order to assess FIB impairment in Newport Bay, weekly transects of FIB concentrations were conducted, specifically Total Coliform, Escherichia coli and Enterococci spp., as well as salinity, temperature, and transmissivity, from the upper reaches of the estuary to an offshore control site. Using salinity as a conservative tracer for water mass mixing and determining the end-member values of FIB and transmissivity in both the creek sites and the offshore control site, we created a simple, two end-member mixing model of FIB and transmissivity within Newport Bay. Deviations from the mixing model would suggest either an additional source of FIB to the bay (e.g. bird feces) or regrowth of FIB within the bay. Our results indicate that, with a few notable exceptions, salinity is a good tracer for FIB concentrations along the transect, but is not particularly effective for transmissivity. This suggests that the largest contributor of FIB loading to Newport Bay comes from the discharge of creeks into the upper reaches of the estuary.

  10. Analysis of oligonucleotide array experiments with repeated measures using mixed models

    PubMed Central

    Li, Hao; Wood, Constance L; Getchell, Thomas V; Getchell, Marilyn L; Stromberg, Arnold J

    2004-01-01

    Background Two or more factor mixed factorial experiments are becoming increasingly common in microarray data analysis. In this case study, the two factors are presence (Patients with Alzheimer's disease) or absence (Control) of the disease, and brain regions including olfactory bulb (OB) or cerebellum (CER). In the design considered in this manuscript, OB and CER are repeated measurements from the same subject and, hence, are correlated. It is critical to identify sources of variability in the analysis of oligonucleotide array experiments with repeated measures and correlations among data points have to be considered. In addition, multiple testing problems are more complicated in experiments with multi-level treatments or treatment combinations. Results In this study we adopted a linear mixed model to analyze oligonucleotide array experiments with repeated measures. We first construct a generalized F test to select differentially expressed genes. The Benjamini and Hochberg (BH) procedure of controlling false discovery rate (FDR) at 5% was applied to the P values of the generalized F test. For those genes with significant generalized F test, we then categorize them based on whether the interaction terms were significant or not at the α-level (αnew = 0.0033) determined by the FDR procedure. Since simple effects may be examined for the genes with significant interaction effect, we adopt the protected Fisher's least significant difference test (LSD) procedure at the level of αnew to control the family-wise error rate (FWER) for each gene examined. Conclusions A linear mixed model is appropriate for analysis of oligonucleotide array experiments with repeated measures. We constructed a generalized F test to select differentially expressed genes, and then applied a specific sequence of tests to identify factorial effects. This sequence of tests applied was designed to control for gene based FWER. PMID:15626348

  11. Parametrization of flavor mixing in the standard model

    SciTech Connect

    Fritzsch, H. |; Xing, Z.

    1998-01-01

    It is shown that there exist nine different ways to describe the flavor mixing, in terms of three rotation angles and one CP-violating phase, within the standard electroweak theory of six quarks. For the assignment of the complex phase there essentially exists a continuum of possibilities, if one allows the phase to appear in more than four elements of the mixing matrix. If the phase is restricted to four elements, the phase assignment is uniquely defined. If one imposes the constraint that the phase disappears in a natural way in the chiral limit in which the masses of the u and d quarks are turned off, only three of the nine parametrizations are acceptable. In particular the {open_quotes}standard{close_quotes} parametrization advocated by the Particle Data Group is not permitted. One parametrization, in which the CP-violating phase is restricted to the light quark sector, stands up as the most favorable description of the flavor mixing. {copyright} {ital 1997} {ital The American Physical Society}

  12. Experimental constraints on the neutrino oscillations and a simple model of three-flavor mixing

    SciTech Connect

    Raczka, P.A.; Szymacha, A. ); Tatur, S. )

    1994-02-01

    A simple model of neutrino mixing is considered which contains only one right-handed neutrino field coupled, via the mass term, to the three usual left-handed fields. This is the simplest model that allows for three-flavor neutrino oscillations. The existing experimental limits on the neutrino oscillations are used to obtain constraints on the two free-mixing parameters of the model. A specific sum rule relating the oscillation probabilities of different flavors is derived.

  13. Population stochastic modelling (PSM)--an R package for mixed-effects models based on stochastic differential equations.

    PubMed

    Klim, Søren; Mortensen, Stig Bousgaard; Kristensen, Niels Rode; Overgaard, Rune Viig; Madsen, Henrik

    2009-06-01

    The extension from ordinary to stochastic differential equations (SDEs) in pharmacokinetic and pharmacodynamic (PK/PD) modelling is an emerging field and has been motivated in a number of articles [N.R. Kristensen, H. Madsen, S.H. Ingwersen, Using stochastic differential equations for PK/PD model development, J. Pharmacokinet. Pharmacodyn. 32 (February(1)) (2005) 109-141; C.W. Tornøe, R.V. Overgaard, H. Agersø, H.A. Nielsen, H. Madsen, E.N. Jonsson, Stochastic differential equations in NONMEM: implementation, application, and comparison with ordinary differential equations, Pharm. Res. 22 (August(8)) (2005) 1247-1258; R.V. Overgaard, N. Jonsson, C.W. Tornøe, H. Madsen, Non-linear mixed-effects models with stochastic differential equations: implementation of an estimation algorithm, J. Pharmacokinet. Pharmacodyn. 32 (February(1)) (2005) 85-107; U. Picchini, S. Ditlevsen, A. De Gaetano, Maximum likelihood estimation of a time-inhomogeneous stochastic differential model of glucose dynamics, Math. Med. Biol. 25 (June(2)) (2008) 141-155]. PK/PD models are traditionally based ordinary differential equations (ODEs) with an observation link that incorporates noise. This state-space formulation only allows for observation noise and not for system noise. Extending to SDEs allows for a Wiener noise component in the system equations. This additional noise component enables handling of autocorrelated residuals originating from natural variation or systematic model error. Autocorrelated residuals are often partly ignored in PK/PD modelling although violating the hypothesis for many standard statistical tests. This article presents a package for the statistical program R that is able to handle SDEs in a mixed-effects setting. The estimation method implemented is the FOCE(1) approximation to the population likelihood which is generated from the individual likelihoods that are approximated using the Extended Kalman Filter's one-step predictions. PMID:19268387

  14. Synergy on catalytic effect of Fe-Zr additives mixed in different proportions on the hydrogen desorption from MgH{sub 2}

    SciTech Connect

    Kale, A.; Bazzanella, N.; Checchetto, R.; Miotello, A.

    2009-05-18

    Mg films with mixed Fe and Zr metallic additives were prepared by rf magnetron sputtering keeping the total metal content constant, about 7 at. %, and changing the [Fe]/[Zr] ratio. Isothermal hydrogen desorption curves showed that the kinetics depends on [Fe]/[Zr] ratio and is fastest when the [Fe]/[Zr] ratio is {approx}1.8. X-ray diffraction analysis revealed formation of Fe nanoclusters and Mg grain refinement. The improvement of the hydrogen desorption kinetics can be explained by the presence of atomically dispersed Zr and Fe nanoclusters acting as nucleation centers, as well as Mg grain refinement.

  15. Mathematical, physical and numerical principles essential for models of turbulent mixing

    SciTech Connect

    Sharp, David Howland; Lim, Hyunkyung; Yu, Yan; Glimm, James G

    2009-01-01

    We propose mathematical, physical and numerical principles which are important for the modeling of turbulent mixing, especially the classical and well studied Rayleigh-Taylor and Richtmyer-Meshkov instabilities which involve acceleration driven mixing of a fluid discontinuity layer, by a steady accerleration or an impulsive force.

  16. Pricing European option under the time-changed mixed Brownian-fractional Brownian model

    NASA Astrophysics Data System (ADS)

    Guo, Zhidong; Yuan, Hongjun

    2014-07-01

    This paper deals with the problem of discrete time option pricing by a mixed Brownian-fractional subdiffusive Black-Scholes model. Under the assumption that the price of the underlying stock follows a time-changed mixed Brownian-fractional Brownian motion, we derive a pricing formula for the European call option in a discrete time setting.

  17. Modeling relationships between calving traits: a comparison between standard and recursive mixed models

    PubMed Central

    2010-01-01

    Background The use of structural equation models for the analysis of recursive and simultaneous relationships between phenotypes has become more popular recently. The aim of this paper is to illustrate how these models can be applied in animal breeding to achieve parameterizations of different levels of complexity and, more specifically, to model phenotypic recursion between three calving traits: gestation length (GL), calving difficulty (CD) and stillbirth (SB). All recursive models considered here postulate heterogeneous recursive relationships between GL and liabilities to CD and SB, and between liability to CD and liability to SB, depending on categories of GL phenotype. Methods Four models were compared in terms of goodness of fit and predictive ability: 1) standard mixed model (SMM), a model with unstructured (co)variance matrices; 2) recursive mixed model 1 (RMM1), assuming that residual correlations are due to the recursive relationships between phenotypes; 3) RMM2, assuming that correlations between residuals and contemporary groups are due to recursive relationships between phenotypes; and 4) RMM3, postulating that the correlations between genetic effects, contemporary groups and residuals are due to recursive relationships between phenotypes. Results For all the RMM considered, the estimates of the structural coefficients were similar. Results revealed a nonlinear relationship between GL and the liabilities both to CD and to SB, and a linear relationship between the liabilities to CD and SB. Differences in terms of goodness of fit and predictive ability of the models considered were negligible, suggesting that RMM3 is plausible. Conclusions The applications examined in this study suggest the plausibility of a nonlinear recursive effect from GL onto CD and SB. Also, the fact that the most restrictive model RMM3, which assumes that the only cause of correlation is phenotypic recursion, performs as well as the others indicates that the phenotypic recursion

  18. Radiative corrections to the Higgs boson couplings in the model with an additional real singlet scalar field

    NASA Astrophysics Data System (ADS)

    Kanemura, Shinya; Kikuchi, Mariko; Yagyu, Kei

    2016-06-01

    We calculate renormalized Higgs boson couplings with gauge bosons and fermions at the one-loop level in the model with an additional isospin singlet real scalar field. These coupling constants can deviate from the predictions in the standard model due to tree-level mixing effects and one-loop contributions of the extra neutral scalar boson. We investigate how they can be significant under the theoretical constraints from perturbative unitarity and vacuum stability and also the condition of avoiding the wrong vacuum. Furthermore, comparing with the predictions in the Type I two Higgs doublet model, we numerically demonstrate how the singlet extension model can be distinguished and identified by using precision measurements of the Higgs boson couplings at future collider experiments.

  19. Wavelet-based functional linear mixed models: an application to measurement error–corrected distributed lag models

    PubMed Central

    Malloy, Elizabeth J.; Morris, Jeffrey S.; Adar, Sara D.; Suh, Helen; Gold, Diane R.; Coull, Brent A.

    2010-01-01

    Frequently, exposure data are measured over time on a grid of discrete values that collectively define a functional observation. In many applications, researchers are interested in using these measurements as covariates to predict a scalar response in a regression setting, with interest focusing on the most biologically relevant time window of exposure. One example is in panel studies of the health effects of particulate matter (PM), where particle levels are measured over time. In such studies, there are many more values of the functional data than observations in the data set so that regularization of the corresponding functional regression coefficient is necessary for estimation. Additional issues in this setting are the possibility of exposure measurement error and the need to incorporate additional potential confounders, such as meteorological or co-pollutant measures, that themselves may have effects that vary over time. To accommodate all these features, we develop wavelet-based linear mixed distributed lag models that incorporate repeated measures of functional data as covariates into a linear mixed model. A Bayesian approach to model fitting uses wavelet shrinkage to regularize functional coefficients. We show that, as long as the exposure error induces fine-scale variability in the functional exposure profile and the distributed lag function representing the exposure effect varies smoothly in time, the model corrects for the exposure measurement error without further adjustment. Both these conditions are likely to hold in the environmental applications we consider. We examine properties of the method using simulations and apply the method to data from a study examining the association between PM, measured as hourly averages for 1–7 days, and markers of acute systemic inflammation. We use the method to fully control for the effects of confounding by other time-varying predictors, such as temperature and co-pollutants. PMID:20156988

  20. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-2

    NASA Astrophysics Data System (ADS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    Two dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  1. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-2

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  2. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-II

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two-dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  3. Intuitive Logic Revisited: New Data and a Bayesian Mixed Model Meta-Analysis

    PubMed Central

    Singmann, Henrik; Klauer, Karl Christoph; Kellen, David

    2014-01-01

    Recent research on syllogistic reasoning suggests that the logical status (valid vs. invalid) of even difficult syllogisms can be intuitively detected via differences in conceptual fluency between logically valid and invalid syllogisms when participants are asked to rate how much they like a conclusion following from a syllogism (Morsanyi & Handley, 2012). These claims of an intuitive logic are at odds with most theories on syllogistic reasoning which posit that detecting the logical status of difficult syllogisms requires effortful and deliberate cognitive processes. We present new data replicating the effects reported by Morsanyi and Handley, but show that this effect is eliminated when controlling for a possible confound in terms of conclusion content. Additionally, we reanalyze three studies () without this confound with a Bayesian mixed model meta-analysis (i.e., controlling for participant and item effects) which provides evidence for the null-hypothesis and against Morsanyi and Handley's claim. PMID:24755777

  4. Analytical models for well-mixed populations of cooperators and defectors under limiting resources

    NASA Astrophysics Data System (ADS)

    Requejo, R. J.; Camacho, J.

    2012-06-01

    In the study of the evolution of cooperation, resource limitations are usually assumed just to provide a finite population size. Recently, however, agent-based models have pointed out that resource limitation may modify the original structure of the interactions and allow for the survival of unconditional cooperators in well-mixed populations. Here, we present analytical simplified versions of two types of agent-based models recently published: one in which the limiting resource constrains the ability of reproduction of individuals but not their survival, and a second one where the limiting resource is necessary for both reproduction and survival. One finds that the analytical models display, with a few differences, the same qualitative behavior of the more complex agent-based models. In addition, the analytical models allow us to expand the study and identify the dimensionless parameters governing the final fate of the system, such as coexistence of cooperators and defectors, or dominance of defectors or of cooperators. We provide a detailed analysis of the occurring phase transitions as these parameters are varied.

  5. Bayesian recursive mixed linear model for gene expression analyses with continuous covariates.

    PubMed

    Casellas, J; Ibáñez-Escriche, N

    2012-01-01

    The analysis of microarray gene expression data has experienced a remarkable growth in scientific research over the last few years and is helping to decipher the genetic background of several productive traits. Nevertheless, most analytical approaches have relied on the comparison of 2 (or a few) well-defined groups of biological conditions where the continuous covariates have no sense (e.g., healthy vs. cancerous cells). Continuous effects could be of special interest when analyzing gene expression in animal production-oriented studies (e.g., birth weight), although very few studies address this peculiarity in the animal science framework. Within this context, we have developed a recursive linear mixed model where not only are linear covariates accounted for during gene expression analyses but also hierarchized and the effects of their genetic, environmental, and residual components on differential gene expression inferred independently. This parameterization allows a step forward in the inference of differential gene expression linked to a given quantitative trait such as birth weight. The statistical performance of this recursive model was exemplified under simulation by accounting for different sample sizes (n), heritabilities for the quantitative trait (h(2)), and magnitudes of differential gene expression (λ). It is important to highlight that statistical power increased with n, h(2), and λ, and the recursive model exceeded the standard linear mixed model with linear (nonrecursive) covariates in the majority of scenarios. This new parameterization would provide new insights about gene expression in the animal science framework, opening a new research scenario where within-covariate sources of differential gene expression could be individualized and estimated. The source code of the program accommodating these analytical developments and additional information about practical aspects on running the program are freely available by request to the corresponding

  6. Eliciting mixed emotions: a meta-analysis comparing models, types, and measures.

    PubMed

    Berrios, Raul; Totterdell, Peter; Kellett, Stephen

    2015-01-01

    The idea that people can experience two oppositely valenced emotions has been controversial ever since early attempts to investigate the construct of mixed emotions. This meta-analysis examined the robustness with which mixed emotions have been elicited experimentally. A systematic literature search identified 63 experimental studies that instigated the experience of mixed emotions. Studies were distinguished according to the structure of the underlying affect model-dimensional or discrete-as well as according to the type of mixed emotions studied (e.g., happy-sad, fearful-happy, positive-negative). The meta-analysis using a random-effects model revealed a moderate to high effect size for the elicitation of mixed emotions (d IG+ = 0.77), which remained consistent regardless of the structure of the affect model, and across different types of mixed emotions. Several methodological and design moderators were tested. Studies using the minimum index (i.e., the minimum value between a pair of opposite valenced affects) resulted in smaller effect sizes, whereas subjective measures of mixed emotions increased the effect sizes. The presence of more women in the samples was also associated with larger effect sizes. The current study indicates that mixed emotions are a robust, measurable and non-artifactual experience. The results are discussed in terms of the implications for an affect system that has greater versatility and flexibility than previously thought. PMID:25926805

  7. Unit physics performance of a mix model in Eulerian fluid computations

    SciTech Connect

    Vold, Erik; Douglass, Rod

    2011-01-25

    In this report, we evaluate the performance of a K-L drag-buoyancy mix model, described in a reference study by Dimonte-Tipton [1] hereafter denoted as [D-T]. The model was implemented in an Eulerian multi-material AMR code, and the results are discussed here for a series of unit physics tests. The tests were chosen to calibrate the model coefficients against empirical data, principally from RT (Rayleigh-Taylor) and RM (Richtmyer-Meshkov) experiments, and the present results are compared to experiments and to results reported in [D-T]. Results show the Eulerian implementation of the mix model agrees well with expectations for test problems in which there is no convective flow of the mass averaged fluid, i.e., in RT mix or in the decay of homogeneous isotropic turbulence (HIT). In RM shock-driven mix, the mix layer moves through the Eulerian computational grid, and there are differences with the previous results computed in a Lagrange frame [D-T]. The differences are attributed to the mass averaged fluid motion and examined in detail. Shock and re-shock mix are not well matched simultaneously. Results are also presented and discussed regarding model sensitivity to coefficient values and to initial conditions (IC), grid convergence, and the generation of atomically mixed volume fractions.

  8. Stabilization of {alpha}-SiAlONs using a rare-earth mixed oxide (RE{sub 2}O{sub 3}) as sintering additive

    SciTech Connect

    Santos, C.; Silva, O.M.M.; Silva, C.R.M.

    2005-07-12

    {alpha}-SiAlONs are commonly produced by liquid phase sintering of Si{sub 3}N{sub 4} with AlN and Y{sub 2}O{sub 3} as additives. The formation of the {alpha}-SiAlONs using a mixed oxide (RE{sub 2}O{sub 3}), containing yttria and rare-earth oxides, as an alternative additive was investigated. Dense {alpha}-SiAlONs were obtained by gas-pressure sintering, starting from {alpha}-Si{sub 3}N{sub 4} and AlN-Y{sub 2}O{sub 3} or AlN-RE{sub 2}O{sub 3} as additives. The mixed oxide powder RE{sub 2}O{sub 3} was characterized by means of high-resolution synchrotron X-ray diffraction and compared to Y{sub 2}O{sub 3}. The X-ray diffraction analysis of the mixed oxide shows a pattern indicating a true solid solution formation. The Rietveld refinement of the crystal structure of the sintered {alpha}-SiAlON using AlN-RE{sub 2}O{sub 3} as additive revealed a similar crystal structure to the {alpha}-SiAlON using AlN-RE{sub 2}O{sub 3} as additive. The comparison of the microstructures of the both {alpha}-SiAlONs produced using pure Y{sub 2}O{sub 3} or RE{sub 2}O{sub 3}, revealed similar grain sizes of about 4.5 {mu}m with aspect ratios of about 5. Both materials show also similar mechanical properties, with hardness of 18.5 GPa and fracture toughness of 5 MPa m{sup 1/2}. It could be, thus, demonstrated that pure Y{sub 2}O{sub 3} can be substituted by the rare-earth solid solution, RE{sub 2}O{sub 3}, in the formation of {alpha}-SiAlONs, presenting similar microstructural and mechanical properties.

  9. Effect of Stevia rebaudiana addition on bioaccessibility of bioactive compounds and antioxidant activity of beverages based on exotic fruits mixed with oat following simulated human digestion.

    PubMed

    Carbonell-Capella, Juana M; Buniowska, Magdalena; Esteve, María J; Frígola, Ana

    2015-10-01

    In order to determine the impact of Stevia rebaudiana (SR) addition on bioactive compounds bioaccessibility of a new developed functional beverage based on exotic fruits (mango juice, papaya juice and açaí) mixed with orange juice and oat, an in vitro gastrointestinal digestion was performed. Ascorbic acid, total carotenoids, total phenolics, total anthocyanins, total antioxidant capacity and steviol glycosides were evaluated before and after a simulated gastrointestinal digestion. Salivary and gastric digestion had no substantial effect on any of the major phenolic compounds, ascorbic acid, total antioxidant capacity and steviol glycosides, whereas carotenoids and anthocyanins diminished significantly during the gastric step. All analysed compounds were significantly altered during the pancreatic-bile digestion and this effect was more marked for carotenoids and total anthocyanins. However, phenolic compounds, anthocyanins, total antioxidant capacity and steviol glycosides bioaccessibility increased as did SR concentration. Ascorbic acid bioaccessibility was negatively affected by the SR addition. PMID:25872434

  10. The Impact of Varied Discrimination Parameters on Mixed-Format Item Response Theory Model Selection

    ERIC Educational Resources Information Center

    Whittaker, Tiffany A.; Chang, Wanchen; Dodd, Barbara G.

    2013-01-01

    Whittaker, Chang, and Dodd compared the performance of model selection criteria when selecting among mixed-format IRT models and found that the criteria did not perform adequately when selecting the more parameterized models. It was suggested by M. S. Johnson that the problems when selecting the more parameterized models may be because of the low…

  11. Stochastic model of Rayleigh-Taylor mixing with time-dependent acceleration

    NASA Astrophysics Data System (ADS)

    Swisher, Nora; Abarzhi, Snezhana

    2015-11-01

    We report the stochastic model of Rayleigh-Taylor (RT) mixing with time-dependent acceleration. RT mixing is a statistically unsteady process, where the means values of the flow quantities as well as the fluctuations around these means are time-dependent. A set of nonlinear stochastic differential equations with multiplicative noise is derived on the basis of rigorous momentum model and group theory analyses to account for the randomness of RT mixing. A broad range of parameter regime is investigated; self-similar asymptotic solutions are found; new regimes of RT mixing dynamics are identified. We show that for power-law asymptotic solutions describing RT mixing the exponent is relatively insensitive and pre-factor is sensitive to the fluctuations, and find the statistic invariants of the dynamics in each of the new regimes. Support of the National Science Foundation is warmly appreciated.

  12. The Brown Muck of $B^0$ and $B^0_s$ Mixing: Beyond the Standard Model

    SciTech Connect

    Bouchard, Christopher Michael

    2011-01-01

    Standard Model contributions to neutral $B$ meson mixing begin at the one loop level where they are further suppressed by a combination of the GIM mechanism and Cabibbo suppression. This combination makes $B$ meson mixing a promising probe of new physics, where as yet undiscovered particles and/or interactions can participate in the virtual loops. Relating underlying interactions of the mixing process to experimental observation requires a precise calculation of the non-perturbative process of hadronization, characterized by hadronic mixing matrix elements. This thesis describes a calculation of the hadronic mixing matrix elements relevant to a large class of new physics models. The calculation is performed via lattice QCD using the MILC collaboration's gauge configurations with $2+1$ dynamical sea quarks.

  13. Evaluation of a Linear Mixing Model to Retrieve Soil and Vegetation Temperatures of Land Targets

    NASA Astrophysics Data System (ADS)

    Yang, Jinxin; Jia, Li; Cui, Yaokui; Zhou, Jie; Menenti, Massimo

    2014-03-01

    A simple linear mixing model of heterogeneous soil-vegetation system and retrieval of component temperatures from directional remote sensing measurements by inverting this model is evaluated in this paper using observations by a thermal camera. The thermal camera was used to obtain multi-angular TIR (Thermal Infra-Red) images over vegetable and orchard canopies. A whole thermal camera image was treated as a pixel of a satellite image to evaluate the model with the two-component system, i.e. soil and vegetation. The evaluation included two parts: evaluation of the linear mixing model and evaluation of the inversion of the model to retrieve component temperatures. For evaluation of the linear mixing model, the RMSE is 0.2 K between the observed and modelled brightness temperatures, which indicates that the linear mixing model works well under most conditions. For evaluation of the model inversion, the RMSE between the model retrieved and the observed vegetation temperatures is 1.6K, correspondingly, the RMSE between the observed and retrieved soil temperatures is 2.0K. According to the evaluation of the sensitivity of retrieved component temperatures on fractional cover, the linear mixing model gives more accurate retrieval accuracies for both soil and vegetation temperatures under intermediate fractional cover conditions.

  14. INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS: A REPLY TO ROBBINS, HILDERBRAND AND FARLEY (2002)

    EPA Science Inventory

    Phillips & Koch (2002) outlined a new stable isotope mixing model which incorporates differences in elemental concentrations in the determinations of source proportions in a mixture. They illustrated their method with sensitivity analyses and two examples from the wildlife ecolog...

  15. A quantitative approach to combine sources in stable isotope mixing models

    EPA Science Inventory

    Stable isotope mixing models, used to estimate source contributions to a mixture, typically yield highly uncertain estimates when there are many sources and relatively few isotope elements. Previously, ecologists have either accepted the uncertain contribution estimates for indiv...

  16. VISUALIZATION-BASED ANALYSIS FOR A MIXED-INHIBITION BINARY PBPK MODEL: DETERMINATION OF INHIBITION MECHANISM

    EPA Science Inventory

    A physiologically-based pharmacokinetic (PBPK) model incorporating mixed enzyme inhibition was used to determine mechanism of the metabolic interactions occurring during simultaneous inhalation exposures to the organic solvents chloroform and trichloroethylene (TCE).

    V...

  17. Experimental testing and modeling analysis of solute mixing at water distribution pipe junctions.

    PubMed

    Shao, Yu; Jeffrey Yang, Y; Jiang, Lijie; Yu, Tingchao; Shen, Cheng

    2014-06-01

    Flow dynamics at a pipe junction controls particle trajectories, solute mixing and concentrations in downstream pipes. The effect can lead to different outcomes of water quality modeling and, hence, drinking water management in a distribution network. Here we have investigated solute mixing behavior in pipe junctions of five hydraulic types, for which flow distribution factors and analytical equations for network modeling are proposed. First, based on experiments, the degree of mixing at a cross is found to be a function of flow momentum ratio that defines a junction flow distribution pattern and the degree of departure from complete mixing. Corresponding analytical solutions are also validated using computational-fluid-dynamics (CFD) simulations. Second, the analytical mixing model is further extended to double-Tee junctions. Correspondingly the flow distribution factor is modified to account for hydraulic departure from a cross configuration. For a double-Tee(A) junction, CFD simulations show that the solute mixing depends on flow momentum ratio and connection pipe length, whereas the mixing at double-Tee(B) is well represented by two independent single-Tee junctions with a potential water stagnation zone in between. Notably, double-Tee junctions differ significantly from a cross in solute mixing and transport. However, it is noted that these pipe connections are widely, but incorrectly, simplified as cross junctions of assumed complete solute mixing in network skeletonization and water quality modeling. For the studied pipe junction types, analytical solutions are proposed to characterize the incomplete mixing and hence may allow better water quality simulation in a distribution network. PMID:24675269

  18. The KL Mix Model Applied to Directly Driven Capsules on the Omega Laser

    SciTech Connect

    Tipton, R E; Mikaelian, K O; Park, H; Dimonte, G; Rygg, J R; Li, C K

    2005-10-10

    The coefficients of the KL mix model were set by Dimonte to match RT and RM instabilities as measured on the Linear Electric Motor (LEM). The KL mix model has been applied to directly-driven capsule implosions with a variety of laser energies, ablator materials, ablator thicknesses and convergence ratios. The KL calculations nearly match the observed Y{sub DD}, Y{sub DT}, Y{sub P}, T{sub ion} and implosion times for many (but not all) capsules.

  19. An explicit SU(12) family and flavor unification model with natural fermion masses and mixings

    SciTech Connect

    Albright, Carl H.; Feger, Robert P.; Kephart, Thomas W.

    2012-07-01

    We present an SU(12) unification model with three light chiral families, avoiding any external flavor symmetries. The hierarchy of quark and lepton masses and mixings is explained by higher dimensional Yukawa interactions involving Higgs bosons that contain SU(5) singlet fields with VEVs about 50 times smaller than the SU(12) unification scale. The presented model has been analyzed in detail and found to be in very good agreement with the observed quark and lepton masses and mixings.

  20. Computation of turbulent high speed mixing layers using a two-equation turbulence model

    NASA Technical Reports Server (NTRS)

    Narayan, J. R.; Sekar, B.

    1991-01-01

    A two-equation turbulence model was extended to be applicable for compressible flows. A compressibility correction based on modelling the dilational terms in the Reynolds stress equations were included in the model. The model is used in conjunction with the SPARK code for the computation of high speed mixing layers. The observed trend of decreasing growth rate with increasing convective Mach number in compressible mixing layers is well predicted by the model. The predictions agree well with the experimental data and the results from a compressible Reynolds stress model. The present model appears to be well suited for the study of compressible free shear flows. Preliminary results obtained for the reacting mixing layers are included.

  1. Factor analysis models for structuring covariance matrices of additive genetic effects: a Bayesian implementation

    PubMed Central

    de los Campos, Gustavo; Gianola, Daniel

    2007-01-01

    Multivariate linear models are increasingly important in quantitative genetics. In high dimensional specifications, factor analysis (FA) may provide an avenue for structuring (co)variance matrices, thus reducing the number of parameters needed for describing (co)dispersion. We describe how FA can be used to model genetic effects in the context of a multivariate linear mixed model. An orthogonal common factor structure is used to model genetic effects under Gaussian assumption, so that the marginal likelihood is multivariate normal with a structured genetic (co)variance matrix. Under standard prior assumptions, all fully conditional distributions have closed form, and samples from the joint posterior distribution can be obtained via Gibbs sampling. The model and the algorithm developed for its Bayesian implementation were used to describe five repeated records of milk yield in dairy cattle, and a one common FA model was compared with a standard multiple trait model. The Bayesian Information Criterion favored the FA model. PMID:17897592

  2. Eliciting mixed emotions: a meta-analysis comparing models, types, and measures

    PubMed Central

    Berrios, Raul; Totterdell, Peter; Kellett, Stephen

    2015-01-01

    The idea that people can experience two oppositely valenced emotions has been controversial ever since early attempts to investigate the construct of mixed emotions. This meta-analysis examined the robustness with which mixed emotions have been elicited experimentally. A systematic literature search identified 63 experimental studies that instigated the experience of mixed emotions. Studies were distinguished according to the structure of the underlying affect model—dimensional or discrete—as well as according to the type of mixed emotions studied (e.g., happy-sad, fearful-happy, positive-negative). The meta-analysis using a random-effects model revealed a moderate to high effect size for the elicitation of mixed emotions (dIG+ = 0.77), which remained consistent regardless of the structure of the affect model, and across different types of mixed emotions. Several methodological and design moderators were tested. Studies using the minimum index (i.e., the minimum value between a pair of opposite valenced affects) resulted in smaller effect sizes, whereas subjective measures of mixed emotions increased the effect sizes. The presence of more women in the samples was also associated with larger effect sizes. The current study indicates that mixed emotions are a robust, measurable and non-artifactual experience. The results are discussed in terms of the implications for an affect system that has greater versatility and flexibility than previously thought. PMID:25926805

  3. Weak Mixing and Rare Decays in the Littlest Higgs Model

    SciTech Connect

    Bardeen, William A.; /Fermilab

    2007-03-01

    Little Higgs models have been introduced to resolve the fine-tuning problems associated with the stability of the electroweak scale and the constraints imposed by the precision electroweak analysis of experiments testing the Standard Model of particle physics. Flavor physics provides a sensitive probe of the new physics contained in these models at next-to-leading order.

  4. A mixed model QTL analysis for sugarcane multiple-harvest-location trial data.

    PubMed

    Pastina, M M; Malosetti, M; Gazaffi, R; Mollinari, M; Margarido, G R A; Oliveira, K M; Pinto, L R; Souza, A P; van Eeuwijk, F A; Garcia, A A F

    2012-03-01

    Sugarcane-breeding programs take at least 12 years to develop new commercial cultivars. Molecular markers offer a possibility to study the genetic architecture of quantitative traits in sugarcane, and they may be used in marker-assisted selection to speed up artificial selection. Although the performance of sugarcane progenies in breeding programs are commonly evaluated across a range of locations and harvest years, many of the QTL detection methods ignore two- and three-way interactions between QTL, harvest, and location. In this work, a strategy for QTL detection in multi-harvest-location trial data, based on interval mapping and mixed models, is proposed and applied to map QTL effects on a segregating progeny from a biparental cross of pre-commercial Brazilian cultivars, evaluated at two locations and three consecutive harvest years for cane yield (tonnes per hectare), sugar yield (tonnes per hectare), fiber percent, and sucrose content. In the mixed model, we have included appropriate (co)variance structures for modeling heterogeneity and correlation of genetic effects and non-genetic residual effects. Forty-six QTLs were found: 13 QTLs for cane yield, 14 for sugar yield, 11 for fiber percent, and 8 for sucrose content. In addition, QTL by harvest, QTL by location, and QTL by harvest by location interaction effects were significant for all evaluated traits (30 QTLs showed some interaction, and 16 none). Our results contribute to a better understanding of the genetic architecture of complex traits related to biomass production and sucrose content in sugarcane. PMID:22159754

  5. Localization-Delocalization in Bridged Mixed-Valence Metal Clusters: Vibronic PKS Model Revisited.

    PubMed

    Palii, A; Tsukerblat, B; Clemente-Juan, J M; Aldoshin, S M

    2015-09-24

    Here we describe a new vibronic model of mixed valence (MV) dimer inspired by the conventional Piepho, Krausz, and Schatz (PKS) approach. We attempted to partially lift the main restriction of the PKS model dealing with the vibronically independent moieties of a MV molecule. The refined version of the PKS model in which the bridging ligands are included deals with the three main interactions: electron transfer (integral t0) related to the high-symmetric ligand configuration, on-site vibronic coupling (parameter υ) arising from the modulation of the crystal field on the metal sites by the breathing displacements of their nearest ligand surroundings, and intercenter vibronic coupling (parameter ζ) describing the dependence of the electron transfer on ligand positions in the course of their breathing movement. We apply the modified model to the analysis of the adiabatic potentials and electronic density distributions in the minima of their lower sheets for the cases of one-electron MV dimer with long and short bridges and for the two-electron MV dimer exhibiting a valence disproportionation effect. The inclusion of the intercenter interaction in addition to the conventional PKS coupling is shown to produce a strong effect on the degree of localization in MV dimers and, in particular, on the assignments to the Robin and Day classes and on the conditions of stabilization of valence disproportionated states in bielectron transfer systems. PMID:26305153

  6. Optimal design of mixed-effects PK/PD models based on differential equations.

    PubMed

    Wang, Yi; Eskridge, Kent M; Nadarajah, Saralees

    2012-01-01

    There is a vast literature on the analysis of optimal design of nonlinear mixed-effects models (NLMMs) described by ordinary differential equations (ODEs) with analytic solution. However, much less has been published on the design of trials to fit such models with nonanalytic solution. In this article, we use the "direct" method to find parameter sensitivities, which are required during the optimization of models defined as ODEs, and apply them to find D-optimal designs for various specific situations relevant to population pharmacokinetic studies using a particular model with first-order absorption and elimination. In addition, we perform two simulation studies. The first one aims to show that the criterion computed from the development of the Fisher information matrix expression is a good measure to compare and optimize population designs, thus avoiding a large number of simulations; In the second one, a sensitivity analysis with respect to parameter misspecification allows us to compare the robustness of different population designs constructed in this article. PMID:22204534

  7. Additive Manufacturing Modeling and Simulation A Literature Review for Electron Beam Free Form Fabrication

    NASA Technical Reports Server (NTRS)

    Seufzer, William J.

    2014-01-01

    Additive manufacturing is coming into industrial use and has several desirable attributes. Control of the deposition remains a complex challenge, and so this literature review was initiated to capture current modeling efforts in the field of additive manufacturing. This paper summarizes about 10 years of modeling and simulation related to both welding and additive manufacturing. The goals were to learn who is doing what in modeling and simulation, to summarize various approaches taken to create models, and to identify research gaps. Later sections in the report summarize implications for closed-loop-control of the process, implications for local research efforts, and implications for local modeling efforts.

  8. Data on copula modeling of mixed discrete and continuous neural time series.

    PubMed

    Hu, Meng; Li, Mingyao; Li, Wu; Liang, Hualou

    2016-06-01

    Copula is an important tool for modeling neural dependence. Recent work on copula has been expanded to jointly model mixed time series in neuroscience ("Hu et al., 2016, Joint Analysis of Spikes and Local Field Potentials using Copula" [1]). Here we present further data for joint analysis of spike and local field potential (LFP) with copula modeling. In particular, the details of different model orders and the influence of possible spike contamination in LFP data from the same and different electrode recordings are presented. To further facilitate the use of our copula model for the analysis of mixed data, we provide the Matlab codes, together with example data. PMID:27158651

  9. Data on copula modeling of mixed discrete and continuous neural time series

    PubMed Central

    Hu, Meng; Li, Mingyao; Li, Wu; Liang, Hualou

    2016-01-01

    Copula is an important tool for modeling neural dependence. Recent work on copula has been expanded to jointly model mixed time series in neuroscience (“Hu et al., 2016, Joint Analysis of Spikes and Local Field Potentials using Copula” [1]). Here we present further data for joint analysis of spike and local field potential (LFP) with copula modeling. In particular, the details of different model orders and the influence of possible spike contamination in LFP data from the same and different electrode recordings are presented. To further facilitate the use of our copula model for the analysis of mixed data, we provide the Matlab codes, together with example data. PMID:27158651

  10. Finite mixture models for the computation of isotope ratios in mixed isotopic samples

    NASA Astrophysics Data System (ADS)

    Koffler, Daniel; Laaha, Gregor; Leisch, Friedrich; Kappel, Stefanie; Prohaska, Thomas

    2013-04-01

    parameters of the algorithm, i.e. the maximum count of ratios, the minimum relative group-size of data points belonging to each ratio has to be defined. Computation of the models can be done with statistical software. In this study Leisch and Grün's flexmix package [2] for the statistical open-source software R was applied. A code example is available in the electronic supplementary material of Kappel et al. [1]. In order to demonstrate the usefulness of finite mixture models in fields dealing with the computation of multiple isotope ratios in mixed samples, a transparent example based on simulated data is presented and problems regarding small group-sizes are illustrated. In addition, the application of finite mixture models to isotope ratio data measured in uranium oxide particles is shown. The results indicate that finite mixture models perform well in computing isotope ratios relative to traditional estimation procedures and can be recommended for more objective and straightforward calculation of isotope ratios in geochemistry than it is current practice. [1] S. Kappel, S. Boulyga, L. Dorta, D. Günther, B. Hattendorf, D. Koffler, G. Laaha, F. Leisch and T. Prohaska: Evaluation Strategies for Isotope Ratio Measurements of Single Particles by LA-MC-ICPMS, Analytical and Bioanalytical Chemistry, 2013, accepted for publication on 2012-12-18 (doi: 10.1007/s00216-012-6674-3) [2] B. Grün and F. Leisch: Fitting finite mixtures of generalized linear regressions in R. Computational Statistics & Data Analysis, 51(11), 5247-5252, 2007. (doi:10.1016/j.csda.2006.08.014)

  11. Experimental assessment of subgrid mixing models for LES

    NASA Astrophysics Data System (ADS)

    Sun, O. S.; Su, L. K.

    2003-11-01

    Large eddy simulation (LES) models for subgrid scalar flux and dissipation include dynamic structure models,(Chumakov, S. and Rutland, C.J., submitted to phAIAA J.) based on scale similarity ideas, as well as one-equation models that relate subgrid variance and dissipation.(Jiménez, C. phet al.) phPhys. Fluids 13 (2001) Previously, these models have only been tested a posteriori, or a priori using data from direct numerical simulations. Here, these models are evaluated a priori using simultaneous planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements in a turbulent crossflowing jet. The models are tested by filtering the experimental data and comparing the results with computed model quantities. The measurements have sufficient resolution to permit accurate determination of subgrid quantities. Of primary interest is the structural accuracy of the models, which can be assessed by computing a correlation coefficient between exact and modeled terms. Preliminary results suggest that the assumptions of scale similarity underlying the dynamic structure models are more valid for modeling subgrid scalar flux than subgrid scalar dissipation.

  12. Development of a competition model for microbial growth in mixed culture.

    PubMed

    Fujikawa, Hiroshi; Munakata, Kanako; Sakha, Mohammad Z

    2014-01-01

    A novel competition model for describing bacterial growth in mixed culture was developed in this study. Several model candidates were made with our logistic growth model that precisely describes the growth of a monoculture of bacteria. These candidates were then evaluated for the usefulness in describing growth of two competing species in mixed culture using Staphylococcus aureus, Escherichia coli, and Salmonella. Bacterial cells of two species grew at initial doses of 10(3), 10(4), and 10(5) CFU/g at 28ºC. Among the candidates, a model where the Lotka-Volterra model, a general competition model in ecology, was incorporated as a new term in our growth model was the best for describing all types of growth of two competitors in mixed culture. Moreover, the values for the competition coefficient in the model were stable at various combinations of the initial populations of the species. The Baranyi model could also successfully describe the above types of growth in mixed culture when it was coupled with the Gimenez and Dalgaard model. However, the values for the competition coefficients in the competition model varied with the conditions. The present study suggested that our model could be a basic model for describing microbial competition. PMID:24975409

  13. Lepton mass and mixing in a neutrino mass model based on S4 flavor symmetry

    NASA Astrophysics Data System (ADS)

    Vien, V. V.

    2016-03-01

    We study a neutrino mass model based on S4 flavor symmetry which accommodates lepton mass, mixing with nonzero θ13 and CP violation phase. The spontaneous symmetry breaking in the model is imposed to obtain the realistic neutrino mass and mixing pattern at the tree-level with renormalizable interactions. Indeed, the neutrinos get small masses from one SU(2)L doublet and two SU(2)L singlets in which one being in 2̲ and the two others in 3̲ under S4 with both the breakings S4 → S3 and S4 → Z3 are taken place in charged lepton sector and S4 →𝒦 in neutrino sector. The model also gives a remarkable prediction of Dirac CP violation δCP = π 2 or ‑π 2 in both the normal and inverted spectrum which is still missing in the neutrino mixing matrix. The relation between lepton mixing angles is also represented.

  14. Toward a nonlinearity model for a heterodyne interferometer: not based on double-frequency mixing.

    PubMed

    Hu, Pengcheng; Bai, Yang; Zhao, Jinlong; Wu, Guolong; Tan, Jiubin

    2015-10-01

    Residual periodic errors detected in picometer-level heterodyne interferometers cannot be explained by the model based on double-frequency mixing. A new model is established and proposed in this paper for analysis of these errors. The multi-order Doppler frequency shift ghost beams from measurement beam itself are involved in final interference leading to multi-order periodic errors, whether or not frequency-mixing originating from the two incident beams occurs. For model validation, a novel setup free from double-frequency mixing is constructed. The analyzed measurement signal shows that phase mixing of measurement beam itself can lead to multi-order periodic errors ranging from tens of picometers to one nanometer. PMID:26480108

  15. Stellar models with microscopic diffusion and rotational mixing. 1: Application to the Sun

    NASA Technical Reports Server (NTRS)

    Chaboyer, Brian; Demarque, P.; Pinsonneault, M. H.

    1995-01-01

    The Yale stellar evolution code has been modified to include the combined effects of diffusion and rotational mixing on H-1, H-4, and the trace elements He, Li-6, Li-7, and Be-9. The interaction between rotational mixing and diffusion is studied by calculating a number of calibrated solar models. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 25%-50%. Conversely, diffusion leads to gradients in mean molecular weight which can inhibit the rotational mixing. The degree to which gradients in mean molecular weight inhibit the rotational mixing is somewhat uncertain. A comparison with the observed solar oblateness suggests that gradients in the mean molecular weight play a smaller role in inhibiting the rotational mixing than previously believed. This is reinforced by the fact that the model with the standard value for the inhibiting effect of mean molecular weight on the rotational mixing depletes no Li on the main sequence. This is clear in contrast to the observations. A reduction in the inhibiting effect of mean molecular weight gradients by a factor of 10 loads to noticeable main-sequence Li depletion.

  16. A mixed time series model of binomial counts

    NASA Astrophysics Data System (ADS)

    Khoo, Wooi Chen; Ong, Seng Huat

    2015-10-01

    Continuous time series modelling has been an active research in the past few decades. However, time series data in terms of correlated counts appear in many situations such as the counts of rainy days and access downloading. Therefore, the study on count data has become popular in time series modelling recently. This article introduces a new mixture model, which is an univariate non-negative stationary time series model with binomial marginal distribution, arising from the combination of the well-known binomial thinning and Pegram's operators. A brief review of important properties will be carried out and the EM algorithm is applied in parameter estimation. A numerical study is presented to show the performance of the model. Finally, a potential real application will be presented to illustrate the advantage of the new mixture model.

  17. Multiprocessing and Correction Algorithm of 3D-models for Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Anamova, R. R.; Zelenov, S. V.; Kuprikov, M. U.; Ripetskiy, A. V.

    2016-07-01

    This article addresses matters related to additive manufacturing preparation. A layer-by-layer model presentation was developed on the basis of a routing method. Methods for correction of errors in the layer-by-layer model presentation were developed. A multiprocessing algorithm for forming an additive manufacturing batch file was realized.

  18. Validation analysis of probabilistic models of dietary exposure to food additives.

    PubMed

    Gilsenan, M B; Thompson, R L; Lambe, J; Gibney, M J

    2003-10-01

    The validity of a range of simple conceptual models designed specifically for the estimation of food additive intakes using probabilistic analysis was assessed. Modelled intake estimates that fell below traditional conservative point estimates of intake and above 'true' additive intakes (calculated from a reference database at brand level) were considered to be in a valid region. Models were developed for 10 food additives by combining food intake data, the probability of an additive being present in a food group and additive concentration data. Food intake and additive concentration data were entered as raw data or as a lognormal distribution, and the probability of an additive being present was entered based on the per cent brands or the per cent eating occasions within a food group that contained an additive. Since the three model components assumed two possible modes of input, the validity of eight (2(3)) model combinations was assessed. All model inputs were derived from the reference database. An iterative approach was employed in which the validity of individual model components was assessed first, followed by validation of full conceptual models. While the distribution of intake estimates from models fell below conservative intakes, which assume that the additive is present at maximum permitted levels (MPLs) in all foods in which it is permitted, intake estimates were not consistently above 'true' intakes. These analyses indicate the need for more complex models for the estimation of food additive intakes using probabilistic analysis. Such models should incorporate information on market share and/or brand loyalty. PMID:14555358

  19. Estimating the Numerical Diapycnal Mixing in the GO5.0 Ocean Model

    NASA Astrophysics Data System (ADS)

    Megann, A.; Nurser, G.

    2014-12-01

    Constant-depth (or "z-coordinate") ocean models such as MOM4 and NEMO have become the de facto workhorse in climate applications, and have attained a mature stage in their development and are well understood. A generic shortcoming of this model type, however, is a tendency for the advection scheme to produce unphysical numerical diapycnal mixing, which in some cases may exceed the explicitly parameterised mixing based on observed physical processes, and this is likely to have effects on the long-timescale evolution of the simulated climate system. Despite this, few quantitative estimations have been made of the magnitude of the effective diapycnal diffusivity due to numerical mixing in these models. GO5.0 is the latest ocean model configuration developed jointly by the UK Met Office and the National Oceanography Centre (Megann et al, 2014), and forms part of the GC1 and GC2 climate models. It uses version 3.4 of the NEMO model, on the ORCA025 ¼° global tripolar grid. We describe various approaches to quantifying the numerical diapycnal mixing in this model, and present results from analysis of the GO5.0 model based on the isopycnal watermass analysis of Lee et al (2002) that indicate that numerical mixing does indeed form a significant component of the watermass transformation in the ocean interior.

  20. Software engineering the mixed model for genome-wide association studies on large samples.

    PubMed

    Zhang, Zhiwu; Buckler, Edward S; Casstevens, Terry M; Bradbury, Peter J

    2009-11-01

    Mixed models improve the ability to detect phenotype-genotype associations in the presence of population stratification and multiple levels of relatedness in genome-wide association studies (GWAS), but for large data sets the resource consumption becomes impractical. At the same time, the sample size and number of markers used for GWAS is increasing dramatically, resulting in greater statistical power to detect those associations. The use of mixed models with increasingly large data sets depends on the availability of software for analyzing those models. While multiple software packages implement the mixed model method, no single package provides the best combination of fast computation, ability to handle large samples, flexible modeling and ease of use. Key elements of association analysis with mixed models are reviewed, including modeling phenotype-genotype associations using mixed models, population stratification, kinship and its estimation, variance component estimation, use of best linear unbiased predictors or residuals in place of raw phenotype, improving efficiency and software-user interaction. The available software packages are evaluated, and suggestions made for future software development. PMID:19933212

  1. Improving the mixing performance of side channel type micromixers using an optimal voltage control model.

    PubMed

    Wu, Chien-Hsien; Yang, Ruey-Jen

    2006-06-01

    Electroosmotic flow in microchannels is restricted to low Reynolds number regimes. Since the inertia forces are extremely weak in such regimes, turbulent conditions do not readily develop, and hence species mixing occurs primarily as a result of diffusion. Consequently, achieving a thorough species mixing generally relies upon the use of extended mixing channels. This paper aims to improve the mixing performance of conventional side channel type micromixers by specifying the optimal driving voltages to be applied to each channel. In the proposed approach, the driving voltages are identified by constructing a simple theoretical scheme based on a 'flow-rate-ratio' model and Kirchhoff's law. The numerical and experimental results confirm that the optimal voltage control approach provides a better mixing performance than the use of a single driving voltage gradient. PMID:16688571

  2. Modeling of cylindrical alkaline cells III. Mixed-reaction model for the anode

    SciTech Connect

    Chen, Jenn-Shing; Cheh, H.Y. )

    1993-05-01

    A mixed-reaction model has been developed to simulate the discharge behavior of cylindrical alkaline zinc-manganese dioxide primary cells. The analysis of the system considers a whole prismatic cell consisting of a zinc amalgam anode, an inert porous separator, and a manganese dioxide cathode. The domain of investigation extends from the anode to the cathode current collector. The model is based on a macrohomogeneous theory of porous electrodes and includes considerations for the ohmic potential drop, diffusion and convection in the electrolyte, change in porosity and electrolyte decomposition due to chemical and electrochemical reactions, charge-transfer effects, and ionic transport in a concentrated electrolyte. The anode is considered to be a reversible, nonpolarizable electrode with two anodic reactions occurring simultaneously. A parameter which is based on the ratio of the extent of the two reactions is used to characterize the anode-mixed reactions. A solid-state proton diffusion as well as a direct charge transfer are used to describe the cathodic reaction. The performance between cells of different sizes is compared at the same galvanostatic discharge rates per unit cathode mass. Sources of polarization are identified, and the influence of cell behavior by the different operating variables are examined.

  3. Culturing oil sands microbes as mixed species communities enhances ex situ model naphthenic acid degradation

    PubMed Central

    Demeter, Marc A.; Lemire, Joseph A.; Yue, Gordon; Ceri, Howard; Turner, Raymond J.

    2015-01-01

    Oil sands surface mining for bitumen results in the formation of oil sands process water (OSPW), containing acutely toxic naphthenic acids (NAs). Potential exists for OSPW toxicity to be mitigated by aerobic degradation of the NAs by microorganisms indigenous to the oil sands tailings ponds, the success of which is dependent on the methods used to exploit the metabolisms of the environmental microbial community. Having hypothesized that the xenobiotic tolerant biofilm mode-of-life may represent a feasible way to harness environmental microbes for ex situ treatment of OSPW NAs, we aerobically grew OSPW microbes as single and mixed species biofilm and planktonic cultures under various conditions for the purpose of assaying their ability to tolerate and degrade NAs. The NAs evaluated were a diverse mixture of eight commercially available model compounds. Confocal microscopy confirmed the ability of mixed and single species OSPW cultures to grow as biofilms in the presence of the NAs evaluated. qPCR enumeration demonstrated that the addition of supplemental nutrients at concentrations of 1 g L-1 resulted in a more numerous population than 0.001 g L-1 supplementation by approximately 1 order of magnitude. GC-FID analysis revealed that mixed species cultures (regardless of the mode of growth) are the most effective at degrading the NAs tested. All constituent NAs evaluated were degraded below detectable limits with the exception of 1-adamantane carboxylic acid (ACA); subsequent experimentation with ACA as the sole NA also failed to exhibit degradation of this compound. Single species cultures degraded select few NA compounds. The degradation trends highlighted many structure-persistence relationships among the eight NAs tested, demonstrating the effect of side chain configuration and alkyl branching on compound recalcitrance. Of all the isolates, the Rhodococcus spp. degraded the greatest number of NA compounds, although still less than the mixed species cultures

  4. Molecular Biomarker-Based Biokinetic Modeling of a PCE-Dechlorinating and Methanogenic Mixed Culture

    SciTech Connect

    Heavner, Gretchen L. W.; Rowe, Annette R.; Mansfeldt, Cresten B.; Pan, Ju Khuan; Gossett, James M.; Richardson, Ruth E.

    2013-04-16

    Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial population-most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA “adjustment factors” were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population’s instantaneous

  5. Molecular biomarker-based biokinetic modeling of a PCE-dechlorinating and methanogenic mixed culture.

    PubMed

    Heavner, Gretchen L W; Rowe, Annette R; Mansfeldt, Cresten B; Pan, Ju Khuan; Gossett, James M; Richardson, Ruth E

    2013-04-16

    Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial populations--most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA "adjustment factors" were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population's instantaneous

  6. Multivariate longitudinal data analysis with mixed effects hidden Markov models.

    PubMed

    Raffa, Jesse D; Dubin, Joel A

    2015-09-01

    Multiple longitudinal responses are often collected as a means to capture relevant features of the true outcome of interest, which is often hidden and not directly measurable. We outline an approach which models these multivariate longitudinal responses as generated from a hidden disease process. We propose a class of models which uses a hidden Markov model with separate but correlated random effects between multiple longitudinal responses. This approach was motivated by a smoking cessation clinical trial, where a bivariate longitudinal response involving both a continuous and a binomial response was collected for each participant to monitor smoking behavior. A Bayesian method using Markov chain Monte Carlo is used. Comparison of separate univariate response models to the bivariate response models was undertaken. Our methods are demonstrated on the smoking cessation clinical trial dataset, and properties of our approach are examined through extensive simulation studies. PMID:25761965

  7. Modeling for Convective Heat Transport Based on Mixing Length Theory

    NASA Astrophysics Data System (ADS)

    Yamagishi, Y.; Yanagisawa, T.

    2002-12-01

    Convection is the most important mechanism for the Earth's internal dynamics, and plays a substantial role on its evolution. On investigating the thermal history of the Earth, convective heat transport should be taken into account. However, it is difficult to treat full convective flow throughout the Earth's entire history. Therefore, the parameterized convection has been developed and widely used. Convection occurring in the Earth's interior has some complicated aspects. It has large variation of viscosity, internal heating, phase boundaries, etc. Especially, the viscosity contrast has significant effect on the efficiency of the heat transport of the convection. The parameterized convection treats viscosity variation artificially, so it has many limitations. We developed an alternative method based on the concept of "mixing length theory". We can relate local thermal gradient with local convective velocity of fluid parcel. Convective heat transport is identified with effective thermal diffusivity, and we can calculate horizontally averaged temperature profile and heat flux by solving a thermal conduction problem. On estimating the parcel's velocity, we can include such as the effect of variable viscosity. In this study, we confirm that the temperature profile can be calculated correctly by this method, on comparing the experimental and 2D calculation results. We further show the effect of the viscosity contrast on the thermal structure of the convective fluid, and calculate the relationship between Nusselt number and modified Rayleigh number.

  8. Prediction of particle deposition in the lungs based on simple modeling of alveolar mixing.

    PubMed

    Georgakakou, S; Gourgoulianis, K; Daniil, Z; Bontozoglou, V

    2016-05-01

    A simplified model of particle deposition in the lungs has been developed and implemented, based on the hypothesis that perfect mixing takes place in the alveolar volume of each airway generation. This key idea is combined with purely convective transport along airways, driven by steady alveolar expansion and contraction, and results in an analytically tractable model. Predictions of the model, and in particular pulmonary deposition, are found in very good agreement with detailed benchmark data in the literature for particle diameters d≥0.1μm. The success of this simple model provides indirect evidence in favor of the role of alveolar mixing in the deposition process. PMID:26790361

  9. The characteristic analysis of a hybrid multifluid turbulent-mix model

    SciTech Connect

    Cheng, B.; Cranfill, C.W.

    1998-07-13

    A thorough analysis of the characteristics of a multifluid turbulent mix model in the case of one-dimensional two phase flows is presented under various physical circumstances. It has been found that the new hybrid multifluid turbulent mix model has all real characteristics if either real or turbulent viscosity is present. When real viscosity vanishes, the model still has all real characteristics for zero relative motion between fluids. For nonzero relative motions between fluids, the model will have all real characteristics if the disordered motions and turbulent viscosity together are generated with the nonzero relative motions simultaneously. The implications of the results are further discussed.

  10. Numerical comparisons of two formulations of the logistic regressive models with the mixed model in segregation analysis of discrete traits.

    PubMed

    Demenais, F M; Laing, A E; Bonney, G E

    1992-01-01

    Segregation analysis of discrete traits can be conducted by the classical mixed model and the recently introduced regressive models. The mixed model assumes an underlying liability to the disease, to which a major gene, a multifactorial component, and random environment contribute independently. Affected persons have a liability exceeding a threshold. The regressive logistic models assume that the logarithm of the odds of being affected is a linear function of major genotype effects, the phenotypes of older relatives, and other covariates. A formulation of the regressive models, based on an underlying liability model, has been recently proposed. The regression coefficients on antecedents are expressed in terms of the relevant familial correlations and a one-to-one correspondence with the parameters of the mixed model can thus be established. Computer simulations are conducted to evaluate the fit of the two formulations of the regressive models to the mixed model on nuclear families. The two forms of the class D regressive model provide a good fit to a generated mixed model, in terms of both hypothesis testing and parameter estimation. The simpler class A regressive model, which assumes that the outcomes of children depend solely on the outcomes of parents, is not robust against a sib-sib correlation exceeding that specified by the model, emphasizing testing class A against class D. The studies reported here show that if the true state of nature is that described by the mixed model, then a regressive model will do just as well. Moreover, the regressive models, allowing for more patterns of family dependence, provide a flexible framework to understand gene-environment interactions in complex diseases. PMID:1487139

  11. An a priori DNS study of the shadow-position mixing model

    DOE PAGESBeta

    Zhao, Xin -Yu; Bhagatwala, Ankit; Chen, Jacqueline H.; Haworth, Daniel C.; Pope, Stephen B.

    2016-01-15

    In this study, the modeling of mixing by molecular diffusion is a central aspect for transported probability density function (tPDF) methods. In this paper, the newly-proposed shadow position mixing model (SPMM) is examined, using a DNS database for a temporally evolving di-methyl ether slot jet flame. Two methods that invoke different levels of approximation are proposed to extract the shadow displacement (equivalent to shadow position) from the DNS database. An approach for a priori analysis of the mixing-model performance is developed. The shadow displacement is highly correlated with both mixture fraction and velocity, and the peak correlation coefficient of themore » shadow displacement and mixture fraction is higher than that of the shadow displacement and velocity. This suggests that the composition-space localness is reasonably well enforced by the model, with appropriate choices of model constants. The conditional diffusion of mixture fraction and major species from DNS and from SPMM are then compared, using mixing rates that are derived by matching the mixture fraction scalar dissipation rates. Good qualitative agreement is found, for the prediction of the locations of zero and maximum/minimum conditional diffusion locations for mixture fraction and individual species. Similar comparisons are performed for DNS and the IECM (interaction by exchange with the conditional mean) model. The agreement between SPMM and DNS is better than that between IECM and DNS, in terms of conditional diffusion iso-contour similarities and global normalized residual levels. It is found that a suitable value for the model constant c that controls the mixing frequency can be derived using the local normalized scalar variance, and that the model constant a controls the localness of the model. A higher-Reynolds-number test case is anticipated to be more appropriate to evaluate the mixing models, and stand-alone transported PDF simulations are required to more fully enforce

  12. Significant Promotion Effect of Mo Additive on a Novel Ce-Zr Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO(x) with NH3.

    PubMed

    Ding, Shipeng; Liu, Fudong; Shi, Xiaoyan; Liu, Kuo; Lian, Zhihua; Xie, Lijuan; He, Hong

    2015-05-13

    A novel Mo-promoted Ce-Zr mixed oxide catalyst prepared by a homogeneous precipitation method was used for the selective catalytic reduction (SCR) of NO(x) with NH3. The optimal catalyst showed high NH3-SCR activity, SO2/H2O durability, and thermal stability under test conditions. The addition of Mo inhibited growth of the CeO2 particle size, improved the redox ability, and increased the amount of surface acidity, especially the Lewis acidity, all of which were favorable for the excellent NH3-SCR performance. It is believed that the catalyst is promising for the removal of NO(x) from diesel engine exhaust. PMID:25894854

  13. Transient modeling/analysis of hyperbolic heat conduction problems employing mixed implicit-explicit alpha method

    NASA Technical Reports Server (NTRS)

    Tamma, Kumar K.; D'Costa, Joseph F.

    1991-01-01

    This paper describes the evaluation of mixed implicit-explicit finite element formulations for hyperbolic heat conduction problems involving non-Fourier effects. In particular, mixed implicit-explicit formulations employing the alpha method proposed by Hughes et al. (1987, 1990) are described for the numerical simulation of hyperbolic heat conduction models, which involves time-dependent relaxation effects. Existing analytical approaches for modeling/analysis of such models involve complex mathematical formulations for obtaining closed-form solutions, while in certain numerical formulations the difficulties include severe oscillatory solution behavior (which often disguises the true response) in the vicinity of the thermal disturbances, which propagate with finite velocities. In view of these factors, the alpha method is evaluated to assess the control of the amount of numerical dissipation for predicting the transient propagating thermal disturbances. Numerical test models are presented, and pertinent conclusions are drawn for the mixed-time integration simulation of hyperbolic heat conduction models involving non-Fourier effects.

  14. Mechanisms and modeling of the effects of additives on the nitrogen oxides emission

    NASA Technical Reports Server (NTRS)

    Kundu, Krishna P.; Nguyen, Hung Lee; Kang, M. Paul

    1991-01-01

    A theoretical study on the emission of the oxides of nitrogen in the combustion of hydrocarbons is presented. The current understanding of the mechanisms and the rate parameters for gas phase reactions were used to calculate the NO(x) emission. The possible effects of different chemical species on thermal NO(x), on a long time scale were discussed. The mixing of these additives at various stages of combustion were considered and NO(x) concentrations were calculated; effects of temperatures were also considered. The chemicals such as hydrocarbons, H2, CH3OH, NH3, and other nitrogen species were chosen as additives in this discussion. Results of these calculations can be used to evaluate the effects of these additives on the NO(x) emission in the industrial combustion system.

  15. The Closure of the Ocean Mixed Layer Temperature Budget using Level-Coordinate Model Fields

    NASA Technical Reports Server (NTRS)

    Kim, Seung-Bum; Fukumori, Ichiro; Lee, Tong

    2005-01-01

    Entrainment is an important element of the mixed layer mass, heat, and temperature budgets. Conventional procedures to estimate entrainment heat advection often do not permit the closure of heat and temperature budgets because of inaccuracies in its formulation. In this study a rigorous approach to evaluate the effect of entrainment using the output of a general circulation model (GCM) that does not have an explicit prognostic mixed layer model is described. The integral elements of the evaluation are 1) the rigorous estimates of the temperature difference between mixed layer water and entrained water at each horizontal grid point, 2) the formulation of the temperature difference such that the budget closes over a volume greater than one horizontal grid point, and 3) the apparent warming of the mixed layer during the mixed layer shoaling to account for the weak vertical temperature gradient within the mixed layer. This evaluation of entrainment heat advection is compared with the estimates by other commonly used ad hoc formulations by applying them in three regions: the north-central Pacific, the Kuroshio Extension, and the Nino-3 areas in the tropical Pacific. In all three areas the imbalance in the mixed layer temperature budget by the ad hoc estimates is significant, reaching a maximum of about 4 K yr(exp -1).

  16. An introduction to modeling longitudinal data with generalized additive models: applications to single-case designs.

    PubMed

    Sullivan, Kristynn J; Shadish, William R; Steiner, Peter M

    2015-03-01

    Single-case designs (SCDs) are short time series that assess intervention effects by measuring units repeatedly over time in both the presence and absence of treatment. This article introduces a statistical technique for analyzing SCD data that has not been much used in psychological and educational research: generalized additive models (GAMs). In parametric regression, the researcher must choose a functional form to impose on the data, for example, that trend over time is linear. GAMs reverse this process by letting the data inform the choice of functional form. In this article we review the problem that trend poses in SCDs, discuss how current SCD analytic methods approach trend, describe GAMs as a possible solution, suggest a GAM model testing procedure for examining the presence of trend in SCDs, present a small simulation to show the statistical properties of GAMs, and illustrate the procedure on 3 examples of different lengths. Results suggest that GAMs may be very useful both as a form of sensitivity analysis for checking the plausibility of assumptions about trend and as a primary data analysis strategy for testing treatment effects. We conclude with a discussion of some problems with GAMs and some future directions for research on the application of GAMs to SCDs. PMID:24885341

  17. Estimating the numerical diapycnal mixing in the GO5.0 ocean model

    NASA Astrophysics Data System (ADS)

    Megann, Alex; Nurser, George

    2014-05-01

    Constant-depth (or "z-coordinate") ocean models such as MOM and NEMO have become the de facto workhorse in climate applications, and have attained a mature stage in their development and are well understood. A generic shortcoming of this model type, however, is a tendency for the advection scheme to produce unphysical numerical diapycnal mixing, which in some cases may exceed the explicitly parameterised mixing based on observed physical processes (e.g. Hofmann and Maqueda, 2006), and this is likely to have effects on the long-timescale evolution of the simulated climate system. Despite this, few quantitative estimations have been made of the typical magnitude of the effective diapycnal diffusivity due to numerical mixing in these models. GO5.0 is the latest ocean model configuration developed jointly by the UK Met Office and the National Oceanography Centre (Megann et al, 2013). It uses version 3.4 of the NEMO model, on the ORCA025 global tripolar grid. Two approaches to quantifying the numerical diapycnal mixing in this model are described: the first is based on the isopycnal watermass analysis of Lee et al (2002), while the second uses a passive tracer to diagnose mixing across density surfaces. Results from these two methods will be compared and contrasted. Hofmann, M. and Maqueda, M. A. M., 2006. Performance of a second-order moments advection scheme in an ocean general circulation model. JGR-Oceans, 111(C5). Lee, M.-M., Coward, A.C., Nurser, A.G., 2002. Spurious diapycnal mixing of deep waters in an eddy-permitting global ocean model. JPO 32, 1522-1535 Megann, A., Storkey, D., Aksenov, Y., Alderson, S., Calvert, D., Graham, T., Hyder, P., Siddorn, J., and Sinha, B., 2013: GO5.0: The joint NERC-Met Office NEMO global ocean model for use in coupled and forced applications, Geosci. Model Dev. Discuss., 6, 5747-5799,.

  18. Application of fall-line mix models to understand degraded yield

    SciTech Connect

    Welser-Sherrill, L; Cooley, J H; Haynes, D A; Wilson, D C; Sherrill, M E; Mancini, R C; Tommasini, R

    2008-02-28

    Mixing between fuel and shell material is an important topic in the inertial confinement fusion community, and is commonly accepted as the primary mechanism for neutron yield degradation. Typically, radiation hydrodynamic simulations that lack mixing (clean simulations) tend to considerably overestimate the neutron yield. We present here a series of yield calculations based on a variety of fall-line inspired mix models. The results are compared to a series of OMEGA experiments which provide total neutron yields and time-dependent yield rates.

  19. Interactive phenomena in supersonic jet mixing problems. I Phenomenology and numerical modeling techniques

    NASA Technical Reports Server (NTRS)

    Dash, S. M.; Wolf, D. E.

    1984-01-01

    The interactive phenomena that occur in supersonic jet mixing flowfields, and numerical modeling techniques developed to analyze such phenomena are discussed. A spatial marching procedure based on solving the parabolized Navier-Stokes jet mixing equations is presented. This procedure combines shock-capturing methodology for the analysis of supersonic mixing regions with pressure-split methodology for the analysis of subsonic mixing regions. The two regions are coupled at viscous sonic lines utilizing a viscous-characteristic coupling procedure. Specialized techniques for the treatment of jet boundary growth, strong discontinuties (Mach disks), and small embedded subsonic zones (behind Mach disks) are presented. Turbulent processes are represented by two-equation turbulence model formulations. In Part II of this article, numerical studies are presented for a variety of supersonic jet interactive phenomena.

  20. A Mixed Approach for Modeling Blood Flow in Brain Microcirculation

    NASA Astrophysics Data System (ADS)

    Peyrounette, M.; Sylvie, L.; Davit, Y.; Quintard, M.

    2014-12-01

    We have previously demonstrated [1] that the vascular system of the healthy human brain cortex is a superposition of two structural components, each corresponding to a different spatial scale. At small-scale, the vascular network has a capillary structure, which is homogeneous and space-filling over a cut-off length. At larger scale, veins and arteries conform to a quasi-fractal branched structure. This structural duality is consistent with the functional duality of the vasculature, i.e. distribution and exchange. From a modeling perspective, this can be viewed as the superposition of: (a) a continuum model describing slow transport in the small-scale capillary network, characterized by a representative elementary volume and effective properties; and (b) a discrete network approach [2] describing fast transport in the arterial and venous network, which cannot be homogenized because of its fractal nature. This problematic is analogous to modeling problems encountered in geological media, e.g, in petroleum engineering, where fast conducting channels (wells or fractures) are embedded in a porous medium (reservoir rock). An efficient method to reduce the computational cost of fractures/continuum simulations is to use relatively large grid blocks for the continuum model. However, this also makes it difficult to accurately couple both structural components. In this work, we solve this issue by adapting the "well model" concept used in petroleum engineering [3] to brain specific 3-D situations. We obtain a unique linear system of equations describing the discrete network, the continuum and the well model coupling. Results are presented for realistic geometries and compared with a non-homogenized small-scale network model of an idealized periodic capillary network of known permeability. [1] Lorthois & Cassot, J. Theor. Biol. 262, 614-633, 2010. [2] Lorthois et al., Neuroimage 54 : 1031-1042, 2011. [3] Peaceman, SPE J. 18, 183-194, 1978.

  1. Unit physics testing of a mix model in an eulerian fluid computation

    SciTech Connect

    Vold, Erik; Douglass, Rod

    2010-01-01

    A K-L turbulence mix model driven with a drag-buoyancy source term is tested in an Eulerian code in a series of basic unit-physics tests, as part of a mix validation milestone. The model and the closure coefficient values are derived in the work of Dimonte-Tipton [D-T] in Phys.Flu.18, 085101 (2006), and many of the test problems were reported there, where the mix model operated in Lagrange computations. The drag-buoyancy K-L mix model was implemented within the Eulerian code framework by A.J. Scannapieco. Mix model performance is evaluated in terms of mix width growth rates compared to experiments in select regimes. Results in our Eulerian code are presented for several unit-physics I-D test problems including the decay of homogeneous isotropic turbulence (HIT), Rayleigh-Taylor (RT) unstable mixing, shock amplification of initial turbulence, Richtmyer-Meshkov (RM) mixing in several single shock test cases and in comparison to two RM experiments including re-shock (Vetter-Sturtevant and Poggi, et.al.). Sensitivity to model parameters, to Atwood number, and to initial conditions are examined. Results here are in good agreement in some tests (HIT, RT) with the previous results reported for the mix model in the Lagrange calculations. The HIT turbulent decay agrees closely with analytic expectations, and the RT growth rate matches experimental values for the default values of the model coefficients proposed in [D-T]. Results for RM characterized with a power law growth rate differ from the previous mix model work but are still within the range for reasonable agreement with experiments. Sensitivity to IC values in the RM studies are examined; results are sensitive to initial values of L[t=O], which largely determines the RM mix layer growth rate, and generally differs from the IC values used in the RT studies. Result sensitivity to initial turbulence, K[t=O], is seen to be small but significant above a threshold value. Initial conditions can be adjusted so that single

  2. Richtmyer-Meshkov mixing: Modeling and simulation of experiments

    NASA Astrophysics Data System (ADS)

    Denissen, Nicholas; Kurien, Susan

    2015-11-01

    Hydrodynamic instabilities that result from the interaction of a shock-wave with a perturbed interface are known as Richtmyer-Meshkov instabilities (RMI). RMI is important in a wide variety of applications including Inertial Confinement Fusion. Recent experiments at Los Alamos National Laboratory (LANL) have focused on careful measurement of initial conditions and repeated statistical measurements of the instability growth and transition to turbulence. This talk will discuss ongoing efforts to model these experiments using weakly non-linear theoretical models, one dimensional Reynolds-Averaged Navier-Stokes models and three-dimensional Implicit Large Eddy Simulations (ILES). Analysis of the experimental data supplies the initial condition for the theoretical model and the ILES calculations. The effect of different initial conditions and mesh resolutions will be examined in light of interest in international collaboration on an RMI test problem. Comparison of the different models to experimental data will be presented. All calculations are performed in the arbitrary Lagrangian/Eulerian (ALE) code FLAG, developed at LANL. The ALE framework allows us to assess the effects of numerical diffusion on RMI computations by varying the remap strategy.

  3. Secondary flows enhance mixing in a model of vibration-assisted dialysis

    NASA Astrophysics Data System (ADS)

    Pitre, John; Mueller, Bruce; Lewis, Susan; Bull, Joseph

    2014-11-01

    Hemodialysis is an integral part of treatment for patients with end stage renal disease. While hemodialysis has traditionally been described as a diffusion-dominated process, recent in vitro work has shown that vibration of the dialyzer can enhance the clearance of certain solutes during treatment. We hypothesize that the addition of vibration generates secondary flows in the dialysate compartment. These flows, perpendicular to the longitudinal axis of the dialysis fibers, advect solute away from the fiber walls, thus maintaining a larger concentration gradient and enhancing diffusion. Using the finite element method, we simulated the flow of dialysate through a hexagonally-packed array of cylinders and the transport of solute away from the cylinder walls. The addition of vibration was modeled using sinusoidal body forces of various frequencies and amplitudes. Using the variance of the concentration field as a metric, we found that vibration improves mixing according to a power law dependency on frequency. We will discuss the implications of these computational results on our understanding of the in vitro experiments and propose optimal vibration patterns for improving clearance in dialysis treatments. This work was supported by the Michigan Institute for Clinical and Health Research and NIH Grant UL1TR000433.

  4. Computational modeling of jet induced mixing of cryogenic propellants in low-G

    NASA Technical Reports Server (NTRS)

    Hochstein, J. I.; Gerhart, P. M.; Aydelot, J. C.

    1984-01-01

    The SOLA-ECLIPSE Code is being developed to enable computational prediction of jet induced mixing in cryogenic propellant tanks in a low-gravity environment. Velocity fields, predicted for scale model tanks, are presented which compare favorably with the available experimental data. A full scale liquid hydrogen tank for a typical Orbit Transfer Vehicle is analyzed with the conclusion that coupling an axial mixing jet with a thermodynamic vent system appears to be a viable concept for the control of tank pressure.

  5. Fluid and thermal mixing in a model cold leg and downcomer with loop flow

    SciTech Connect

    Rothe, P.H.; Ackerson, M.F.

    1982-04-01

    This report describes an experimental program of fluid mixing experiments performed at atmospheric pressure in a 1/5-scale transparent model of the cold leg and downcomer of typical Westinghouse and Combustion Engineering pressurized water reactors. The results include transient data from a grid of thermocouples and exensive flow visualization photographs. Substantial mixing of cold injected water with hot primary coolant occurred during many of the tests.

  6. Evaluation of thermal mixing data from a model cold leg and downcomer. [PWR

    SciTech Connect

    Rothe, P.H.; Fanning, M.W.

    1982-12-01

    This report describes an evaluation of thermal mixing data obtained in a 1/5-scale, transparent model of the cold leg and downcomer of a Pressurized Water Reactor (PWR). The data are relevant to the phenomenon of fluid and thermal mixing following HPI (High Pressure Injection) of coolant water in a PWR loop. The data are reduced, correlated and compared with theoretically derived values and scaling approaches.

  7. Synergism in the desorption of polycyclic aromatic hydrocarbons from soil models by mixed surfactant solutions.

    PubMed

    Sales, Pablo S; Fernández, Mariana A

    2016-05-01

    This study investigates the effect of a mixed surfactant system on the desorption of polycyclic aromatic hydrocarbons (PAHs) from soil model systems. The interaction of a non-ionic surfactant, Tween 80, and an anionic one, sodium laurate, forming mixed micelles, produces several beneficial effects, including reduction of adsorption onto solid of the non-ionic surfactant, decrease in the precipitation of the fatty acid salt, and synergism to solubilize PAHs from solids compared with individual surfactants. PMID:26873826

  8. Simplified renormalizable T{sup '} model for tribimaximal mixing and Cabibbo angle

    SciTech Connect

    Frampton, Paul H.; Matsuzaki, Shinya; Kephart, Thomas W.

    2008-10-01

    In a simplified renormalizable model where the neutrinos have Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixings tan{sup 2}{theta}{sub 12}=(1/2), {theta}{sub 13}=0, {theta}{sub 23}={pi}/4 and with flavor symmetry T{sup '} there is a corresponding prediction where the quarks have Cabibbo-Kobayashi-Maskawa (CKM) mixings tan2{theta}{sub 12}=({radical}(2)/3), {theta}{sub 13}=0, {theta}{sub 23}=0.

  9. Semiparametric regression of multidimensional genetic pathway data: least-squares kernel machines and linear mixed models.

    PubMed

    Liu, Dawei; Lin, Xihong; Ghosh, Debashis

    2007-12-01

    We consider a semiparametric regression model that relates a normal outcome to covariates and a genetic pathway, where the covariate effects are modeled parametrically and the pathway effect of multiple gene expressions is modeled parametrically or nonparametrically using least-squares kernel machines (LSKMs). This unified framework allows a flexible function for the joint effect of multiple genes within a pathway by specifying a kernel function and allows for the possibility that each gene expression effect might be nonlinear and the genes within the same pathway are likely to interact with each other in a complicated way. This semiparametric model also makes it possible to test for the overall genetic pathway effect. We show that the LSKM semiparametric regression can be formulated using a linear mixed model. Estimation and inference hence can proceed within the linear mixed model framework using standard mixed model software. Both the regression coefficients of the covariate effects and the LSKM estimator of the genetic pathway effect can be obtained using the best linear unbiased predictor in the corresponding linear mixed model formulation. The smoothing parameter and the kernel parameter can be estimated as variance components using restricted maximum likelihood. A score test is developed to test for the genetic pathway effect. Model/variable selection within the LSKM framework is discussed. The methods are illustrated using a prostate cancer data set and evaluated using simulations. PMID:18078480

  10. Conflicts Management Model in School: A Mixed Design Study

    ERIC Educational Resources Information Center

    Dogan, Soner

    2016-01-01

    The object of this study is to evaluate the reasons for conflicts occurring in school according to perceptions and views of teachers and resolution strategies used for conflicts and to build a model based on the results obtained. In the research, explanatory design including quantitative and qualitative methods has been used. The quantitative part…

  11. Mixing and Transport in the Small Intestine: A Lattice-Boltzmann Model

    NASA Astrophysics Data System (ADS)

    Banco, Gino; Brasseur, James; Wang, Yanxing; Aliani, Amit; Webb, Andrew

    2007-11-01

    The two primary functions of the small intestine are absorption of nutrients into the blood stream and transport of material along the gut for eventual evacuation. The primary transport mechanism is peristalsis. The time scales for absorption, however, rely on mixing and transport of molecules between the bulk flow and epithelial surface. Two basic motions contribute to mixing: peristalsis and repetitive segmental contraction of short segments of the gut. In this study we evaluate the relative roles of peristalsis vs. segmental contraction on the degree of mixing and time scales of nutrient transport to the epithelium using a two-dimensional model of flow and mixing in the small intestine. The model uses the lattice-Boltzmann framework with second-order moving boundary conditions and passive scalar (Sc = 10). Segmental and peristaltic contractions were parameterized using magnetic resonance imaging data from rat models. The Reynolds numbers (1.9), segment lengths (33 mm), max radii (2.75 mm) and occlusion ratios (0.33) were matched for direct comparison. Mixing is quantified by the rate of dispersion of scalar from an initial concentration in the center of the segment. We find that radial mixing is more rapid with segmental than peristaltic motion, that radial dispersion is much more rapid than axial, and that axial is comparable between the motions.

  12. The use of copulas to practical estimation of multivariate stochastic differential equation mixed effects models

    NASA Astrophysics Data System (ADS)

    Rupšys, P.

    2015-10-01

    A system of stochastic differential equations (SDE) with mixed-effects parameters and multivariate normal copula density function were used to develop tree height model for Scots pine trees in Lithuania. A two-step maximum likelihood parameter estimation method is used and computational guidelines are given. After fitting the conditional probability density functions to outside bark diameter at breast height, and total tree height, a bivariate normal copula distribution model was constructed. Predictions from the mixed-effects parameters SDE tree height model calculated during this research were compared to the regression tree height equations. The results are implemented in the symbolic computational language MAPLE.

  13. The use of copulas to practical estimation of multivariate stochastic differential equation mixed effects models

    SciTech Connect

    Rupšys, P.

    2015-10-28

    A system of stochastic differential equations (SDE) with mixed-effects parameters and multivariate normal copula density function were used to develop tree height model for Scots pine trees in Lithuania. A two-step maximum likelihood parameter estimation method is used and computational guidelines are given. After fitting the conditional probability density functions to outside bark diameter at breast height, and total tree height, a bivariate normal copula distribution model was constructed. Predictions from the mixed-effects parameters SDE tree height model calculated during this research were compared to the regression tree height equations. The results are implemented in the symbolic computational language MAPLE.

  14. Experience with mixed MPI/threaded programming models

    SciTech Connect

    May, J M; Supinski, B R

    1999-04-01

    A shared memory cluster is a parallel computer that consists of multiple nodes connected through an interconnection network. Each node is a symmetric multiprocessor (SMP) unit in which multiple CPUs share uniform access to a pool of main memory. The SGI Origin 2000, Compaq (formerly DEC) AlphaServer Cluster, and recent IBM RS6000/SP systems are all variants of this architecture. The SGI Origin 2000 has hardware that allows tasks running on any processor to access any main memory location in the system, so all the memory in the nodes forms a single shared address space. This is called a nonuniform memory access (NUMA) architecture because it gives programs a single shared address space, but the access time to different memory locations varies. In the IBM and Compaq systems, each node's memory forms a separate address space, and tasks communicate between nodes by passing messages or using other explicit mechanisms. Many large parallel codes use standard MPI calls to exchange data between tasks in a parallel job, and this is a natural programming model for distributed memory architectures. On a shared memory architecture, message passing is unnecessary if the code is written to use multithreading: threads run in parallel on different processors, and they exchange data simply by reading and writing shared memory locations. Shared memory clusters combine architectural elements of both distributed memory and shared memory systems, and they support both message passing and multithreaded programming models. Application developers are now trying to determine which programming model is best for these machines. This paper presents initial results of a study aimed at answering that question. We interviewed developers representing nine scientific code groups at Lawrence Livermore National Laboratory (LLNL). All of these groups are attempting to optimize their codes to run on shared memory clusters, specifically the IBM and DEC platforms at LLNL. This paper will focus on ease

  15. Calibrating the updated overshoot mixing model on eclipsing binary stars: HY Vir, YZ Cas, χ{sup 2} Hya, and VV Crv

    SciTech Connect

    Meng, Y.; Zhang, Q. S.

    2014-06-01

    Detached eclipsing binary stars with convective cores provide a good tool to investigate convective core overshoot. It has been performed on some binary stars to restrict the classical overshoot model which simply extends the boundary of the fully mixed region. However, the classical overshoot model is physically unreasonable and inconsistent with helioseismic investigations. An updated model of overshoot mixing was established recently. There is a key parameter in the model. In this paper, we use observations of four eclipsing binary stars, i.e., HY Vir, YZ Cas, χ{sup 2} Hya, and VV Crv, to investigate a suitable value for the parameter. It is found that the value suggested by calibrations on eclipsing binary stars is the same as the value recommended by other methods. In addition, we have studied the effects of the updated overshoot model on the stellar structure. The diffusion coefficient of convective/overshoot mixing is very high in the convection zone, then quickly decreases near the convective boundary, and exponentially decreases in the overshoot region. The low value of the diffusion coefficient in the overshoot region leads to weak mixing and a partially mixed overshoot region. Semi-convection, which appears in the standard stellar models of low-mass stars with convective cores, is removed by partial overshoot mixing.

  16. Behavior changes in SIS STD models with selective mixing

    SciTech Connect

    Hyman, J.M.; Li, J.

    1997-08-01

    The authors propose and analyze a heterogeneous, multigroup, susceptible-infective-susceptible (SIS) sexually transmitted disease (STD) model where the desirability and acceptability in partnership formations are functions of the infected individuals. They derive explicit formulas for the epidemic thresholds, prove the existence and uniqueness of the equilibrium states for the two-group model and provide a complete analysis of their local and global stability. The authors then investigate the effects of behavior changes on the transmission dynamics and analyze the sensitivity of the epidemic to the magnitude of the behavior changes. They verify that if people modify their behavior to reduce the probability of infection with individuals in highly infected groups, through either reduced contacts, reduced partner formations, or using safe sex, the infection level may be decreased. However, if people continue to have intragroup and intergroup partnerships, then changing the desirability and acceptability formation cannot eradicate the epidemic once it exceeds the epidemic threshold.

  17. Non-local ocean mixing model and a new plume model for deep convection

    NASA Astrophysics Data System (ADS)

    Canuto, V. M.; Cheng, Y.; Howard, A. M.

    Turbulent fluxes can be represented by a diffusivity tensor, the symmetric part of which describes " turbulent diffusion" while the anti-symmetric part describes " advection". Diffusion is a local process in the sense that it depends only on the local gradients of the mean fields while advection is non-local for it is represented by an integral over all length scales (all eddies) that can "fit" from say the bottom of the physical domain to the z where the fluxes are computed. In the ocean, there are two main regimes where non-local transport is important. One regime is where storms release a sudden burst of mechanical energy to the ocean surface that is then transported downward by energetic eddies that deepen the mixed layer. Even relatively simple non-local models yield results considerably more realistic than those of local models. The second regime is deep convection (DC) caused by loss of surface buoyancy, the description of which is required for a reliable assessment of water masses formation. At present, there is no reliable model for either of these non-local regimes individually or much less a formalism capable of accounting for both regimes simultaneously. The goal of this paper is to present a formalism that provides the expressions for the non-local fluxes for momentum, heat and salinity encompassing both cases. Since the resulting number of dynamic equations involves is however large, we work out two sub-models, one when only shear must be treated non-locally (e.g., when storms release mechanical energy) and one when only buoyancy is to be treated non-locally (the DC case). We employ the Reynolds Stress formalism in which non-locality is represented by the third-order moments which in turn depend on the fourth-order moments for which we employ a new model that has been tested against LES data, aircraft data and a full PBL simulation. For the DC case, we rewrite the non-local model in terms of Plumes since thus far the only non-local model used to treat

  18. Rubber yield prediction by meteorological conditions using mixed models and multi-model inference techniques.

    PubMed

    Golbon, Reza; Ogutu, Joseph Ochieng; Cotter, Marc; Sauerborn, Joachim

    2015-12-01

    Linear mixed models were developed and used to predict rubber (Hevea brasiliensis) yield based on meteorological conditions to which rubber trees had been exposed for periods ranging from 1 day to 2 months prior to tapping events. Predictors included a range of moving averages of meteorological covariates spanning different windows of time before the date of the tapping events. Serial autocorrelation in the latex yield measurements was accounted for using random effects and a spatial generalization of the autoregressive error covariance structure suited to data sampled at irregular time intervals. Information theoretics, specifically the Akaike information criterion (AIC), AIC corrected for small sample size (AICc), and Akaike weights, was used to select models with the greatest strength of support in the data from a set of competing candidate models. The predictive performance of the selected best model was evaluated using both leave-one-out cross-validation (LOOCV) and an independent test set. Moving averages of precipitation, minimum and maximum temperature, and maximum relative humidity with a 30-day lead period were identified as the best yield predictors. Prediction accuracy expressed in terms of the percentage of predictions within a measurement error of 5 g for cross-validation and also for the test dataset was above 99 %. PMID:25824122

  19. Rubber yield prediction by meteorological conditions using mixed models and multi-model inference techniques

    NASA Astrophysics Data System (ADS)

    Golbon, Reza; Ogutu, Joseph Ochieng; Cotter, Marc; Sauerborn, Joachim

    2015-12-01

    Linear mixed models were developed and used to predict rubber ( Hevea brasiliensis) yield based on meteorological conditions to which rubber trees had been exposed for periods ranging from 1 day to 2 months prior to tapping events. Predictors included a range of moving averages of meteorological covariates spanning different windows of time before the date of the tapping events. Serial autocorrelation in the latex yield measurements was accounted for using random effects and a spatial generalization of the autoregressive error covariance structure suited to data sampled at irregular time intervals. Information theoretics, specifically the Akaike information criterion (AIC), AIC corrected for small sample size (AICc), and Akaike weights, was used to select models with the greatest strength of support in the data from a set of competing candidate models. The predictive performance of the selected best model was evaluated using both leave-one-out cross-validation (LOOCV) and an independent test set. Moving averages of precipitation, minimum and maximum temperature, and maximum relative humidity with a 30-day lead period were identified as the best yield predictors. Prediction accuracy expressed in terms of the percentage of predictions within a measurement error of 5 g for cross-validation and also for the test dataset was above 99 %.

  20. Zero-inflated negative binomial mixed model: an application to two microbial organisms important in oesophagitis.

    PubMed

    Fang, R; Wagner, B D; Harris, J K; Fillon, S A

    2016-08-01

    Altered microbial communities are thought to play an important role in eosinophilic oesophagitis, an allergic inflammatory condition of the oesophagus. Identification of the majority of organisms present in human-associated microbial communities is feasible with the advent of high throughput sequencing technology. However, these data consist of non-negative, highly skewed sequence counts with a large proportion of zeros. In addition, hierarchical study designs are often performed with repeated measurements or multiple samples collected from the same subject, thus requiring approaches to account for within-subject variation, yet only a small number of microbiota studies have applied hierarchical regression models. In this paper, we describe and illustrate the use of a hierarchical regression-based approach to evaluate multiple factors for a small number of organisms individually. More specifically, the zero-inflated negative binomial mixed model with random effects in both the count and zero-inflated parts is applied to evaluate associations with disease state while adjusting for potential confounders for two organisms of interest from a study of human microbiota sequence data in oesophagitis. PMID:27049299

  1. Parallel Computation of Flow in Heterogeneous Media Modelled by Mixed Finite Elements

    NASA Astrophysics Data System (ADS)

    Cliffe, K. A.; Graham, I. G.; Scheichl, R.; Stals, L.

    2000-11-01

    In this paper we describe a fast parallel method for solving highly ill-conditioned saddle-point systems arising from mixed finite element simulations of stochastic partial differential equations (PDEs) modelling flow in heterogeneous media. Each realisation of these stochastic PDEs requires the solution of the linear first-order velocity-pressure system comprising Darcy's law coupled with an incompressibility constraint. The chief difficulty is that the permeability may be highly variable, especially when the statistical model has a large variance and a small correlation length. For reasonable accuracy, the discretisation has to be extremely fine. We solve these problems by first reducing the saddle-point formulation to a symmetric positive definite (SPD) problem using a suitable basis for the space of divergence-free velocities. The reduced problem is solved using parallel conjugate gradients preconditioned with an algebraically determined additive Schwarz domain decomposition preconditioner. The result is a solver which exhibits a good degree of robustness with respect to the mesh size as well as to the variance and to physically relevant values of the correlation length of the underlying permeability field. Numerical experiments exhibit almost optimal levels of parallel efficiency. The domain decomposition solver (DOUG, http://www.maths.bath.ac.uk/~parsoft) used here not only is applicable to this problem but can be used to solve general unstructured finite element systems on a wide range of parallel architectures.

  2. Mixing carrots and sticks to conserve forests in the Brazilian Amazon: a spatial probabilistic modeling approach.

    PubMed

    Börner, Jan; Marinho, Eduardo; Wunder, Sven

    2015-01-01

    Annual forest loss in the Brazilian Amazon had in 2012 declined to less than 5,000 sqkm, from over 27,000 in 2004. Mounting empirical evidence suggests that changes in Brazilian law enforcement strategy and the related governance system may account for a large share of the overall success in curbing deforestation rates. At the same time, Brazil is experimenting with alternative approaches to compensate farmers for conservation actions through economic incentives, such as payments for environmental services, at various administrative levels. We develop a spatially explicit simulation model for deforestation decisions in response to policy incentives and disincentives. The model builds on elements of optimal enforcement theory and introduces the notion of imperfect payment contract enforcement in the context of avoided deforestation. We implement the simulations using official deforestation statistics and data collected from field-based forest law enforcement operations in the Amazon region. We show that a large-scale integration of payments with the existing regulatory enforcement strategy involves a tradeoff between the cost-effectiveness of forest conservation and landholder incomes. Introducing payments as a complementary policy measure increases policy implementation cost, reduces income losses for those hit hardest by law enforcement, and can provide additional income to some land users. The magnitude of the tradeoff varies in space, depending on deforestation patterns, conservation opportunity and enforcement costs. Enforcement effectiveness becomes a key determinant of efficiency in the overall policy mix. PMID:25650966

  3. Mixing Carrots and Sticks to Conserve Forests in the Brazilian Amazon: A Spatial Probabilistic Modeling Approach

    PubMed Central

    Börner, Jan; Marinho, Eduardo; Wunder, Sven

    2015-01-01

    Annual forest loss in the Brazilian Amazon had in 2012 declined to less than 5,000 sqkm, from over 27,000 in 2004. Mounting empirical evidence suggests that changes in Brazilian law enforcement strategy and the related governance system may account for a large share of the overall success in curbing deforestation rates. At the same time, Brazil is experimenting with alternative approaches to compensate farmers for conservation actions through economic incentives, such as payments for environmental services, at various administrative levels. We develop a spatially explicit simulation model for deforestation decisions in response to policy incentives and disincentives. The model builds on elements of optimal enforcement theory and introduces the notion of imperfect payment contract enforcement in the context of avoided deforestation. We implement the simulations using official deforestation statistics and data collected from field-based forest law enforcement operations in the Amazon region. We show that a large-scale integration of payments with the existing regulatory enforcement strategy involves a tradeoff between the cost-effectiveness of forest conservation and landholder incomes. Introducing payments as a complementary policy measure increases policy implementation cost, reduces income losses for those hit hardest by law enforcement, and can provide additional income to some land users. The magnitude of the tradeoff varies in space, depending on deforestation patterns, conservation opportunity and enforcement costs. Enforcement effectiveness becomes a key determinant of efficiency in the overall policy mix. PMID:25650966

  4. Modeling seasonal circulation, upwelling and tidal mixing in the Arafura and Timor Seas

    NASA Astrophysics Data System (ADS)

    Condie, Scott A.

    2011-09-01

    The extensive shallow tropical seas off northern Australia, encompassing the Arafura and Timor Seas, have been identified as one of the most pristine marine environments on the planet. However, the remoteness and the absence of major industrial development that has contributed to this status have the additional consequence that relatively little is known about these systems. This study is the first to model oceanographic conditions across the tidally dominated Arafura and Timor Seas, and their seasonal variability. The results are based on a high-resolution (0.05°) ocean circulation model forced by realistic winds, waves and tides. The main focus of the study is on physical processes that influence the distributions of sediments and primary productivity across the system. Regions of high bottom stress and tidal mixing have been identified, including a large offshore area around Van Diemen Rise (Timor Sea). Lagrangian particle tracks have revealed a seasonal overturning cell that stretches across the Gulf of Carpentaria (Arafura Sea) with upwelling and downwelling on either side of the Gulf. The presence of coastal upwelling and downwelling is shown to provide a dynamically consistent explanation for the persistent turbid boundary layer observed around the shallow coastal waters of the Gulf.

  5. Marketing for a Web-Based Master's Degree Program in Light of Marketing Mix Model

    ERIC Educational Resources Information Center

    Pan, Cheng-Chang

    2012-01-01

    The marketing mix model was applied with a focus on Web media to re-strategize a Web-based Master's program in a southern state university in U.S. The program's existing marketing strategy was examined using the four components of the model: product, price, place, and promotion, in hopes to repackage the program (product) to prospective students…

  6. The Performance of IRT Model Selection Methods with Mixed-Format Tests

    ERIC Educational Resources Information Center

    Whittaker, Tiffany A.; Chang, Wanchen; Dodd, Barbara G.

    2012-01-01

    When tests consist of multiple-choice and constructed-response items, researchers are confronted with the question of which item response theory (IRT) model combination will appropriately represent the data collected from these mixed-format tests. This simulation study examined the performance of six model selection criteria, including the…

  7. Generalized Path Analysis and Generalized Simultaneous Equations Model for Recursive Systems with Responses of Mixed Types

    ERIC Educational Resources Information Center

    Tsai, Tien-Lung; Shau, Wen-Yi; Hu, Fu-Chang

    2006-01-01

    This article generalizes linear path analysis (PA) and simultaneous equations models (SiEM) to deal with mixed responses of different types in a recursive or triangular system. An efficient instrumental variable (IV) method for estimating the structural coefficients of a 2-equation partially recursive generalized path analysis (GPA) model and…

  8. Taking Advantage of Model-Driven Engineering Foundations for Mixed Interaction Design

    NASA Astrophysics Data System (ADS)

    Gauffre, Guillaume; Dubois, Emmanuel

    New forms of interactive systems, hereafter referred to as Mixed Interactive Systems (MIS), are based on the use of physical artefacts present in the environment. Mixing the digital and physical worlds affects the development of interactive systems, especially from the point of view of the design resources which need to express new dimensions. Consequently, there is a crucial need to clearly describe the content and utility of the recent models associated to these new interaction forms. Based on existing initiatives in the field of HCI, this chapter first highlights the interest of using a Model-Driven Engineering (MDE) approach for the design of MIS. Then, this chapter retraces the application of a MDE approach on a specific Mixed Interaction design resource. The resulted contribution is a motivated, explicit, complete and standardized definition of the ASUR model, a model for mixed interaction design. This definition constitutes a basis to promote the use of this model, to support its diffusion and to derive design tools from this model. The model-driven development of a flexible ASUR editor is finally introduced, thus facilitating the insertion of model extensions and articulations.

  9. MODELS AND STATISTICAL METHODS FOR GASEOUS EMISSION TESTING OF FINITE SOURCES IN WELL-MIXED CHAMBERS

    EPA Science Inventory

    The paper proposes two families of mathematical models to represent either the concentration of a gaseous emission in (or the accumulated amount exiting from) a well-mixed, environmentally controlled test chamber. A thin film model, which seems applicable to such sources as carpe...

  10. On the Non Unitary Neutrino Mixing Matrix in 331 Model with Three Higgs Triplets

    NASA Astrophysics Data System (ADS)

    Mebarki, N.

    2015-04-01

    The neutrino mixing phenomenon is studied within the non unitary Pontecorvo- Maki-Nakagawa-Sakata modified matrix (PMNS) in the context of the low energy limit of the minimal 331 model without right handed neutrinos as a deviation from the standard model. Moreover, comparison with the recent experimental data gives some stringent bounds on some physical parameters.

  11. A Second-Order Conditionally Linear Mixed Effects Model with Observed and Latent Variable Covariates

    ERIC Educational Resources Information Center

    Harring, Jeffrey R.; Kohli, Nidhi; Silverman, Rebecca D.; Speece, Deborah L.

    2012-01-01

    A conditionally linear mixed effects model is an appropriate framework for investigating nonlinear change in a continuous latent variable that is repeatedly measured over time. The efficacy of the model is that it allows parameters that enter the specified nonlinear time-response function to be stochastic, whereas those parameters that enter in a…

  12. Examples of Mixed-Effects Modeling with Crossed Random Effects and with Binomial Data

    ERIC Educational Resources Information Center

    Quene, Hugo; van den Bergh, Huub

    2008-01-01

    Psycholinguistic data are often analyzed with repeated-measures analyses of variance (ANOVA), but this paper argues that mixed-effects (multilevel) models provide a better alternative method. First, models are discussed in which the two random factors of participants and items are crossed, and not nested. Traditional ANOVAs are compared against…

  13. BAYESIAN PARAMETER ESTIMATION IN A MIXED-ORDER MODEL OF BOD DECAY. (U915590)

    EPA Science Inventory

    We describe a generalized version of the BOD decay model in which the reaction is allowed to assume an order other than one. This is accomplished by making the exponent on BOD concentration a free parameter to be determined by the data. This "mixed-order" model may be ...

  14. Fitting additive hazards models for case-cohort studies: a multiple imputation approach.

    PubMed

    Jung, Jinhyouk; Harel, Ofer; Kang, Sangwook

    2016-07-30

    In this paper, we consider fitting semiparametric additive hazards models for case-cohort studies using a multiple imputation approach. In a case-cohort study, main exposure variables are measured only on some selected subjects, but other covariates are often available for the whole cohort. We consider this as a special case of a missing covariate by design. We propose to employ a popular incomplete data method, multiple imputation, for estimation of the regression parameters in additive hazards models. For imputation models, an imputation modeling procedure based on a rejection sampling is developed. A simple imputation modeling that can naturally be applied to a general missing-at-random situation is also considered and compared with the rejection sampling method via extensive simulation studies. In addition, a misspecification aspect in imputation modeling is investigated. The proposed procedures are illustrated using a cancer data example. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26194861

  15. Fitting and Calibrating a Multilevel Mixed-Effects Stem Taper Model for Maritime Pine in NW Spain

    PubMed Central

    Arias-Rodil, Manuel; Castedo-Dorado, Fernando; Cámara-Obregón, Asunción; Diéguez-Aranda, Ulises

    2015-01-01

    Stem taper data are usually hierarchical (several measurements per tree, and several trees per plot), making application of a multilevel mixed-effects modelling approach essential. However, correlation between trees in the same plot/stand has often been ignored in previous studies. Fitting and calibration of a variable-exponent stem taper function were conducted using data from 420 trees felled in even-aged maritime pine (Pinus pinaster Ait.) stands in NW Spain. In the fitting step, the tree level explained much more variability than the plot level, and therefore calibration at plot level was omitted. Several stem heights were evaluated for measurement of the additional diameter needed for calibration at tree level. Calibration with an additional diameter measured at between 40 and 60% of total tree height showed the greatest improvement in volume and diameter predictions. If additional diameter measurement is not available, the fixed-effects model fitted by the ordinary least squares technique should be used. Finally, we also evaluated how the expansion of parameters with random effects affects the stem taper prediction, as we consider this a key question when applying the mixed-effects modelling approach to taper equations. The results showed that correlation between random effects should be taken into account when assessing the influence of random effects in stem taper prediction. PMID:26630156

  16. Fitting and Calibrating a Multilevel Mixed-Effects Stem Taper Model for Maritime Pine in NW Spain.

    PubMed

    Arias-Rodil, Manuel; Castedo-Dorado, Fernando; Cámara-Obregón, Asunción; Diéguez-Aranda, Ulises

    2015-01-01

    Stem taper data are usually hierarchical (several measurements per tree, and several trees per plot), making application of a multilevel mixed-effects modelling approach essential. However, correlation between trees in the same plot/stand has often been ignored in previous studies. Fitting and calibration of a variable-exponent stem taper function were conducted using data from 420 trees felled in even-aged maritime pine (Pinus pinaster Ait.) stands in NW Spain. In the fitting step, the tree level explained much more variability than the plot level, and therefore calibration at plot level was omitted. Several stem heights were evaluated for measurement of the additional diameter needed for calibration at tree level. Calibration with an additional diameter measured at between 40 and 60% of total tree height showed the greatest improvement in volume and diameter predictions. If additional diameter measurement is not available, the fixed-effects model fitted by the ordinary least squares technique should be used. Finally, we also evaluated how the expansion of parameters with random effects affects the stem taper prediction, as we consider this a key question when applying the mixed-effects modelling approach to taper equations. The results showed that correlation between random effects should be taken into account when assessing the influence of random effects in stem taper prediction. PMID:26630156

  17. Seasonal mixed-layer dynamics in an eddy-resolving ocean circulation model

    NASA Astrophysics Data System (ADS)

    Schiller, Andreas; Ridgway, Ken R.

    2013-07-01

    Mean and seasonal mixed-layer depths (MLDs) derived from an eddy-resolving ocean general circulation model with a horizontal resolution of (1/10)° are validated with climatological observations. Associated heat budgets on seasonal timescales are analyzed for six boundary current regions with high eddy kinetic energy (Somali Current, Agulhas Current region, Kuroshio, East Australian Current, Gulf Stream, and Brazil-Malvinas/Falkland Confluence). In all of these regions and on seasonal timescales, (a) horizontal advection significantly contributes to the mixed-layer heat budget (MLHB) on eddy scales and locally exceeds ±5°C/month; (b) lateral mixing (calculated as a residual term) is similar in size to surface net heat flux, horizontal advection, and vertical entrainment in defining the mixed-layer temperature; (c) seasonal vertical entrainment has a cooling effect on mixed-layer temperature throughout the year in the regions investigated; and (d) a phase lag between MLD and changes in mixed-layer heat content exists such that local cooling (warming) in the mixed layer precedes maxima (minima) in MLD by 1-3 months. A rather complex picture emerges where the MLHB in ocean boundary currents on larger spatial scales is determined by net surface heat fluxes and entrainment, whereas local, eddy-related advection and stirring modulate the large-scale signals.

  18. The Stagger-grid: A grid of 3D stellar atmosphere models. III. The relation to mixing length convection theory

    NASA Astrophysics Data System (ADS)

    Magic, Z.; Weiss, A.; Asplund, M.

    2015-01-01

    Aims: We investigate the relation between 1D atmosphere models that rely on the mixing length theory and models based on full 3D radiative hydrodynamic (RHD) calculations to describe convection in the envelopes of late-type stars. Methods: The adiabatic entropy value of the deep convection zone, sbot, and the entropy jump, Δs, determined from the 3D RHD models, were matched with the mixing length parameter, αMLT, from 1D hydrostatic atmosphere models with identical microphysics (opacities and equation-of-state). We also derived the mass mixing length parameter, αm, and the vertical correlation length of the vertical velocity, C[vz,vz], directly from the 3D hydrodynamical simulations of stellar subsurface convection. Results: The calibrated mixing length parameter for the Sun is α๏MLT (Sbot) = 1.98. . For different stellar parameters, αMLT varies systematically in the range of 1.7 - 2.4. In particular, αMLT decreases towards higher effective temperature, lower surface gravity and higher metallicity. We find equivalent results for α๏MLT (ΔS). In addition, we find a tight correlation between the mixing length parameter and the inverse entropy jump. We derive an analytical expression from the hydrodynamic mean-field equations that motivates the relation to the mass mixing length parameter, αm, and find that it qualitatively shows a similar variation with stellar parameter (between 1.6 and 2.4) with the solar value of α๏m = 1.83.. The vertical correlation length scaled with the pressure scale height yields 1.71 for the Sun, but only displays a small systematic variation with stellar parameters, the correlation length slightly increases with Teff. Conclusions: We derive mixing length parameters for various stellar parameters that can be used to replace a constant value. Within any convective envelope, αm and related quantities vary strongly. Our results will help to replace a constant αMLT. Appendices are available in electronic form at http

  19. How does the Redi parameter for mesoscale mixing impact global climate in an Earth System Model?

    NASA Astrophysics Data System (ADS)

    Pradal, Marie-Aude; Gnanadesikan, Anand

    2014-09-01

    A coupled climate model is used to examine the impact of an increase in the mixing due to mesoscale eddies on the global climate system. A sixfold increase in the Redi mixing coefficient ARedi, which is within the admissible range of variation, has the overall effect of warming the global-mean surface air and sea surface temperatures by more than 1°C. Locally, sea surface temperatures increase by up to 7°C in the North Pacific and by up to 4°C in the Southern Ocean, with corresponding impacts on the ice concentration and ice extent in polar regions. However, it is not clear that the changes in heat transport from tropics to poles associated with changing this coefficient are primarily responsible for these changes. We found that the changes in the transport of heat are often much smaller than changes in long-wave trapping and short-wave absorption. Additionally, changes in the advective and diffusive transport of heat toward the poles often oppose each other. However, we note that the poleward transport of salt increases near the surface as ARedi increases. We suggest a causal chain in which enhanced eddy stirring leads to increased high-latitude surface salinity reducing salt stratification and water column stability and enhancing convection, triggering two feedback loops. In one, deeper convection prevents sea ice formation, which decreases albedo, which increases SW absorption, further increasing SST and decreasing sea ice formation. In the other, increased SST and reduced sea ice allow for more water vapor in the atmosphere, trapping long-wave radiation. Destratifying the polar regions is thus a potential way in which changes in ocean circulation might warm the planet.

  20. Simulation of mixed convection flow in a room with a two-layer turbulence model.

    PubMed

    Xu, W; Chen, Q

    2000-12-01

    Most indoor airflows are mixed convection. In order to simulate mixed convection accurately and efficiently, this paper uses a two-layer turbulence model. The two-layer model combines a one-equation model for near wall flow together with the standard k-epsilon model for outer-wall flow. The model has been used to predict the mixed convection by displacement ventilation in an office. The computed results agree well with the corresponding airflow pattern and the distributions of air temperature, air velocity, air velocity fluctuation, and tracer-gas concentration. The model can predict correctly heat transfer from a wall where the standard k-epsilon model and re-normalization group (RNG) k-epsilon model with wall functions often fails. The computing cost required by the two-layer model is comparable to that of the standard k-epsilon model and RNG k-epsilon model and is significantly less than that by a low-Reynolds number model. PMID:11089334

  1. Analytical and numerical modeling of non-collinear shear wave mixing at an imperfect interface

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyin; Nagy, Peter B.; Hassan, Waled

    2016-02-01

    Non-collinear shear wave mixing at an imperfect interface between two solids can be exploited for nonlinear ultrasonic assessment of bond quality. In this study we developed two analytical models for nonlinear imperfect interfaces. The first model uses a finite nonlinear interfacial stiffness representation of an imperfect interface of vanishing thickness, while the second model relies on a thin nonlinear interphase layer to represent an imperfect interface region. The second model is actually a derivative of the first model obtained by calculating the equivalent interfacial stiffness of a thin isotropic nonlinear interphase layer in the quasi-static approximation. The predictions of both analytical models were numerically verified by comparison to COMSOL finite element simulations. These models can accurately predict the excess nonlinearity caused by interface imperfections based on the strength of the reflected and transmitted mixed longitudinal waves produced by them under non-collinear shear wave interrogation.

  2. Comparing Bayesian stable isotope mixing models: Which tools are best for sediments?

    NASA Astrophysics Data System (ADS)

    Morris, David; Macko, Stephen

    2016-04-01

    Bayesian stable isotope mixing models have received much attention as a means of coping with multiple sources and uncertainty in isotope ecology (e.g. Phillips et al., 2014), enabling the probabilistic determination of the contributions made by each food source to the total diet of the organism in question. We have applied these techniques to marine sediments for the first time. The sediments of the Chukchi Sea and Beaufort Sea offer an opportunity to utilize these models for organic geochemistry, as there are three likely sources of organic carbon; pelagic phytoplankton, sea ice algae and terrestrial material from rivers and coastal erosion, as well as considerable variation in the marine δ13C values. Bayesian mixing models using bulk δ13C and δ15N data from Shelf Basin Interaction samples allow for the probabilistic determination of the contributions made by each of the sources to the organic carbon budget, and can be compared with existing source contribution estimates based upon biomarker models (e.g. Belicka & Harvey, 2009, Faux, Belicka, & Rodger Harvey, 2011). The δ13C of this preserved material varied from -22.1 to -16.7‰ (mean -19.4±1.3‰), while δ15N varied from 4.1 to 7.6‰ (mean 5.7±1.1‰). Using the SIAR model, we found that water column productivity was the source of between 50 and 70% of the organic carbon buried in this portion of the western Arctic with the remainder mainly supplied by sea ice algal productivity (25-35%) and terrestrial inputs (15%). With many mixing models now available, this study will compare SIAR with MixSIAR and the new FRUITS model. Monte Carlo modeling of the mixing polygon will be used to validate the models, and hierarchical models will be utilised to glean more information from the data set.

  3. The Apollo 16 regolith - A petrographically-constrained chemical mixing model

    NASA Technical Reports Server (NTRS)

    Kempa, M. J.; Papike, J. J.; White, C.

    1980-01-01

    A mixing model for Apollo 16 regolith samples has been developed, which differs from other A-16 mixing models in that it is both petrographically constrained and statistically sound. The model was developed using three components representative of rock types present at the A-16 site, plus a representative mare basalt. A linear least-squares fitting program employing the chi-squared test and sum of components was used to determine goodness of fit. Results for surface soils indicate that either there are no significant differences between Cayley and Descartes material at the A-16 site or, if differences do exist, they have been obscured by meteoritic reworking and mixing of the lithologies.

  4. Mixed-mode oscillations in a three time-scale model for the dopaminergic neuron

    NASA Astrophysics Data System (ADS)

    Krupa, Martin; Popović, Nikola; Kopell, Nancy; Rotstein, Horacio G.

    2008-03-01

    Mixed-mode dynamics is a complex type of dynamical behavior that has been observed both numerically and experimentally in numerous prototypical systems in the natural sciences. The compartmental Wilson-Callaway model for the dopaminergic neuron is an example of a system that exhibits a wide variety of mixed-mode patterns upon variation of a control parameter. One characteristic feature of this system is the presence of multiple time scales. In this article, we study the Wilson-Callaway model from a geometric point of view. We show that the observed mixed-mode dynamics is caused by a slowly varying canard structure. By appropriately transforming the model equations, we reduce them to an underlying three-dimensional canonical form that can be analyzed via a slight adaptation of the approach developed by M. Krupa, N. Popović, and N. Kopell (unpublished).

  5. A Mixed-Effects Model with Different Strategies for Modeling Volume in Cunninghamia lanceolata Plantations

    PubMed Central

    Guangyi, Mei; Yujun, Sun; Hao, Xu; de-Miguel, Sergio

    2015-01-01

    A systematic evaluation of nonlinear mixed-effect taper models for volume prediction was performed. Of 21 taper equations with fewer than 5 parameters each, the best 4-parameter fixed-effect model according to fitting statistics was then modified by comparing its values for the parameters total height (H), diameter at breast height (DBH), and aboveground height (h) to modeling data. Seven alternative prediction strategies were compared using the best new equation in the absence of calibration data, which is often unavailable in forestry practice. The results of this study suggest that because calibration may sometimes be a realistic option, though it is rarely used in practical applications, one of the best strategies for improving the accuracy of volume prediction is the strategy with 7 calculated total heights of 3, 6 and 9 trees in the largest, smallest and medium-size categories, respectively. We cannot use the average trees or dominant trees for calculating the random parameter for further predictions. The method described here will allow the user to make the best choices of taper type and the best random-effect calculated strategy for each practical application and situation at tree level. PMID:26445505

  6. A Mixed-Effects Model with Different Strategies for Modeling Volume in Cunninghamia lanceolata Plantations.

    PubMed

    Guangyi, Mei; Yujun, Sun; Hao, Xu; de-Miguel, Sergio

    2015-01-01

    A systematic evaluation of nonlinear mixed-effect taper models for volume prediction was performed. Of 21 taper equations with fewer than 5 parameters each, the best 4-parameter fixed-effect model according to fitting statistics was then modified by comparing its values for the parameters total height (H), diameter at breast height (DBH), and aboveground height (h) to modeling data. Seven alternative prediction strategies were compared using the best new equation in the absence of calibration data, which is often unavailable in forestry practice. The results of this study suggest that because calibration may sometimes be a realistic option, though it is rarely used in practical applications, one of the best strategies for improving the accuracy of volume prediction is the strategy with 7 calculated total heights of 3, 6 and 9 trees in the largest, smallest and medium-size categories, respectively. We cannot use the average trees or dominant trees for calculating the random parameter for further predictions. The method described here will allow the user to make the best choices of taper type and the best random-effect calculated strategy for each practical application and situation at tree level. PMID:26445505

  7. Application of the mixing-reaction in series model to NO/x/-O3 plume chemistry

    NASA Technical Reports Server (NTRS)

    Carmichael, G. R.; Peters, L. K.

    1981-01-01

    The mixing-reaction in series model developed by Ghodsizadem (1978) is successfully applied to the study of NO oxidation in the near-source portion of the Potomac Electric Company's Morgantown, Maryland power plant plume. The model employs a single parameter. With initial conditions consistent with the plume data measured by Davis et al. (1974) and utilizing the mixing parameter estimated from the study by Shu et al. (1978), the predicted temporal profiles of the ratio of the concentration of NO2 to NO, of NO2 to NO plus NO2, in-plume concentrations of NO and O3, and fraction of NO remaining are consistent with field study data. In addition, the model predicts large deviations from the photostationary state in the near-source portion of the plume, also consistent with field study data. In the far field region of this plume (t greater than approximately 20 min), the mixing processes are essentially complete over much of the plume cross-section.

  8. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. I: Single layer cloud

    SciTech Connect

    Klein, Stephen A.; McCoy, Renata; Morrison, H.; Ackerman, Andrew; Avramov, Alexander; DeBoer, GIJS; Chen, Mingxuan; Cole, Jason N.; DelGenio, Anthony D.; Falk, Michael; Foster, Mike; Fridlind, Ann; Golaz, Jean-Christophe; Hashino, Tempei; Harrington, Jerry Y.; Hoose, Corinna; Khairoutdinov, Marat; Larson, Vince; Liu, Xiaohong; Luo, Yali; McFarquhar, Greg; Menon, Surabi; Neggers, Roel; Park, Sungsu; Poellot, M. R.; Schmidt, Jerome M.; Sednev, Igor; Shipway, Ben; Shupe, Matthew D.; Spangenberg, D.; Sud, Yogesh; Turner, David D.; Veron, Dana; Von Salzen, Knut; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey; Xie, Shaocheng; Xu, Kuan-Man; Yang, Fanglin; Zhang, G.

    2009-05-21

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the ARM Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of –15°C. While the cloud was water dominated, ice precipitation appears to have lowered the liquid water path to about 2/3 of the adiabatic value. The simulations, which were performed by seventeen single column and nine cloud-resolving models, generally underestimate the liquid water path with the median single-column and cloud-resolving model liquid water path a factor of 3 smaller than observed. While the simulated ice water path is in general agreement with the observed values, results from a sensitivity study in which models removed ice microphysics indicate that in many models the interaction between liquid and ice phase microphysics is responsible for the strong model underestimate of liquid water path. Although no single factor is found to lead to a good simulation, these results emphasize the need for care in the model treatment of mixed-phase microphysics. This case study, which has been well observed from both aircraft and ground-based remote sensors, could be benchmark for model simulations of mixed-phase clouds.

  9. Modelling lactation curve for milk fat to protein ratio in Iranian buffaloes (Bubalus bubalis) using non-linear mixed models.

    PubMed

    Hossein-Zadeh, Navid Ghavi

    2016-08-01

    The aim of this study was to compare seven non-linear mathematical models (Brody, Wood, Dhanoa, Sikka, Nelder, Rook and Dijkstra) to examine their efficiency in describing the lactation curves for milk fat to protein ratio (FPR) in Iranian buffaloes. Data were 43 818 test-day records for FPR from the first three lactations of Iranian buffaloes which were collected on 523 dairy herds in the period from 1996 to 2012 by the Animal Breeding Center of Iran. Each model was fitted to monthly FPR records of buffaloes using the non-linear mixed model procedure (PROC NLMIXED) in SAS and the parameters were estimated. The models were tested for goodness of fit using Akaike's information criterion (AIC), Bayesian information criterion (BIC) and log maximum likelihood (-2 Log L). The Nelder and Sikka mixed models provided the best fit of lactation curve for FPR in the first and second lactations of Iranian buffaloes, respectively. However, Wood, Dhanoa and Sikka mixed models provided the best fit of lactation curve for FPR in the third parity buffaloes. Evaluation of first, second and third lactation features showed that all models, except for Dijkstra model in the third lactation, under-predicted test time at which daily FPR was minimum. On the other hand, minimum FPR was over-predicted by all equations. Evaluation of the different models used in this study indicated that non-linear mixed models were sufficient for fitting test-day FPR records of Iranian buffaloes. PMID:27600968

  10. Estimation of count data using mixed Poisson, generalized Poisson and finite Poisson mixture regression models

    NASA Astrophysics Data System (ADS)

    Zamani, Hossein; Faroughi, Pouya; Ismail, Noriszura

    2014-06-01

    This study relates the Poisson, mixed Poisson (MP), generalized Poisson (GP) and finite Poisson mixture (FPM) regression models through mean-variance relationship, and suggests the application of these models for overdispersed count data. As an illustration, the regression models are fitted to the US skin care count data. The results indicate that FPM regression model is the best model since it provides the largest log likelihood and the smallest AIC, followed by Poisson-Inverse Gaussion (PIG), GP and negative binomial (NB) regression models. The results also show that NB, PIG and GP regression models provide similar results.

  11. $$B^0_{(s)}$$-mixing matrix elements from lattice QCD for the Standard Model and beyond

    DOE PAGESBeta

    Bazavov, A.; Bernard, C.; Bouchard, C. M.; Chang, C. C.; DeTar, C.; Du, Daping; El-Khadra, A. X.; Freeland, E. D.; Gamiz, E.; Gottlieb, Steven; et al

    2016-06-28

    We calculate—for the first time in three-flavor lattice QCD—the hadronic matrix elements of all five local operators that contribute to neutral B0- and Bs-meson mixing in and beyond the Standard Model. We present a complete error budget for each matrix element and also provide the full set of correlations among the matrix elements. We also present the corresponding bag parameters and their correlations, as well as specific combinations of the mixing matrix elements that enter the expression for the neutral B-meson width difference. We obtain the most precise determination to date of the SU(3)-breaking ratio ξ=1.206(18)(6), where the second errormore » stems from the omission of charm-sea quarks, while the first encompasses all other uncertainties. The threefold reduction in total uncertainty, relative to the 2013 Flavor Lattice Averaging Group results, tightens the constraint from B mixing on the Cabibbo-Kobayashi-Maskawa (CKM) unitarity triangle. Our calculation employs gauge-field ensembles generated by the MILC Collaboration with four lattice spacings and pion masses close to the physical value. We use the asqtad-improved staggered action for the light-valence quarks and the Fermilab method for the bottom quark. We use heavy-light meson chiral perturbation theory modified to include lattice-spacing effects to extrapolate the five matrix elements to the physical point. We combine our results with experimental measurements of the neutral B-meson oscillation frequencies to determine the CKM matrix elements |Vtd| = 8.00(34)(8)×10-3, |Vts| = 39.0(1.2)(0.4)×10-3, and |Vtd/Vts| = 0.2052(31)(10), which differ from CKM-unitarity expectations by about 2σ. In addition, these results and others from flavor-changing-neutral currents point towards an emerging tension between weak processes that are mediated at the loop and tree levels.« less

  12. Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere

    NASA Technical Reports Server (NTRS)

    Bowman, Kenneth P.

    1997-01-01

    The following is the final technical report for grant NAGW-3442, 'Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere'. Research efforts in the first year concentrated on transport and mixing processes in the polar vortices. Three papers on mixing in the Antarctic were published. The first was a numerical modeling study of wavebreaking and mixing and their relationship to the period of observed stratospheric waves (Bowman). The second paper presented evidence from TOMS for wavebreaking in the Antarctic (Bowman and Mangus 1993). The third paper used Lagrangian trajectory calculations from analyzed winds to show that there is very little transport into the Antarctic polar vortex prior to the vortex breakdown (Bowman). Mixing is significantly greater at lower levels. This research helped to confirm theoretical arguments for vortex isolation and data from the Antarctic field experiments that were interpreted as indicating isolation. A Ph.D. student, Steve Dahlberg, used the trajectory approach to investigate mixing and transport in the Arctic. While the Arctic vortex is much more disturbed than the Antarctic, there still appears to be relatively little transport across the vortex boundary at 450 K prior to the vortex breakdown. The primary reason for the absence of an ozone hole in the Arctic is the earlier warming and breakdown of the vortex compared to the Antarctic, not replenishment of ozone by greater transport. Two papers describing these results have appeared (Dahlberg and Bowman; Dahlberg and Bowman). Steve Dahlberg completed his Ph.D. thesis (Dahlberg and Bowman) and is now teaching in the Physics Department at Concordia College. We also prepared an analysis of the QBO in SBUV ozone data (Hollandsworth et al.). A numerical study in collaboration with Dr. Ping Chen investigated mixing by barotropic instability, which is the probable origin of the 4-day wave in the upper stratosphere (Bowman and Chen). The important result from

  13. Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study

    SciTech Connect

    Ho, Chiu Man; Boyanovsky, D.; Ho, C. M.

    2006-12-22

    The non-equilibrium dynamics of mixing, oscillations and equilibration is studied in a field theory of flavored neutral mesons that effectively models two flavors of mixed neutrinos, in interaction with other mesons that represent a thermal bath of hadrons or quarks and charged leptons. This model describes the general features of neutrino mixing and relaxation via charged currents in a medium. The reduced density matrix and the non-equilibrium effective action that describes the propagation of neutrinos is obtained by integrating out the bath degrees of freedom. We obtain the dispersion relations, mixing angles and relaxation rates of ``neutrino'' quasiparticles. The dispersion relations and mixing angles are of the same form as those of neutrinos in the medium, and the relaxation rates are given by $\\Gamma_1(k) = \\Gamma_{ee}(k) \\cos^2\\theta_m(k)+\\Gamma_{\\mu\\mu}(k)\\sin^2\\theta_m(k); \\Gamma_2(k)= \\Gamma_{\\mu\\mu}(k) \\cos^2\\theta_m(k)+\\Gamma_{ee}(k)\\sin^2\\theta_m(k) $ where $\\Gamma_{\\alpha\\alpha}(k)$ are the relaxation rates of the flavor fields in \\emph{absence} of mixing, and $\\theta_m(k)$ is the mixing angle in the medium. A Weisskopf-Wigner approximation that describes the asymptotic time evolution in terms of a non-hermitian Hamiltonian is derived. At long time $>>\\Gamma^{-1}_{1,2}$ ``neutrinos'' equilibrate with the bath. The equilibrium density matrix is nearly diagonal in the basis of eigenstates of an \\emph{effective Hamiltonian that includes self-energy corrections in the medium}. The equilibration of ``sterile neutrinos'' via active-sterile mixing is discussed.

  14. A nonlinear mixed effects modelling analysis of topiramate pharmacokinetics in patients with epilepsy.

    PubMed

    Vovk, Tomaz; Jakovljević, Mihajlo B; Kos, Mojca Kerec; Janković, Slobodan M; Mrhar, Ales; Grabnar, Iztok

    2010-01-01

    Topiramate pharmacokinetics is influenced by individual factors such as patient age, renal function and co-treatment. The aim of this study was to develop a population pharmacokinetic model of topiramate to assist dosage adjustments in individual patients. Steady-state topiramate plasma concentrations in patients with epilepsy were determined by HPLC using fluorescent labelling. Demographic, biochemical data and dosing history including concomitant drug therapy were collected from patients' charts. Nonlinear mixed effects modelling was used to fit a one-compartment pharmacokinetic model. The influence of patient weight and gender, body surface area, age, creatinine clearance, serum transaminases, topiramate daily dose and co-treatment with carbamazepine, valproic acid, benzodiazepines, and risperidone on topiramate pharmacokinetics was evaluated. Additionally, the relationship between topiramate plasma concentration and clinical response was investigated. Volume of distribution of topiramate was 0.518 l/kg. For a typical patient oral clearance was estimated at 1.47 l/h, with interindividual variability of 39.2%. Clearance was 70% higher in patients co-treated with carbamazepine and was found to increase with patient age. Somnolence was the most frequently observed adverse event. Incidence of headache was associated with topiramate plasma concentration. Somnolence, ataxia, tremor, speech disorders and fatigue were associated with adjunctive therapy with carbamazepine, valproic acid, benzodiazepines, risperidone, and clozapine. No association of topiramate plasma concentration with frequency of seizures or patient quality of life was observed. The developed model can be used for Bayesian estimation of pharmacokinetic parameters based on sparse plasma samples and for selection of optimum dosing in routine patient care. PMID:20606310

  15. Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement.

    PubMed

    Dornseiffer, P; Meyer, B; Heinzle, E

    1995-02-01

    The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H(13)CO(3) (-) pulses and measurement of (12)CH(4) and (13)CH(4) production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO(2)/CH(4) production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high K(s) value of 2.5 mmol m(-3), it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO(2) and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. (c) 1995 John Wiley & Sons, Inc. PMID:18623141

  16. Neutrino mixing with nonzero θ13 in Zee-Babu model

    NASA Astrophysics Data System (ADS)

    Long, Hoang Ngoc; Vien, Vo Van

    2014-05-01

    The exact solution for the neutrino mass matrix of the Zee-Babu model is derived. Tribimaximal mixing imposes conditions on the Yukawa couplings, from which the normal mass hierarchy is preferred. The derived conditions give a possibility of Majorana maximal CP violation in the neutrino sector. We have shown that nonzero θ13 is generated if Yukawa couplings between leptons almost equal to each other. The model gives some regions of the parameters where neutrino mixing angles and the normal neutrino mass hierarchy obtained are consistent with the recent experimental data.

  17. Why can't current large-scale models predict mixed-phase clouds correctly?

    NASA Astrophysics Data System (ADS)

    Barrett, Andrew; Hogan, Robin; Forbes, Richard

    2013-04-01

    Stratiform mid-level mixed-phase clouds have a significant radiative impact but are often missing from numerical model simulations for a number of reasons. This is particularly true more recently as models move towards treating cloud ice as a prognostic variable. This presentation will demonstrate three important findings that will help lead to better simulations of mixed-phase clouds by models in the future. Each is briefly covered in the paragraphs below. 1) The occurrence of mid-level mixed-phase clouds in models is compared with ground based remote sensors, finding an under-prediction of the supercooled liquid water content in the models of a factor of 2 or more. This is accompanied by a low bias in the liquid cloud fraction whilst the ice properties are better simulated. Models with more sophisticated microphysics schemes that include prognostic cloud ice are the worst performing models. 2) A new single column model is used to investigate which processes are important for the maintenance of supercooled liquid layers. By running the model over multiple days and exploring the parameter-space of numerous physical parameterizations it was determined that the most sensitive areas of the model are ice microphysical processes and vertical resolution. 3) Vertical resolutions finer than 200 metres are required to capture the thin liquid layers in these clouds and therefore their important radiative effect. Leading models are still far coarser than this in the mid-troposphere, limiting hope of simulating these clouds properly. A new parameterization of the vertical structure of these clouds is developed and allows their properties to be correctly simulated in a resolution independent way by numerical models with coarse vertical resolution. This parameterization is explained and demonstrated here and could enable significant improvement in model simulations of stratiform mixed-phase clouds.

  18. On the formulation of the dynamic mixed subgrid-scale model

    NASA Astrophysics Data System (ADS)

    Vreman, Bert; Geurts, Bernard; Kuerten, Hans

    1994-12-01

    The dynamic mixed subgrid-scale model of Zang et al. [Phys. Fluids A 5, 3186 (1993)] (DMM1) is modified with respect to the incorporation of the similarity model in order to remove a mathematical inconsistency. Compared to DMM1, the magnitude of the dynamic model coefficient of the modified model (DMM2) is increased considerably, while it is still significantly smaller than as occurs in the dynamic subgrid-scale eddy-viscosity model of Germano [J. Fluid Mech. 238, 325 (1992)] (DSM). Large eddy simulations (LES) for the weakly compressible mixing layer are conducted using these three models and results are compared with direct numerical simulation (DNS) data. LES based on DMM1 gives a significant improvement over LES using DSM, while even better agreement is achieved with DMM2.

  19. Mixed Phase Modeling in GlennICE with Application to Engine Icing

    NASA Technical Reports Server (NTRS)

    Wright, William B.; Jorgenson, Philip C. E.; Veres, Joseph P.

    2011-01-01

    A capability for modeling ice crystals and mixed phase icing has been added to GlennICE. Modifications have been made to the particle trajectory algorithm and energy balance to model this behavior. This capability has been added as part of a larger effort to model ice crystal ingestion in aircraft engines. Comparisons have been made to four mixed phase ice accretions performed in the Cox icing tunnel in order to calibrate an ice erosion model. A sample ice ingestion case was performed using the Energy Efficient Engine (E3) model in order to illustrate current capabilities. Engine performance characteristics were supplied using the Numerical Propulsion System Simulation (NPSS) model for this test case.

  20. New Theory of Stellar Convection without the mixing-length parameter: new stellar atmosphere models

    NASA Astrophysics Data System (ADS)

    Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.

    2015-08-01

    Stellar convection is customarily described by the mixing-length theory, which makes use of the mixing-length scale to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun.No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in literature are hampered by this basic uncertainty.In a recent paper (Pasetto et al 2014) we presented a new theory of stellar convection that does not require the mixing length parameter. Our self-consistent analytical formulation of stellar convection determines all the properties of stellar convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium. The new theory of stellar convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of stellar convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism.We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory are now compared with those from the standard mixing-length paradigm with very satisfactory results for atmosphere models of the Sun and all the stars around the Hertzsprung-Russell diagram.