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Sample records for growth curve model

  1. Modeling Math Growth Trajectory--An Application of Conventional Growth Curve Model and Growth Mixture Model to ECLS K-5 Data

    Science.gov (United States)

    Lu, Yi

    2016-01-01

    To model students' math growth trajectory, three conventional growth curve models and three growth mixture models are applied to the Early Childhood Longitudinal Study Kindergarten-Fifth grade (ECLS K-5) dataset in this study. The results of conventional growth curve model show gender differences on math IRT scores. When holding socio-economic…

  2. Growth curve models and statistical diagnostics

    CERN Document Server

    Pan, Jian-Xin

    2002-01-01

    Growth-curve models are generalized multivariate analysis-of-variance models. These models are especially useful for investigating growth problems on short times in economics, biology, medical research, and epidemiology. This book systematically introduces the theory of the GCM with particular emphasis on their multivariate statistical diagnostics, which are based mainly on recent developments made by the authors and their collaborators. The authors provide complete proofs of theorems as well as practical data sets and MATLAB code.

  3. Modeling error distributions of growth curve models through Bayesian methods.

    Science.gov (United States)

    Zhang, Zhiyong

    2016-06-01

    Growth curve models are widely used in social and behavioral sciences. However, typical growth curve models often assume that the errors are normally distributed although non-normal data may be even more common than normal data. In order to avoid possible statistical inference problems in blindly assuming normality, a general Bayesian framework is proposed to flexibly model normal and non-normal data through the explicit specification of the error distributions. A simulation study shows when the distribution of the error is correctly specified, one can avoid the loss in the efficiency of standard error estimates. A real example on the analysis of mathematical ability growth data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 is used to show the application of the proposed methods. Instructions and code on how to conduct growth curve analysis with both normal and non-normal error distributions using the the MCMC procedure of SAS are provided.

  4. Growth Curve Models and Applications : Indian Statistical Institute

    CERN Document Server

    2017-01-01

    Growth curve models in longitudinal studies are widely used to model population size, body height, biomass, fungal growth, and other variables in the biological sciences, but these statistical methods for modeling growth curves and analyzing longitudinal data also extend to general statistics, economics, public health, demographics, epidemiology, SQC, sociology, nano-biotechnology, fluid mechanics, and other applied areas.   There is no one-size-fits-all approach to growth measurement. The selected papers in this volume build on presentations from the GCM workshop held at the Indian Statistical Institute, Giridih, on March 28-29, 2016. They represent recent trends in GCM research on different subject areas, both theoretical and applied. This book includes tools and possibilities for further work through new techniques and modification of existing ones. The volume includes original studies, theoretical findings and case studies from a wide range of app lied work, and these contributions have been externally r...

  5. Residual Structures in Latent Growth Curve Modeling

    Science.gov (United States)

    Grimm, Kevin J.; Widaman, Keith F.

    2010-01-01

    Several alternatives are available for specifying the residual structure in latent growth curve modeling. Two specifications involve uncorrelated residuals and represent the most commonly used residual structures. The first, building on repeated measures analysis of variance and common specifications in multilevel models, forces residual variances…

  6. Developmental trajectories of adolescent popularity: a growth curve modelling analysis.

    Science.gov (United States)

    Cillessen, Antonius H N; Borch, Casey

    2006-12-01

    Growth curve modelling was used to examine developmental trajectories of sociometric and perceived popularity across eight years in adolescence, and the effects of gender, overt aggression, and relational aggression on these trajectories. Participants were 303 initially popular students (167 girls, 136 boys) for whom sociometric data were available in Grades 5-12. The popularity and aggression constructs were stable but non-overlapping developmental dimensions. Growth curve models were run with SAS MIXED in the framework of the multilevel model for change [Singer, J. D., & Willett, J. B. (2003). Applied longitudinal data analysis. Oxford, UK: Oxford University Press]. Sociometric popularity showed a linear change trajectory; perceived popularity showed nonlinear change. Overt aggression predicted low sociometric popularity but an increase in perceived popularity in the second half of the study. Relational aggression predicted a decrease in sociometric popularity, especially for girls, and continued high-perceived popularity for both genders. The effect of relational aggression on perceived popularity was the strongest around the transition from middle to high school. The importance of growth curve models for understanding adolescent social development was discussed, as well as specific issues and challenges of growth curve analyses with sociometric data.

  7. Investigation of Mediational Processes Using Parallel Process Latent Growth Curve Modeling

    Science.gov (United States)

    Cheong, JeeWon; MacKinnon, David P.; Khoo, Siek Toon

    2010-01-01

    This study investigated a method to evaluate mediational processes using latent growth curve modeling. The mediator and the outcome measured across multiple time points were viewed as 2 separate parallel processes. The mediational process was defined as the independent variable influencing the growth of the mediator, which, in turn, affected the growth of the outcome. To illustrate modeling procedures, empirical data from a longitudinal drug prevention program, Adolescents Training and Learning to Avoid Steroids, were used. The program effects on the growth of the mediator and the growth of the outcome were examined first in a 2-group structural equation model. The mediational process was then modeled and tested in a parallel process latent growth curve model by relating the prevention program condition, the growth rate factor of the mediator, and the growth rate factor of the outcome. PMID:20157639

  8. Modelling growth curves of Nigerian indigenous normal feather ...

    African Journals Online (AJOL)

    This study was conducted to predict the growth curve parameters using Bayesian Gompertz and logistic models and also to compare the two growth function in describing the body weight changes across age in Nigerian indigenous normal feather chicken. Each chick was wing-tagged at day old and body weights were ...

  9. Predicting Madura cattle growth curve using non-linear model

    Science.gov (United States)

    Widyas, N.; Prastowo, S.; Widi, T. S. M.; Baliarti, E.

    2018-03-01

    Madura cattle is Indonesian native. It is a composite breed that has undergone hundreds of years of selection and domestication to reach nowadays remarkable uniformity. Crossbreeding has reached the isle of Madura and the Madrasin, a cross between Madura cows and Limousine semen emerged. This paper aimed to compare the growth curve between Madrasin and one type of pure Madura cows, the common Madura cattle (Madura) using non-linear models. Madura cattles are kept traditionally thus reliable records are hardly available. Data were collected from small holder farmers in Madura. Cows from different age classes (5years) were observed, and body measurements (chest girth, body length and wither height) were taken. In total 63 Madura and 120 Madrasin records obtained. Linear model was built with cattle sub-populations and age as explanatory variables. Body weights were estimated based on the chest girth. Growth curves were built using logistic regression. Results showed that within the same age, Madrasin has significantly larger body compared to Madura (plogistic models fit better for Madura and Madrasin cattle data; with the estimated MSE for these models were 39.09 and 759.28 with prediction accuracy of 99 and 92% for Madura and Madrasin, respectively. Prediction of growth curve using logistic regression model performed well in both types of Madura cattle. However, attempts to administer accurate data on Madura cattle are necessary to better characterize and study these cattle.

  10. Mediation Analysis in a Latent Growth Curve Modeling Framework

    Science.gov (United States)

    von Soest, Tilmann; Hagtvet, Knut A.

    2011-01-01

    This article presents several longitudinal mediation models in the framework of latent growth curve modeling and provides a detailed account of how such models can be constructed. Logical and statistical challenges that might arise when such analyses are conducted are also discussed. Specifically, we discuss how the initial status (intercept) and…

  11. The Biasing Effects of Unmodeled ARMA Time Series Processes on Latent Growth Curve Model Estimates

    Science.gov (United States)

    Sivo, Stephen; Fan, Xitao; Witta, Lea

    2005-01-01

    The purpose of this study was to evaluate the robustness of estimated growth curve models when there is stationary autocorrelation among manifest variable errors. The results suggest that when, in practice, growth curve models are fitted to longitudinal data, alternative rival hypotheses to consider would include growth models that also specify…

  12. Growth Curve and Structural Equation Modeling : Topics from the Indian Statistical Institute

    CERN Document Server

    2015-01-01

    This book describes some recent trends in GCM research on different subject areas, both theoretical and applied. This includes tools and possibilities for further work through new techniques and modification of existing ones. A growth curve is an empirical model of the evolution of a quantity over time. Growth curves in longitudinal studies are used in disciplines including biology, statistics, population studies, economics, biological sciences, sociology, nano-biotechnology, and fluid mechanics. The volume includes original studies, theoretical findings and case studies from a wide range of applied work. This volume builds on presentations from a GCM workshop held at the Indian Statistical Institute, Giridih, January 18-19, 2014. This book follows the volume Advances in Growth Curve Models, published by Springer in 2013. The results have meaningful application in health care, prediction of crop yield, child nutrition, poverty measurements, estimation of growth rate, and other research areas.

  13. Sensitivity of Fit Indices to Misspecification in Growth Curve Models

    Science.gov (United States)

    Wu, Wei; West, Stephen G.

    2010-01-01

    This study investigated the sensitivity of fit indices to model misspecification in within-individual covariance structure, between-individual covariance structure, and marginal mean structure in growth curve models. Five commonly used fit indices were examined, including the likelihood ratio test statistic, root mean square error of…

  14. Growth curves for Laron syndrome.

    Science.gov (United States)

    Laron, Z; Lilos, P; Klinger, B

    1993-01-01

    Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls completed their growth between the age of 16-19 years to a final mean (SD) height of 119 (8.5) cm whereas the boys continued growing beyond the age of 20 years, achieving a final height of 124 (8.5) cm. At all ages the upper to lower body segment ratio was more than 2 SD above the normal mean. These growth curves constitute a model not only for primary, hereditary insulin-like growth factor-I (IGF-I) deficiency (Laron syndrome) but also for untreated secondary IGF-I deficiencies such as growth hormone gene deletion and idiopathic congenital isolated growth hormone deficiency. They should also be useful in the follow up of children with Laron syndrome treated with biosynthetic recombinant IGF-I. PMID:8333769

  15. Nonlinear Growth Curves in Developmental Research

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  16. Nonlinear Growth Curves in Developmental Research

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and asymptotic levels can be estimated. A variety of growth models are described beginning with the linear growth model and moving to nonlinear models of varying complexity. A detailed discussion of nonlinear models is provided, highlighting the added insights into complex developmental processes associated with their use. A collection of growth models are fit to repeated measures of height from participants of the Berkeley Growth and Guidance Studies from early childhood through adulthood. PMID:21824131

  17. Surface growth kinematics via local curve evolution

    KAUST Repository

    Moulton, Derek E.

    2012-11-18

    A mathematical framework is developed to model the kinematics of surface growth for objects that can be generated by evolving a curve in space, such as seashells and horns. Growth is dictated by a growth velocity vector field defined at every point on a generating curve. A local orthonormal basis is attached to each point of the generating curve and the velocity field is given in terms of the local coordinate directions, leading to a fully local and elegant mathematical structure. Several examples of increasing complexity are provided, and we demonstrate how biologically relevant structures such as logarithmic shells and horns emerge as analytical solutions of the kinematics equations with a small number of parameters that can be linked to the underlying growth process. Direct access to cell tracks and local orientation enables for connections to be made to the underlying growth process. © 2012 Springer-Verlag Berlin Heidelberg.

  18. Empirical Percentile Growth Curves with Z-scores Considering Seasonal Compensatory Growths for Japanese Thoroughbred Horses

    Science.gov (United States)

    ONODA, Tomoaki; YAMAMOTO, Ryuta; SAWAMURA, Kyohei; MURASE, Harutaka; NAMBO, Yasuo; INOUE, Yoshinobu; MATSUI, Akira; MIYAKE, Takeshi; HIRAI, Nobuhiro

    2013-01-01

    Percentile growth curves are often used as a clinical indicator to evaluate variations of children’s growth status. In this study, we propose empirical percentile growth curves using Z-scores adapted for Japanese Thoroughbred horses, with considerations of the seasonal compensatory growth that is a typical characteristic of seasonal breeding animals. We previously developed new growth curve equations for Japanese Thoroughbreds adjusting for compensatory growth. Individual horses and residual effects were included as random effects in the growth curve equation model and their variance components were estimated. Based on the Z-scores of the estimated variance components, empirical percentile growth curves were constructed. A total of 5,594 and 5,680 body weight and age measurements of male and female Thoroughbreds, respectively, and 3,770 withers height and age measurements were used in the analyses. The developed empirical percentile growth curves using Z-scores are computationally feasible and useful for monitoring individual growth parameters of body weight and withers height of young Thoroughbred horses, especially during compensatory growth periods. PMID:24834004

  19. Genome association study through nonlinear mixed models revealed new candidate genes for pig growth curves

    Directory of Open Access Journals (Sweden)

    Fabyano Fonseca e Silva

    Full Text Available ABSTRACT: Genome association analyses have been successful in identifying quantitative trait loci (QTLs for pig body weights measured at a single age. However, when considering the whole weight trajectories over time in the context of genome association analyses, it is important to look at the markers that affect growth curve parameters. The easiest way to consider them is via the two-step method, in which the growth curve parameters and marker effects are estimated separately, thereby resulting in a reduction of the statistical power and the precision of estimates. One efficient solution is to adopt nonlinear mixed models (NMM, which enables a joint modeling of the individual growth curves and marker effects. Our aim was to propose a genome association analysis for growth curves in pigs based on NMM as well as to compare it with the traditional two-step method. In addition, we also aimed to identify the nearest candidate genes related to significant SNP (single nucleotide polymorphism markers. The NMM presented a higher number of significant SNPs for adult weight (A and maturity rate (K, and provided a direct way to test SNP significance simultaneously for both the A and K parameters. Furthermore, all significant SNPs from the two-step method were also reported in the NMM analysis. The ontology of the three candidate genes (SH3BGRL2, MAPK14, and MYL9 derived from significant SNPs (simultaneously affecting A and K allows us to make inferences with regards to their contribution to the pig growth process in the population studied.

  20. An introduction to latent variable growth curve modeling concepts, issues, and application

    CERN Document Server

    Duncan, Terry E; Strycker, Lisa A

    2013-01-01

    This book provides a comprehensive introduction to latent variable growth curve modeling (LGM) for analyzing repeated measures. It presents the statistical basis for LGM and its various methodological extensions, including a number of practical examples of its use. It is designed to take advantage of the reader's familiarity with analysis of variance and structural equation modeling (SEM) in introducing LGM techniques. Sample data, syntax, input and output, are provided for EQS, Amos, LISREL, and Mplus on the book's CD. Throughout the book, the authors present a variety of LGM techniques that are useful for many different research designs, and numerous figures provide helpful diagrams of the examples.Updated throughout, the second edition features three new chapters-growth modeling with ordered categorical variables, growth mixture modeling, and pooled interrupted time series LGM approaches. Following a new organization, the book now covers the development of the LGM, followed by chapters on multiple-group is...

  1. Growth curves for twins in Slovenia.

    Science.gov (United States)

    Bricelj, Katja; Blickstein, Isaac; Bržan-Šimenc, Gabrijela; Janša, Vid; Lučovnik, Miha; Verdenik, Ivan; Trojner-Bregar, Andreja; Tul, Nataša

    2017-02-01

    Abnormalities of fetal growth are more common in twins. We introduce the growth curves for monitoring fetal growth in twin pregnancies in Slovenia. Slovenian National Perinatal Information System for the period between 2002 and 2010 was used to calculate birth weight percentiles for all live born twins for each week from 22nd to 40th week. The calculated percentiles of birth weight for all live-born twins in Slovenia served as the basis for drawing 'growth' curves. The calculated growth curves for twins will help accurately diagnose small or large twin fetuses for their gestational age in the native central European population.

  2. Growth curves for Laron syndrome.

    OpenAIRE

    Laron, Z; Lilos, P; Klinger, B

    1993-01-01

    Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls co...

  3. Escaping the snare of chronological growth and launching a free curve alternative: general deviance as latent growth model.

    Science.gov (United States)

    Wood, Phillip Karl; Jackson, Kristina M

    2013-08-01

    Researchers studying longitudinal relationships among multiple problem behaviors sometimes characterize autoregressive relationships across constructs as indicating "protective" or "launch" factors or as "developmental snares." These terms are used to indicate that initial or intermediary states of one problem behavior subsequently inhibit or promote some other problem behavior. Such models are contrasted with models of "general deviance" over time in which all problem behaviors are viewed as indicators of a common linear trajectory. When fit of the "general deviance" model is poor and fit of one or more autoregressive models is good, this is taken as support for the inhibitory or enhancing effect of one construct on another. In this paper, we argue that researchers consider competing models of growth before comparing deviance and time-bound models. Specifically, we propose use of the free curve slope intercept (FCSI) growth model (Meredith & Tisak, 1990) as a general model to typify change in a construct over time. The FCSI model includes, as nested special cases, several statistical models often used for prospective data, such as linear slope intercept models, repeated measures multivariate analysis of variance, various one-factor models, and hierarchical linear models. When considering models involving multiple constructs, we argue the construct of "general deviance" can be expressed as a single-trait multimethod model, permitting a characterization of the deviance construct over time without requiring restrictive assumptions about the form of growth over time. As an example, prospective assessments of problem behaviors from the Dunedin Multidisciplinary Health and Development Study (Silva & Stanton, 1996) are considered and contrasted with earlier analyses of Hussong, Curran, Moffitt, and Caspi (2008), which supported launch and snare hypotheses. For antisocial behavior, the FCSI model fit better than other models, including the linear chronometric growth curve

  4. Growth curve registration for evaluating salinity tolerance in barley

    KAUST Repository

    Meng, Rui

    2017-03-23

    Background: Smarthouses capable of non-destructive, high-throughput plant phenotyping collect large amounts of data that can be used to understand plant growth and productivity in extreme environments. The challenge is to apply the statistical tool that best analyzes the data to study plant traits, such as salinity tolerance, or plant-growth-related traits. Results: We derive family-wise salinity sensitivity (FSS) growth curves and use registration techniques to summarize growth patterns of HEB-25 barley families and the commercial variety, Navigator. We account for the spatial variation in smarthouse microclimates and in temporal variation across phenotyping runs using a functional ANOVA model to derive corrected FSS curves. From FSS, we derive corrected values for family-wise salinity tolerance, which are strongly negatively correlated with Na but not significantly with K, indicating that Na content is an important factor affecting salinity tolerance in these families, at least for plants of this age and grown in these conditions. Conclusions: Our family-wise methodology is suitable for analyzing the growth curves of a large number of plants from multiple families. The corrected curves accurately account for the spatial and temporal variations among plants that are inherent to high-throughput experiments.

  5. Growth curve registration for evaluating salinity tolerance in barley

    KAUST Repository

    Meng, Rui; Saade, Stephanie; Kurtek, Sebastian; Berger, Bettina; Brien, Chris; Pillen, Klaus; Tester, Mark A.; Sun, Ying

    2017-01-01

    Background: Smarthouses capable of non-destructive, high-throughput plant phenotyping collect large amounts of data that can be used to understand plant growth and productivity in extreme environments. The challenge is to apply the statistical tool that best analyzes the data to study plant traits, such as salinity tolerance, or plant-growth-related traits. Results: We derive family-wise salinity sensitivity (FSS) growth curves and use registration techniques to summarize growth patterns of HEB-25 barley families and the commercial variety, Navigator. We account for the spatial variation in smarthouse microclimates and in temporal variation across phenotyping runs using a functional ANOVA model to derive corrected FSS curves. From FSS, we derive corrected values for family-wise salinity tolerance, which are strongly negatively correlated with Na but not significantly with K, indicating that Na content is an important factor affecting salinity tolerance in these families, at least for plants of this age and grown in these conditions. Conclusions: Our family-wise methodology is suitable for analyzing the growth curves of a large number of plants from multiple families. The corrected curves accurately account for the spatial and temporal variations among plants that are inherent to high-throughput experiments.

  6. Genomic growth curves of an outbred pig population

    Directory of Open Access Journals (Sweden)

    Fabyano Fonseca e Silva

    2013-01-01

    Full Text Available In the current post-genomic era, the genetic basis of pig growth can be understood by assessing SNP marker effects and genomic breeding values (GEBV based on estimates of these growth curve parameters as phenotypes. Although various statistical methods, such as random regression (RR-BLUP and Bayesian LASSO (BL, have been applied to genomic selection (GS, none of these has yet been used in a growth curve approach. In this work, we compared the accuracies of RR-BLUP and BL using empirical weight-age data from an outbred F2 (Brazilian Piau X commercial population. The phenotypes were determined by parameter estimates using a nonlinear logistic regression model and the halothane gene was considered as a marker for evaluating the assumptions of the GS methods in relation to the genetic variation explained by each locus. BL yielded more accurate values for all of the phenotypes evaluated and was used to estimate SNP effects and GEBV vectors. The latter allowed the construction of genomic growth curves, which showed substantial genetic discrimination among animals in the final growth phase. The SNP effect estimates allowed identification of the most relevant markers for each phenotype, the positions of which were coincident with reported QTL regions for growth traits.

  7. A longitudinal study of interethnic contacts in Germany: estimates from a multilevel growth curve model

    NARCIS (Netherlands)

    Martinovic, B.; van Tubergen, F.; Maas, I.

    2015-01-01

    Interethnic ties are considered important for the cohesion in society. Previous research has studied the determinants of interethnic ties with cross-sectional data or lagged panel designs. This study improves on prior research by applying multilevel growth curve modelling techniques with lagged

  8. A longitudinal study of interethnic contacts in Germany : Estimates from a multilevel growth curve model

    NARCIS (Netherlands)

    Martinovic, Borja|info:eu-repo/dai/nl/304822752; van Tubergen, Frank|info:eu-repo/dai/nl/271429534; Maas, Ineke|info:eu-repo/dai/nl/075229390

    2015-01-01

    Interethnic ties are considered important for the cohesion in society. Previous research has studied the determinants of interethnic ties with cross-sectional data or lagged panel designs. This study improves on prior research by applying multilevel growth curve modelling techniques with lagged

  9. Nonlinear models for fitting growth curves of Nellore cows reared in the Amazon Biome

    Directory of Open Access Journals (Sweden)

    Kedma Nayra da Silva Marinho

    2013-09-01

    Full Text Available Growth curves of Nellore cows were estimated by comparing six nonlinear models: Brody, Logistic, two alternatives by Gompertz, Richards and Von Bertalanffy. The models were fitted to weight-age data, from birth to 750 days of age of 29,221 cows, born between 1976 and 2006 in the Brazilian states of Acre, Amapá, Amazonas, Pará, Rondônia, Roraima and Tocantins. The models were fitted by the Gauss-Newton method. The goodness of fit of the models was evaluated by using mean square error, adjusted coefficient of determination, prediction error and mean absolute error. Biological interpretation of parameters was accomplished by plotting estimated weights versus the observed weight means, instantaneous growth rate, absolute maturity rate, relative instantaneous growth rate, inflection point and magnitude of the parameters A (asymptotic weight and K (maturing rate. The Brody and Von Bertalanffy models fitted the weight-age data but the other models did not. The average weight (A and growth rate (K were: 384.6±1.63 kg and 0.0022±0.00002 (Brody and 313.40±0.70 kg and 0.0045±0.00002 (Von Bertalanffy. The Brody model provides better goodness of fit than the Von Bertalanffy model.

  10. Self-Regulation and Recall: Growth Curve Modeling of Intervention Outcomes for Older Adults

    OpenAIRE

    West, Robin L.; Hastings, Erin C.

    2011-01-01

    Memory training has often been supported as a potential means to improve performance for older adults. Less often studied are the characteristics of trainees that benefit most from training. Using a self-regulatory perspective, the current project examined a latent growth curve model to predict training-related gains for middle-aged and older adult trainees from individual differences (e.g., education), information processing skills (strategy use) and self-regulatory factors such as self-effi...

  11. Growth Curves for Girls with Turner Syndrome

    Directory of Open Access Journals (Sweden)

    Fabio Bertapelli

    2014-01-01

    Full Text Available The objective of this study was to review the growth curves for Turner syndrome, evaluate the methodological and statistical quality, and suggest potential growth curves for clinical practice guidelines. The search was carried out in the databases Medline and Embase. Of 1006 references identified, 15 were included. Studies constructed curves for weight, height, weight/height, body mass index, head circumference, height velocity, leg length, and sitting height. The sample ranged between 47 and 1,565 (total = 6,273 girls aged 0 to 24 y, born between 1950 and 2006. The number of measures ranged from 580 to 9,011 (total = 28,915. Most studies showed strengths such as sample size, exclusion of the use of growth hormone and androgen, and analysis of confounding variables. However, the growth curves were restricted to height, lack of information about selection bias, limited distributional properties, and smoothing aspects. In conclusion, we observe the need to construct an international growth reference for girls with Turner syndrome, in order to provide support for clinical practice guidelines.

  12. [Reference curves for assessing the physical growth of male Wistar rats].

    Science.gov (United States)

    Cossio-Bolaños, Marco; Gómez Campos, Rossana; Vargas Vitoria, Rodrigo; Hochmuller Fogaça, Rosalvo Tadeu; de Arruda, Miguel

    2013-11-01

    Wistar rats are one of the most popular strains routinely used for research in the laboratory to serve as an important research tool, so it requires strict control of variables such as age, sex and body weight, and Thus to extrapolate the results to the human model. To develop reference curves for assessing the physical growth of male Wistar rats according to chronological age and somatic maturation from a non-invasive. The subjects studied were 731 male Wistar rats transversely. We assessed age, body weight and body surface. LMS method was used to construct percentile curves based on weight and somatic maturation. The proposed physical growth curves are used to track the physical growth and nutritional status diagnosis of male Wistar rats. Budgets by cutting points are: P3, P10, P25, P50, P75, P90 and P97. The results suggest that scientists from different areas can use such references, in order to extrapolate somatic growth phases of the laboratory rat and the human model is a non-invasive alternative to assess growth and nutritional status. Copyright AULA MEDICA EDICIONES 2013. Published by AULA MEDICA. All rights reserved.

  13. Growth curves and the international standard: How children's growth reflects challenging conditions in rural Timor-Leste.

    Science.gov (United States)

    Spencer, Phoebe R; Sanders, Katherine A; Judge, Debra S

    2018-02-01

    Population-specific growth references are important in understanding local growth variation, especially in developing countries where child growth is poor and the need for effective health interventions is high. In this article, we use mixed longitudinal data to calculate the first growth curves for rural East Timorese children to identify where, during development, deviation from the international standards occurs. Over an eight-year period, 1,245 children from two ecologically distinct rural areas of Timor-Leste were measured a total of 4,904 times. We compared growth to the World Health Organization (WHO) standards using z-scores, and modeled height and weight velocity using the SuperImposition by Translation And Rotation (SITAR) method. Using the Generalized Additive Model for Location, Scale and Shape (GAMLSS) method, we created the first growth curves for rural Timorese children for height, weight and body mass index (BMI). Relative to the WHO standards, children show early-life growth faltering, and stunting throughout childhood and adolescence. The median height and weight for this population tracks below the WHO fifth centile. Males have poorer growth than females in both z-BMI (p = .001) and z-height-for-age (p = .018) and, unlike females, continue to grow into adulthood. This is the most comprehensive investigation to date of rural Timorese children's growth, and the growth curves created may potentially be used to identify future secular trends in growth as the country develops. We show significant deviation from the international standard that becomes most pronounced at adolescence, similar to the growth of other Asian populations. Males and females show different growth responses to challenging conditions in this population. © 2017 Wiley Periodicals, Inc.

  14. Two Aspects of the Simplex Model: Goodness of Fit to Linear Growth Curve Structures and the Analysis of Mean Trends.

    Science.gov (United States)

    Mandys, Frantisek; Dolan, Conor V.; Molenaar, Peter C. M.

    1994-01-01

    Studied the conditions under which the quasi-Markov simplex model fits a linear growth curve covariance structure and determined when the model is rejected. Presents a quasi-Markov simplex model with structured means and gives an example. (SLD)

  15. On the solar curve of growth of titanium

    International Nuclear Information System (INIS)

    Foy, R.

    1975-01-01

    Our purpose in the present work is to investigate whether or not the splitting of the solar curve of growth found in the case of iron applies to other elements. We show that, contrary to the solar curve of growth for iron, that for titanium is not split in its damping part; this result emphasizes that reference curves of growth have to be used very carefully in detailed analysis of stellar atmospheres. We confirm that the microturbulent velocity is very low in the solar photosphere, namely within the limits: 0.5 [de

  16. ECONOMIC GROWTH AND AIR POLLUTION IN THECZECHREPUBLIC: DECOUPLING CURVES

    Directory of Open Access Journals (Sweden)

    Petr Šauer

    2012-07-01

    Full Text Available The decoupling curve, together with the Environmental Kuznets Curve, has beenrecognized as one of the important indicators showing relations betweeneconomic growth and environmental degradation/pollution. Many boththeoreticaland empirical studies have been published on it. Our paper brings models whichinvestigate relations between the economic growth per capita and selectedindicators of air pollution in theCzechRepublic. The analysis tried to go beforethe year 1990, despite the difficulties when dealing with different macroeconomicindicators published during the socialist period and those introduced after thetransition to a market economy. The results might be somehow surprising forthose dealing only with data generated after the year 1990: it is possible todiscover the turning points for some of the airborne pollutants already in the1980s.

  17. From Experiment to Theory: What Can We Learn from Growth Curves?

    Science.gov (United States)

    Kareva, Irina; Karev, Georgy

    2018-01-01

    Finding an appropriate functional form to describe population growth based on key properties of a described system allows making justified predictions about future population development. This information can be of vital importance in all areas of research, ranging from cell growth to global demography. Here, we use this connection between theory and observation to pose the following question: what can we infer about intrinsic properties of a population (i.e., degree of heterogeneity, or dependence on external resources) based on which growth function best fits its growth dynamics? We investigate several nonstandard classes of multi-phase growth curves that capture different stages of population growth; these models include hyperbolic-exponential, exponential-linear, exponential-linear-saturation growth patterns. The constructed models account explicitly for the process of natural selection within inhomogeneous populations. Based on the underlying hypotheses for each of the models, we identify whether the population that it best fits by a particular curve is more likely to be homogeneous or heterogeneous, grow in a density-dependent or frequency-dependent manner, and whether it depends on external resources during any or all stages of its development. We apply these predictions to cancer cell growth and demographic data obtained from the literature. Our theory, if confirmed, can provide an additional biomarker and a predictive tool to complement experimental research.

  18. Supplementary Material for: Growth curve registration for evaluating salinity tolerance in barley

    KAUST Repository

    Meng, Rui

    2017-01-01

    Abstract Background Smarthouses capable of non-destructive, high-throughput plant phenotyping collect large amounts of data that can be used to understand plant growth and productivity in extreme environments. The challenge is to apply the statistical tool that best analyzes the data to study plant traits, such as salinity tolerance, or plant-growth-related traits. Results We derive family-wise salinity sensitivity (FSS) growth curves and use registration techniques to summarize growth patterns of HEB-25 barley families and the commercial variety, Navigator. We account for the spatial variation in smarthouse microclimates and in temporal variation across phenotyping runs using a functional ANOVA model to derive corrected FSS curves. From FSS, we derive corrected values for family-wise salinity tolerance, which are strongly negatively correlated with Na but not significantly with K, indicating that Na content is an important factor affecting salinity tolerance in these families, at least for plants of this age and grown in these conditions. Conclusions Our family-wise methodology is suitable for analyzing the growth curves of a large number of plants from multiple families. The corrected curves accurately account for the spatial and temporal variations among plants that are inherent to high-throughput experiments.

  19. Nonlinear Growth Models as Measurement Models: A Second-Order Growth Curve Model for Measuring Potential.

    Science.gov (United States)

    McNeish, Daniel; Dumas, Denis

    2017-01-01

    Recent methodological work has highlighted the promise of nonlinear growth models for addressing substantive questions in the behavioral sciences. In this article, we outline a second-order nonlinear growth model in order to measure a critical notion in development and education: potential. Here, potential is conceptualized as having three components-ability, capacity, and availability-where ability is the amount of skill a student is estimated to have at a given timepoint, capacity is the maximum amount of ability a student is predicted to be able to develop asymptotically, and availability is the difference between capacity and ability at any particular timepoint. We argue that single timepoint measures are typically insufficient for discerning information about potential, and we therefore describe a general framework that incorporates a growth model into the measurement model to capture these three components. Then, we provide an illustrative example using the public-use Early Childhood Longitudinal Study-Kindergarten data set using a Michaelis-Menten growth function (reparameterized from its common application in biochemistry) to demonstrate our proposed model as applied to measuring potential within an educational context. The advantage of this approach compared to currently utilized methods is discussed as are future directions and limitations.

  20. The Growth Path of Agricultural Labor Productivity in China: A Latent Growth Curve Model at the Prefectural Level

    Directory of Open Access Journals (Sweden)

    Peng Bin

    2016-06-01

    Full Text Available Given the shrinking proportion of agriculture output and the growing mobility of the labor force in China, how agricultural labor productivity develops has become an increasingly attractive topic for researchers and policy makers. This study aims to depict the development trajectory of agricultural labor productivity in China after its WTO entry. Based on a balanced panel data containing 287 Chinese prefectures from 2000 to 2013, this study applies the Latent Growth Curve Model (LGCM and finds that the agricultural labor productivity follows a piecewise growth path with two breaking points in the years of 2004 and 2009. This may stem from some exogenous stimulus, such as supporting policies launched in the breaking years. Further statistical analysis shows an expanding gap of agricultural labor productivity among different Chinese prefectures.

  1. Growth Curve Analysis and Change-Points Detection in Extremes

    KAUST Repository

    Meng, Rui

    2016-05-15

    The thesis consists of two coherent projects. The first project presents the results of evaluating salinity tolerance in barley using growth curve analysis where different growth trajectories are observed within barley families. The study of salinity tolerance in plants is crucial to understanding plant growth and productivity. Because fully-automated smarthouses with conveyor systems allow non-destructive and high-throughput phenotyping of large number of plants, it is now possible to apply advanced statistical tools to analyze daily measurements and to study salinity tolerance. To compare different growth patterns of barley variates, we use functional data analysis techniques to analyze the daily projected shoot areas. In particular, we apply the curve registration method to align all the curves from the same barley family in order to summarize the family-wise features. We also illustrate how to use statistical modeling to account for spatial variation in microclimate in smarthouses and for temporal variation across runs, which is crucial for identifying traits of the barley variates. In our analysis, we show that the concentrations of sodium and potassium in leaves are negatively correlated, and their interactions are associated with the degree of salinity tolerance. The second project studies change-points detection methods in extremes when multiple time series data are available. Motived by the scientific question of whether the chances to experience extreme weather are different in different seasons of a year, we develop a change-points detection model to study changes in extremes or in the tail of a distribution. Most of existing models identify seasons from multiple yearly time series assuming a season or a change-point location remains exactly the same across years. In this work, we propose a random effect model that allows the change-point to vary from year to year, following a given distribution. Both parametric and nonparametric methods are developed

  2. Estimation of growth curve parameters in Konya Merino sheep ...

    African Journals Online (AJOL)

    The objective of this study was to determine the fitness of Quadratic, Cubic, Gompertz and Logistic functions to the growth curves of Konya Merino lambs obtained by using monthly records of live weight from birth to 480 days of age. The models were evaluated according to determination coefficient (R2), mean square ...

  3. Integrated healthcare networks' performance: a growth curve modeling approach.

    Science.gov (United States)

    Wan, Thomas T H; Wang, Bill B L

    2003-05-01

    This study examines the effects of integration on the performance ratings of the top 100 integrated healthcare networks (IHNs) in the United States. A strategic-contingency theory is used to identify the relationship of IHNs' performance to their structural and operational characteristics and integration strategies. To create a database for the panel study, the top 100 IHNs selected by the SMG Marketing Group in 1998 were followed up in 1999 and 2000. The data were merged with the Dorenfest data on information system integration. A growth curve model was developed and validated by the Mplus statistical program. Factors influencing the top 100 IHNs' performance in 1998 and their subsequent rankings in the consecutive years were analyzed. IHNs' initial performance scores were positively influenced by network size, number of affiliated physicians and profit margin, and were negatively associated with average length of stay and technical efficiency. The continuing high performance, judged by maintaining higher performance scores, tended to be enhanced by the use of more managerial or executive decision-support systems. Future studies should include time-varying operational indicators to serve as predictors of network performance.

  4. An Approach of Estimating Individual Growth Curves for Young Thoroughbred Horses Based on Their Birthdays

    Science.gov (United States)

    ONODA, Tomoaki; YAMAMOTO, Ryuta; SAWAMURA, Kyohei; MURASE, Harutaka; NAMBO, Yasuo; INOUE, Yoshinobu; MATSUI, Akira; MIYAKE, Takeshi; HIRAI, Nobuhiro

    2014-01-01

    ABSTRACT We propose an approach of estimating individual growth curves based on the birthday information of Japanese Thoroughbred horses, with considerations of the seasonal compensatory growth that is a typical characteristic of seasonal breeding animals. The compensatory growth patterns appear during only the winter and spring seasons in the life of growing horses, and the meeting point between winter and spring depends on the birthday of each horse. We previously developed new growth curve equations for Japanese Thoroughbreds adjusting for compensatory growth. Based on the equations, a parameter denoting the birthday information was added for the modeling of the individual growth curves for each horse by shifting the meeting points in the compensatory growth periods. A total of 5,594 and 5,680 body weight and age measurements of Thoroughbred colts and fillies, respectively, and 3,770 withers height and age measurements of both sexes were used in the analyses. The results of predicted error difference and Akaike Information Criterion showed that the individual growth curves using birthday information better fit to the body weight and withers height data than not using them. The individual growth curve for each horse would be a useful tool for the feeding managements of young Japanese Thoroughbreds in compensatory growth periods. PMID:25013356

  5. Using the Yield Curve in Forecasting Output Growth and In‡flation

    DEFF Research Database (Denmark)

    Hillebrand, Eric Tobias; Huang, Huiyu; Lee, Tae-Hwy

    Following Diebold and Li (2006), we use the Nelson-Siegel (NS, 1987) yield curve factors. However the NS yield curve factors are not supervised for a specifi…c forecast target in the sense that the same factors are used for forecasting different variables, e.g., output growth or infl‡ation. We...... analytically and numerically how supervision works. For both CF and CI schemes, principal components (PC) may be used in place of the NS factors. In out-of-sample forecasting of U.S. monthly output growth and infl‡ation, we fi…nd that supervised CF-factor models (CF-NS, CF-PC) are substantially better than...

  6. PENILAIAN PROGRAM PRAKTIKUM TERHADAP PENINGKATAN KUALITI GURU PRA PERKHIDMATAN: ANALISIS BERDASARKAN LATENT GROWTH CURVE MODELLING

    Directory of Open Access Journals (Sweden)

    Azizah Sarkowi

    2015-12-01

    Full Text Available Practicum is an important component in teacher education programs. This study identify the improvement in the quality of pre-service teachers for three phases practicum. Multi-point prospective panel study has been conducted on a 541 pre-service teachers at the Institute of Teacher Education. Teacher’s quality is measured based on the achievement of program learning outcomes. Based on matching last six digit identification card number for three studies series, 337 questionnaires were analyzed using a latent growth curve model using AMOS 18.0. Latent Analysis shows that the model achieve goodness of fit. There is a linear trend of improvement in the performance of the three phases of the practicum. This increase varies between individuals and the rate of growth depends on the level of achievement at practicum phase I. Studies indicate that the increase in the practicum period of teacher education policy should be continued.

  7. Nonlinear Growth Models in M"plus" and SAS

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam

    2009-01-01

    Nonlinear growth curves or growth curves that follow a specified nonlinear function in time enable researchers to model complex developmental patterns with parameters that are easily interpretable. In this article we describe how a variety of sigmoid curves can be fit using the M"plus" structural modeling program and the nonlinear…

  8. PMAnalyzer: a new web interface for bacterial growth curve analysis.

    Science.gov (United States)

    Cuevas, Daniel A; Edwards, Robert A

    2017-06-15

    Bacterial growth curves are essential representations for characterizing bacteria metabolism within a variety of media compositions. Using high-throughput, spectrophotometers capable of processing tens of 96-well plates, quantitative phenotypic information can be easily integrated into the current data structures that describe a bacterial organism. The PMAnalyzer pipeline performs a growth curve analysis to parameterize the unique features occurring within microtiter wells containing specific growth media sources. We have expanded the pipeline capabilities and provide a user-friendly, online implementation of this automated pipeline. PMAnalyzer version 2.0 provides fast automatic growth curve parameter analysis, growth identification and high resolution figures of sample-replicate growth curves and several statistical analyses. PMAnalyzer v2.0 can be found at https://edwards.sdsu.edu/pmanalyzer/ . Source code for the pipeline can be found on GitHub at https://github.com/dacuevas/PMAnalyzer . Source code for the online implementation can be found on GitHub at https://github.com/dacuevas/PMAnalyzerWeb . dcuevas08@gmail.com. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press.

  9. Interactions of cosmic rays in the atmosphere: growth curves revisited

    Energy Technology Data Exchange (ETDEWEB)

    Obermeier, A.; Boyle, P.; Müller, D. [Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States); Hörandel, J., E-mail: a.obermeier@astro.ru.nl [Radboud Universiteit Nijmegen, 6525-HP Nijmegen (Netherlands)

    2013-12-01

    Measurements of cosmic-ray abundances on balloons are affected by interactions in the residual atmosphere above the balloon. Corrections for such interactions are particularly important for observations of rare secondary particles such as boron, antiprotons, and positrons. These corrections either can be calculated if the relevant cross sections in the atmosphere are known or may be empirically determined by extrapolation of the 'growth curves', i.e., the individual particle intensities as functions of atmospheric depth. The growth-curve technique is particularly attractive for long-duration balloon flights where the periodic daily altitude variations permit rather precise determinations of the corresponding particle intensity variations. We determine growth curves for nuclei from boron (Z = 5) to iron (Z = 26) using data from the 2006 Arctic balloon flight of the TRACER detector for cosmic-ray nuclei, and we compare the growth curves with predictions from published cross section values. In general, good agreement is observed. We then study the boron/carbon abundance ratio and derive a simple and energy-independent correction term for this ratio. We emphasize that the growth-curve technique can be developed further to provide highly accurate tests of published interaction cross section values.

  10. [Customized and non-customized French intrauterine growth curves. II - Comparison with existing curves and benefits of customization].

    Science.gov (United States)

    Ego, A; Prunet, C; Blondel, B; Kaminski, M; Goffinet, F; Zeitlin, J

    2016-02-01

    Our aim is to compare the new French EPOPé intrauterine growth curves, developed to address the guidelines 2013 of the French College of Obstetricians and Gynecologists, with reference curves currently used in France, and to evaluate the consequences of their adjustment for fetal sex and maternal characteristics. Eight intrauterine and birthweight curves, used in France were compared to the EPOPé curves using data from the French Perinatal Survey 2010. The influence of adjustment on the rate of SGA births and the characteristics of these births was analysed. Due to their birthweight values and distribution, the selected intrauterine curves are less suitable for births in France than the new curves. Birthweight curves led to low rates of SGA births from 4.3 to 8.5% compared to 10.0% with the EPOPé curves. The adjustment for maternal and fetal characteristics avoids the over-representation of girls among SGA births, and reclassifies 4% of births. Among births reclassified as SGA, the frequency of medical and obstetrical risk factors for growth restriction, smoking (≥10 cigarettes/day), and neonatal transfer is higher than among non-SGA births (P<0.01). The EPOPé curves are more suitable for French births than currently used curves, and their adjustment improves the identification of mothers and babies at risk of growth restriction and poor perinatal outcomes. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  11. Colombian reference growth curves for height, weight, body mass index and head circumference.

    Science.gov (United States)

    Durán, Paola; Merker, Andrea; Briceño, Germán; Colón, Eugenia; Line, Dionne; Abad, Verónica; Del Toro, Kenny; Chahín, Silvia; Matallana, Audrey Mary; Lema, Adriana; Llano, Mauricio; Céspedes, Jaime; Hagenäs, Lars

    2016-03-01

    Published Growth studies from Latin America are limited to growth references from Argentina and Venezuela. The aim of this study was to construct reference growth curves for height, weight, body mass index (BMI) and head circumference of Colombian children in a format that is useful for following the growth of the individual child and as a tool for public health. Prospective measurements from 27 209 Colombian children from middle and upper socio-economic level families were processed using the generalised additive models for location, scale and shape (GAMLSS). Descriptive statistics for length and height, weight, BMI and head circumference for age are given as raw and smoothed values. Final height was 172.3 cm for boys and 159.4 cm for girls. Weight at 18 years of age was 64.0 kg for boys and 54 kg for girls. Growth curves are presented in a ± 3 SD format using logarithmic axes. The constructed reference growth curves are a start for following secular trends in Colombia and are also in the presented layout an optimal clinical tool for health care. ©2015 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  12. Parent Involvement and Science Achievement: A Cross-Classified Multilevel Latent Growth Curve Analysis

    Science.gov (United States)

    Johnson, Ursula Y.; Hull, Darrell M.

    2014-01-01

    The authors examined science achievement growth at Grades 3, 5, and 8 and parent school involvement at the same time points using the Early Childhood Longitudinal Study-Kindergarten Class of 1998-1999. Data were analyzed using cross-classified multilevel latent growth curve modeling with time invariant and varying covariates. School-based…

  13. Computerized tomography and head growth curve infantile macrocephaly with normal psychomotor development

    International Nuclear Information System (INIS)

    Eda, Isematsu; Kitahara, Tadashi; Takashima, Sachio; Takeshita, Kenzo

    1982-01-01

    Macrocephaly was defined as a head measuring larger than 98th percentile. We have evaluated CT findings and head growth curves in 25 infants with large heads. Ten (40%) of 25 infants with large heads were normal developmentally and neurologically. Five (20%) of those were mentally retarded. The other 10 infants (40%) included hydrocephalus (4 cases), malformation syndrome (3 cases), brain tumor (1 case), metabolic disorder (1 case) and degenerative disorder (1 case). Their head growth curves were typed as (I), (II) and (III): Type (I) (excessive head growth curve to 2 SDs above normal); Type (II) (head growth curve gradually approached to 2 SDs above normal); Type (III) (head growth curve parallel to 2 SDs above normal). Ten of macrocephaly with normal psychomotor development were studied clinically and radiologically in details. They were all male. CT pictures of those showed normal or various abnormal findings: ventricular dilatations, wide frontal and temporal subdural spaces, wide interhemispheric fissures, wide cerebral sulci, and large sylvian fissures. CT findings in 2 of those, which because normal after repeated CT examinations, resembled benign subdural collection. CT findings in one of those were external hydrocephalus. Head growth curves were obtained from 8 of those. Six cases revealed type (II) and two cases did type (III). The remaining 2 cases could not be followed up. We consider that CT findings of infants showed macrocephaly with normal psychomotor development reveals normal or various abnormal (ventricular dilatations, benign subdural collection, external hydrocephalus) and their head growth curves are not at least excessive. Infants with mental retardation showed similar CT findings and head growth curves as those with normal psychomotor development. It was difficult to distinguish normal from mentally retarded infants by either CT findings or head growth curves. (author)

  14. Assessing Trust and Effectiveness in Virtual Teams: Latent Growth Curve and Latent Change Score Models

    Directory of Open Access Journals (Sweden)

    Michael D. Coovert

    2017-08-01

    Full Text Available Trust plays a central role in the effectiveness of work groups and teams. This is the case for both face-to-face and virtual teams. Yet little is known about the development of trust in virtual teams. We examined cognitive and affective trust and their relationship to team effectiveness as reflected through satisfaction with one’s team and task performance. Latent growth curve analysis reveals both trust types start at a significant level with individual differences in that initial level. Cognitive trust follows a linear growth pattern while affective trust is overall non-linear, but becomes linear once established. Latent change score models are utilized to examine change in trust and also its relationship with satisfaction with the team and team performance. In examining only change in trust and its relationship to satisfaction there appears to be a straightforward influence of trust on satisfaction and satisfaction on trust. However, when incorporated into a bivariate coupling latent change model the dynamics of the relationship are revealed. A similar pattern holds for trust and task performance; however, in the bivariate coupling change model a more parsimonious representation is preferred.

  15. Non-linear Growth Models in Mplus and SAS

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam

    2013-01-01

    Non-linear growth curves or growth curves that follow a specified non-linear function in time enable researchers to model complex developmental patterns with parameters that are easily interpretable. In this paper we describe how a variety of sigmoid curves can be fit using the Mplus structural modeling program and the non-linear mixed-effects modeling procedure NLMIXED in SAS. Using longitudinal achievement data collected as part of a study examining the effects of preschool instruction on academic gain we illustrate the procedures for fitting growth models of logistic, Gompertz, and Richards functions. Brief notes regarding the practical benefits, limitations, and choices faced in the fitting and estimation of such models are included. PMID:23882134

  16. Longitudinal Examination of Procrastination and Anxiety, and Their Relation to Self-Efficacy for Self- Regulated Learning: Latent Growth Curve Modeling

    Science.gov (United States)

    Yerdelen, Sündüs; McCaffrey, Adam; Klassen, Robert M.

    2016-01-01

    This study investigated the longitudinal association between students' anxiety and procrastination and the relation of self-efficacy for self-regulation to these constructs. Latent Growth Curve Modeling was used to analyze data gathered from 182 undergraduate students (134 female, 48 male) at 4 times during a semester. Our results showed that…

  17. Curve-of-growth analysis of M-type giants. beta. and. beta. Peg

    Energy Technology Data Exchange (ETDEWEB)

    Hanni, L.; Kipper, M.

    1975-01-01

    The curve-of-growth analysis is carried out with high-dispersion spectrograms of the region lambda lambda 5050--6150 for two M-type stars ..beta.. And (MOIII) and ..beta.. Peg (M2II-III) by using the newest oscillator strengths available. It has been found that the form of our empirical curve of growth is consistent with that of the theoretical curve by Wrubel. By making use of the data derived from the curve-of-growth analyses, atmospheric parameters such as THETA/sub ex/, rho/sub e/, ..nu../sub t/ and the abundances of the elements have been determined.

  18. Self-regulation and recall: growth curve modeling of intervention outcomes for older adults.

    Science.gov (United States)

    West, Robin L; Hastings, Erin C

    2011-12-01

    Memory training has often been supported as a potential means to improve performance for older adults. Less often studied are the characteristics of trainees that benefit most from training. Using a self-regulatory perspective, the current project examined a latent growth curve model to predict training-related gains for middle-aged and older adult trainees from individual differences (e.g., education), information processing skills (strategy use) and self-regulatory factors such as self-efficacy, control, and active engagement in training. For name recall, a model including strategy usage and strategy change as predictors of memory gain, along with self-efficacy and self-efficacy change, showed comparable fit to a more parsimonious model including only self-efficacy variables as predictors. The best fit to the text recall data was a model focusing on self-efficacy change as the main predictor of memory change, and that model showed significantly better fit than a model also including strategy usage variables as predictors. In these models, overall performance was significantly predicted by age and memory self-efficacy, and subsequent training-related gains in performance were best predicted directly by change in self-efficacy (text recall), or indirectly through the impact of active engagement and self-efficacy on gains (name recall). These results underscore the benefits of targeting self-regulatory factors in intervention programs designed to improve memory skills.

  19. Growth curve of buffalo grazing on a grass pasture

    Directory of Open Access Journals (Sweden)

    Teresa Cristina Alves

    2015-09-01

    Full Text Available ABSTRACTThe objective of this study was to evaluate the performance of 17 buffaloes (Mediterranean, from birth to slaughter age (720 days with monthly measures of weight, thoracic perimeter, body length, and height at withers. At the end of experimental period, the animals were separated into two different groups for statistical analysis according to slaughter weight: light body weight (LBW, mean 517 kg and heavy body weight (HBW, mean 568 kg. Buffalo growth occurs in the same way up to weaning age, and after that, two distinct groups grow in different forms in the same conditions of management and feeding. Body weight can be estimated according to age, thoracic perimeter, height, and length, showing high correlations. Buffaloes show growth in a sigmoid-curve model.

  20. The Impact of Student Teaching Experience on Pre-Service Teachers' Readiness for Technology Integration: A Mixed Methods Study with Growth Curve Modeling

    Science.gov (United States)

    Sun, Yan; Strobel, Johannes; Newby, Timothy J.

    2017-01-01

    Adopting a two-phase explanatory sequential mixed methods research design, the current study examined the impact of student teaching experiences on pre-service teachers' readiness for technology integration. In phase-1 of quantitative investigation, 2-level growth curve models were fitted using online repeated measures survey data collected from…

  1. Distortion-product otoacoustic emission growth curves in neonates

    Directory of Open Access Journals (Sweden)

    Tania Alves Barbosa

    2014-12-01

    Full Text Available Background: The recording of otoacoustic emissions (OAE enabled us to prove that the cochlea is able not only to receive sounds but also to produce acoustic energy. Through the use of distortion-product otoacoustic emission measurements, the growth of the response was seen according to the intensity of the sound stimulus presented (growth curve. Objective: to determine the thresholds for the emergence of distortion-product otoacoustic emissions (DPOAE on frequencies of 2000 and 4000 Hz with a stimulus varying from 20 to 65dB SPL, and to establish the slope values obtained in the growth curves. Methods: 39 neonates aged 5 to 28 days without risk indicators of hearing loss were studied. The DPOAE growth curves were obtained on the frequencies from 2000 Hz and 4000 Hz with a level of intensity ranging from 20 to 65dB SPL divided into two paradigms (20 to 40dB SPL and 40-65dB SPL. Results: there was a statistically significant difference in the thresholds for the emergence of DPOAE depending on the criteria used. The thresholds were on average higher at 4000 Hz than 2000 Hz and the slope was higher on average at 2000 Hz than 4000 Hz, although not statistically significant in either case. Conclusion: the thresholds were on average 30dB SPL at 2000Hz and 35dB SPL at 4000Hz. The slope values varied between 3 and 4 on average, reaching 15 in some cases.

  2. Trend in BMI z-score among Private Schools’ Students in Delhi using Multiple Imputation for Growth Curve Model

    Directory of Open Access Journals (Sweden)

    Vinay K Gupta

    2016-06-01

    Full Text Available Objective: The aim of the study is to assess the trend in mean BMI z-score among private schools’ students from their anthropometric records when there were missing values in the outcome. Methodology: The anthropometric measurements of student from class 1 to 12 were taken from the records of two private schools in Delhi, India from 2005 to 2010. These records comprise of an unbalanced longitudinal data that is not all the students had measurements recorded at each year. The trend in mean BMI z-score was estimated through growth curve model. Prior to that, missing values of BMI z-score were imputed through multiple imputation using the same model. A complete case analysis was also performed after excluding missing values to compare the results with those obtained from analysis of multiply imputed data. Results: The mean BMI z-score among school student significantly decreased over time in imputed data (β= -0.2030, se=0.0889, p=0.0232 after adjusting age, gender, class and school. Complete case analysis also shows a decrease in mean BMI z-score though it was not statistically significant (β= -0.2861, se=0.0987, p=0.065. Conclusions: The estimates obtained from multiple imputation analysis were better than those of complete data after excluding missing values in terms of lower standard errors. We showed that anthropometric measurements from schools records can be used to monitor the weight status of children and adolescents and multiple imputation using growth curve model can be useful while analyzing such data

  3. Brief Report: Examining children’s disruptive behavior in the wake of trauma - A two-piece growth curve model before and after a school shooting

    Science.gov (United States)

    Liao, Yue; Shonkoff, Eleanor T.; Barnett, Elizabeth; Wen, CK Fred; Miller, Kimberly A.; Eddy, J. Mark

    2015-01-01

    School shootings may have serious negative impacts on children years after the event. Previous research suggests that children exposed to traumatic events experience heightened fear, anxiety, and feelings of vulnerability, but little research has examined potential aggressive and disruptive behavioral reactions. Utilizing a longitudinal dataset in which a local school shooting occurred during the course of data collection, this study sought to investigate whether the trajectory of disruptive behaviors was affected by the shooting. A two-piece growth curve model was used to examine the trajectory of disruptive behaviors during the pre-shooting years (i.e., piece one) and post-shooting years (i.e., piece two). Results indicated that the two-piece growth curve model fit the data better than the one-piece model and that the school shooting precipitated a faster decline in aggressive behaviors. This study demonstrated a novel approach to examining effects of an unexpected traumatic event on behavioral trajectories using an existing longitudinal data set. PMID:26298676

  4. Brief report: Examining children's disruptive behavior in the wake of trauma - A two-piece growth curve model before and after a school shooting.

    Science.gov (United States)

    Liao, Yue; Shonkoff, Eleanor T; Barnett, Elizabeth; Wen, C K Fred; Miller, Kimberly A; Eddy, J Mark

    2015-10-01

    School shootings may have serious negative impacts on children years after the event. Previous research suggests that children exposed to traumatic events experience heightened fear, anxiety, and feelings of vulnerability, but little research has examined potential aggressive and disruptive behavioral reactions. Utilizing a longitudinal dataset in which a local school shooting occurred during the course of data collection, this study sought to investigate whether the trajectory of disruptive behaviors was affected by the shooting. A two-piece growth curve model was used to examine the trajectory of disruptive behaviors during the pre-shooting years (i.e., piece one) and post-shooting years (i.e., piece two). Results indicated that the two-piece growth curve model fit the data better than the one-piece model and that the school shooting precipitated a faster decline in aggressive behaviors. This study demonstrated a novel approach to examining effects of an unexpected traumatic event on behavioral trajectories using an existing longitudinal data set. Copyright © 2015 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

  5. Estimation of heritability and genetic correlation of body weight gain and growth curve parameters in Korean native chicken

    Directory of Open Access Journals (Sweden)

    Prabuddha Manjula

    2018-01-01

    Full Text Available Objective This study estimated the genetic parameters for body weight gain and growth curve parameter traits in Korean native chicken (KNC. Methods A total of 585 F1 chickens were used along with 88 of their F0 birds. Body weights were measured every 2 weeks from hatching to 20 weeks of age to measure weight gain at 2-week intervals. For each individual, a logistic growth curve model was fitted to the longitudinal growth dataset to obtain three growth curve parameters (α, asymptotic final body weight; β, inflection point; and γ, constant scale that was proportional to the overall growth rate. Genetic parameters were estimated based on the linear-mixed model using a restricted maximum likelihood method. Results Heritability estimates of body weight gain traits were low to high (0.057 to 0.458. Heritability estimates for α, β, and γ were 0.211±0.08, 0.249±0.09, and 0.095±0.06, respectively. Both genetic and phenotypic correlations between weight gain traits ranged from −0.527 to 0.993. Genetic and phenotypic correlation between the growth curve parameters and weight gain traits ranged from −0.968 to 0.987. Conclusion Based on the results of this study population, we suggest that the KNC could be used for selective breeding between 6 and 8 weeks of age to enhance the overall genetic improvement of growth traits. After validation of these results in independent studies, these findings will be useful for further optimization of breeding programs for KNC.

  6. Parent Prevention Communication Profiles and Adolescent Substance Use: A Latent Profile Analysis and Growth Curve Model

    Science.gov (United States)

    Choi, Hye Jeong; Miller-Day, Michelle; Shin, YoungJu; Hecht, Michael L.; Pettigrew, Jonathan; Krieger, Janice L.; Lee, JeongKyu; Graham, John W.

    2017-01-01

    This current study identifies distinct parent prevention communication profiles and examines whether youth with different parental communication profiles have varying substance use trajectories over time. Eleven schools in two rural school districts in the Midwestern United States were selected, and 784 students were surveyed at three time points from the beginning of 7th grade to the end of 8th grade. A series of latent profile analyses were performed to identify discrete profiles/subgroups of substance-specific prevention communication (SSPC). The results revealed a 4-profile model of SSPC: Active-Open, Passive-Open, Active-Silent, and Passive-Silent. A growth curve model revealed different rates of lifetime substance use depending on the youth’s SSPC profile. These findings have implications for parenting interventions and tailoring messages for parents to fit specific SSPC profiles. PMID:29056872

  7. Modification of the FRI crack growth model formulation from a mathematical viewpoint

    International Nuclear Information System (INIS)

    Hashimoto, Tsuneyuki; Koshiishi, Masato

    2009-01-01

    The FRI model of crack growth, which incorporates mechanical properties into the slip oxidation mechanism of crack advance, is an extension of the well-known Ford-Andresen model. When the exponent of the oxidation current decay curve is set close to 1, however, the FRI model gives an infinite crack growth rate. Here, the oxidation decay curve integral is revised to eliminate this divergence, and modified crack growth rate equations are derived. Also presented here is a procedure for determining the oxidation current parameters from the curve-fitting to measurements of crack growth rate. Parameter value determination and crack growth calculations are illustrated for cold-worked Type 316L stainless steel. (author)

  8. Estimation of the growth curve and heritability of the growth rate for giant panda (Ailuropoda melanoleuca) cubs.

    Science.gov (United States)

    Che, T D; Wang, C D; Jin, L; Wei, M; Wu, K; Zhang, Y H; Zhang, H M; Li, D S

    2015-03-27

    Giant panda cubs have a low survival rate during the newborn and early growth stages. However, the growth and developmental parameters of giant panda cubs during the early lactation stage (from birth to 6 months) are not well known. We examined the growth and development of giant panda cubs by the Chapman growth curve model and estimated the heritability of the maximum growth rate at the early lactation stage. We found that 83 giant panda cubs reached their maximum growth rate at approximately 75-120 days after birth. The body weight of cubs at 75 days was 4285.99 g. Furthermore, we estimated that the heritability of the maximum growth rate was moderate (h(2) = 0.38). Our study describes the growth and development of giant panda cubs at the early lactation stage and provides valuable growth benchmarks. We anticipate that our results will be a starting point for more detailed research on increasing the survival rate of giant panda cubs. Feeding programs for giant panda cubs need further improvement.

  9. Short communication Estimation of growth curve parameters in ...

    African Journals Online (AJOL)

    ikeskin

    The shape of growth curves has been reported to vary according to the species of .... a,b,c The means within columns with different superscripts are significantly .... J. Anim. Sci. 84, 2642-2654. The South African Journal of Animal Science is ...

  10. Symphysis-fundal height curve in the diagnosis of fetal growth deviations

    Directory of Open Access Journals (Sweden)

    Djacyr Magna Cabral Freire

    2010-12-01

    Full Text Available OBJECTIVE: To validate a new symphysis-fundal curve for screening fetal growth deviations and to compare its performance with the standard curve adopted by the Brazilian Ministry of Health. METHODS: Observational study including a total of 753 low-risk pregnant women with gestational age above 27 weeks between March to October 2006 in the city of João Pessoa, Northeastern Brazil. Symphisys-fundal was measured using a standard technique recommended by the Brazilian Ministry of Health. Estimated fetal weight assessed through ultrasound using the Brazilian fetal weight chart for gestational age was the gold standard. A subsample of 122 women with neonatal weight measurements was taken up to seven days after estimated fetal weight measurements and symphisys-fundal classification was compared with Lubchenco growth reference curve as gold standard. Sensitivity, specificity, positive and negative predictive values were calculated. The McNemar χ2 test was used for comparing sensitivity of both symphisys-fundal curves studied. RESULTS: The sensitivity of the new curve for detecting small for gestational age fetuses was 51.6% while that of the Brazilian Ministry of Health reference curve was significantly lower (12.5%. In the subsample using neonatal weight as gold standard, the sensitivity of the new reference curve was 85.7% while that of the Brazilian Ministry of Health was 42.9% for detecting small for gestational age. CONCLUSIONS: The diagnostic performance of the new curve for detecting small for gestational age fetuses was significantly higher than that of the Brazilian Ministry of Health reference curve.

  11. A versatile curve-fit model for linear to deeply concave rank abundance curves

    NARCIS (Netherlands)

    Neuteboom, J.H.; Struik, P.C.

    2005-01-01

    A new, flexible curve-fit model for linear to concave rank abundance curves was conceptualized and validated using observational data. The model links the geometric-series model and log-series model and can also fit deeply concave rank abundance curves. The model is based ¿ in an unconventional way

  12. Academia-industry collaboration feeds exponential growth curve

    CERN Document Server

    Jones Bey Hassaun, A

    2004-01-01

    The use of silicon strip detectors in high-energy particle tracking is discussed. The functional strength of silicon for high-energy particle physics as well as astrophysics lies in the ability to detect passage of charged particles with micron-scale spatial resolution. In addition to vertex detection, silicon strip detectors also provide full tracking detection to include momentum determination of particles in the magnetic field. Even if silicon detectors for basic science applications do not continue to grow larger, exponential growth of the technology for terrestrial commercial applications is likely to follow a healthy growth curve, as researchers continue to adapt silicon detector technology for low- dose medical x-ray imaging. (Edited abstract)

  13. Environmental Kuznets curve and growth source in Iran

    Directory of Open Access Journals (Sweden)

    Asghari Maryam

    2012-01-01

    Full Text Available Recent empirical research has examined the relationship between certain indicators of environmental degradation and income, concluding that in some cases an inverted U-shaped relationship, which has been called an environmental Kuznets curve (EKC, exists between these variables. The source of growth explanation is important for two reasons. First, it demonstrates how the pollution consequences of growth depend on the source of growth. Therefore, the analogy drawn by some in the environmental community between the damaging effects of economic development and those of liberalized trade is, at best, incomplete. Second, the source of growth explanation demonstrates that a strong policy response to income gains is not necessary for pollution to fall with growth. The aim of this paper investigates the role of differences source of growth in environmental quality of Iran. The results show the two growth resources in Iran cause, in the early stages, CO2 emission decreases until turning point but beyond this level of income per capita, economic growth leads to environmental degradation. I find a U relationship between environmental degradation (CO2 emission and economic growth in Iran.

  14. High-resolution time series of Pseudomonas aeruginosa gene expression and rhamnolipid secretion through growth curve synchronization

    Directory of Open Access Journals (Sweden)

    Xavier João B

    2011-06-01

    Full Text Available Abstract Background Online spectrophotometric measurements allow monitoring dynamic biological processes with high-time resolution. Contrastingly, numerous other methods require laborious treatment of samples and can only be carried out offline. Integrating both types of measurement would allow analyzing biological processes more comprehensively. A typical example of this problem is acquiring quantitative data on rhamnolipid secretion by the opportunistic pathogen Pseudomonas aeruginosa. P. aeruginosa cell growth can be measured by optical density (OD600 and gene expression can be measured using reporter fusions with a fluorescent protein, allowing high time resolution monitoring. However, measuring the secreted rhamnolipid biosurfactants requires laborious sample processing, which makes this an offline measurement. Results Here, we propose a method to integrate growth curve data with endpoint measurements of secreted metabolites that is inspired by a model of exponential cell growth. If serial diluting an inoculum gives reproducible time series shifted in time, then time series of endpoint measurements can be reconstructed using calculated time shifts between dilutions. We illustrate the method using measured rhamnolipid secretion by P. aeruginosa as endpoint measurements and we integrate these measurements with high-resolution growth curves measured by OD600 and expression of rhamnolipid synthesis genes monitored using a reporter fusion. Two-fold serial dilution allowed integrating rhamnolipid measurements at a ~0.4 h-1 frequency with high-time resolved data measured at a 6 h-1 frequency. We show how this simple method can be used in combination with mutants lacking specific genes in the rhamnolipid synthesis or quorum sensing regulation to acquire rich dynamic data on P. aeruginosa virulence regulation. Additionally, the linear relation between the ratio of inocula and the time-shift between curves produces high-precision measurements of

  15. A mathematical model of microalgae growth in cylindrical photobioreactor

    Science.gov (United States)

    Bakeri, Noorhadila Mohd; Jamaian, Siti Suhana

    2017-08-01

    Microalgae are unicellular organisms, which exist individually or in chains or groups but can be utilized in many applications. Researchers have done various efforts in order to increase the growth rate of microalgae. Microalgae have a potential as an effective tool for wastewater treatment, besides as a replacement for natural fuel such as coal and biodiesel. The growth of microalgae can be estimated by using Geider model, which this model is based on photosynthesis irradiance curve (PI-curve) and focused on flat panel photobioreactor. Therefore, in this study a mathematical model for microalgae growth in cylindrical photobioreactor is proposed based on the Geider model. The light irradiance is the crucial part that affects the growth rate of microalgae. The absorbed photon flux will be determined by calculating the average light irradiance in a cylindrical system illuminated by unidirectional parallel flux and considering the cylinder as a collection of differential parallelepipeds. Results from this study showed that the specific growth rate of microalgae increases until the constant level is achieved. Therefore, the proposed mathematical model can be used to estimate the rate of microalgae growth in cylindrical photobioreactor.

  16. ECONOMIC GROWTH, TRADE AND ENVIRONMENTAL ISSUES: TESTING ENVIRONMENTAL KUZNETS CURVE

    Directory of Open Access Journals (Sweden)

    Dedi Budiman Hakim

    2013-04-01

    Full Text Available ASEAN experiences a dynamic economic growth due to its liberalised markets. However concerns arise related to environmental issues resulting from the economic activities. It reflects tradeoffs between economic growth driven by trade and foreign direct investment (FDI, and environment. To investigate such a relation the Environmental Kuznets Curve was applied by regressing amount of carbon emission with gross domestic product (GDP, quadratic GDP, trade openness and FDI. The result reveals that amount of carbon emission is linearly and positively correlated with GDP per capita. It is predicted that as ASEAN economies grow, carbon emission increases. Trade openness is also found to contribute to carbon emission. Keywords: Kuznets curve, carbon emission, gross domestic product, trade, foreign direct investment JEL classification number: F15, F18

  17. Growth Kinetics and Modeling of Direct Oxynitride Growth with NO-O2 Gas Mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Everist, Sarah; Nelson, Jerry; Sharangpani, Rahul; Smith, Paul Martin; Tay, Sing-Pin; Thakur, Randhir

    1999-05-03

    We have modeled growth kinetics of oxynitrides grown in NO-O2 gas mixtures from first principles using modified Deal-Grove equations. Retardation of oxygen diffusion through the nitrided dielectric was assumed to be the dominant growth-limiting step. The model was validated against experimentally obtained curves with good agreement. Excellent uniformity, which exceeded expected walues, was observed.

  18. Coupling of online control and inhibitory systems in children with atypical motor development: A growth curve modelling study.

    Science.gov (United States)

    Ruddock, Scott; Caeyenberghs, Karen; Piek, Jan; Sugden, David; Hyde, Christian; Morris, Sue; Rigoli, Daniela; Steenbergen, Bert; Wilson, Peter

    2016-11-01

    Previous research indicates that children with Developmental Coordination Disorder (DCD) show deficits performing online corrections, an issue exacerbated by adding inhibitory constraints; however, cross-sectional data suggests that these deficits may reduce with age. Using a longitudinal design, the aim of the study presented here was to model the coupling that occurs between inhibitory systems and (predictive) online control in typically developing children (TDC) and in those with Developmental Coordination Disorder (DCD) over an extended period of time, using a framework of interactive specialization. We predicted that TDC would show a non-linear growth pattern, consistent with re-organisation in the coupling during the middle childhood period, while DCD would display a developmental lag. A group of 196 children (111 girls and 85 boys) aged between 6 and 12years participated in the study. Children were classified as DCD according to research criteria. Using a cohort sequential design, both TDC and DCD groups were divided into age cohorts. Predictive (online) control was defined operationally by performance on a Double-Jump Reaching Task (DJRT), which was assessed at 6-month intervals over two years (5 time points in total). Inhibitory control was examined using an anti-jump condition of the DJRT paradigm whereby children were instructed to touch a target location in the hemispace opposite a cued location. For the TDC group, model comparison using growth curve analysis revealed that a quadratic trend was the most appropriate fit with evidence of rapid improvement in anti-reach performance up until middle childhood (around 8-9years of age), followed by a more gradual rate of improvement into late childhood and early adolescence. This pattern was evident on both chronometric and kinematic measures. In contrast, for children with DCD, a linear function provided the best to fit on the key metrics, with a slower rate of improvement than controls. We conclude that

  19. Modelling subject-specific childhood growth using linear mixed-effect models with cubic regression splines.

    Science.gov (United States)

    Grajeda, Laura M; Ivanescu, Andrada; Saito, Mayuko; Crainiceanu, Ciprian; Jaganath, Devan; Gilman, Robert H; Crabtree, Jean E; Kelleher, Dermott; Cabrera, Lilia; Cama, Vitaliano; Checkley, William

    2016-01-01

    Childhood growth is a cornerstone of pediatric research. Statistical models need to consider individual trajectories to adequately describe growth outcomes. Specifically, well-defined longitudinal models are essential to characterize both population and subject-specific growth. Linear mixed-effect models with cubic regression splines can account for the nonlinearity of growth curves and provide reasonable estimators of population and subject-specific growth, velocity and acceleration. We provide a stepwise approach that builds from simple to complex models, and account for the intrinsic complexity of the data. We start with standard cubic splines regression models and build up to a model that includes subject-specific random intercepts and slopes and residual autocorrelation. We then compared cubic regression splines vis-à-vis linear piecewise splines, and with varying number of knots and positions. Statistical code is provided to ensure reproducibility and improve dissemination of methods. Models are applied to longitudinal height measurements in a cohort of 215 Peruvian children followed from birth until their fourth year of life. Unexplained variability, as measured by the variance of the regression model, was reduced from 7.34 when using ordinary least squares to 0.81 (p linear mixed-effect models with random slopes and a first order continuous autoregressive error term. There was substantial heterogeneity in both the intercept (p modeled with a first order continuous autoregressive error term as evidenced by the variogram of the residuals and by a lack of association among residuals. The final model provides a parametric linear regression equation for both estimation and prediction of population- and individual-level growth in height. We show that cubic regression splines are superior to linear regression splines for the case of a small number of knots in both estimation and prediction with the full linear mixed effect model (AIC 19,352 vs. 19

  20. Piecewise Linear-Linear Latent Growth Mixture Models with Unknown Knots

    Science.gov (United States)

    Kohli, Nidhi; Harring, Jeffrey R.; Hancock, Gregory R.

    2013-01-01

    Latent growth curve models with piecewise functions are flexible and useful analytic models for investigating individual behaviors that exhibit distinct phases of development in observed variables. As an extension of this framework, this study considers a piecewise linear-linear latent growth mixture model (LGMM) for describing segmented change of…

  1. Is cancer a pure growth curve or does it follow a kinetics of dynamical structural transformation?

    Science.gov (United States)

    González, Maraelys Morales; Joa, Javier Antonio González; Cabrales, Luis Enrique Bergues; Pupo, Ana Elisa Bergues; Schneider, Baruch; Kondakci, Suleyman; Ciria, Héctor Manuel Camué; Reyes, Juan Bory; Jarque, Manuel Verdecia; Mateus, Miguel Angel O'Farril; González, Tamara Rubio; Brooks, Soraida Candida Acosta; Cáceres, José Luis Hernández; González, Gustavo Victoriano Sierra

    2017-03-07

    Unperturbed tumor growth kinetics is one of the more studied cancer topics; however, it is poorly understood. Mathematical modeling is a useful tool to elucidate new mechanisms involved in tumor growth kinetics, which can be relevant to understand cancer genesis and select the most suitable treatment. The classical Kolmogorov-Johnson-Mehl-Avrami as well as the modified Kolmogorov-Johnson-Mehl-Avrami models to describe unperturbed fibrosarcoma Sa-37 tumor growth are used and compared with the Gompertz modified and Logistic models. Viable tumor cells (1×10 5 ) are inoculated to 28 BALB/c male mice. Modified Gompertz, Logistic, Kolmogorov-Johnson-Mehl-Avrami classical and modified Kolmogorov-Johnson-Mehl-Avrami models fit well to the experimental data and agree with one another. A jump in the time behaviors of the instantaneous slopes of classical and modified Kolmogorov-Johnson-Mehl-Avrami models and high values of these instantaneous slopes at very early stages of tumor growth kinetics are observed. The modified Kolmogorov-Johnson-Mehl-Avrami equation can be used to describe unperturbed fibrosarcoma Sa-37 tumor growth. It reveals that diffusion-controlled nucleation/growth and impingement mechanisms are involved in tumor growth kinetics. On the other hand, tumor development kinetics reveals dynamical structural transformations rather than a pure growth curve. Tumor fractal property prevails during entire TGK.

  2. Modelling curves of manufacturing feasibilities and demand

    Directory of Open Access Journals (Sweden)

    Soloninko K.S.

    2017-03-01

    Full Text Available The authors research the issue of functional properties of curves of manufacturing feasibilities and demand. Settlement of the problem, and its connection with important scientific and practical tasks. According to its nature, the market economy is unstable and is in constant movement. Economy has an effective instrument for explanation of changes in economic environment; this tool is called the modelling of economic processes. The modelling of economic processes depends first and foremost on the building of economic model which is the base for the formalization of economic process, that is, the building of mathematical model. The effective means for formalization of economic process is the creation of the model of hypothetic or imaginary economy. The building of demand model is significant for the market of goods and services. The problem includes the receiving (as the result of modelling definite functional properties of curves of manufacturing feasibilities and demand according to which one can determine their mathematical model. Another problem lies in obtaining majorant properties of curves of joint demand on the market of goods and services. Analysis of the latest researches and publications. Many domestic and foreign scientists dedicated their studies to the researches and building of the models of curves of manufacturing feasibilities and demand. In spite of considerable work of the scientists, such problems as functional properties of the curves and their practical use in modelling. The purpose of the article is to describe functional properties of curves of manufacturing feasibilities and demand on the market of goods and services on the base of modelling of their building. Scientific novelty and practical value. The theoretical regulations (for functional properties of curves of manufacturing feasibilities and demand received as a result of the present research, that is convexity, give extra practical possibilities in a microeconomic

  3. Proposal of fatigue crack growth rate curve in air for nickel-base alloys used in BWR

    International Nuclear Information System (INIS)

    Ogawa, Takuya; Itatani, Masao; Nagase, Hiroshi; Aoike, Satoru; Yoneda, Hideki

    2013-01-01

    When the defects are detected in the nuclear components in Japan, structural integrity assessment should be performed for the technical judgment on continuous service based on the Rules on Fitness-for-Service for Nuclear Power Plants of the Japan Society of Mechanical Engineers Code (JSME FFS Code). Fatigue crack growth analysis is required when the cyclic loading would be applied for the components. Recently, fatigue crack growth rate curve in air environment for Nickel-base alloys weld metal used in BWR was proposed by the authors and it was adopted as a code case of JSME FFS Code to evaluate the embedded flaw. In this study, fatigue crack growth behavior for heat-affected zone (HAZ) of Nickel-base alloys in air was investigated. And a unified fatigue crack growth rate curve in air for HAZ and weld metal of Nickel-base alloys used in BWR was evaluated. As a result, it was found that the curve for weld metal could be applied as a curve for both HAZ and weld metal since moderately conservative assessment of fatigue crack growth rate of HAZ is possible by the curve for weld metal in the Paris region. And the threshold value of stress intensity far range (ΔK th ) is determined to 3.0 MPa√m based on the fatigue crack growth rate of HAZ. (author)

  4. Predicting Change in Postpartum Depression: An Individual Growth Curve Approach.

    Science.gov (United States)

    Buchanan, Trey

    Recently, methodologists interested in examining problems associated with measuring change have suggested that developmental researchers should focus upon assessing change at both intra-individual and inter-individual levels. This study used an application of individual growth curve analysis to the problem of maternal postpartum depression.…

  5. Longitudinal associations between exercise identity and exercise motivation: A multilevel growth curve model approach.

    Science.gov (United States)

    Ntoumanis, N; Stenling, A; Thøgersen-Ntoumani, C; Vlachopoulos, S; Lindwall, M; Gucciardi, D F; Tsakonitis, C

    2018-02-01

    Past work linking exercise identity and exercise motivation has been cross-sectional. This is the first study to model the relations between different types of exercise identity and exercise motivation longitudinally. Understanding the dynamic associations between these sets of variables has implications for theory development and applied research. This was a longitudinal survey study. Participants were 180 exercisers (79 men, 101 women) from Greece, who were recruited from fitness centers and were asked to complete questionnaires assessing exercise identity (exercise beliefs and role-identity) and exercise motivation (intrinsic, identified, introjected, external motivation, and amotivation) three times within a 6 month period. Multilevel growth curve modeling examined the role of motivational regulations as within- and between-level predictors of exercise identity, and a model in which exercise identity predicted exercise motivation at the within- and between-person levels. Results showed that within-person changes in intrinsic motivation, introjected, and identified regulations were positively and reciprocally related to within-person changes in exercise beliefs; intrinsic motivation was also a positive predictor of within-person changes in role-identity but not vice versa. Between-person differences in the means of predictor variables were predictive of initial levels and average rates of change in the outcome variables. The findings show support to the proposition that a strong exercise identity (particularly exercise beliefs) can foster motivation for behaviors that reinforce this identity. We also demonstrate that such relations can be reciprocal overtime and can depend on the type of motivation in question as well as between-person differences in absolute levels of these variables. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Growth curve of Atlantoscia floridana (van Name (Crustacea, Isopoda, Philosciidae from a Brazilian Restinga Forest

    Directory of Open Access Journals (Sweden)

    Paula Beatriz Araujo

    2004-03-01

    Full Text Available The terrestrial isopod Atlantoscia floridana (van Name, 1940 occurs from the U.S.A. (Florida to Brazil and Argentina. In the southernmost Brazilian State, Rio Grande do Sul, the species is recorded in many localities, in urban and in non-urban areas. The growth curve of Atlantoscia floridana based on field data is presented. The specimens were sampled from April, 2000 to October, 2001 at the Reserva Biológica do Lami (RBL, Rio Grande do Sul. Captured individuals were sexed and had their cephalothorax width measured, with the data analyzed with von Bertalanffy's model. The growth curves for males and females are described, respectively, by the equations: Wt = 1.303 [1 - e-0.00941 (t + 50.37] and Wt = 1.682 [1 - e-0.00575 (t + 59.13]. The curves showed differential growth between sexes, where females reach a higher Wµ with a slower growth rate. Based on the growth curves it was also possible to estimate life expectancy for males and females.O isópodo terrestre Atlantoscia floridana (van Name, 1940 ocorre desde os Estados Unidos (Flórida até o Brasil e Argentina. No Rio Grande do Sul a espécie é registrada em muitas localidades, em áreas urbanas e não-urbanas. Este trabalho apresenta a curva de crescimento de Atlantoscia floridana, baseada em dados de campo. Os espécimes foram amostrados desde abril, 2000 a outubro, 2001 na Reserva Biológica do Lami (RBL, Rio Grande do Sul. Os indivíduos capturados foram sexados e tiveram o cefalotórax medido. Os dados foram analisados utilizando-se o modelo de von Bertalanffy. A curva de crescimento para machos e fêmeas são descritas, respectivamente, pelas equações Wt = 1.303 [1 - e-0.00941 (t + 50.37] e Wt = 1.682 [1 - e -0.00575 (t + 59.13]. As curvas mostraram crescimento diferencial entre os sexos, onde as fêmeas atingem o maior Wµ com uma taxa de crescimento menor. Com base nas curvas de crescimento também foi possível estimar a expectativa de vida para machos e fêmeas.

  7. Economic growth and emissions reconsidering the empirical basis of environmental Kuznets curves

    International Nuclear Information System (INIS)

    De Bruyn, S.M.; Van den Bergh, J.C.J.M.; Opschoor, J.B.

    1998-01-01

    Recent empirical research indicates that certain types of emissions follow an inverted-U or environmental Kuznets curve (EKC) as income grows. This regularity has been interpreted as a possible de-linking of economic growth and patterns of certain pollutants for developed economies. In this paper the empirical basis of this result is investigated, by considering some statistical particularities of the various EKC studies performed. It is argued that the inverted-U relationship between income and emissions estimated from panel data need not hold for specific individual countries over time. Based on insights from 'intensity-of-use' analysis in resource economics an alternative growth model is specified and estimated for three types of emissions (CO 2 , NO x and SO 2 ) in four countries (Netherlands, UK, USA and Western Germany). It is found that the time patterns of these emissions correlate positively with economic growth and that emission reductions may have been achieved as a result of structural and technological changes in the economy. 'Sustainable growth' is defined as the rate of economic growth that does not lead to growth in emissions. Its rate is calculated for each type of emission and country, based on estimated parameter values. The resulting indicators reflect a balance between the positive influence of growth and negative influence of structural change and technological progress on emission levels

  8. MODELING THE TRANSITION CURVE ON A LIMITED TERAIN

    Directory of Open Access Journals (Sweden)

    V. D. Borisenko

    2017-04-01

    Full Text Available Purpose. Further development of the method of geometric modelling of transition curves, which are placed between rectilinear and circular sections of railway tracks and are created in localities, the relief of which causes certain restrictions on the size of the transition curves of the railway track. Methodology. The equation of the transition curve is taken in parametric form, in which the length of the arc of the modelled curve is used as a parameter. As initial data in the modelling of the transition curve, the coordinates of its initial point and the angle of inclination in it are tangent, the radius of the circumference of the circular section and the parameter that is used as a constraint when placing a section of the railway track. The transition curve is modelled under the condition that the distribution of its curvature from the length of the arc - the natural parameter - is described by a cubic dependence. This dependence contains four unknown coefficients; the unknown is also the length of the arc. The coefficients of the cubic dependence and the length of the arc of the transition curve, the coordinates of its end point, the angle of inclination in it of the tangent are determined during the simulation of the transition curve. The application of boundary conditions and methods of differential geometry with respect to the distribution of the slope angle of the tangent to the simulated curve from the initial to the end points of the transition curve and the calculation of the coordinates of the end point of the curve allows us to reduce the problem of modelling the transition curve to determine the arc length of this curve. Directly the length of the transition curve is in the process of minimizing the deviation of the circumference of the circular path from its current value obtained when searching for the arc length. Findings. As a result of the computational experiment, the possibility of modelling a transition curve between a

  9. Super-quantum curves from super-eigenvalue models

    Energy Technology Data Exchange (ETDEWEB)

    Ciosmak, Paweł [Faculty of Mathematics, Informatics and Mechanics, University of Warsaw,ul. Banacha 2, 02-097 Warsaw (Poland); Hadasz, Leszek [M. Smoluchowski Institute of Physics, Jagiellonian University,ul. Łojasiewicza 11, 30-348 Kraków (Poland); Manabe, Masahide [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Sułkowski, Piotr [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E. California Blvd, Pasadena, CA 91125 (United States)

    2016-10-10

    In modern mathematical and theoretical physics various generalizations, in particular supersymmetric or quantum, of Riemann surfaces and complex algebraic curves play a prominent role. We show that such supersymmetric and quantum generalizations can be combined together, and construct supersymmetric quantum curves, or super-quantum curves for short. Our analysis is conducted in the formalism of super-eigenvalue models: we introduce β-deformed version of those models, and derive differential equations for associated α/β-deformed super-matrix integrals. We show that for a given model there exists an infinite number of such differential equations, which we identify as super-quantum curves, and which are in one-to-one correspondence with, and have the structure of, super-Virasoro singular vectors. We discuss potential applications of super-quantum curves and prospects of other generalizations.

  10. Super-quantum curves from super-eigenvalue models

    International Nuclear Information System (INIS)

    Ciosmak, Paweł; Hadasz, Leszek; Manabe, Masahide; Sułkowski, Piotr

    2016-01-01

    In modern mathematical and theoretical physics various generalizations, in particular supersymmetric or quantum, of Riemann surfaces and complex algebraic curves play a prominent role. We show that such supersymmetric and quantum generalizations can be combined together, and construct supersymmetric quantum curves, or super-quantum curves for short. Our analysis is conducted in the formalism of super-eigenvalue models: we introduce β-deformed version of those models, and derive differential equations for associated α/β-deformed super-matrix integrals. We show that for a given model there exists an infinite number of such differential equations, which we identify as super-quantum curves, and which are in one-to-one correspondence with, and have the structure of, super-Virasoro singular vectors. We discuss potential applications of super-quantum curves and prospects of other generalizations.

  11. Super-quantum curves from super-eigenvalue models

    Science.gov (United States)

    Ciosmak, Paweł; Hadasz, Leszek; Manabe, Masahide; Sułkowski, Piotr

    2016-10-01

    In modern mathematical and theoretical physics various generalizations, in particular supersymmetric or quantum, of Riemann surfaces and complex algebraic curves play a prominent role. We show that such supersymmetric and quantum generalizations can be combined together, and construct supersymmetric quantum curves, or super-quantum curves for short. Our analysis is conducted in the formalism of super-eigenvalue models: we introduce β-deformed version of those models, and derive differential equations for associated α/ β-deformed super-matrix integrals. We show that for a given model there exists an infinite number of such differential equations, which we identify as super-quantum curves, and which are in one-to-one correspondence with, and have the structure of, super-Virasoro singular vectors. We discuss potential applications of super-quantum curves and prospects of other generalizations.

  12. Neck curve polynomials in neck rupture model

    International Nuclear Information System (INIS)

    Kurniadi, Rizal; Perkasa, Yudha S.; Waris, Abdul

    2012-01-01

    The Neck Rupture Model is a model that explains the scission process which has smallest radius in liquid drop at certain position. Old fashion of rupture position is determined randomly so that has been called as Random Neck Rupture Model (RNRM). The neck curve polynomials have been employed in the Neck Rupture Model for calculation the fission yield of neutron induced fission reaction of 280 X 90 with changing of order of polynomials as well as temperature. The neck curve polynomials approximation shows the important effects in shaping of fission yield curve.

  13. Customized versus population-based growth curves: prediction of low body fat percent at term corrected gestational age following preterm birth.

    Science.gov (United States)

    Law, Tameeka L; Katikaneni, Lakshmi D; Taylor, Sarah N; Korte, Jeffrey E; Ebeling, Myla D; Wagner, Carol L; Newman, Roger B

    2012-07-01

    Compare customized versus population-based growth curves for identification of small-for-gestational-age (SGA) and body fat percent (BF%) among preterm infants. Prospective cohort study of 204 preterm infants classified as SGA or appropriate-for-gestational-age (AGA) by population-based and customized growth curves. BF% was determined by air-displacement plethysmography. Differences between groups were compared using bivariable and multivariable linear and logistic regression analyses. Customized curves reclassified 30% of the preterm infants as SGA. SGA infants identified by customized method only had significantly lower BF% (13.8 ± 6.0) than the AGA (16.2 ± 6.3, p = 0.02) infants and similar to the SGA infants classified by both methods (14.6 ± 6.7, p = 0.51). Customized growth curves were a significant predictor of BF% (p = 0.02), whereas population-based growth curves were not a significant independent predictor of BF% (p = 0.50) at term corrected gestational age. Customized growth potential improves the differentiation of SGA infants and low BF% compared with a standard population-based growth curve among a cohort of preterm infants.

  14. A New Method for Re-Analyzing Evaluation Bias: Piecewise Growth Curve Modeling Reveals an Asymmetry in the Evaluation of Pro and Con Arguments.

    Directory of Open Access Journals (Sweden)

    Jens Jirschitzka

    Full Text Available In four studies we tested a new methodological approach to the investigation of evaluation bias. The usage of piecewise growth curve modeling allowed for investigation into the impact of people's attitudes on their persuasiveness ratings of pro- and con-arguments, measured over the whole range of the arguments' polarity from an extreme con to an extreme pro position. Moreover, this method provided the opportunity to test specific hypotheses about the course of the evaluation bias within certain polarity ranges. We conducted two field studies with users of an existing online information portal (Studies 1a and 2a as participants, and two Internet laboratory studies with mostly student participants (Studies 1b and 2b. In each of these studies we presented pro- and con-arguments, either for the topic of MOOCs (massive open online courses, Studies 1a and 1b or for the topic of M-learning (mobile learning, Studies 2a and 2b. Our results indicate that using piecewise growth curve models is more appropriate than simpler approaches. An important finding of our studies was an asymmetry of the evaluation bias toward pro- or con-arguments: the evaluation bias appeared over the whole polarity range of pro-arguments and increased with more and more extreme polarity. This clear-cut result pattern appeared only on the pro-argument side. For the con-arguments, in contrast, the evaluation bias did not feature such a systematic picture.

  15. Trajectories and models of individual growth

    Directory of Open Access Journals (Sweden)

    Arseniy Karkach

    2006-11-01

    Full Text Available It has long been recognized that the patterns of growth play an important role in the evolution of age trajectories of fertility and mortality (Williams, 1957. Life history studies would benefit from a better understanding of strategies and mechanisms of growth, but still no comparative research on individual growth strategies has been conducted. Growth patterns and methods have been shaped by evolution and a great variety of them are observed. Two distinct patterns - determinate and indeterminate growth - are of a special interest for these studies since they present qualitatively different outcomes of evolution. We attempt to draw together studies covering growth in plant and animal species across a wide range of phyla focusing primarily on the noted qualitative features. We also review mathematical descriptions of growth, namely empirical growth curves and growth models, and discuss the directions of future research.

  16. An integral parametrization of the bacterial growth curve experimental demonstration with E. coli C600 bacteria

    International Nuclear Information System (INIS)

    Garces, F.; Vidania, R. de

    1984-01-01

    In this work an integral parametrization of the bacterial growth curve is presented. The values of the parameters are obtained by fitting to the experimental data. Those parameters, with allow to describe the growth in its different phases, are the followings: slopes of the curve in its three parts and the time which divides the last two phases of the bacterial growth. The experimental data are bacterial densities measured by optical methods. The bacteria used was the E. coli C 6 00. (Author)

  17. Parent involvement and science achievement: A latent growth curve analysis

    Science.gov (United States)

    Johnson, Ursula Yvette

    This study examined science achievement growth across elementary and middle school and parent school involvement using the Early Childhood Longitudinal Study - Kindergarten Class of 1998--1999 (ECLS-K). The ECLS-K is a nationally representative kindergarten cohort of students from public and private schools who attended full-day or half-day kindergarten class in 1998--1999. The present study's sample (N = 8,070) was based on students that had a sampling weight available from the public-use data file. Students were assessed in science achievement at third, fifth, and eighth grades and parents of the students were surveyed at the same time points. Analyses using latent growth curve modeling with time invariant and varying covariates in an SEM framework revealed a positive relationship between science achievement and parent involvement at eighth grade. Furthermore, there were gender and racial/ethnic differences in parents' school involvement as a predictor of science achievement. Findings indicated that students with lower initial science achievement scores had a faster rate of growth across time. The achievement gap between low and high achievers in earth, space and life sciences lessened from elementary to middle school. Parents' involvement with school usually tapers off after elementary school, but due to parent school involvement being a significant predictor of eighth grade science achievement, later school involvement may need to be supported and better implemented in secondary schooling.

  18. Using Growth Curves To Determine the Timing of the Booster Sessions.

    Science.gov (United States)

    Hennessy, Michael; Bolan, Gail A.; Hoxworth, Tamara; Iatesta, Michael; Rhodes, Fen; Zenilman, Jonathan M.

    1999-01-01

    Demonstrates an application of a method for using growth curves to determine the timing of booster sessions to reinforce the cognitive messages or behavior changes of interventions. Uses data from a multisite randomized experiment that compared three counseling and testing methods for preventing sexual disease transmission. Presents…

  19. Economic growth and CO2 emissions in Malaysia: A cointegration analysis of the Environmental Kuznets Curve

    International Nuclear Information System (INIS)

    Saboori, Behnaz; Sulaiman, Jamalludin; Mohd, Saidatulakmal

    2012-01-01

    This paper attempts to establish a long-run as well as causal relationship between economic growth and carbon dioxide (CO 2 ) emissions for Malaysia. Using data for the years from 1980 to 2009, the Environmental Kuznets Curve (EKC) hypothesis was tested utilizing the Auto Regressive Distributed Lag (ARDL) methodology. The empirical results suggest the existence of a long-run relationship between per capita CO 2 emissions and real per capita Gross Domestic Product (GDP) when the CO 2 emissions level is the dependent variable. We found an inverted-U shape relationship between CO 2 emissions and GDP in both short and long-run, thus supporting the EKC hypothesis. The Granger Causality test based on the Vector Error Correction Model (VECM) presents an absence of causality between CO 2 emissions and economic growth in the short-run while demonstrating uni-directional causality from economic growth to CO 2 emissions in the long-run. - Highlights: ► We tested the dynamic relationship between economic growth and CO 2 emissions. ► The Environmental Kuznets Curve hypothesis was tested using bounds testing approach. ► The empirical analysis confirms the existence of EKC for Malaysia. ► Causality results in an absence of causality between CO 2 and income in the short-run. ► There is uni-directional causality from income to CO 2 emissions in the long-run.

  20. String Sigma Models on Curved Supermanifolds

    Directory of Open Access Journals (Sweden)

    Roberto Catenacci

    2018-04-01

    Full Text Available We use the techniques of integral forms to analyze the easiest example of two-dimensional sigma models on a supermanifold. We write the action as an integral of a top integral form over a D = 2 supermanifold, and we show how to interpolate between different superspace actions. Then, we consider curved supermanifolds, and we show that the definitions used for flat supermanifolds can also be used for curved supermanifolds. We prove it by first considering the case of a curved rigid supermanifold and then the case of a generic curved supermanifold described by a single superfield E.

  1. Learning curves in energy planning models

    Energy Technology Data Exchange (ETDEWEB)

    Barreto, L; Kypreos, S [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    This study describes the endogenous representation of investment cost learning curves into the MARKAL energy planning model. A piece-wise representation of the learning curves is implemented using Mixed Integer Programming. The approach is briefly described and some results are presented. (author) 3 figs., 5 refs.

  2. Relations between the development of school investment, self-confidence, and language achievement in elementary education: A multivariate latent growth curve approach

    NARCIS (Netherlands)

    Stoel, R.D.; Peetsma, T.T.D.; Roeleveld, J.

    2001-01-01

    Latent growth curve (LGC) analysis of longitudinal data for pupils' school investment, self confidence and language ability is presented. A multivariate model is tested that relates the three developmental processes to each other and to intelligence. All processes show significant differences

  3. On the analysis of Canadian Holstein dairy cow lactation curves using standard growth functions.

    Science.gov (United States)

    López, S; France, J; Odongo, N E; McBride, R A; Kebreab, E; AlZahal, O; McBride, B W; Dijkstra, J

    2015-04-01

    Six classical growth functions (monomolecular, Schumacher, Gompertz, logistic, Richards, and Morgan) were fitted to individual and average (by parity) cumulative milk production curves of Canadian Holstein dairy cows. The data analyzed consisted of approximately 91,000 daily milk yield records corresponding to 122 first, 99 second, and 92 third parity individual lactation curves. The functions were fitted using nonlinear regression procedures, and their performance was assessed using goodness-of-fit statistics (coefficient of determination, residual mean squares, Akaike information criterion, and the correlation and concordance coefficients between observed and adjusted milk yields at several days in milk). Overall, all the growth functions evaluated showed an acceptable fit to the cumulative milk production curves, with the Richards equation ranking first (smallest Akaike information criterion) followed by the Morgan equation. Differences among the functions in their goodness-of-fit were enlarged when fitted to average curves by parity, where the sigmoidal functions with a variable point of inflection (Richards and Morgan) outperformed the other 4 equations. All the functions provided satisfactory predictions of milk yield (calculated from the first derivative of the functions) at different lactation stages, from early to late lactation. The Richards and Morgan equations provided the most accurate estimates of peak yield and total milk production per 305-d lactation, whereas the least accurate estimates were obtained with the logistic equation. In conclusion, classical growth functions (especially sigmoidal functions with a variable point of inflection) proved to be feasible alternatives to fit cumulative milk production curves of dairy cows, resulting in suitable statistical performance and accurate estimates of lactation traits. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  4. Natural Disasters in a Two-Sector Model of Endogenous Growth

    OpenAIRE

    Masako Ikefuji; Ryo Horii

    2006-01-01

    Using an endogenous growth model with physical and human capital accumulation, this paper considers the sustainability of economic growth when the use of a polluting input (e.g., fossil fuels) intensifies the risk of capital destruction through natural disasters. We find that growth is sustainable only if the tax rate on the polluting input increases over time. The long-term rate of economic growth follows an inverted V-shaped curve relative to the growth rate of the environmental tax, and it...

  5. Growth curves of preschool children in the northeast of iran: a population based study using quantile regression approach.

    Science.gov (United States)

    Payande, Abolfazl; Tabesh, Hamed; Shakeri, Mohammad Taghi; Saki, Azadeh; Safarian, Mohammad

    2013-01-14

    Growth charts are widely used to assess children's growth status and can provide a trajectory of growth during early important months of life. The objectives of this study are going to construct growth charts and normal values of weight-for-age for children aged 0 to 5 years using a powerful and applicable methodology. The results compare with the World Health Organization (WHO) references and semi-parametric LMS method of Cole and Green. A total of 70737 apparently healthy boys and girls aged 0 to 5 years were recruited in July 2004 for 20 days from those attending community clinics for routine health checks as a part of a national survey. Anthropometric measurements were done by trained health staff using WHO methodology. The nonparametric quantile regression method obtained by local constant kernel estimation of conditional quantiles curves using for estimation of curves and normal values. The weight-for-age growth curves for boys and girls aged from 0 to 5 years were derived utilizing a population of children living in the northeast of Iran. The results were similar to the ones obtained by the semi-parametric LMS method in the same data. Among all age groups from 0 to 5 years, the median values of children's weight living in the northeast of Iran were lower than the corresponding values in WHO reference data. The weight curves of boys were higher than those of girls in all age groups. The differences between growth patterns of children living in the northeast of Iran versus international ones necessitate using local and regional growth charts. International normal values may not properly recognize the populations at risk for growth problems in Iranian children. Quantile regression (QR) as a flexible method which doesn't require restricted assumptions, proposed for estimation reference curves and normal values.

  6. Curve Modulation and Apex Migration Using Shilla Growth Guidance Rods for Early-onset Scoliosis at 5-Year Follow-up.

    Science.gov (United States)

    Wilkinson, John T; Songy, Chad E; Bumpass, David B; McCullough, Francis L; McCarthy, Richard E

    2017-04-03

    The Shilla procedure was designed to correct and control early-onset spinal deformity while harnessing a child's remaining spinal growth. It allows for controlled axial skeletal growth within the construct, avoiding the need for frequent surgeries to lengthen implants. We hypothesized that curve characteristics evolve over time after initial apex fusion and placement of the Shilla implants. The purpose of this study was to identify trends in curve evolution after Shilla implantation and understand how these changes influence ultimate outcome. A single-center, retrospective review of all patients with Shilla implants in place for ≥5 years yielded 21 patients. Charts and radiographs were reviewed to compare coronal curve characteristics preoperatively, postoperatively, and at last follow-up to note changes in the apex of the primary curve. Also noted were the development of adjacent compensatory curves, the overall vertical spinal growth, and the need for definitive spinal fusion once skeletal maturity was reached. Of the 21 patients, the curve apex migrated caudally in 12 patients (57%) and cephalad in 1 patient (5%), with a mean migration of 2.7 vertebral levels. Two patients (10%) developed new, significant compensatory curves (1 caudal and 1 cephalad). All patients demonstrated spinal growth in T1-S1 length following index surgery (mean, 45 mm). At skeletal maturity, 10 patients underwent definitive posterior spinal fusion and instrumentation, and 3 underwent implant removal alone. This study constitutes the longest follow-up of Shilla patients evaluating curve and implant behavior. Results of this review suggest that the apex of the fused primary curve shifts in approximately 62% of patients, with nearly all of these (92%) involving a distal migration. Compensatory curves did develop after Shilla placement as well. Overall, these findings represent adding-on distal to the apex after Shilla instrumentation rather than a crankshaft phenomenon about the apex. A

  7. Evaluation of water beef buffalo from birth to two years using different growth curves

    Directory of Open Access Journals (Sweden)

    W.R. Lamberson

    2010-02-01

    Full Text Available The buffalo is a domestic animal species of growing world-wide importance. Research to improve genetic improvement programs is important to maintain the productivity of buffalo. The objective this research was to evaluate the growth of Brazilian buffalo to two years of age with different growth curves. Growth curves consolidate the information contained in the weight-age data into three or four biologically meaningful parameters. The data included 31,452 weights at birth and 120, 205, 365, 550 and 730 days of buffalo (n = 5,178 raised on pasture without supplementation. Logistic, Gompertz, quadratic logarithmic, and linear hyperbolic curves (designated L, G, QL, and LH, respectively were fitted to the data by using proc NLIN of SAS (SAS Institute, Inc., Cary, NC, USA. The parameters estimates for L [WT= A * (((1 + exp (-k * AGE**-m] were A = 865.1 ± 5.42; k= 0.0028 ± 0.00002; M= 3.808 ± 0.007; R2 = 0.95. For G [WT= A * exp (-b * exp (-k * age] the parameters estimates were A= 967.6 ± 7.23; k = 0.00217 ± 0.000015; b = -2.8152 ± 0.00532. For QL [WT= A + b*age + k*(age*age + m*log (age] parameters estimates were A= 37.41 ± 0.48; k= 0.00019 ± 6.4E-6; b= 0.539 ± 0.006; m= 2.32 ± 0.23; R2=0.96. For LH [WT= A + b*AGE + k*(1/AGE] the parameters estimates were A= 23.15 ± 0.44; k=15.16 ± 0.66; b= 0.707 ± 0.001; R2= 0.96. Each of these curves fit these data equally well and could be used for characterizing growth to two years in beef buffalo.

  8. Structural Acoustic Physics Based Modeling of Curved Composite Shells

    Science.gov (United States)

    2017-09-19

    NUWC-NPT Technical Report 12,236 19 September 2017 Structural Acoustic Physics -Based Modeling of Curved Composite Shells Rachel E. Hesse...SUBTITLE Structural Acoustic Physics -Based Modeling of Curved Composite Shells 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...study was to use physics -based modeling (PBM) to investigate wave propagations through curved shells that are subjected to acoustic excitation. An

  9. Structural equation modeling of latent growth curves of weight gain among treated tuberculosis patients.

    Directory of Open Access Journals (Sweden)

    Mahalingam Vasantha

    Full Text Available Tuberculosis still remains a major public health problem even though it is treatable and curable. Weight gain measurement during anti tuberculosis (TB treatment period is an important component to assess the progress of TB patients. In this study, Latent Growth Models (LGMs were implemented in a longitudinal design to predict the change in weight of TB patients who were given three different regimens under randomized controlled clinical trial for anti-TB treatment. Linear and Quadratic LGMs were fitted using Mplus software. The age, sex and treatment response of the TB patients were used as time invariant independent variables of the growth trajectories. The quadratic trend was found to be better in explaining the changes in weight without grouping than the quadratic model for three group comparisons. A significant increase in the change of weight over time was identified while a significant quadratic effect indicated that weights were sustained over time. The growth rate was similar in both the groups. The treatment response had significant association with the growth rate of weight scores of the patients.

  10. The nonlinear Maxwell-type model for viscoelastoplastic materials: simulation of temperature influence on creep, relaxation and strain-stress curves

    Directory of Open Access Journals (Sweden)

    Andrew V. Khokhlov

    2017-04-01

    Full Text Available The nonlinear Maxwell-type constitutive relation with two arbitrary material functions for viscoelastoplastic multi-modulus materials is studied analytically in uniaxial isothermic case to reveal the model abilities and applicability scope and to develop techniques of its identification, tuning and fitting. The constitutive equation is aimed at adequate modeling of the rheological phenomena set which is typical for reonomic materials exhibiting non-linear hereditary properties, strong strain rate sensitivity, secondary creep, yielding at constant stress, tension compression asymmetry and such temperature effects as increase of material compliance, strain rate sensitivity and rates of dissipation, relaxation, creep and plastic strain accumulation with temperature growth. The model is applicable for simulation of mechanical behaviour of various polymers, their solutions and melts, solid propellants, sand-asphalt concretes, composite materials, titanium and aluminum alloys, ceramics at high temperature and so on. To describe the influence of temperature on material mechanical behavior (under isothermic conditions, two scalar material parameters of the model (viscosity coefficient and “modulus of elasticity” are considered as a functions of temperature level. The general restrictions on their properties which are necessary and sufficient for adequate qualitative description of the basic thermomechanical phenomena related to typical temperature influence on creep and relaxation curves, creep recovery curves, creep curves under step-wise loading and quasi-static stress-strain curves of viscoelastoplastic materials are obtained. The restrictions are derived using systematic analytical study of general qualitative features of the theoretic creep and relaxation curves, creep curves under step-wise loading, long-term strength curves and stress-strain curves at constant strain or stress rates generated by the constitutive equation (under minimal

  11. Measuring Model Rocket Engine Thrust Curves

    Science.gov (United States)

    Penn, Kim; Slaton, William V.

    2010-01-01

    This paper describes a method and setup to quickly and easily measure a model rocket engine's thrust curve using a computer data logger and force probe. Horst describes using Vernier's LabPro and force probe to measure the rocket engine's thrust curve; however, the method of attaching the rocket to the force probe is not discussed. We show how a…

  12. Using Calculus to Model the Growth of L. Plantarum Bacteria

    Directory of Open Access Journals (Sweden)

    Erin Carey

    2009-01-01

    Full Text Available Experimental data for the growth of Lactobacillus plantarum bacteria have been obtained over time, creating the need for mathematical means to model this data. We use the Gompertz model because it is a sigmoid function for a time series, where growth is slowest at the start and end of a time period. The Gompertz model is especially useful because it defines specific parameters that characterize the S-shaped curve. In addition, the Gompertz model uses relative growth, which is the logarithm of the given population compared to the initial population. This reflects the fact that bacteria grow exponentially. The important parameters that were found were the lag time and the asymptote.

  13. Relationship Between Crack Growth Resistance KR Curve and Specimen Width for 2060 - T8E30 Lithium Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Tong Di Hua

    2016-01-01

    Full Text Available KR crack growth resistance curve can be used to predict crack propagation behavior, estimate the crack component bearing capacity after the crack, so KR curve research occupies very important position in the fracture mechanics. Based on crack growth resistance KR test curve of 2060 - T8E30 lithium aluminum alloy under the same thickness for different width, studies have shown that under the same thickness, the influence of the width on the resistance curve of crack propagation can be neglected. Empirical equation of resistance curve of crack extension of the smaller width specimen is given. Extending the fitting equation to that of larger width, it can be found that it is highly coincided with the experimental results.

  14. Use of mathematical models in the study of bodily growth in GIFT strain Nile tilapia

    Directory of Open Access Journals (Sweden)

    Alda Lúcia de Lima Amancio

    Full Text Available The objective of this study was to evaluate the accuracy of five mathematical models (Gompertz, Logistic, Linear Hyperbolic, Quadratic and Quadratic Logarithmic to describe the growth curve of GIFT strain Nile tilapia, Oreochromis niloticus, and to characterize the growth trajectory of body parts. To do this, 1,000 fingerlings, with an initial weight of 2.4 g were placed into 20 brick tanks of 2 m³ each, at a density of 25 fish m-3, for 180 days. The animals were fed daily, using the protein levels and number of meals appropriate to each stage. Every two weeks 20 fish were randomly sampled, submitted to a fasting period of 48 h and then slaughtered by thermal shock, in order to determine the weight of the whole fish, the skin without scales, skinless fillets, heart, liver, gills and gastrointestinal tract. The Gompertz and Logistic models presented the best fit to the growth curve for live weight, fillet and skin, however the Logistic model underestimated the asymptotic weights. Therefore, to describe the growth curve in GIFT strain Nile tilapia, the Gompertz model is suggested. According to the parameters estimated by the Gompertz model, Nile tilapia reach the age for maximum growth of the fillet and skin before that of body weight. Among the organs studied, growth of the gastrointestinal tract and gills takes place earlier than that of the heart and liver.

  15. Candidate genes and growth curves for adiposity in African- and European-American youth

    NARCIS (Netherlands)

    Podolsky, R. H.; Barbeau, P.; Kang, H-S; Zhu, H.; Treiber, F. A.; Snieder, H.

    2007-01-01

    Objective: Obesity is associated with multiple health problems and often originates in childhood. This study investigated the association of genes with the development of general and central obesity from childhood into adulthood. Design: Individual growth curves for measures of general adiposity

  16. Predicting growth of the healthy infant using a genome scale metabolic model

    DEFF Research Database (Denmark)

    Nilsson, Avlant; Mardinoglu, Adil; Nielsen, Jens

    2017-01-01

    to simulate the mechanisms of growth and integrate data about breast-milk intake and composition with the infant's biomass and energy expenditure of major organs. The model predicted daily metabolic fluxes from birth to age 6 months, and accurately reproduced standard growth curves and changes in body...

  17. NONLINEAR MODELS FOR DESCRIPTION OF CACAO FRUIT GROWTH WITH ASSUMPTION VIOLATIONS

    Directory of Open Access Journals (Sweden)

    JOEL AUGUSTO MUNIZ

    2017-01-01

    Full Text Available Cacao (Theobroma cacao L. is an important fruit in the Brazilian economy, which is mainly cultivated in the southern State of Bahia. The optimal stage for harvesting is a major factor for fruit quality and the knowledge on its growth curves can help, especially in identifying the ideal maturation stage for harvesting. Nonlinear regression models have been widely used for description of growth curves. However, several studies in this subject do not consider the residual analysis, the existence of a possible dependence between longitudinal observations, or the sample variance heterogeneity, compromising the modeling quality. The objective of this work was to compare the fit of nonlinear regression models, considering residual analysis and assumption violations, in the description of the cacao (clone Sial-105 fruit growth. The data evaluated were extracted from Brito and Silva (1983, who conducted the experiment in the Cacao Research Center, Ilheus, State of Bahia. The variables fruit length, diameter and volume as a function of fruit age were studied. The use of weighting and incorporation of residual dependencies was efficient, since the modeling became more consistent, improving the model fit. Considering the first-order autoregressive structure, when needed, leads to significant reduction in the residual standard deviation, making the estimates more reliable. The Logistic model was the most efficient for the description of the cacao fruit growth.

  18. Development of site index curves for Pinus kesiya in the Philippines ...

    African Journals Online (AJOL)

    Development of site index curves for Pinus kesiya in the Philippines. RIC Lumbres, YJ Lee, YO Seo, FG Calora JR. Abstract. This study was conducted to develop a height–age growth model and site index curves for site quality evaluation of old secondary-growth stands of Pinus kesiya in the northern Philippines.

  19. Nonlinear Structured Growth Mixture Models in M"plus" and OpenMx

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam; Estabrook, Ryne

    2010-01-01

    Growth mixture models (GMMs; B. O. Muthen & Muthen, 2000; B. O. Muthen & Shedden, 1999) are a combination of latent curve models (LCMs) and finite mixture models to examine the existence of latent classes that follow distinct developmental patterns. GMMs are often fit with linear, latent basis, multiphase, or polynomial change models…

  20. The Moderated Mediating Effect of Self-Efficacy on Exercise Among Older Adults in an Online Bone Health Intervention Study: A Parallel Process Latent Growth Curve Model.

    Science.gov (United States)

    Zhu, Shijun; Nahm, Eun-Shim; Resnick, Barbara; Friedmann, Erika; Brown, Clayton; Park, Jumin; Cheon, Jooyoung; Park, DoHwan

    2017-07-01

    This secondary data analyses of a longitudinal study assessed whether self-efficacy for exercise (SEE) mediated online intervention effects on exercise among older adults and whether age (50-64 vs. ≥65 years) moderated the mediation. Data were from an online bone health intervention study. Eight hundred sixty-six older adults (≥50 years) were randomized to three arms: Bone Power (n = 301), Bone Power Plus (n = 302), or Control (n = 263). Parallel process latent growth curve modeling (LGCM) was used to jointly model growths in SEE and in exercise and to assess the mediating effect of SEE on the effect of intervention on exercise. SEE was a significant mediator in 50- to 64-year-old adults (0.061, 95 BCI: 0.011, 0.163) but not in the ≥65 age group (-0.004, 95% BCI: -0.047, 0.025). Promotion of SEE is critical to improve exercise among 50- to 64-year-olds.

  1. Simultaneity modeling analysis of the environmental Kuznets curve hypothesis

    International Nuclear Information System (INIS)

    Ben Youssef, Adel; Hammoudeh, Shawkat; Omri, Anis

    2016-01-01

    The environmental Kuznets curve (EKC) hypothesis has been recognized in the environmental economics literature since the 1990's. Various statistical tests have been used on time series, cross section and panel data related to single and groups of countries to validate this hypothesis. In the literature, the validation has always been conducted by using a single equation. However, since both the environment and income variables are endogenous, the estimation of a single equation model when simultaneity exists produces inconsistent and biased estimates. Therefore, we formulate simultaneous two-equation models to investigate the EKC hypothesis for fifty-six countries, using annual panel data from 1990 to 2012, with the end year is determined by data availability for the panel. To make the panel data analysis more homogeneous, we investigate this issue for a three income-based panels (namely, high-, middle-, and low-income panels) given several explanatory variables. Our results indicate that there exists a bidirectional causality between economic growth and pollution emissions in the overall panels. We also find that the relationship is nonlinear and has an inverted U-shape for all the considered panels. Policy implications are provided. - Highlights: • We have given a new look for the validity of the EKC hypothesis. • We formulate two-simultaneous equation models to validate this hypothesis for fifty-six countries. • We find a bidirectional causality between economic growth and pollution emissions. • We also discover an inverted U-shaped between environmental degradation and economic growth. • This relationship varies at different stages of economic development.

  2. The role of the intervertebral disc in correction of scoliotic curves. A theoretical model of idiopathic scoliosis pathogenesis.

    Science.gov (United States)

    Grivas, T B; Vasiliadis, E S; Rodopoulos, G; Bardakos, N

    2008-01-01

    Wedging of the scoliotic inter-vertebral disc (IVD) was previously reported as a contributory factor for progression of idiopathic scoliotic (IS) curves. The present study introduces a theoretical model of IVD's role in IS pathogenesis and examines if, by reversing IVD wedging with conservative treatment (full- and night-time braces and exercises) or fusionless IS surgery with staples, we can correct the deformity of the immature spine. The proposed model implies the role of the diurnal variation and the asymmetric water distribution in the scoliotic IVD and the subsequent alteration of the mechanical environment of the adjacent vertebral growth plates. Modulation of the IVD by applying corrective forces on the scoliotic curve restores a close-to-normal force application on the vertebral growth plates through the Hueter-Volkmann principle and consequently prevents curve progression. The forces are now transmitted evenly to the growth plate and increase the rate of proliferation of chondrocytes at the corrected pressure side, the concave. Application of appropriately directed forces, ideally opposite to the apex of the deformity, likely leads to optimal correction. The wedging of the elastic IVD in the immature scoliotic spine could be reversed by application of corrective forces on it. Reversal of IVD wedging is thus amended into a "corrective", rather than "progressive", factor of the deformity. Through the proposed model, treatment of progressive IS with braces, exercises and fusionless surgery by anterior stapling could be effective.

  3. Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy

    International Nuclear Information System (INIS)

    Davidsson, Simon; Grandell, Leena; Wachtmeister, Henrik; Höök, Mikael

    2014-01-01

    Several recent studies have proposed fast transitions to energy systems based on renewable energy technology. Many of them dismiss potential physical constraints and issues with natural resource supply, and do not consider the growth rates of the individual technologies needed or how the energy systems are to be sustained over longer time frames. A case study is presented modelling potential growth rates of the wind energy required to reach installed capacities proposed in other studies, taking into account the expected service life of wind turbines. A sustained commissioning model is proposed as a theoretical foundation for analysing reasonable growth patterns for technologies that can be sustained in the future. The annual installation and related resource requirements to reach proposed wind capacity are quantified and it is concluded that these factors should be considered when assessing the feasibility, and even the sustainability, of fast energy transitions. Even a sustained commissioning scenario would require significant resource flows, for the transition as well as for sustaining the system, indefinitely. Recent studies that claim there are no potential natural resource barriers or other physical constraints to fast transitions to renewable energy appear inadequate in ruling out these concerns. - Highlights: • Growth rates and service life is important when evaluating energy transitions. • A sustained commissioning model is suggested for analysing renewable energy. • Natural resource requirements for renewable energy are connected to growth rates. • Arguments by recent studies ruling out physical constraints appear inadequate

  4. The Effect of Divergent Selection on 4-wk BW on the Shape of Growth Curve in Japanese Quail

    Directory of Open Access Journals (Sweden)

    H Beyki

    2011-12-01

    Full Text Available The current study was conducted to investigate the effect of short-term divergent selection on the shape growth curve in different lines of Japanese quail. The Quail lines utilized in this study were two divergently selected for high (HW and low (LW 4-wk body weight during 7 generation and also a control line (C. The Richard function parameters were used to describe growth curves of different lines. The weight at hatch was approximately similar among lines (8.08 g, 7.55 g and 8.76 g for HW, LW and C line respectively. The results of current study indicated that the selected lines (HW & LW were immediately diverged from the C line after hatch. Sexes within each line had no difference in average growth rate, age and body weight at inflection point and adult body weight. However significant differences were found in the growth curve parameters among lines. The results of current study indicated that short term divergent selection for 4-wk BW in Japanese quail can change the growth pattern and the carcass compartments of the selected birds. Therefore to avoid undesirable side effects due to selection in Japanese quails it is recommended to consider the growth pattern changes of the selected birds in the breeding programs

  5. Analysis of growth characteristics in short-term divergently selected ...

    African Journals Online (AJOL)

    weeks of age body weight in divergent lines of Japanese quail. Growth curves for both sexes within each selection group resembled the general sigmoid shape of a typical growth curve. Gompertz model curves and the observed growth curves were ...

  6. Existence of a common growth curve for silt-sized quartz OSL of loess from different continents

    International Nuclear Information System (INIS)

    Lai Zhongping; Brueckner, Helmut; Zoeller, Ludwig; Fuelling, Alexander

    2007-01-01

    Recent publications revealed different opinions regarding the existence of a common growth curve (CGC) for OSL of quartz. In the current study, 18 loess samples were collected from four continents (Asia, America, Africa, and Europe) in order to further examine this issue. Except the three samples from Chile in South America, 15 samples display similar dose-response curves up to a regeneration dose of 200 Gy using the SAR protocol, suggesting the existence of a global CGC for loess from different continents. For samples with equivalent doses (D e ) from ∼10 to ∼170Gy, the D e s determined by the CGC are in good agreement with the D e s by the SAR protocol. The Chilean samples posses a growth curve that differs from the CGC, showing much lower saturation doses. We suggest that it may be due to contamination with heavy minerals

  7. Teacher-student interpersonal relationships do change and affect academic motivation: a multilevel growth curve modelling.

    Science.gov (United States)

    Maulana, Ridwan; Opdenakker, Marie-Christine; Bosker, Roel

    2014-09-01

    Research has shown that the teacher-student interpersonal relationship (TSIR) is important for student motivation. Although TSIR has received a growing interest, there are only few studies that focus on changes and links between TSIR and student academic motivation in a longitudinal fashion in non-Western contexts. This study investigated changes in TSIR and links with academic motivation as perceived by first-grade secondary school students in Indonesia. TSIR was studied from the perspective of interpersonal behaviour in terms of Influence and Proximity. Students' academic motivation was studied from the perspective of self-determination theory. A total of 504 first-grade secondary school students of 16 mathematics and English classes participated in the study. Surveys were administered in five waves throughout the school year. Multilevel growth curve modelling was applied. Contrary to the (limited) general research findings from Western contexts, we found that the quality of TSIR (student perceptions) increased over time. The increase was slightly more pronounced for Proximity than for Influence. In accordance with the findings for the Western countries, the level of students' controlled motivation increased, while that of autonomous motivation decreased over time. However, the negative change in autonomous motivation was less pronounced. As in Western countries, TSIR was longitudinally linked with academic motivation, in particular, with autonomous motivation. Evidence is found that TSIR can change in a favourable way, and this positively affects student motivation. Future research could benefit from unravelling the influences of cultures on changes in TSIR in broader contexts. © 2013 The British Psychological Society.

  8. On the analysis of Canadian Holstein dairy cow lactation curves using standard growth functions

    NARCIS (Netherlands)

    López, S.; France, J.; Odongo, N.E.; McBride, R.A.; Kebreab, E.; Alzahal, O.; McBride, B.W.; Dijkstra, J.

    2015-01-01

    Six classical growth functions (monomolecular, Schumacher, Gompertz, logistic, Richards, and Morgan) were fitted to individual and average (by parity) cumulative milk production curves of Canadian Holstein dairy cows. The data analyzed consisted of approximately 91,000 daily milk yield records

  9. Hierarchical Bayesian analysis to incorporate age uncertainty in growth curve analysis and estimates of age from length: Florida manatee (Trichechus manatus) carcasses

    Science.gov (United States)

    Schwarz, L.K.; Runge, M.C.

    2009-01-01

    Age estimation of individuals is often an integral part of species management research, and a number of ageestimation techniques are commonly employed. Often, the error in these techniques is not quantified or accounted for in other analyses, particularly in growth curve models used to describe physiological responses to environment and human impacts. Also, noninvasive, quick, and inexpensive methods to estimate age are needed. This research aims to provide two Bayesian methods to (i) incorporate age uncertainty into an age-length Schnute growth model and (ii) produce a method from the growth model to estimate age from length. The methods are then employed for Florida manatee (Trichechus manatus) carcasses. After quantifying the uncertainty in the aging technique (counts of ear bone growth layers), we fit age-length data to the Schnute growth model separately by sex and season. Independent prior information about population age structure and the results of the Schnute model are then combined to estimate age from length. Results describing the age-length relationship agree with our understanding of manatee biology. The new methods allow us to estimate age, with quantified uncertainty, for 98% of collected carcasses: 36% from ear bones, 62% from length.

  10. Application of a Predictive Growth Model of Pseudomonas spp. for Estimating Shelf Life of Fresh Agaricus bisporus.

    Science.gov (United States)

    Wang, Jianming; Chen, Junran; Hu, Yunfeng; Hu, Hanyan; Liu, Guohua; Yan, Ruixiang

    2017-10-01

    For prediction of the shelf life of the mushroom Agaricus bisporus, the growth curve of the main spoilage microorganisms was studied under isothermal conditions at 2 to 22°C with a modified Gompertz model. The effect of temperature on the growth parameters for the main spoilage microorganisms was quantified and modeled using the square root model. Pseudomonas spp. were the main microorganisms causing A. bisporus decay, and the modified Gompertz model was useful for modelling the growth curve of Pseudomonas spp. All the bias factors values of the model were close to 1. By combining the modified Gompertz model with the square root model, a prediction model to estimate the shelf life of A. bisporus as a function of storage temperature was developed. The model was validated for A. bisporus stored at 6, 12, and 18°C, and adequate agreement was found between the experimental and predicted data.

  11. Traditional and alternative nonlinear models for estimating the growth of Morada Nova sheep

    Directory of Open Access Journals (Sweden)

    Laaina de Andrade Souza

    2013-09-01

    Full Text Available In the present study, alternative and traditional nonlinear models to describe growth curves of Morada Nova sheep reared in the state of Bahia, Brazil, were applied. The nonlinear models were: Schnute, Mitscherlich, Gompertz, Logistic, Meloun I Meloun II, III Meloun, Gamito and Meloun IV. The model adjustment was evaluated by using: Adjusted Coefficient of Determination (R²aj, Akaike Information Criterion (AIC, Bayesian Information Criterion (BIC, Mean Squared Error of Prediction (MEP and Coefficient of Determination of Prediction (R²p. The selection of the best model was based on cluster analysis, using the evaluators as variables. Six out of the nine tested models converged, while Meloun I and Meloun IV were equally effective in explaining animal growth, without significant influence of sex or type of parturition over the curve parameters. The models Meloun I and IV have the best adjustment and reveal a remarkable reduction of weight gain after 150 days of age, which indicates special attention should be given to feeding at this stage.

  12. Nonparametric estimation of age-specific reference percentile curves with radial smoothing.

    Science.gov (United States)

    Wan, Xiaohai; Qu, Yongming; Huang, Yao; Zhang, Xiao; Song, Hanping; Jiang, Honghua

    2012-01-01

    Reference percentile curves represent the covariate-dependent distribution of a quantitative measurement and are often used to summarize and monitor dynamic processes such as human growth. We propose a new nonparametric method based on a radial smoothing (RS) technique to estimate age-specific reference percentile curves assuming the underlying distribution is relatively close to normal. We compared the RS method with both the LMS and the generalized additive models for location, scale and shape (GAMLSS) methods using simulated data and found that our method has smaller estimation error than the two existing methods. We also applied the new method to analyze height growth data from children being followed in a clinical observational study of growth hormone treatment, and compared the growth curves between those with growth disorders and the general population. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. GHG emissions, GDP growth and the Kyoto Protocol: A revisit of Environmental Kuznets Curve hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wei Ming; Lee, Grace W.M. [Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Road, Taipei 106 (China); Wu, Chih Cheng [Energy and Air Pollution Control Section, New Materials R and D Department, China Steel Corporation, 1, Chung-Kang Road, Siaogang District, Kaohsiung 81233 (China)

    2008-01-15

    The Kyoto Protocol attempts through political negotiations to guide participating industrialized countries' greenhouse gas (GHG) emissions from a positive growing trend, to reach a peak point (or turning point), and then be reduced to a negative growth. That means the relationship between decreasing GHG emissions and economic growth may be described by an inverted-U curve (or called a bell-shaped curve), which is consistent with the concept of the Environmental Kuznets Curve (EKC) hypothesis. This research observed that the economic development and GHG emissions in Economies in Transition (EITs) exhibit a hockey-stick curve trend (or called quasi-L-shape curve), that also generates a lot of 'hot air' which is significant to the implementation of the Kyoto Protocol. In addition, through the analysis of single-country time series data and GDP data, this research demonstrated that statistical data for most of the Annex II countries do not possess evidence that supports the EKC hypothesis for GHG emissions. The results from this study also indicated that the 38 industrialized countries are unable to meet their targets under the Kyoto Protocol within the specified time period, which are probably caused by the econometric method's inability to predict accurately the extents and development of innovative technologies and Clean Development Mechanism (CDM) projects. If the international community truly wants to reduce the GHG emissions, the effectiveness of the existing international framework for emissions reduction needs to be reconsidered seriously, and the global cooperation mechanism also needs to be greatly enhanced. (author)

  14. GHG emissions, GDP growth and the Kyoto Protocol: A revisit of Environmental Kuznets Curve hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Huang Weiming [Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Road, Taipei 106, Taiwan (China); Lee, Grace W.M. [Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Road, Taipei 106, Taiwan (China)], E-mail: gracelee@ntu.edu.tw; Wu Chihcheng [Energy and Air Pollution Control Section, New Materials R and D Department, China Steel Corporation, 1, Chung-Kang Road, Siaogang District, Kaohsiung 81233, Taiwan (China)

    2008-01-15

    The Kyoto Protocol attempts through political negotiations to guide participating industrialized countries' greenhouse gas (GHG) emissions from a positive growing trend, to reach a peak point (or turning point), and then be reduced to a negative growth. That means the relationship between decreasing GHG emissions and economic growth may be described by an inverted-U curve (or called a bell-shaped curve), which is consistent with the concept of the Environmental Kuznets Curve (EKC) hypothesis. This research observed that the economic development and GHG emissions in Economies in Transition (EITs) exhibit a hockey-stick curve trend (or called quasi-L-shape curve), that also generates a lot of 'hot air' which is significant to the implementation of the Kyoto Protocol. In addition, through the analysis of single-country time series data and GDP data, this research demonstrated that statistical data for most of the Annex II countries do not possess evidence that supports the EKC hypothesis for GHG emissions. The results from this study also indicated that the 38 industrialized countries are unable to meet their targets under the Kyoto Protocol within the specified time period, which are probably caused by the econometric method's inability to predict accurately the extents and development of innovative technologies and Clean Development Mechanism (CDM) projects. If the international community truly wants to reduce the GHG emissions, the effectiveness of the existing international framework for emissions reduction needs to be reconsidered seriously, and the global cooperation mechanism also needs to be greatly enhanced.

  15. GHG emissions, GDP growth and the Kyoto Protocol: A revisit of Environmental Kuznets Curve hypothesis

    International Nuclear Information System (INIS)

    Huang Weiming; Lee, Grace W.M.; Wu Chihcheng

    2008-01-01

    The Kyoto Protocol attempts through political negotiations to guide participating industrialized countries' greenhouse gas (GHG) emissions from a positive growing trend, to reach a peak point (or turning point), and then be reduced to a negative growth. That means the relationship between decreasing GHG emissions and economic growth may be described by an inverted-U curve (or called a bell-shaped curve), which is consistent with the concept of the Environmental Kuznets Curve (EKC) hypothesis. This research observed that the economic development and GHG emissions in Economies in Transition (EITs) exhibit a hockey-stick curve trend (or called quasi-L-shape curve), that also generates a lot of 'hot air' which is significant to the implementation of the Kyoto Protocol. In addition, through the analysis of single-country time series data and GDP data, this research demonstrated that statistical data for most of the Annex II countries do not possess evidence that supports the EKC hypothesis for GHG emissions. The results from this study also indicated that the 38 industrialized countries are unable to meet their targets under the Kyoto Protocol within the specified time period, which are probably caused by the econometric method's inability to predict accurately the extents and development of innovative technologies and Clean Development Mechanism (CDM) projects. If the international community truly wants to reduce the GHG emissions, the effectiveness of the existing international framework for emissions reduction needs to be reconsidered seriously, and the global cooperation mechanism also needs to be greatly enhanced

  16. Modelling stochastic chances in curve shape, with an application to cancer diagnostics

    DEFF Research Database (Denmark)

    Hobolth, A; Jensen, Eva B. Vedel

    2000-01-01

    Often, the statistical analysis of the shape of a random planar curve is based on a model for a polygonal approximation to the curve. In the present paper, we instead describe the curve as a continuous stochastic deformation of a template curve. The advantage of this continuous approach is that t......Often, the statistical analysis of the shape of a random planar curve is based on a model for a polygonal approximation to the curve. In the present paper, we instead describe the curve as a continuous stochastic deformation of a template curve. The advantage of this continuous approach...... is that the parameters in the model do not relate to a particular polygonal approximation. A somewhat similar approach has been used by Kent et al. (1996), who describe the limiting behaviour of a model with a first-order Markov property as the landmarks on the curve become closely spaced; see also Grenander(1993...

  17. Modeling Nonlinear Change via Latent Change and Latent Acceleration Frameworks: Examining Velocity and Acceleration of Growth Trajectories

    Science.gov (United States)

    Grimm, Kevin; Zhang, Zhiyong; Hamagami, Fumiaki; Mazzocco, Michele

    2013-01-01

    We propose the use of the latent change and latent acceleration frameworks for modeling nonlinear growth in structural equation models. Moving to these frameworks allows for the direct identification of "rates of change" and "acceleration" in latent growth curves--information available indirectly through traditional growth…

  18. Using bivariate latent basis growth curve analysis to better understand treatment outcome in youth with anorexia nervosa.

    Science.gov (United States)

    Byrne, Catherine E; Wonderlich, Joseph A; Curby, Timothy; Fischer, Sarah; Lock, James; Le Grange, Daniel

    2018-04-25

    This study explored the relation between eating-related obsessionality and weight restoration utilizing bivariate latent basis growth curve modelling. Eating-related obsessionality is a moderator of treatment outcome for adolescents with anorexia nervosa (AN). This study examined the degree to which the rate of change in eating-related obsessionality was associated with the rate of change in weight over time in family-based treatment (FBT) and individual therapy for AN. Data were drawn from a 2-site randomized controlled trial that compared FBT and adolescent focused therapy for AN. Bivariate latent basis growth curves were used to examine the differences of the relations between trajectories of body weight and symptoms associated with eating and weight obsessionality. In the FBT group, the slope of eating-related obsessionality scores and the slope of weight were significantly (negatively) correlated. This finding indicates that a decrease in overall eating-relating obsessionality is significantly associated with an increase in weight for individuals who received FBT. However, there was no relation between change in obsessionality scores and change in weight in the adolescent focused therapy group. Results suggest that FBT has a specific impact on both weight gain and obsessive compulsive behaviour that is distinct from individual therapy. Copyright © 2018 John Wiley & Sons, Ltd and Eating Disorders Association.

  19. Modeling pitting growth data and predicting degradation trend

    International Nuclear Information System (INIS)

    Viglasky, T.; Awad, R.; Zeng, Z.; Riznic, J.

    2007-01-01

    A non-statistical modeling approach to predict material degradation is presented in this paper. In this approach, the original data series is processed using Accumulated Generating Operation (AGO). With the aid of the AGO which weakens the random fluctuation embedded in the data series, an approximately exponential curve is established. The generated data series described by the exponential curve is then modeled by a differential equation. The coefficients of the differential equation can be deduced by approximate difference formula based on least-squares algorithm. By solving the differential equation and processing an inverse AGO, a predictive model can be obtained. As this approach is not established on the basis of statistics, the prediction can be performed with a limited amount of data. Implementation of this approach is demonstrated by predicting the pitting growth rate in specimens and wear trend in steam generator tubes. The analysis results indicate that this approach provides a powerful tool with reasonable precision to predict material degradation. (author)

  20. Bacterial growth kinetics

    International Nuclear Information System (INIS)

    Boonkitticharoen, V.; Ehrhardt, J.C.; Kirchner, P.T.

    1989-01-01

    Quantitative measurement of bacterial growth may be made using a radioassay technique. This method measures, by scintillation counting, the 14 CO 2 derived from the bacterial metabolism of a 14 C-labeled substrate. Mathematical growth models may serve as reliable tools for estimation of the generation rate constant (or slope of the growth curve) and provide a basis for evaluating assay performance. Two models, i.e., exponential and logistic, are proposed. Both models yielded an accurate fit to the data from radioactive measurement of bacterial growth. The exponential model yielded high precision values of the generation rate constant, with an average relative standard deviation of 1.2%. Under most conditions the assay demonstrated no changes in the slopes of growth curves when the number of bacteria per inoculation was changed. However, the radiometric assay by scintillation method had a growth-inhibiting effect on a few strains of bacteria. The source of this problem was thought to be hypersensitivity to trace amounts of toluene remaining on the detector

  1. A Multilevel Latent Growth Curve Approach to Predicting Student Proficiency

    Science.gov (United States)

    Choi, Kilchan; Goldschmidt, Pete

    2012-01-01

    Value-added models and growth-based accountability aim to evaluate school's performance based on student growth in learning. The current focus is on linking the results from value-added models to the ones from growth-based accountability systems including Adequate Yearly Progress decisions mandated by No Child Left Behind. We present a new…

  2. Breast meat quality of chickens with divergent growth rates and its relation to growth curve parameters

    Directory of Open Access Journals (Sweden)

    P. C. Muth

    2017-11-01

    Full Text Available The effects of the increase of body weight of contemporary broilers during growth on functional meat quality and color characteristics of the chicken breast muscle are controversially debated. Therefore, male chickens (n = 264 of a fast-growing commercial broiler (Ross 308 and two slow-growing experimental meat-type chicken lines were compared at equal age and at similar body weight in order to investigate the effect of growth rate on selected functional breast meat traits and meat color. Additionally, the breast meat characteristics of birds with different growth profiles were compared within lines. When the body weight of commercial broilers reached about 40 to 60 % of their growth potential, they exhibited particularly high ultimate pH values compared with slow-growing lines. The ability of the meat of fast-growing broilers to retain water during cooking was impaired (5 to 16 percentage points increased cooking loss compared to slow-growing lines, which, in contrast to pH, was only marginally affected by body weight and/or age at slaughter. No unfavorable correlations of breast meat quality traits with the growth profile, represented by growth curve parameters derived from the Gompertz–Laird equation, were detected within any of the investigated chicken lines. It is noteworthy that the associations of ultimate pH and cooking loss with maximum growth speed indicate a non-linear relationship. Thus, some of the functional characteristics of breast meat of the fast-growing broiler resembled the white-striping defect described for poultry meat, but the hypothesis that selection on increased growth rates is detrimental for meat quality per se could not be confirmed. In fact, an elevated growth potential in particular, i.e., body weight at maturity, could have some beneficial effects for the water-holding capacity of breast meat, regardless of the genotypic growth rate.

  3. The Impact of Salient Role Stress on Trajectories of Health in Late Life among Survivors of a Seven-Year Panel Study: Analyses of Individual Growth Curves

    Science.gov (United States)

    Shaw, Benjamin A.; Krause, Neal

    2002-01-01

    The purpose of this study is twofold: 1) to model changes in health over time among older adults; and 2) to assess the degree to which stress arising in salient social roles accounts for individual variation in these changes. Individual growth curve analyses using Hierarchical Linear Modeling (HLM) software were employed with longitudinal data…

  4. Predicting growth of the healthy infant using a genome scale metabolic model.

    Science.gov (United States)

    Nilsson, Avlant; Mardinoglu, Adil; Nielsen, Jens

    2017-01-01

    An estimated 165 million children globally have stunted growth, and extensive growth data are available. Genome scale metabolic models allow the simulation of molecular flux over each metabolic enzyme, and are well adapted to analyze biological systems. We used a human genome scale metabolic model to simulate the mechanisms of growth and integrate data about breast-milk intake and composition with the infant's biomass and energy expenditure of major organs. The model predicted daily metabolic fluxes from birth to age 6 months, and accurately reproduced standard growth curves and changes in body composition. The model corroborates the finding that essential amino and fatty acids do not limit growth, but that energy is the main growth limiting factor. Disruptions to the supply and demand of energy markedly affected the predicted growth, indicating that elevated energy expenditure may be detrimental. The model was used to simulate the metabolic effect of mineral deficiencies, and showed the greatest growth reduction for deficiencies in copper, iron, and magnesium ions which affect energy production through oxidative phosphorylation. The model and simulation method were integrated to a platform and shared with the research community. The growth model constitutes another step towards the complete representation of human metabolism, and may further help improve the understanding of the mechanisms underlying stunting.

  5. Modeling of alpha mass-efficiency curve

    International Nuclear Information System (INIS)

    Semkow, T.M.; Jeter, H.W.; Parsa, B.; Parekh, P.P.; Haines, D.K.; Bari, A.

    2005-01-01

    We present a model for efficiency of a detector counting gross α radioactivity from both thin and thick samples, corresponding to low and high sample masses in the counting planchette. The model includes self-absorption of α particles in the sample, energy loss in the absorber, range straggling, as well as detector edge effects. The surface roughness of the sample is treated in terms of fractal geometry. The model reveals a linear dependence of the detector efficiency on the sample mass, for low masses, as well as a power-law dependence for high masses. It is, therefore, named the linear-power-law (LPL) model. In addition, we consider an empirical power-law (EPL) curve, and an exponential (EXP) curve. A comparison is made of the LPL, EPL, and EXP fits to the experimental α mass-efficiency data from gas-proportional detectors for selected radionuclides: 238 U, 230 Th, 239 Pu, 241 Am, and 244 Cm. Based on this comparison, we recommend working equations for fitting mass-efficiency data. Measurement of α radioactivity from a thick sample can determine the fractal dimension of its surface

  6. Functional dynamic factor models with application to yield curve forecasting

    KAUST Repository

    Hays, Spencer

    2012-09-01

    Accurate forecasting of zero coupon bond yields for a continuum of maturities is paramount to bond portfolio management and derivative security pricing. Yet a universal model for yield curve forecasting has been elusive, and prior attempts often resulted in a trade-off between goodness of fit and consistency with economic theory. To address this, herein we propose a novel formulation which connects the dynamic factor model (DFM) framework with concepts from functional data analysis: a DFM with functional factor loading curves. This results in a model capable of forecasting functional time series. Further, in the yield curve context we show that the model retains economic interpretation. Model estimation is achieved through an expectation- maximization algorithm, where the time series parameters and factor loading curves are simultaneously estimated in a single step. Efficient computing is implemented and a data-driven smoothing parameter is nicely incorporated. We show that our model performs very well on forecasting actual yield data compared with existing approaches, especially in regard to profit-based assessment for an innovative trading exercise. We further illustrate the viability of our model to applications outside of yield forecasting.

  7. Curve-of-growth analysis of a red giant in the globular cluster M13

    International Nuclear Information System (INIS)

    Griffin, R.

    1979-01-01

    A coude spectrogram of a red giant (L973) in the globular cluster M13 is analysed, with respect to α Boo, by the differential curve-of-growth technique. The overall metal abundance is found to be approximately one-tenth of that of α Boo, or one-fortieth that of the Sun. (author)

  8. Structure of S-shaped growth in innovation diffusion

    Science.gov (United States)

    Shimogawa, Shinsuke; Shinno, Miyuki; Saito, Hiroshi

    2012-05-01

    A basic question on innovation diffusion is why the growth curve of the adopter population in a large society is often S shaped. From macroscopic, microscopic, and mesoscopic viewpoints, the growth of the adopter population is observed as the growth curve, individual adoptions, and differences among individual adoptions, respectively. The S shape can be explained if an empirical model of the growth curve can be deduced from models of microscopic and mesoscopic structures. However, even the structure of growth curve has not been revealed yet because long-term extrapolations by proposed models of S-shaped curves are unstable and it has been very difficult to predict the long-term growth and final adopter population. This paper studies the S-shaped growth from the viewpoint of social regularities. Simple methods to analyze power laws enable us to extract the structure of the growth curve directly from the growth data of recent basic telecommunication services. This empirical model of growth curve is singular at the inflection point and a logarithmic function of time after this point, which explains the unstable extrapolations obtained using previously proposed models and the difficulty in predicting the final adopter population. Because the empirical S curve can be expressed in terms of two power laws of the regularity found in social performances of individuals, we propose the hypothesis that the S shape represents the heterogeneity of the adopter population, and the heterogeneity parameter is distributed under the regularity in social performances of individuals. This hypothesis is so powerful as to yield models of microscopic and mesoscopic structures. In the microscopic model, each potential adopter adopts the innovation when the information accumulated by the learning about the innovation exceeds a threshold. The accumulation rate of information is heterogeneous among the adopter population, whereas the threshold is a constant, which is the opposite of previously

  9. Growth curves and age-related changes in carcass characteristics, organs, serum parameters, and intestinal transporter gene expression in domestic pigeon (Columba livia).

    Science.gov (United States)

    Gao, C Q; Yang, J X; Chen, M X; Yan, H C; Wang, X Q

    2016-04-01

    Two experiments were conducted to fit growth curves, and determine age-related changes in carcass characteristics, organs, serum biochemical parameters, and gene expression of intestinal nutrient transporters in domestic pigeon (Columba livia). In experiment 1, body weight (BW) of 30 pigeons was respectively determined at 1, 3, 7, 14, 21, 28, and 35 days old to fit growth curves and to describe the growth of pigeons. In experiment 2, eighty-four 1-day-old squabs were grouped by weight into 7 groups. On d 1, 3, 7, 14, 21, 28, and 35, twelve birds from each group were randomly selected for slaughter and post-slaughter analysis. The results showed that BW of pigeons increased rapidly from d 1 to d 28 (a 25.7-fold increase), and then had little change until d 35. The Logistic, Gompertz, and Von Bertalanffy functions can all be well fitted with the growth curve of domestic pigeons (R2>0.90) and the Gompertz model showed the highest R2value among the models (R2=0.9997). The equation of Gompertz model was Y=507.72×e-(3.76exp(-0.17t))(Y=BW of pigeon (g); t=time (day)). In addition, breast meat yield (%) increased with age throughout the experiment, whereas the leg meat yield (%) reached to the peak on d 14. Serum total protein, albumin, globulin, and glucose concentration were increased with age, whereas serum uric acid concentration was decreased (P<0.05). Furthermore, the gene expressions of nutrient transporters (y+LAT2, LAT1, B0AT1, PepT1, and NHE2) in jejunum of pigeon were increased with age. The results of correlation analysis showed the gene expressions of B0AT1, PepT1, and NHE2 had positive correlations with BW (0.73

  10. Economic growth and environmental pollution in Myanmar: an analysis of environmental Kuznets curve.

    Science.gov (United States)

    Aung, Thiri Shwesin; Saboori, Behnaz; Rasoulinezhad, Ehsan

    2017-09-01

    This empirical study examines the short- and long-run relationship between GDP as an economic growth indicator and CO 2 emissions as an environmental pollution indicator in Myanmar by using annual time series data over the period of 1970-2014. It also carefully considered other proxies, such as trade openness, financial openness and urbanization, and structural breaks in the country. The fundamental objective of this study is to test the validity of environmental Kuznets curve (EKC) in the context of Myanmar. The dynamic estimates of the long- and short-term relationship among greenhouse gases (CO 2 , CH 4 , N 2 O), GDP, trade intensity, financial openness, and urbanization growth are built through an autoregressive distributed lag (ARDL) model. The empirical findings indicate that there is positive short- and long-run relationship between CO 2 and GDP and thus, no evidence of EKC hypothesis is found for CO 2 in Myanmar. Nevertheless, the existence of the EKC is observed for CH 4 and N 2 O. On the other hand, trade and financial openness have inverse relationship with CO 2 emissions. These results demonstrate that trade liberalization and financial openness will improve the environment quality in Myanmar in the long run.

  11. Transcriptome Analysis of Liangshan Pig Muscle Development at the Growth Curve Inflection Point and Asymptotic Stages Using Digital Gene Expression Profiling

    Science.gov (United States)

    Du, Jingjing; Liu, Chendong; Wu, Xiaoqian; Pu, Qiang; Fu, Yuhua; Tang, Qianzi; Liu, Yuanrui; Li, Qiang; Yang, Runlin; Li, Xuewei; Tang, Guoqing; Jiang, Yanzhi; Li, Mingzhou; Zhang, Shunhua; Zhu, Li

    2015-01-01

    Animal growth curves can provide essential information for animal breeders to optimize feeding and management strategies. However, the genetic mechanism underlying the phenotypic differentiation between the inflection point and asymptotic stages of the growth curve is not well characterized. Here, we employed Liangshan pigs in stages of growth at the inflection point (under inflection point: UIP) and the two asymptotic stages (before the inflection point: BIP, after the inflection point: AIP) as models to survey global gene expression in the longissimus dorsi muscle using digital gene expression (DGE) tag profiling. We found Liangshan pigs reached maximum growth rate (UIP) at 163.6 days of age and a weight of 134.6 kg. The DGE libraries generated 117 million reads of 5.89 gigabases in length. 21,331, 20,996 and 20,139 expressed transcripts were identified BIP, UIP and AIP, respectively. Among them, we identified 757 differentially expressed genes (DEGs) between BIP and UIP, and 271 DEGs between AIP and UIP. An enrichment analysis of DEGs proved the immune system was strengthened in the AIP stage. Energy metabolism rate, global transcriptional activity and bone development intensity were highest UIP. Meat from Liangshan pigs had the highest intramuscular fat content and most favorable fatty acid composition in the AIP. Three hundred eighty (27.70%) specific expression genes were highly enriched in QTL regions for growth and meat quality traits. This study completed a comprehensive analysis of diverse genetic mechanisms underlying the inflection point and asymptotic stages of growth. Our findings will serve as an important resource in the understanding of animal growth and development in indigenous pig breeds. PMID:26292092

  12. Modeling of Triangular Lattice Space Structures with Curved Battens

    Science.gov (United States)

    Chen, Tzikang; Wang, John T.

    2005-01-01

    Techniques for simulating an assembly process of lattice structures with curved battens were developed. The shape of the curved battens, the tension in the diagonals, and the compression in the battens were predicted for the assembled model. To be able to perform the assembly simulation, a cable-pulley element was implemented, and geometrically nonlinear finite element analyses were performed. Three types of finite element models were created from assembled lattice structures for studying the effects of design and modeling variations on the load carrying capability. Discrepancies in the predictions from these models were discussed. The effects of diagonal constraint failure were also studied.

  13. Weight-for-length/height growth curves for children and adolescents in China in comparison with body mass index in prevalence estimates of malnutrition.

    Science.gov (United States)

    Zong, Xinnan; Li, Hui; Zhang, Yaqin; Wu, Huahong

    2017-05-01

    It is important to update weight-for-length/height growth curves in China and re-examine their performance in screening malnutrition. To develop weight-for-length/height growth curves for Chinese children and adolescents. A total of 94 302 children aged 0-19 years with complete sex, age, weight and length/height data were obtained from two cross-sectional large-scaled national surveys in China. Weight-for-length/height growth curves were constructed using the LMS method before and after average spermarcheal/menarcheal ages, respectively. Screening performance in prevalence estimates of wasting, overweight and obesity was compared between weight-for-height and body mass index (BMI) criteria based on a test population of 21 416 children aged 3-18. The smoothed weight-for-length percentiles and Z-scores growth curves with length 46-110 cm for both sexes and weight-for-height with height 70-180 cm for boys and 70-170 cm for girls were established. The weight-for-height and BMI-for-age had strong correlation in screening wasting, overweight and obesity in each age-sex group. There was no striking difference in prevalence estimates of wasting, overweight and obesity between two indicators except for obesity prevalence at ages 6-11. This set of smoothed weight-for-length/height growth curves may be useful in assessing nutritional status from infants to post-pubertal adolescents.

  14. Non-linear modelling to describe lactation curve in Gir crossbred cows

    Directory of Open Access Journals (Sweden)

    Yogesh C. Bangar

    2017-02-01

    Full Text Available Abstract Background The modelling of lactation curve provides guidelines in formulating farm managerial practices in dairy cows. The aim of the present study was to determine the suitable non-linear model which most accurately fitted to lactation curves of five lactations in 134 Gir crossbred cows reared in Research-Cum-Development Project (RCDP on Cattle farm, MPKV (Maharashtra. Four models viz. gamma-type function, quadratic model, mixed log function and Wilmink model were fitted to each lactation separately and then compared on the basis of goodness of fit measures viz. adjusted R2, root mean square error (RMSE, Akaike’s Informaion Criteria (AIC and Bayesian Information Criteria (BIC. Results In general, highest milk yield was observed in fourth lactation whereas it was lowest in first lactation. Among the models investigated, mixed log function and gamma-type function provided best fit of the lactation curve of first and remaining lactations, respectively. Quadratic model gave least fit to lactation curve in almost all lactations. Peak yield was observed as highest and lowest in fourth and first lactation, respectively. Further, first lactation showed highest persistency but relatively higher time to achieve peak yield than other lactations. Conclusion Lactation curve modelling using gamma-type function may be helpful to setting the management strategies at farm level, however, modelling must be optimized regularly before implementing them to enhance productivity in Gir crossbred cows.

  15. SERIAL ULTRASOUND TO ESTIMATE FETAL GROWTH CURVES IN SOUTHERN TAMANDUA (TAMANDUA TETRADACTYLA).

    Science.gov (United States)

    Thompson, Rachel; Wolf, Tiffany M; Robertson, Heather; Colburn, Margarita Woc; Moreno, Alexis; Moresco, Anneke; Napier, Anne Elise; Nofs, Sally A

    2017-06-01

    From 2012 to 2015, 16 pregnancies were monitored by ultrasonography in nine tamanduas ( Tamandua tetradactyla ) housed in three zoological facilities. Sonographic measurements were recorded to establish fetal growth curves using thoracic and skull landmarks described for giant anteaters ( Myrmecophaga tridactyla ). All pregnancies resulted in the uncomplicated delivery of healthy offspring, thus gestational development was considered normal. These data may be used as a reference for normal fetal development with potential for estimating parturition date in the absence of breeding data.

  16. S-curve networks and an approximate method for estimating degree distributions of complex networks

    Science.gov (United States)

    Guo, Jin-Li

    2010-12-01

    In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions (i.e., Barabási-Albert method) is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabási-Albert method commonly used in current network research.

  17. S-curve networks and an approximate method for estimating degree distributions of complex networks

    International Nuclear Information System (INIS)

    Guo Jin-Li

    2010-01-01

    In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions (i.e., Barabási-Albert method) is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabási-Albert method commonly used in current network research. (general)

  18. Anthropometric evaluation of indigenous Brazilian children under 60 months of age using NCHS/1977 and WHO/2005 growth curves.

    Science.gov (United States)

    Orellana, Jesem D Y; Santos, Ricardo V; Coimbra, Carlos E A; Leite, Maurício S

    2009-01-01

    To perform a comparative analysis of anthropometric data from Suruí, Xavánte and Wari' indigenous children under 60 months of age using the NCHS/1977 and the WHO/2005 growth curves. Anthropometric measurements followed standard procedures and the data obtained were converted into z scores using the Epi-Info (Version 3.4) and WHO-Anthro (Version Beta) softwares. The indices height/age (H/A), weight/age (W/A) and weight/height (W/H) were descriptors of nutritional status for all children under 60 months of age, as well as the body mass index (BMI) for children 24-59 months old. The frequencies of Suruí children Wari' 61.7 and 68.3%. The frequencies of Suruí children Wari' 51.7 and 45.0%. None of the Suruí children were Wari' 1.7 and 0.0%. The frequencies of Suruí children > 2 z scores for W/H were 3.9 (NCHS/1977) and 3.9% (WHO/2005); Xavánte 0.0 and 0.8%; Wari' 0.0 and 0.0%. The frequency of Suruí children aged 24-59 months > 2 z scores for BMI was 5.4% (WHO/2005); Xavánte 9.5%; and Wari' 0.0%. Our findings revealed important differences in the results from nutritional assessment, according to the set of growth curves used; however, the use of both growth curves revealed a high prevalence of malnutrition. Therefore, future studies with indigenous populations should present their results using two sets of growth curves to allow consistent comparison.

  19. Modelling of isothermal remanence magnetisation curves for an assembly of macrospins

    International Nuclear Information System (INIS)

    Tournus, F.

    2015-01-01

    We present a robust and efficient framework to compute isothermal remanent magnetisation (IRM) curves for magnetic nanoparticle assemblies. The assembly is modelled by independent, randomly oriented, uniaxial macrospins and we use a Néel model to take into account the thermal relaxation. A simple analytic expression is established for a single size, in a sudden switching approximation, and is compared to more evolved models. We show that for realistic samples (necessarily presenting a size dispersion) the simple model is very satisfactory. With this framework, it is then possible to reliably simulate IRM curves, which can be compared to experimental measurements and used in a best fit procedure. We also examine the influence of several parameters on the IRM curves and we discuss the link between the irreversible susceptibility and the switching field distribution. - Highlights: • A framework to compute IRM curves for nanoparticle assemblies is presented. • A simple analytic expression (for a single size) is compared to more evolved models. • The simple expression can reliably simulate IRM curves for realistic samples. • Irreversible susceptibility and the influence of several parameters is discussed

  20. Behavior and sensitivity of an optimal tree diameter growth model under data uncertainty

    Science.gov (United States)

    Don C. Bragg

    2005-01-01

    Using loblolly pine, shortleaf pine, white oak, and northern red oak as examples, this paper considers the behavior of potential relative increment (PRI) models of optimal tree diameter growth under data uncertainity. Recommendations on intial sample size and the PRI iteractive curve fitting process are provided. Combining different state inventories prior to PRI model...

  1. Application of Learning Curves for Didactic Model Evaluation: Case Studies

    Directory of Open Access Journals (Sweden)

    Felix Mödritscher

    2013-01-01

    Full Text Available The success of (online courses depends, among other factors, on the underlying didactical models which have always been evaluated with qualitative and quantitative research methods. Several new evaluation techniques have been developed and established in the last years. One of them is ‘learning curves’, which aim at measuring error rates of users when they interact with adaptive educational systems, thereby enabling the underlying models to be evaluated and improved. In this paper, we report how we have applied this new method to two case studies to show that learning curves are useful to evaluate didactical models and their implementation in educational platforms. Results show that the error rates follow a power law distribution with each additional attempt if the didactical model of an instructional unit is valid. Furthermore, the initial error rate, the slope of the curve and the goodness of fit of the curve are valid indicators for the difficulty level of a course and the quality of its didactical model. As a conclusion, the idea of applying learning curves for evaluating didactical model on the basis of usage data is considered to be valuable for supporting teachers and learning content providers in improving their online courses.

  2. New Insight into Combined Model and Revised Model for RTD Curves in a Multi-strand Tundish

    Science.gov (United States)

    Lei, Hong

    2015-12-01

    The analysis for the residence time distribution (RTD) curve is one of the important experimental technologies to optimize the tundish design. But there are some issues about RTD analysis model. Firstly, the combined (or mixed) model and the revised model give different analysis results for the same RTD curve. Secondly, different upper limits of integral in the numerator for the mean residence time give different results for the same RTD curve. Thirdly, the negative dead volume fraction sometimes appears at the outer strand of the multi-strand tundish. In order to solve the above problems, it is necessary to have a deep insight into the RTD curve and to propose a reasonable method to analyze the RTD curve. The results show that (1) the revised model is not appropriate to treat with the RTD curve; (2) the conception of the visual single-strand tundish and the combined model with the dimensionless time at the cut-off point are applied to estimate the flow characteristics in the multi-strand tundish; and that (3) the mean residence time at each exit is the key parameter to estimate the similarity of fluid flow among strands.

  3. Reinforcement Toolbox, a Parametric Reinforcement Modelling Tool for Curved Surface Structures

    NARCIS (Netherlands)

    Lauppe, J.; Rolvink, A.; Coenders, J.L.

    2013-01-01

    This paper presents a computational strategy and parametric modelling toolbox which aim at enhancing the design- and production process of reinforcement in freeform curved surface structures. The computational strategy encompasses the necessary steps of raising an architectural curved surface model

  4. Thermal effect on water retention curve of bentonite: experiment and thermodynamic modeling

    International Nuclear Information System (INIS)

    Qin Bing; Chen Zhenghai; Sun Faxin; Liu Yuemiao; Wang Ju

    2012-01-01

    The thermal effects on water retention curve of GMZ bentonite were investigated experimentally and theoretically. Water retention tests were conducted on GMZ bentonite at five temperatures ranging from 20℃ to 100℃. Test results showed that the water retention capacity and the hysteresis of the water retention curve decreased with increasing temperature, and that the water retention curves at different temperatures were almost parallel to each other. Based on the thermodynamics of sorption, a model was established to describe the temperature influence on the water retention curve. The model was validated by comparing the model predictions and the test results. (authors)

  5. Arctic curves in path models from the tangent method

    Science.gov (United States)

    Di Francesco, Philippe; Lapa, Matthew F.

    2018-04-01

    Recently, Colomo and Sportiello introduced a powerful method, known as the tangent method, for computing the arctic curve in statistical models which have a (non- or weakly-) intersecting lattice path formulation. We apply the tangent method to compute arctic curves in various models: the domino tiling of the Aztec diamond for which we recover the celebrated arctic circle; a model of Dyck paths equivalent to the rhombus tiling of a half-hexagon for which we find an arctic half-ellipse; another rhombus tiling model with an arctic parabola; the vertically symmetric alternating sign matrices, where we find the same arctic curve as for unconstrained alternating sign matrices. The latter case involves lattice paths that are non-intersecting but that are allowed to have osculating contact points, for which the tangent method was argued to still apply. For each problem we estimate the large size asymptotics of a certain one-point function using LU decomposition of the corresponding Gessel–Viennot matrices, and a reformulation of the result amenable to asymptotic analysis.

  6. Complex curve of the two-matrix model and its tau-function

    International Nuclear Information System (INIS)

    Kazakov, Vladimir A; Marshakov, Andrei

    2003-01-01

    We study the Hermitian and normal two-matrix models in planar approximation for an arbitrary number of eigenvalue supports. Its planar graph interpretation is given. The study reveals a general structure of the underlying analytic complex curve, different from the hyperelliptic curve of the one-matrix model. The matrix model quantities are expressed through the periods of meromorphic generating differential on this curve and the partition function of the multiple support solution, as a function of filling numbers and coefficients of the matrix potential, is shown to be a quasiclassical tau-function. The relation to N = 1 supersymmetric Yang-Mills theories is discussed. A general class of solvable multi-matrix models with tree-like interactions is considered

  7. A generative Bezier curve model for surf-zone tracking in coastal image sequences

    CSIR Research Space (South Africa)

    Burke, Michael G

    2017-09-01

    Full Text Available This work introduces a generative Bezier curve model suitable for surf-zone curve tracking in coastal image sequences. The model combines an adaptive curve parametrised by control points governed by local random walks with a global sinusoidal motion...

  8. Evolutionary model of the growth and size of firms

    Science.gov (United States)

    Kaldasch, Joachim

    2012-07-01

    The key idea of this model is that firms are the result of an evolutionary process. Based on demand and supply considerations the evolutionary model presented here derives explicitly Gibrat's law of proportionate effects as the result of the competition between products. Applying a preferential attachment mechanism for firms, the theory allows to establish the size distribution of products and firms. Also established are the growth rate and price distribution of consumer goods. Taking into account the characteristic property of human activities to occur in bursts, the model allows also an explanation of the size-variance relationship of the growth rate distribution of products and firms. Further the product life cycle, the learning (experience) curve and the market size in terms of the mean number of firms that can survive in a market are derived. The model also suggests the existence of an invariant of a market as the ratio of total profit to total revenue. The relationship between a neo-classic and an evolutionary view of a market is discussed. The comparison with empirical investigations suggests that the theory is able to describe the main stylized facts concerning the size and growth of firms.

  9. Relationship between Industrial Water Use and Economic Growth in China: Insights from an Environmental Kuznets Curve

    Directory of Open Access Journals (Sweden)

    Alun Gu

    2017-07-01

    Full Text Available Global inequity and the unbalance of water resources has been a critical issue for many years; and the Chinese per capita water resources are only 1/4 of the global average. Meanwhile, as the Chinese economy is growing rapidly, the demand of Chinese industrial water use is also increasing. In this case, it is important to balance the relationship between economic growth and industrial water use. In this study, a reduction model is established for the northeastern, northern coastal, eastern coastal, southern coastal, middle Yellow River, middle Yangtze River, southwestern, and northwestern regions to verify the environmental Kuznets curve (EKC for their respective industrial water use and provide theoretical support for decision making from an economic perspective. It adopts the per capita industrial water use and GDP of the eight economic zones from 2002 to 2014. The unit root test and co-integration test were adopted to analyze the stationarity of the data, and the triple reduction model was used for the fitting of variables. The relationship between per capita industrial water use and GDP showed an inverted U-shaped curve from 2002 to 2014 for China, as well as for the eastern coastal and middle Yangtze River regions, with the coordinates of the turning points being (9.8749, 4.6735, (10.3098, 5.4783, and (9.8184, 5.0622, respectively. The per capita GDP at the turning point of the inverted U-shaped curve is 18,000–30,000 Yuan (at constant prices from 2000. This study provides important thoughts and lessons for collaborative research into the relationship between industrial water consumption and economic development. The central government should focus on the central and western regions when creating policies for water resource management and technological development to improve their industrial water use efficiency.

  10. Curve fitting methods for solar radiation data modeling

    Energy Technology Data Exchange (ETDEWEB)

    Karim, Samsul Ariffin Abdul, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my; Singh, Balbir Singh Mahinder, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my [Department of Fundamental and Applied Sciences, Faculty of Sciences and Information Technology, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia)

    2014-10-24

    This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R{sup 2}. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods.

  11. Curve fitting methods for solar radiation data modeling

    Science.gov (United States)

    Karim, Samsul Ariffin Abdul; Singh, Balbir Singh Mahinder

    2014-10-01

    This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R2. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods.

  12. Curve fitting methods for solar radiation data modeling

    International Nuclear Information System (INIS)

    Karim, Samsul Ariffin Abdul; Singh, Balbir Singh Mahinder

    2014-01-01

    This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R 2 . The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods

  13. Growth in Adolescent Self-Regulation and Impact on Sexual Risk-Taking: A Curve-of-Factors Analysis.

    Science.gov (United States)

    Crandall, AliceAnn; Magnusson, Brianna M; Novilla, M Lelinneth B

    2018-04-01

    Adolescent self-regulation is increasingly seen as an important predictor of sexual risk-taking behaviors, but little is understood about how changes in self-regulation affect later sexual risk-taking. Family financial stress may affect the development of self-regulation and later engagement in sexual risk-taking. We examined whether family financial stress influences self-regulation in early adolescence (age 13) and growth in self-regulation throughout adolescence (from age 13-17 years). We then assessed the effects of family financial stress, baseline self-regulation, and the development of self-regulation on adolescent sexual risk-taking behaviors at age 18 years. Using a curve-of-factors model, we examined these relationships in a 6-year longitudinal study of 470 adolescents (52% female) and their parents from a large northwestern city in the United States. Results indicated that family financial stress was negatively associated with baseline self-regulation but not with growth in self-regulation throughout adolescence. Both baseline self-regulation and growth in self-regulation were predictive of decreased likelihood of engaging in sexual risk-taking. Family financial stress was not predictive of later sexual risk-taking. Intervening to support the development of self-regulation in adolescence may be especially protective against later sexual risk-taking.

  14. Environmental degradation, economic growth and energy consumption: Evidence of the environmental Kuznets curve in Malaysia

    International Nuclear Information System (INIS)

    Saboori, Behnaz; Sulaiman, Jamalludin

    2013-01-01

    This paper tests for the short and long-run relationship between economic growth, carbon dioxide (CO 2 ) emissions and energy consumption, using the Environmental Kuznets Curve (EKC) by employing both the aggregated and disaggregated energy consumption data in Malaysia for the period 1980–2009. The Autoregressive Distributed Lag (ARDL) methodology and Johansen–Juselius maximum likelihood approach were used to test the cointegration relationship; and the Granger causality test, based on the vector error correction model (VECM), to test for causality. The study does not support an inverted U-shaped relationship (EKC) when aggregated energy consumption data was used. When data was disaggregated based on different energy sources such as oil, coal, gas and electricity, the study does show evidences of the EKC hypothesis. The long-run Granger causality test shows that there is bi-directional causality between economic growth and CO 2 emissions, with coal, gas, electricity and oil consumption. This suggests that decreasing energy consumption such as coal, gas, electricity and oil appears to be an effective way to control CO 2 emissions but simultaneously will hinder economic growth. Thus suitable policies related to the efficient consumption of energy resources and consumption of renewable sources are required. - Highlights: • We investigated the EKC hypothesis by using Malaysian energy aggregated and disaggregated data. • It was found that the EKC is not supported, using the aggregated data (energy consumption). • However using disaggregated energy data (oil, coal and electricity) there is evidence of EKC. • Causality shows no causal relationship between economic growth and energy consumption in the short-run. • Economic growth Granger causes energy consumption and energy consumption causes CO 2 emissions in long-run

  15. Models of genus one curves

    OpenAIRE

    Sadek, Mohammad

    2010-01-01

    In this thesis we give insight into the minimisation problem of genus one curves defined by equations other than Weierstrass equations. We are interested in genus one curves given as double covers of P1, plane cubics, or complete intersections of two quadrics in P3. By minimising such a curve we mean making the invariants associated to its defining equations as small as possible using a suitable change of coordinates. We study the non-uniqueness of minimisations of the genus one curves des...

  16. Bayesian modeling of Clostridium perfringens growth in beef-in-sauce products.

    Science.gov (United States)

    Jaloustre, S; Cornu, M; Morelli, E; Noël, V; Delignette-Muller, M L

    2011-04-01

    Models on Clostridium perfringens growth which have been published to date have all been deterministic. A probabilistic model describing growth under non-isothermal conditions was thus proposed for predicting C. perfringens growth in beef-in-sauce products cooked and distributed in a French hospital. Model parameters were estimated from different types of data from various studies. A Bayesian approach was proposed to model the overall uncertainty regarding parameters and potential variability on the 'work to be done' (h(0)) during the germination, outgrowth and lag phase. Three models which differed according to their description of this parameter h(0) were tested. The model with inter-curve variability on h(0) was found to be the best one, on the basis of goodness-of-fit assessment and validation with literature data on results obtained under non-isothermal conditions. This model was used in two-dimensional Monte Carlo simulations to predict C. perfringens growth throughout the preparation of beef-in-sauce products, using temperature profiles recorded in a hospital kitchen. The median predicted growth was 7.8×10(-2) log(10) cfu·g(-1) (95% credibility interval [2.4×10(-2), 0.8]) despite the fact that for more than 50% of the registered temperature profiles cooling steps were longer than those required by French regulations. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Nonlinear Gompertz Curve Models of Achievement Gaps in Mathematics and Reading

    Science.gov (United States)

    Cameron, Claire E.; Grimm, Kevin J.; Steele, Joel S.; Castro-Schilo, Laura; Grissmer, David W.

    2015-01-01

    This study examined achievement trajectories in mathematics and reading from school entry through the end of middle school with linear and nonlinear growth curves in 2 large longitudinal data sets (National Longitudinal Study of Youth--Children and Young Adults and Early Childhood Longitudinal Study--Kindergarten Cohort [ECLS-K]). The S-shaped…

  18. Model for analyzing growth kinetics of a slowly growing Mycobacterium sp

    International Nuclear Information System (INIS)

    Lambrecht, R.S.; Carriere, J.F.; Collins, M.T.

    1988-01-01

    This report describes a simple method for quantifying viable mycobacteria and for determining generation time. We used statistical models and computer analysis of growth curves generated for the slowly growing mycobacterium Mycobacterium paratuberculosis under controlled conditions to derive a mathematical formula relating the dependent variable, growth, to the independent variables, log10 number of organisms in the inoculum (inoculum size) and incubation time. Growth was measured by a radiometric method which detects 14 CO 2 release during metabolism of a 14 C-labeled substrate. The radiometric method allowed for early detection of growth and detected as few as three viable bacteria. The coefficient of variation between culture vials inoculated with the same number of M. paratuberculosis was 0.083. Radiometric measurements were highly correlated to spectrophotometric and plate count methods for measuring growth (r = 0.962 and 0.992, respectively). The proportion of the total variability explained by the model in a goodness of fit test was 0.9994. Application of the model to broth cultures provided accurate estimates of the number of M. paratuberculosis (standard error = 0.21, log10 scale) and the growth rate (coefficient of variation, 0.03). Generation time was observed to be dependent upon the number of organisms in the inoculum. The model accurately described all phases of growth of M. paratuberculosis and can likely be applied to other slowly growing microorganisms

  19. Modeling Patterns of Activities using Activity Curves.

    Science.gov (United States)

    Dawadi, Prafulla N; Cook, Diane J; Schmitter-Edgecombe, Maureen

    2016-06-01

    Pervasive computing offers an unprecedented opportunity to unobtrusively monitor behavior and use the large amount of collected data to perform analysis of activity-based behavioral patterns. In this paper, we introduce the notion of an activity curve , which represents an abstraction of an individual's normal daily routine based on automatically-recognized activities. We propose methods to detect changes in behavioral routines by comparing activity curves and use these changes to analyze the possibility of changes in cognitive or physical health. We demonstrate our model and evaluate our change detection approach using a longitudinal smart home sensor dataset collected from 18 smart homes with older adult residents. Finally, we demonstrate how big data-based pervasive analytics such as activity curve-based change detection can be used to perform functional health assessment. Our evaluation indicates that correlations do exist between behavior and health changes and that these changes can be automatically detected using smart homes, machine learning, and big data-based pervasive analytics.

  20. Revisiting a model of ontogenetic growth: estimating model parameters from theory and data.

    Science.gov (United States)

    Moses, Melanie E; Hou, Chen; Woodruff, William H; West, Geoffrey B; Nekola, Jeffery C; Zuo, Wenyun; Brown, James H

    2008-05-01

    The ontogenetic growth model (OGM) of West et al. provides a general description of how metabolic energy is allocated between production of new biomass and maintenance of existing biomass during ontogeny. Here, we reexamine the OGM, make some minor modifications and corrections, and further evaluate its ability to account for empirical variation on rates of metabolism and biomass in vertebrates both during ontogeny and across species of varying adult body size. We show that the updated version of the model is internally consistent and is consistent with other predictions of metabolic scaling theory and empirical data. The OGM predicts not only the near universal sigmoidal form of growth curves but also the M(1/4) scaling of the characteristic times of ontogenetic stages in addition to the curvilinear decline in growth efficiency described by Brody. Additionally, the OGM relates the M(3/4) scaling across adults of different species to the scaling of metabolic rate across ontogeny within species. In providing a simple, quantitative description of how energy is allocated to growth, the OGM calls attention to unexplained variation, unanswered questions, and opportunities for future research.

  1. Analysis of the relationship between economic growth and industrial pollution in Zaozhuang, China-based on the hypothesis of the environmental Kuznets curve.

    Science.gov (United States)

    Liu, Xiao-Hui; Wang, Wei-Liang; Lu, Shao-Yong; Wang, Yu-Fan; Ren, Zongming

    2016-08-01

    In Zaozhuang, economic development affects the discharge amount of industrial wastewater, chemical oxygen demand (COD), and ammonia nitrogen (NH3-N). To reveal the trend of water environmental quality related to the economy in Zaozhuang, this paper simulated the relationships between industrial wastewater discharge, COD, NH3-N load, and gross domestic product (GDP) per capita for Zaozhuang (2002-2012) using environmental Kuznets curve (EKC) models. The results showed that the added value of industrial GDP, the per capita GDP, and wastewater emission had average annual growth rates of 16.62, 16.19, and 17.89 %, respectively, from 2002 to 2012, while COD and NH3-N emission in 2012, compared with 2002, showed average annual decreases of 10.70 and 31.12 %, respectively. The export of EKC models revealed that industrial wastewater discharge had a typical inverted-U-shaped relationship with per capita GDP. However, both COD and NH3-N showed the binding curve of the left side of the "U" curve and left side U-shaped curve. The economy in Zaozhuang had been at the "fast-growing" stage, with low environmental pollution according to the industrial pollution level. In recent years, Zaozhuang has abated these heavy-pollution industries emphatically, so pollutants have been greatly reduced. Thus, Zaozhuang industrial wastewater treatment has been quite effective, with water quality improved significantly. The EKC models provided scientific evidence for estimating industrial wastewater discharge, COD, and NH3-N load as well as their changeable trends for Zaozhuang from an economic perspective.

  2. Early light curves for Type Ia supernova explosion models

    Science.gov (United States)

    Noebauer, U. M.; Kromer, M.; Taubenberger, S.; Baklanov, P.; Blinnikov, S.; Sorokina, E.; Hillebrandt, W.

    2017-12-01

    Upcoming high-cadence transient survey programmes will produce a wealth of observational data for Type Ia supernovae. These data sets will contain numerous events detected very early in their evolution, shortly after explosion. Here, we present synthetic light curves, calculated with the radiation hydrodynamical approach STELLA for a number of different explosion models, specifically focusing on these first few days after explosion. We show that overall the early light curve evolution is similar for most of the investigated models. Characteristic imprints are induced by radioactive material located close to the surface. However, these are very similar to the signatures expected from ejecta-CSM or ejecta-companion interaction. Apart from the pure deflagration explosion models, none of our synthetic light curves exhibit the commonly assumed power-law rise. We demonstrate that this can lead to substantial errors in the determination of the time of explosion. In summary, we illustrate with our calculations that even with very early data an identification of specific explosion scenarios is challenging, if only photometric observations are available.

  3. Modeling individual differences in randomized experiments using growth models: Recommendations for design, statistical analysis and reporting of results of internet interventions

    Directory of Open Access Journals (Sweden)

    Hugo Hesser

    2015-05-01

    Full Text Available Growth models (also known as linear mixed effects models, multilevel models, and random coefficients models have the capability of studying change at the group as well as the individual level. In addition, these methods have documented advantages over traditional data analytic approaches in the analysis of repeated-measures data. These advantages include, but are not limited to, the ability to incorporate time-varying predictors, handle dependence among repeated observations in a very flexible manner, and to provide accurate estimates with missing data under fairly unrestrictive missing data assumptions. The flexibility of the growth curve modeling approach to the analysis of change makes it the preferred choice in the evaluation of direct, indirect and moderated intervention effects. Although offering many benefits, growth models present challenges in terms of design, analysis and reporting of results. This paper provides a nontechnical overview of growth models in the analysis of change in randomized experiments and advocates for their use in the field of internet interventions. Practical recommendations for design, analysis and reporting of results from growth models are provided.

  4. News Impact Curve for Stochastic Volatility Models

    OpenAIRE

    Makoto Takahashi; Yasuhiro Omori; Toshiaki Watanabe

    2012-01-01

    This paper proposes a new method to compute the news impact curve for stochastic volatility (SV) models. The new method incorporates the joint movement of return and volatility, which has been ignored by the extant literature, by simply adding a couple of steps to the Bayesian MCMC estimation procedures for SV models. This simple procedure is versatile and applicable to various SV type models. Contrary to the monotonic news impact functions in the extant literature, the new method gives a U-s...

  5. Bezier Curve Modeling for Neutrosophic Data Problem

    Directory of Open Access Journals (Sweden)

    Ferhat Tas

    2017-02-01

    Full Text Available Neutrosophic set concept is defined with membership, non-membership and indeterminacy degrees. This concept is the solution and representation of the problems with various fields. In this paper, a geometric model is introduced for Neutrosophic data problem for the first time. This model is based on neutrosophic sets and neutrosophic relations. Neutrosophic control points are defined according to these points, resulting in neutrosophic Bezier curves.

  6. Construction of long-term isochronous stress-strain curves by a modeling of short-term creep curves for a Grade 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Kim, Woo-Gon; Yin, Song-Nan; Koo, Gyeong-Hoi

    2009-01-01

    This study dealt with the construction of long-term isochronous stress-strain curves (ISSC) by a modeling of short-term creep curves for a Grade 9Cr-1Mo steel (G91) which is a candidate material for structural applications in the next generation nuclear reactors as well as in fusion reactors. To do this, tensile material data used in the inelastic constitutive equations was obtained by tensile tests at 550degC. Creep curves were obtained by a series of creep tests with different stress levels of 300MPa to 220MPa at an identical controlled temperature of 550degC. On the basis of these experimental data, the creep curves were characterized by Garofalo's creep model. Three parameters of P 1 , P 2 and P 3 in Garofalo's model were properly optimized by a nonlinear least square fitting (NLSF) analysis. The stress dependency of the three parameters was found to be a linear relationship. But, the P 3 parameter representing the steady state creep rate exhibited a two slope behavior with different stress exponents at a transient stress of about 250 MPa. The long-term creep curves of the G91 steel was modeled by Garofalo's model with only a few short-term creep data. Using the modeled creep curves, the long-term isochronous curves up to 10 5 hours were successfully constructed. (author)

  7. Modeling plasma flow in straight and curved solenoids

    International Nuclear Information System (INIS)

    Boercker, D.B.; Sanders, D.M.; Storer, J.; Falabella, S.

    1991-01-01

    The ''flux-tube'' model originated by Morozov is a very simple and numerically efficient method for simulating ion motion in plasma filters. In order to test its utility as a design tool, we compare the predictions of the model to recent experimental measurements of plasma flow in both straight and curved solenoids

  8. Lorenz curves in a new science-funding model

    Science.gov (United States)

    Huang, Ding-wei

    2017-12-01

    We propose an agent-based model to theoretically and systematically explore the implications of a new approach to fund science, which has been suggested recently by J. Bollen et al.[?] We introduce various parameters and examine their effects. The concentration of funding is shown by the Lorenz curve and the Gini coefficient. In this model, all scientists are treated equally and follow the well-intended regulations. All scientists give a fixed ratio of their funding to others. The fixed ratio becomes an upper bound for the Gini coefficient. We observe two distinct regimes in the parameter space: valley and plateau. In the valley regime, the fluidity of funding is significant. The Lorenz curve is smooth. The Gini coefficient is well below the upper bound. The funding distribution is the desired result. In the plateau regime, the cumulative advantage is significant. The Lorenz curve has a sharp turn. The Gini coefficient saturates to the upper bound. The undue concentration of funding happens swiftly. The funding distribution is the undesired results, where a minority of scientists take the majority of funding. Phase transitions between these two regimes are discussed.

  9. Economic growth and energy regulation in the environmental Kuznets curve.

    Science.gov (United States)

    Lorente, Daniel Balsalobre; Álvarez-Herranz, Agustín

    2016-08-01

    This study establishes the existence of a pattern of behavior, between economic growth and environmental degradation, consistent with the environmental Kuznets curve (EKC) hypothesis for 17 Organization for Economic Cooperation and Development (OECD) countries between 1990 and 2012. Based on this EKC pattern, it shows that energy regulation measures help reduce per capita greenhouse gas (GHG) emissions. To validate this hypothesis, we also add the explanatory variables: renewable energy promotion, energy innovation processes, and the suppression effect of income level on the contribution of renewable energy sources to total energy consumption. It aims to be a tool for decision-making regarding energy policy. This paper provides a two-stage econometric analysis of instrumental variables with the aim of correcting the existence of endogeneity in the variable GDP per capita, verifying that the instrumental variables used in this research are appropriate for our aim. To this end, it first makes a methodological contribution before incorporating additional variables associated with environmental air pollution into the EKC hypothesis and showing how they positively affect the explanation of the correction in the GHG emission levels. This study concludes that air pollution will not disappear on its own as economic growth increases. Therefore, it is necessary to promote energy regulation measures to reduce environmental pollution.

  10. Rational Multi-curve Models with Counterparty-risk Valuation Adjustments

    DEFF Research Database (Denmark)

    Crépey, Stéphane; Macrina, Andrea; Nguyen, Tuyet Mai

    2016-01-01

    We develop a multi-curve term structure set-up in which the modelling ingredients are expressed by rational functionals of Markov processes. We calibrate to London Interbank Offer Rate swaptions data and show that a rational two-factor log-normal multi-curve model is sufficient to match market da...... with regulatory obligations. In order to compute counterparty-risk valuation adjustments, such as credit valuation adjustment, we show how default intensity processes with rational form can be derived. We flesh out our study by applying the results to a basis swap contract....... with accuracy. We elucidate the relationship between the models developed and calibrated under a risk-neutral measure Q and their consistent equivalence class under the real-world probability measure P. The consistent P-pricing models are applied to compute the risk exposures which may be required to comply...

  11. Beyond Rating Curves: Time Series Models for in-Stream Turbidity Prediction

    Science.gov (United States)

    Wang, L.; Mukundan, R.; Zion, M.; Pierson, D. C.

    2012-12-01

    The New York City Department of Environmental Protection (DEP) manages New York City's water supply, which is comprised of over 20 reservoirs and supplies over 1 billion gallons of water per day to more than 9 million customers. DEP's "West of Hudson" reservoirs located in the Catskill Mountains are unfiltered per a renewable filtration avoidance determination granted by the EPA. While water quality is usually pristine, high volume storm events occasionally cause the reservoirs to become highly turbid. A logical strategy for turbidity control is to temporarily remove the turbid reservoirs from service. While effective in limiting delivery of turbid water and reducing the need for in-reservoir alum flocculation, this strategy runs the risk of negatively impacting water supply reliability. Thus, it is advantageous for DEP to understand how long a particular turbidity event will affect their system. In order to understand the duration, intensity and total load of a turbidity event, predictions of future in-stream turbidity values are important. Traditionally, turbidity predictions have been carried out by applying streamflow observations/forecasts to a flow-turbidity rating curve. However, predictions from rating curves are often inaccurate due to inter- and intra-event variability in flow-turbidity relationships. Predictions can be improved by applying an autoregressive moving average (ARMA) time series model in combination with a traditional rating curve. Since 2003, DEP and the Upstate Freshwater Institute have compiled a relatively consistent set of 15-minute turbidity observations at various locations on Esopus Creek above Ashokan Reservoir. Using daily averages of this data and streamflow observations at nearby USGS gauges, flow-turbidity rating curves were developed via linear regression. Time series analysis revealed that the linear regression residuals may be represented using an ARMA(1,2) process. Based on this information, flow-turbidity regressions with

  12. Supplementary Material for: Growth curve registration for evaluating salinity tolerance in barley

    KAUST Repository

    Meng, Rui; Saade, Stephanie; Kurtek, Sebastian; Berger, Bettina; Brien, Chris; Pillen, Klaus; Tester, Mark A.; Sun, Ying

    2017-01-01

    of HEB-25 barley families and the commercial variety, Navigator. We account for the spatial variation in smarthouse microclimates and in temporal variation across phenotyping runs using a functional ANOVA model to derive corrected FSS curves. From FSS, we

  13. Visible bands of ammonia: band strengths, curves of growth, and the spatial distribution of ammonia on Jupiter

    International Nuclear Information System (INIS)

    Lutz, B.L.; Owen, T.

    1980-01-01

    We report room-temperature laboratory studies of the 5520 A (6ν 1 ) and 6475 A (5ν 1 ) bands of self-broadened ammonia at column densities ranging from 1.7--435.7 meter-amagats (m-am). Detailed equivalent-width measurements at 24 different pressure-pathlength combinations corresponding to four pressures between 44 and 689 torr and pathlengths between 32 and 512 m are used to determin curves of growth and integrated band strengths. The band strengths for the 6ν 1 and 5ν 1 overtones are 5520 A: S=0.096 +- 0.005 cm -1 (m-am) -1 and 6475 A: S=0.63 +- 0.03 cm -1 (m-am) -1 , respectively.Using these band strengths and curves of growth, we analyze new spatially resolved spectra of Jupiter showing a nonhomogeneous distribution of ammonia in the Jovian atmosphere. The observed variations in the CH 4 /NH 3 mixing ratio are interpreted as evidence of altitude-dependent depletion of ammonia in the atmosphere

  14. Validity limits in J-resistance curve determination: A computational approach to ductile crack growth under large-scale yielding conditions. Volume 2

    International Nuclear Information System (INIS)

    Shih, C.F.; Xia, L.; Hutchinson, J.W.

    1995-02-01

    In this report, Volume 2, Mode I crack initiation and growth under plane strain conditions in tough metals are computed using an elastic/plastic continuum model which accounts for void growth and coalescence ahead of the crack tip. The material parameters include the stress-strain properties, along with the parameters characterizing the spacing and volume fraction of voids in material elements lying in the plane of the crack. For a given set of these parameters and a specific specimen, or component, subject to a specific loading, relationships among load, load-line displacement and crack advance can be computed with no restrictions on the extent of plastic deformation. Similarly, there is no limit on crack advance, except that it must take place on the symmetry plane ahead of the initial crack. Suitably defined measures of crack tip loading intensity, such as those based on the J-integral, can also be computed, thereby directly generating crack growth resistance curves. In this report, the model is applied to five specimen geometries which are known to give rise to significantly different crack tip constraints and crack growth resistance behaviors. Computed results are compared with sets of experimental data for two tough steels for four of the specimen types. Details of the load, displacement and crack growth histories are accurately reproduced, even when extensive crack growth takes place under conditions of fully plastic yielding. A description of material resistance to crack initiation and subsequent growth is essential for assessing structural integrity such as nuclear pressure vessels and piping

  15. A Bayesian hierarchical model for demand curve analysis.

    Science.gov (United States)

    Ho, Yen-Yi; Nhu Vo, Tien; Chu, Haitao; Luo, Xianghua; Le, Chap T

    2018-07-01

    Drug self-administration experiments are a frequently used approach to assessing the abuse liability and reinforcing property of a compound. It has been used to assess the abuse liabilities of various substances such as psychomotor stimulants and hallucinogens, food, nicotine, and alcohol. The demand curve generated from a self-administration study describes how demand of a drug or non-drug reinforcer varies as a function of price. With the approval of the 2009 Family Smoking Prevention and Tobacco Control Act, demand curve analysis provides crucial evidence to inform the US Food and Drug Administration's policy on tobacco regulation, because it produces several important quantitative measurements to assess the reinforcing strength of nicotine. The conventional approach popularly used to analyze the demand curve data is individual-specific non-linear least square regression. The non-linear least square approach sets out to minimize the residual sum of squares for each subject in the dataset; however, this one-subject-at-a-time approach does not allow for the estimation of between- and within-subject variability in a unified model framework. In this paper, we review the existing approaches to analyze the demand curve data, non-linear least square regression, and the mixed effects regression and propose a new Bayesian hierarchical model. We conduct simulation analyses to compare the performance of these three approaches and illustrate the proposed approaches in a case study of nicotine self-administration in rats. We present simulation results and discuss the benefits of using the proposed approaches.

  16. Predicting Condom Use Using the Information-Motivation-Behavioral Skills (IMB) Model: A Multivariate Latent Growth Curve Analysis

    Science.gov (United States)

    Senn, Theresa E.; Scott-Sheldon, Lori A. J.; Vanable, Peter A.; Carey, Michael P.

    2011-01-01

    Background The Information-Motivation-Behavioral Skills (IMB) model often guides sexual risk reduction programs even though no studies have examined covariation in the theory’s constructs in a dynamic fashion with longitudinal data. Purpose Using new developments in latent growth modeling, we explore how changes in information, motivation, and behavioral skills over 9 months relate to changes in condom use among STD clinic patients. Methods Participants (N = 1281, 50% female, 66% African American) completed measures of IMB constructs at three time points. We used parallel process latent growth modeling to examine associations among intercepts and slopes of IMB constructs. Results Initial levels of motivation, behavioral skills, and condom use were all positively associated, with behavioral skills partially mediating associations between motivation and condom use. Changes over time in behavioral skills positively related to changes in condom use. Conclusions Results support the key role of behavioral skills in sexual risk reduction, suggesting these skills should be targeted in HIV prevention interventions. PMID:21638196

  17. Growth curves in Down syndrome with congenital heart disease

    Directory of Open Access Journals (Sweden)

    Caroline D’Azevedo Sica

    Full Text Available SUMMARY Introduction: To assess dietary habits, nutritional status and food frequency in children and adolescents with Down syndrome (DS and congenital heart disease (CHD. Additionally, we attempted to compare body mass index (BMI classifications according to the World Health Organization (WHO curves and curves developed for individuals with DS. Method: Cross-sectional study including individuals with DS and CHD treated at a referral center for cardiology, aged 2 to 18 years. Weight, height, BMI, total energy and food frequency were measured. Nutritional status was assessed using BMI for age and gender, using curves for evaluation of patients with DS and those set by the WHO. Results: 68 subjects with DS and CHD were evaluated. Atrioventricular septal defect (AVSD was the most common heart disease (52.9%. There were differences in BMI classification between the curves proposed for patients with DS and those proposed by the WHO. There was an association between consumption of vitamin E and polyunsaturated fatty acids. Conclusion: Results showed that individuals with DS are mostly considered normal weight for age, when evaluated using specific curves for DS. Reviews on specific curves for DS would be the recommended practice for health professionals so as to avoid precipitated diagnosis of overweight and/or obesity in this population.

  18. Growth curve and diet density affect eating motivation, behaviour, and body composition of broiler breeders during rearing

    NARCIS (Netherlands)

    Mozos, de los J.; Garcia Ruiz, A.I.; Hartog, den L.A.; Villamide, M.J.

    2017-01-01

    The aim of this work has been to assess the effect of diet density [control (CON) or 15% diluted (DIL)] and growth curve [recommended by the genetic line (RBW) or 15% heavier (HBW)] and their interaction on BW uniformity, feeding motivation, behavior, and body composition of broiler breeder pullets.

  19. Paleomagnetic analysis of curved thrust belts reproduced by physical models

    Science.gov (United States)

    Costa, Elisabetta; Speranza, Fabio

    2003-12-01

    This paper presents a new methodology for studying the evolution of curved mountain belts by means of paleomagnetic analyses performed on analogue models. Eleven models were designed aimed at reproducing various tectonic settings in thin-skinned tectonics. Our models analyze in particular those features reported in the literature as possible causes for peculiar rotational patterns in the outermost as well as in the more internal fronts. In all the models the sedimentary cover was reproduced by frictional low-cohesion materials (sand and glass micro-beads), which detached either on frictional or on viscous layers. These latter were reproduced in the models by silicone. The sand forming the models has been previously mixed with magnetite-dominated powder. Before deformation, the models were magnetized by means of two permanent magnets generating within each model a quasi-linear magnetic field of intensity variable between 20 and 100 mT. After deformation, the models were cut into closely spaced vertical sections and sampled by means of 1×1-cm Plexiglas cylinders at several locations along curved fronts. Care was taken to collect paleomagnetic samples only within virtually undeformed thrust sheets, avoiding zones affected by pervasive shear. Afterwards, the natural remanent magnetization of these samples was measured, and alternating field demagnetization was used to isolate the principal components. The characteristic components of magnetization isolated were used to estimate the vertical-axis rotations occurring during model deformation. We find that indenters pushing into deforming belts from behind form non-rotational curved outer fronts. The more internal fronts show oroclinal-type rotations of a smaller magnitude than that expected for a perfect orocline. Lateral symmetrical obstacles in the foreland colliding with forward propagating belts produce non-rotational outer curved fronts as well, whereas in between and inside the obstacles a perfect orocline forms

  20. SPOTTED STAR LIGHT CURVES WITH ENHANCED PRECISION

    International Nuclear Information System (INIS)

    Wilson, R. E.

    2012-01-01

    The nearly continuous timewise coverage of recent photometric surveys is free of the large gaps that compromise attempts to follow starspot growth and decay as well as motions, thereby giving incentive to improve computational precision for modeled spots. Due to the wide variety of star systems in the surveys, such improvement should apply to light/velocity curve models that accurately include all the main phenomena of close binaries and rotating single stars. The vector fractional area (VFA) algorithm that is introduced here represents surface elements by small sets of position vectors so as to allow accurate computation of circle-triangle overlap by spherical geometry. When computed by VFA, spots introduce essentially no noticeable scatter in light curves at the level of one part in 10,000. VFA has been put into the Wilson-Devinney light/velocity curve program and all logic and mathematics are given so as to facilitate entry into other such programs. Advantages of precise spot computation include improved statistics of spot motions and aging, reduced computation time (intrinsic precision relaxes needs for grid fineness), noise-free illustration of spot effects in figures, and help in guarding against false positives in exoplanet searches, where spots could approximately mimic transiting planets in unusual circumstances. A simple spot growth and decay template quantifies time profiles, and specifics of its utilization in differential corrections solutions are given. Computational strategies are discussed, the overall process is tested in simulations via solutions of synthetic light curve data, and essential simulation results are described. An efficient time smearing facility by Gaussian quadrature can deal with Kepler mission data that are in 30 minute time bins.

  1. Gain curves and hydrodynamic modeling for shock ignition

    International Nuclear Information System (INIS)

    Lafon, M.; Ribeyre, X.; Schurtz, G.

    2010-01-01

    Ignition of a precompressed thermonuclear fuel by means of a converging shock is now considered as a credible scheme to obtain high gains for inertial fusion energy. This work aims at modeling the successive stages of the fuel time history, from compression to final thermonuclear combustion, in order to provide the gain curves of shock ignition (SI). The leading physical mechanism at work in SI is pressure amplification, at first by spherical convergence, and by collision with the shock reflected at center during the stagnation process. These two effects are analyzed, and ignition conditions are provided as functions of the shock pressure and implosion velocity. Ignition conditions are obtained from a non-isobaric fuel assembly, for which we present a gain model. The corresponding gain curves exhibit a significantly lower ignition threshold and higher target gains than conventional central ignition.

  2. Economic growth, trade and energy. Implications for the environmental Kuznets curve

    International Nuclear Information System (INIS)

    Suri, Vivek; Chapman, Duane

    1998-01-01

    The environmental Kuznets curve (EKC) hypothesis asserts that pollution follows an inverted-U path with respect to economic growth. The EKC has been explained in terms of structural changes in the composition of economic output and increased environmental regulation at higher income levels. While some authors have incorporated the impact of trade policy orientation on the EKC, the impact of the actual movement between countries of goods that embody pollution has not been considered. This paper attempts to econometrically quantify the effect using pooled cross-country and time-series data. The EKC hypothesis is examined with respect to commercial energy consumption, the source of many serious environmental problems. It was found that while both industrializing and industrialized countries have added to their energy requirements by exporting manufactured goods, the growth has been substantially higher in the former. At the same time, industrialized countries have been able to reduce their energy requirements by importing manufactured goods. Exports of manufactured goods by industrialized countries has thus been an important factor in generating the upward sloping portion of the EKC and imports by industrialized countries have contributed to the downward slope

  3. Modeling growth performances, survival, and feed efficiency of four ...

    African Journals Online (AJOL)

    Evolution of growth rate with age was similar in the four groups, but significant differences of growth curve parameters were found among breeds and/or sexes. Estimated hatch weight was lower in C hens and higher in FT hens. Initial specific growth rates and asymptotic body weight were higher in males for all breeds.

  4. New limb-darkening coefficients for modeling binary star light curves

    Science.gov (United States)

    Van Hamme, W.

    1993-01-01

    We present monochromatic, passband-specific, and bolometric limb-darkening coefficients for a linear as well as nonlinear logarithmic and square root limb-darkening laws. These coefficients, including the bolometric ones, are needed when modeling binary star light curves with the latest version of the Wilson-Devinney light curve progam. We base our calculations on the most recent ATLAS stellar atmosphere models for solar chemical composition stars with a wide range of effective temperatures and surface gravitites. We examine how well various limb-darkening approximations represent the variation of the emerging specific intensity across a stellar surface as computed according to the model. For binary star light curve modeling purposes, we propose the use of a logarithmic or a square root law. We design our tables in such a manner that the relative quality of either law with respect to another can be easily compared. Since the computation of bolometric limb-darkening coefficients first requires monochromatic coefficients, we also offer tables of these coefficients (at 1221 wavelength values between 9.09 nm and 160 micrometer) and tables of passband-specific coefficients for commonly used photometric filters.

  5. Repair models of cell survival and corresponding computer program for survival curve fitting

    International Nuclear Information System (INIS)

    Shen Xun; Hu Yiwei

    1992-01-01

    Some basic concepts and formulations of two repair models of survival, the incomplete repair (IR) model and the lethal-potentially lethal (LPL) model, are introduced. An IBM-PC computer program for survival curve fitting with these models was developed and applied to fit the survivals of human melanoma cells HX118 irradiated at different dose rates. Comparison was made between the repair models and two non-repair models, the multitar get-single hit model and the linear-quadratic model, in the fitting and analysis of the survival-dose curves. It was shown that either IR model or LPL model can fit a set of survival curves of different dose rates with same parameters and provide information on the repair capacity of cells. These two mathematical models could be very useful in quantitative study on the radiosensitivity and repair capacity of cells

  6. Modeling two strains of disease via aggregate-level infectivity curves.

    Science.gov (United States)

    Romanescu, Razvan; Deardon, Rob

    2016-04-01

    Well formulated models of disease spread, and efficient methods to fit them to observed data, are powerful tools for aiding the surveillance and control of infectious diseases. Our project considers the problem of the simultaneous spread of two related strains of disease in a context where spatial location is the key driver of disease spread. We start our modeling work with the individual level models (ILMs) of disease transmission, and extend these models to accommodate the competing spread of the pathogens in a two-tier hierarchical population (whose levels we refer to as 'farm' and 'animal'). The postulated interference mechanism between the two strains is a period of cross-immunity following infection. We also present a framework for speeding up the computationally intensive process of fitting the ILM to data, typically done using Markov chain Monte Carlo (MCMC) in a Bayesian framework, by turning the inference into a two-stage process. First, we approximate the number of animals infected on a farm over time by infectivity curves. These curves are fit to data sampled from farms, using maximum likelihood estimation, then, conditional on the fitted curves, Bayesian MCMC inference proceeds for the remaining parameters. Finally, we use posterior predictive distributions of salient epidemic summary statistics, in order to assess the model fitted.

  7. A new methodology for the evaluation of the J-R curve

    International Nuclear Information System (INIS)

    Donoso, J. R.; Zahr, J.; Landes, J. D.

    2005-01-01

    A new methodology for the construction of J-R curves for ductile materials, based upon the analytical integration of the P-ν relation, is presented. This method is based on the Common and Concise Formats, and on a postulated crack growth law, that relates the amount of stable crack growth with plastic displacement. The model developed, denoted asnC and C, reproduces quite well the experimentally obtained P-ν, Δa-ν and J-Δa curves. The results suggest that the amount of stable crack growth in a ductile material follows a power-law behaviour in its dependence with plastic displacement. This methodology may be used to evaluate instability conditions, through the adequate analytical treatment of the P-ν and J-Δa relations. (Author) 35 refs

  8. Size and temperature consideration in the liquid layer growth from nanovoids and the melting model construction

    International Nuclear Information System (INIS)

    Li, H.; Liang, X.H.; Li, M.

    2014-01-01

    A new model for the solid melting point T m (D) from nanovoids is proposed through considering the liquid layer growth behavior. This model, which does not have any adjustable parameter, introduces the classical thermodynamic treatment, i.e., the liquid nucleation and growth theory, for nanoparticle melting. With increased void diameter D, T m (D) approaches to T m0 . Moreover, T m (D) > T m0 for a small void (T m0 is the bulk melting point). In other words, the solid can be significantly superheated especially when D decreases, even if the difference of interface energy is larger than zero. This finding can be expected from the negatively curved surface of the void. The model predictions are consistent with the molecular dynamic (MD) simulation results for argon solids. Moreover, the growth of liquid layer from void surface relies on both size and temperature, which directly determine liquid layer thickness, and only when liquid layer thickness reaches to a critical value, can void become instable. - Highlights: • A united model for the crystal melting point from nanovoids is established. • Melting point increases with decreased void size. • The result is expected from the negatively curved surface of the void. • The prediction is agreed well with the MD simulation results

  9. Atmospheric emissions and economic growth. Environmental Kuznets Curve and Kyoto protocol; Emisiones atmosfericas y crecimiento economico en Espana. La Curve de Kuznets ambiental y el protocolo de Kyoto

    Energy Technology Data Exchange (ETDEWEB)

    Roca Jusmet, J.; Padilla Rosa, E.

    2004-07-01

    From the beginning of the 90s the analysis of the relationships between economic growth and environmental pressures has been influenced by the Environmental Kuznets Curve hypothesis or inverted-U shaped relationship between environmental pressure and per capita income. Following this hypothesis, once achieved certain income level, more economic growth is followed by environmental quality improvement. In this paper, we analyse and discuss the theories that support this hypothesis as well as the empirical evidence on this subject. Further on we analyse the relationship between per capita income and the main environmental pollutants for the case does not support the hypothesis. The empirical evidence shows that economic growth, by itself, does not entail a pollution reduction. (Author) 35 refs.

  10. Peak oil analyzed with a logistic function and idealized Hubbert curve

    International Nuclear Information System (INIS)

    Gallagher, Brian

    2011-01-01

    A logistic function is used to characterize peak and ultimate production of global crude oil and petroleum-derived liquid fuels. Annual oil production data were incrementally summed to construct a logistic curve in its initial phase. Using a curve-fitting approach, a population-growth logistic function was applied to complete the cumulative production curve. The simulated curve was then deconstructed into a set of annual oil production data producing an 'idealized' Hubbert curve. An idealized Hubbert curve (IHC) is defined as having properties of production data resulting from a constant growth-rate under fixed resource limits. An IHC represents a potential production curve constructed from cumulative production data and provides a new perspective for estimating peak production periods and remaining resources. The IHC model data show that idealized peak oil production occurred in 2009 at 83.2 Mb/d (30.4 Gb/y). IHC simulations of truncated historical oil production data produced similar results and indicate that this methodology can be useful as a prediction tool. - Research Highlights: →Global oil production data were analyzed by a simple curve fitting method. →Best fit-curve results were obtained using two logistic functions on select data. →A broad potential oil production peak is forecast for the years from 2004 to 2014. →Similar results were obtained using historical data from about 10 to 30 years ago. →Two potential oil production decline scenarios were presented and compared.

  11. Estimation Curve Numbers using GIS and Hec-GeoHMS Model

    Directory of Open Access Journals (Sweden)

    Hayat Kareem Shukur

    2017-05-01

    Full Text Available Recently, the development and application of the hydrological models based on Geographical Information System (GIS has increased around the world. One of the most important applications of GIS is mapping the Curve Number (CN of a catchment. In this research, three softwares, such as an ArcView GIS 9.3 with ArcInfo, Arc Hydro Tool and Geospatial Hydrologic Modeling Extension (Hec-GeoHMS model for ArcView GIS 9.3, were used to calculate CN of (19210 ha Salt Creek watershed (SC which is located in Osage County, Oklahoma, USA. Multi layers were combined and examined using the Environmental Systems Research Institute (ESRI ArcMap 2009. These layers are soil layer (Soil Survey Geographic SSURGO, 30 m x 30 m resolution of Digital Elevation Model (DEM, land use layer (LU, “Look–Up tables” and other layers resulted from running the software. Curve Number which expresses a catchment’s response to a storm event has been estimated in this study to each land parcel based on LU layer and soil layer within each parcel. The results showed that a CN of 100 (dark Blue means surface water. The high curve numbers (100 -81 (Blue and light Blue corresponding to urbanized areas means high runoff and low infiltration; whereas low curve numbers (77- 58 (Brown and light Brown corresponding to the forested area means low runoff and high infiltration. Four classes of land cover have been identified; these are surface water, medium residential, forest and agriculture.

  12. Modeling the growth of Listeria monocytogenes in mold-ripened cheeses.

    Science.gov (United States)

    Lobacz, Adriana; Kowalik, Jaroslaw; Tarczynska, Anna

    2013-06-01

    This study presents possible applications of predictive microbiology to model the safety of mold-ripened cheeses with respect to bacteria of the species Listeria monocytogenes during (1) the ripening of Camembert cheese, (2) cold storage of Camembert cheese at temperatures ranging from 3 to 15°C, and (3) cold storage of blue cheese at temperatures ranging from 3 to 15°C. The primary models used in this study, such as the Baranyi model and modified Gompertz function, were fitted to growth curves. The Baranyi model yielded the most accurate goodness of fit and the growth rates generated by this model were used for secondary modeling (Ratkowsky simple square root and polynomial models). The polynomial model more accurately predicted the influence of temperature on the growth rate, reaching the adjusted coefficients of multiple determination 0.97 and 0.92 for Camembert and blue cheese, respectively. The observed growth rates of L. monocytogenes in mold-ripened cheeses were compared with simulations run with the Pathogen Modeling Program (PMP 7.0, USDA, Wyndmoor, PA) and ComBase Predictor (Institute of Food Research, Norwich, UK). However, the latter predictions proved to be consistently overestimated and contained a significant error level. In addition, a validation process using independent data generated in dairy products from the ComBase database (www.combase.cc) was performed. In conclusion, it was found that L. monocytogenes grows much faster in Camembert than in blue cheese. Both the Baranyi and Gompertz models described this phenomenon accurately, although the Baranyi model contained a smaller error. Secondary modeling and further validation of the generated models highlighted the issue of usability and applicability of predictive models in the food processing industry by elaborating models targeted at a specific product or a group of similar products. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  13. Modelling the benchmark spot curve for the Serbian

    Directory of Open Access Journals (Sweden)

    Drenovak Mikica

    2010-01-01

    Full Text Available The objective of this paper is to estimate Serbian benchmark spot curves using the Svensson parametric model. The main challenges that we tackle are: sparse data, different currency denominations of short and longer term maturities, and infrequent transactions in the short-term market segment vs daily traded medium and long-term market segment. We find that the model is flexible enough to account for most of the data variability. The model parameters are interpreted in economic terms.

  14. Natural and laboratory OSL growth curve–Verification of the basic assumption of luminescence dating

    International Nuclear Information System (INIS)

    Kijek, N.; Chruścińska, A.

    2016-01-01

    The basic assumption of luminescence dating is the equality between the growth curve of OSL generated by the natural radiation and the OSL growth curve reconstructed in laboratory conditions. The dose rates that generate the OSL in nature and in laboratory experiments differ by about ten orders of magnitude. Recently some discrepancies between the natural and laboratory growth curves have been observed. It is important to establish their reasons in order to introduce appropriate correction into the OSL dating protocol or to find a test that allows to eliminate the samples which should not be used for dating. For this purpose, both growth curves, natural and laboratory, were reconstructed by means of computer simulations of the processes occurring in the sample during its deposition time in environment as well as those which occur in a laboratory during dating procedure. The simulations were carried out for three models including one shallow trap, two OSL traps, one disconnected deep and one luminescence center. The OSL model for quartz can be more complex than the one used in the presented simulations, but in spite of that the results show effects of growth curves discrepancies similar to those observed in experiments. It is clear that the consistency of growth curves is not a general feature of the OSL processes, but rather a result of an advantageous configuration of trap parameters. The deep disconnected traps play the key role and their complete filling before the zeroing of OSL signal is a necessary condition of the growth curves' consistency. - Highlights: • Process of OSL growth curve generation in nature and in laboratory was simulated. • Discrepancies between the natural and the laboratory growth curves are observed. • Deep disconnected traps play the key role in growth curve inequality. • Empty deep traps before zeroing of OSL cause the inequality of growth curves.

  15. Model-based methodology to develop the isochronous stress-strain curves for modified 9Cr steels

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Yin, Song Nan; Kim, Sung Ho; Lee, Chan Bock; Jung, Ik Hee

    2008-01-01

    Since high temperature materials are designed with a target life based on a specified amount of allowable strain and stress, their Isochronous Stress-Strain Curves (ISSC) are needed to avoid an excessive deformation during an intended service life. In this paper, a model-based methodology to develop the isochronous curves for a G91 steel is described. Creep strain-time curves were reviewed for typical high-temperature materials, and Garofalo's model which conforms well to the primary and secondary creep stages was proper for the G91 steel. Procedures to obtain an instantaneous elastic-plastic strain, ε i were given in detail. Also, to accurately determine the P 1 , P 2 and P 3 parameters in the Garofalo's model, a Nonlinear Least Square Fitting (NLSF) method was adopted and useful. The long-term creep curves for the G91 steel can be modeled by the Garofalo's model, and the long-term ISSCs can be developed using the modeled creep curves

  16. Ablation front rayleigh taylor dispersion curve in indirect drive

    International Nuclear Information System (INIS)

    Budil, K.S.; Lasinski, B.; Edwards, M.J.; Wan, A.S.; Remington, B.A.; Weber, S.V.; Glendinning, S.G.; Suter, L.; Stry, P.

    2000-01-01

    The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. We present here the results of a series of laser experiments designed to probe the roll-over and cutoff region of the ablation-front RT dispersion curve in indirect drive. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 pm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an ∼2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths (ge) 20 (micro)m experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a 2-D radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launched by the drive. We performed numerical simulations to elucidate the influence of the rippled shock wave on the eventual growth of the perturbations, allowing comparisons to the analytic model developed by Betti et al. This combination of experiments, simulations and analytic modeling illustrates the qualitative simplicity yet quantitative complexity of the compressible RT instability. We have measured the Rayleigh-Taylor (RT) dispersion curve for a radiatively-driven sample in a series of experiments on the Nova laser facility. Planar aluminum foils were ablatively-accelerated and the subsequent perturbation growth was

  17. Use of structure-activity landscape index curves and curve integrals to evaluate the performance of multiple machine learning prediction models.

    Science.gov (United States)

    Ledonne, Norman C; Rissolo, Kevin; Bulgarelli, James; Tini, Leonard

    2011-02-07

    Standard approaches to address the performance of predictive models that used common statistical measurements for the entire data set provide an overview of the average performance of the models across the entire predictive space, but give little insight into applicability of the model across the prediction space. Guha and Van Drie recently proposed the use of structure-activity landscape index (SALI) curves via the SALI curve integral (SCI) as a means to map the predictive power of computational models within the predictive space. This approach evaluates model performance by assessing the accuracy of pairwise predictions, comparing compound pairs in a manner similar to that done by medicinal chemists. The SALI approach was used to evaluate the performance of continuous prediction models for MDR1-MDCK in vitro efflux potential. Efflux models were built with ADMET Predictor neural net, support vector machine, kernel partial least squares, and multiple linear regression engines, as well as SIMCA-P+ partial least squares, and random forest from Pipeline Pilot as implemented by AstraZeneca, using molecular descriptors from SimulationsPlus and AstraZeneca. The results indicate that the choice of training sets used to build the prediction models is of great importance in the resulting model quality and that the SCI values calculated for these models were very similar to their Kendall τ values, leading to our suggestion of an approach to use this SALI/SCI paradigm to evaluate predictive model performance that will allow more informed decisions regarding model utility. The use of SALI graphs and curves provides an additional level of quality assessment for predictive models.

  18. Residual stress behaviors induced by laser peening along the edge of curved models

    International Nuclear Information System (INIS)

    Im, Jong Bin; Grandhi, Ramana V.; Ro, Young Hee

    2012-01-01

    Laser peening (LP) induces high magnitude compressive residual stresses in a small region of a component. The compressive residual stresses cause plastic deformation that is resistant to fatigue fracture. Fatigue cracks are generally nucleated at critical areas, and LP is applied for those regions so as to delay the crack initiation. Many critical regions are located on the edge of the curved portion of structures because of stress concentration effects. Several investigations that are available for straight components may not give meaningful guidelines for peening curved components. Therefore, in this paper, we investigate residual stress behaviors induced by LP along the edge of curved models. Three curved models that have different curvatures are investigated for peening performance. Two types of peening configurations, which are simultaneous corner shot and sequential corner shots, are considered in order to obtain compressive residual stresses along an edge. LP simulations of multiple shots are performed to identify overlapping effects on the edge portion of a curved model. In addition, the uncertainty calculation of residual stress induced by LP considering laser pulse duration is performed

  19. Morphometric growth characteristics and body composition of bullfrog tadpoles in captivity

    Directory of Open Access Journals (Sweden)

    Cleber Menegasso Mansano

    2014-10-01

    Full Text Available Feed management needs to be improved in frog farming to reduce the indirect effects of inadequate feeding and, consequently, to increase growth rates and nutrient deposition, obtaining better quality animals. The objective of this study was to establish morphometric growth curves for bullfrog tadpoles (Lithobates catesbeianus and to determine nutrient deposition in the carcass. A total of 6,480 bullfrogs (Gosner stage 25 received an experimental diet (26.23% digestible protein and 32.68% crude protein and a commercial diet (37.92% crude protein ad libitum. A Gompertz model was used to describe the growth curve. Tadpoles fed the experimental diet presented higher final protein deposition. In addition, the sigmoidal curve was much more homogenous, indicating a more constant daily protein deposition rate. The Gompertz model provided an excellent fit of the data to describe the morphometric growth curve and carcass nutrient deposition of bullfrog tadpoles, showing that animals fed the experimental diet presented a better growth rate and nutrient deposition.

  20. Influence of Asthma on the Longitudinal Trajectories of Cigarette Use Behaviors From Adolescence to Adulthood Using Latent Growth Curve Models

    Directory of Open Access Journals (Sweden)

    Jisuk Bae

    2015-03-01

    Full Text Available Objectives: While epidemiologic research indicates that the prevalence of risk-taking behaviors including cigarette smoking among young people with asthma is substantial, the longitudinal patterns of cigarette smoking in this vulnerable population have received little attention. The aim of this study was to evaluate differences in the longitudinal trajectories of cigarette use behaviors from adolescence to adulthood between young people with and without asthma. Methods: Data from the National Longitudinal Study of Adolescent to Adult Health (Add Health during the years 1994 to 1995 (Wave I, adolescence, 2001 to 2002 (Wave III, young adulthood, and 2007 to 2008 (Wave IV, adulthood were analyzed (n=12 244. Latent growth curve models were used to examine the longitudinal trajectories of cigarette use behaviors during the transition to adulthood according to asthma status. Results: Regardless of asthma status, the trajectory means of cigarette use behaviors were found to increase, and then slightly decrease from adolescence to adulthood. In total participants, there were no statistically significant differences in initial levels and changes in cigarette use behaviors according to asthma status. However, in select sex and race subgroups (i.e., females and non-whites, former asthmatics showed greater escalation in cigarette use behaviors than did non-asthmatics or current asthmatics. Conclusions: This study indicated that the changing patterns of cigarette use behaviors during the transition to adulthood among young people with asthma are comparable to or even more drastic than those among young people without asthma.

  1. Curvas de crescimento intra-uterino de uma população de alto nível socioeconômico Intrauterine growth curves in a high-income population

    Directory of Open Access Journals (Sweden)

    Conceição A. M. Segre

    2001-06-01

    Full Text Available OBJETIVO: as curvas de percentil constituem uma das formas de avaliação do crescimento intra-uterino e podem predizer doenças do recém-nascido como também caracterizar uma população. Este trabalho teve por objetivo construir as curvas de crescimento intra-uterino dos recém-nascidos da Maternidade do Hospital Albert Einstein (MAE, hospital que atende a uma população de alto nível socioeconômico, e comparar com as curvas de crescimento intra-uterino de uma população norte-americana da Califórnia. MÉTODOS: foram construídas curvas de crescimento intra-uterino a partir do peso do recém-nascido de parto único, tomado logo após o nascimento, e da idade gestacional segundo informações maternas, a partir da 32ª. semana de idade gestacional, abrangendo os nascimentos ocorridos na MAE no período de fevereiro de 1995 a fevereiro de 1999. Foram calculados os percentis 10, 50 e 90 do peso ao nascer para cada idade gestacional e comparados com os das curvas da Califórnia. RESULTADOS: as curvas dos percentis 10 e 50 na população da MAE não diferiram das curvas da Califórnia. Para o percentil 90, a curva da MAE ficou abaixo das curvas da Califórnia. Houve número menor de pequenos e grandes para a idade gestacional (PIG e GIG quando classificados pelas curvas da Califórnia. A classificação em PIG, AIG, GIG mostrou-se relacionada significantemente com o ganho de peso materno nos dois sexos. CONCLUSÕES: as duas populações analisadas segundo as curvas de crescimento intra-uterino são diferentes entre si; deverão ser identificados fatores específicos que atuem na população da MAE.OBJECTIVE: growth curves can be used to assess intrauterine growth, to predict diseases in newborns, and to characterize different populations. The objective of this study was to obtain intrauterine growth curves of newborns from the maternity ward of the Hospital Albert Einstein (MAE and compare them with intrauterine growth curves of a population

  2. The influence of maternal care and overprotection on youth adrenocortical stress response: a multiphase growth curve analysis.

    Science.gov (United States)

    Vergara-Lopez, Chrystal; Chaudoir, Stephenie; Bublitz, Margaret; O'Reilly Treter, Maggie; Stroud, Laura

    2016-11-01

    We examined the association between two dimensions of maternal parenting style (care and overprotection) and cortisol response to an acute laboratory-induced stressor in healthy youth. Forty-three participants completed the Parental Bonding Instrument and an adapted version of the Trier Social Stress Test-Child (TSST-C). Nine cortisol samples were collected to investigate heterogeneity in different phases of youth's stress response. Multiphase growth-curve modeling was utilized to create latent factors corresponding to individual differences in cortisol during baseline, reactivity, and recovery to the TSST-C. Youth report of maternal overprotection was associated with lower baseline cortisol levels, and a slower cortisol decline during recovery, controlling for maternal care, puberty, and gender. No additive or interactive effects involving maternal care emerged. These findings suggest that maternal overprotection may exert a unique and important influence on youth's stress response.

  3. Can extrauterine growth approximate intrauterine growth? Should it?

    NARCIS (Netherlands)

    Sauer, Pieter J. J.

    Most studies evaluating the growth of preterm infants use the so-called intrauterine growth curve and reference fetus as standards. These curves might not be the optimal standards, however, for several reasons. The curves were constructed from small numbers of infants with uncertainty about

  4. System dynamics modelling and the environmental Kuznets curve in Ecuador (1980–2025)

    International Nuclear Information System (INIS)

    Robalino-López, Andrés; García-Ramos, José-Enrique; Golpe, Antonio A.; Mena-Nieto, Ángel

    2014-01-01

    Is it possible for a country in the process of development to comply with the environmental Kuznets curve (EKC) hypothesis in the medium term? This is the question that inspired this study. This paper is an extension of a previous study focused on economic development and CO 2 emissions in the coming years in Ecuador (Robalino-López et al., submitted for publication). The main goal of this paper is to analyze whether the EKC hypothesis holds within the period 1980–2025 under four different scenarios. This paper uses co-integration techniques (Stock and Watson, 2010) to test the existence of the EKC hypothesis in Ecuador in the medium term using Jaunky's (2011) specification. Our proposal goes a step further than previous contributions, and intends to see under which conditions a country could approach the fulfilment of this hypothesis in the medium term. Results do not support the fulfilment of the EKC, nevertheless, our estimations show that Ecuador could be on the way to achieving environmental stabilization in the near future if economic growth is combined with an increase in the use of renewable energies, an improvement of the productive sectoral structure, and the use of a more efficient fossil fuel technology. - Author-Highlights: • We model the CO 2 emissions in Ecuador for the next decade under several scenarios. • We study the environmental Kuznets curve in the medium term in Ecuador. • We show that Ecuador will enter into stage 2 of the environmental Kuznets curve in the near future

  5. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, 4 Ivy Lane, Princeton, NJ 08534 (United States); Basri, Gibor [Astronomy Department, University of California at Berkeley, Hearst Field Annex, Berkeley, CA 94720 (United States); Valenti, Jeff A. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  6. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    International Nuclear Information System (INIS)

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-01-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  7. Use of structure-activity landscape index curves and curve integrals to evaluate the performance of multiple machine learning prediction models

    Directory of Open Access Journals (Sweden)

    LeDonne Norman C

    2011-02-01

    Full Text Available Abstract Background Standard approaches to address the performance of predictive models that used common statistical measurements for the entire data set provide an overview of the average performance of the models across the entire predictive space, but give little insight into applicability of the model across the prediction space. Guha and Van Drie recently proposed the use of structure-activity landscape index (SALI curves via the SALI curve integral (SCI as a means to map the predictive power of computational models within the predictive space. This approach evaluates model performance by assessing the accuracy of pairwise predictions, comparing compound pairs in a manner similar to that done by medicinal chemists. Results The SALI approach was used to evaluate the performance of continuous prediction models for MDR1-MDCK in vitro efflux potential. Efflux models were built with ADMET Predictor neural net, support vector machine, kernel partial least squares, and multiple linear regression engines, as well as SIMCA-P+ partial least squares, and random forest from Pipeline Pilot as implemented by AstraZeneca, using molecular descriptors from SimulationsPlus and AstraZeneca. Conclusion The results indicate that the choice of training sets used to build the prediction models is of great importance in the resulting model quality and that the SCI values calculated for these models were very similar to their Kendall τ values, leading to our suggestion of an approach to use this SALI/SCI paradigm to evaluate predictive model performance that will allow more informed decisions regarding model utility. The use of SALI graphs and curves provides an additional level of quality assessment for predictive models.

  8. Modeling Breakthrough Curves of Citric Acid Adsorption onto Anionic Resins in an Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Sohrabali Ghorbanian

    2015-01-01

    Full Text Available Breakthrough curves for citric acid adsorption from aqueous solution onto ion-exchange resin at 20, 35, and 55°C have been investigated. To predict breakthrough curves, three mathematical models have been analyzed based on the values of the least square method parameters, Durbin-Watson test, and mean relative percent error and, finally, appropriate models have been achieved. Models are in good agreement with experimental data based on the results. To examine models reliabilities and accuracy, models have been compared by various breakthrough curve data obtained by other investigators. The results show appropriate agreement and in some cases regression errors have been reduced to less than 1.0 percent.

  9. Microscopic Model of Automobile Lane-changing Virtual Desire Trajectory by Spline Curves

    Directory of Open Access Journals (Sweden)

    Yulong Pei

    2010-05-01

    Full Text Available With the development of microscopic traffic simulation models, they have increasingly become an important tool for transport system analysis and management, which assist the traffic engineer to investigate and evaluate the performance of transport network systems. Lane-changing model is a vital component in any traffic simulation model, which could improve road capacity and reduce vehicles delay so as to reduce the likelihood of congestion occurrence. Therefore, this paper addresses the virtual desire trajectory, a vital part to investigate the behaviour divided into four phases. Based on the boundary conditions, β-spline curves and the corresponding reverse algorithm are introduced firstly. Thus, the relation between the velocity and length of lane-changing is constructed, restricted by the curvature, steering velocity and driving behaviour. Then the virtual desire trajectory curves are presented by Matlab and the error analysis results prove that this proposed description model has higher precision in automobile lane-changing process reconstruction, compared with the surveyed result. KEY WORDS: traffic simulation, lane-changing model, virtual desire trajectory, β-spline curves, driving behaviour

  10. S-curve networks and an approximate method for estimating degree distributions of complex networks

    OpenAIRE

    Guo, Jin-Li

    2010-01-01

    In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (Logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference value for optimizing the distribution of IPv4 address resource and the development of IPv6. Based o...

  11. Exploring the link between environmental pollution and economic growth in EU-28 countries: Is there an environmental Kuznets curve?

    Science.gov (United States)

    Armeanu, Daniel; Vintilă, Georgeta; Andrei, Jean Vasile; Gherghina, Ştefan Cristian; Drăgoi, Mihaela Cristina; Teodor, Cristian

    2018-01-01

    This study examines the Environmental Kuznets Curve hypothesis (EKC), considering the primary energy consumption among other country-specific variables, for a panel of the EU-28 countries during the period 1990-2014. By estimating pooled OLS regressions with Driscoll-Kraay standard errors in order to account for cross-sectional dependence, the results confirm the EKC hypothesis in the case of emissions of sulfur oxides and emissions of non-methane volatile organic compounds. In addition to pooled estimations, the output of fixed-effects regressions with Driscoll-Kraay standard errors support the EKC hypothesis for greenhouse gas emissions, greenhouse gas emissions intensity of energy consumption, emissions of nitrogen oxides, emissions of non-methane volatile organic compounds and emissions of ammonia. Additionally, the empirical findings from panel vector error correction model reveal a short-run unidirectional causality from GDP per capita growth to greenhouse gas emissions, as well as a bidirectional causal link between primary energy consumption and greenhouse gas emissions. Furthermore, since there occurred no causal link between economic growth and primary energy consumption, the neo-classical view was confirmed, namely the neutrality hypothesis.

  12. Bracing can reduce high degree curves and improve aesthetics immediately after the end of growth. Final results of a retrospective case series.

    Science.gov (United States)

    Negrini, Stefano; Donzelli, Sabrina; Lusini, Monia; Zaina, Fabio

    2012-01-01

    Recently it has been shown that idiopathic scoliosis (IS) curves can be reduced with bracing, and it has been proposed that this could be useful in non-surgically treated high degree curves even after Risser 3. Moreover, bracing has been shown to be able to improve aesthetics, and this could be another reason to treat some patients with cosmetic needs. Our aim is to preliminary check if results can be obtained in IS patients after Risser 3. Design. Retrospective uncontrolled cohort study. Inclusion criteria. All IS patients treated on a voluntary basis for aesthetic reasons and/or for curve reduction; Risser 4-5 at start; end of treatment reached. Population. 34 females and 2 males, age 16.2±1.6 years, Cobb angle 27.6°±8.9°. Treatment. Lyon or SPoRT braces 18 to 24 hours/day, specific SEAS exercises, rapid weaning (2-3 hours every 6 months). Outcome criteria: SRS (unchanged; worsened over 6°; over 45° at the end of treatment; surgically treated), radiographic and clinical. Statistics. ANOVA and chi-test. The reported compliance during the 2.8 ± 1.1 treatment years was 95.1%, while residual growth was 0.9 ± 1.1 cm. Improvements were found in 39% of this cohort, (46% in curves over 30°). Only 1 patient progressed 6°. We found highly statistically significant reductions of maximal (-4.4°), thoracic (-6.0°) and thoracolumbar (-6.6°) curves. Statistically significant improvements were found for Aesthetic Index. Before 20 years of age, even in skeletally mature patients, it is possible to reach radiographic and aesthetic improvements, although not as good as during growth. Correction is based on bone growth, but ligaments and neuromuscular control of posture can also be involved.

  13. Effect of single-dose x irradiation on the growth curves of a human malignant melanoma transplanted into nude mice

    International Nuclear Information System (INIS)

    Spang-Thomsen, M.; Visfeldt, J.; Nielsen, A.

    1981-01-01

    A human malignant melanoma transplanted into nude mice was exposed to single-dose x irradiation. Experimental growth data described mathematically according to a transformed Gompertz function were used to determine the effect of irradiation on growth delay, growth rate, and tumor shrinkage. The radiation-induced changes in the histology of the tumors were also described. The results showed that irradiation induced a dose-dependent growth delay; this parameter was therefore found suitable for the assessment of relative therapeutic effect. The treatment also induced a dose-dependent reduction in growth rate during regrowth. As a result of this effect on growth rate, extrapolation of tumor shrinkage to the time of treatment became directly misleading as a measure of the effect of the treatment. From this it can be deduced that in therapeutic studies where treatment induces nonparallel posttherapeutic growth curves, growth delay for various tumors and therapies cannot be compared directly. The transformed Gompertz function proved to be extremely well suited for evaluating these conditions

  14. Multilevel models for longitudinal data

    OpenAIRE

    Fiona Steele

    2008-01-01

    Repeated measures and repeated events data have a hierarchical structure which can be analysed by using multilevel models. A growth curve model is an example of a multilevel random-coefficients model, whereas a discrete time event history model for recurrent events can be fitted as a multilevel logistic regression model. The paper describes extensions to the basic growth curve model to handle auto-correlated residuals, multiple-indicator latent variables and correlated growth processes, and e...

  15. Nonlinear Structured Growth Mixture Models in Mplus and OpenMx

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam; Estabrook, Ryne

    2014-01-01

    Growth mixture models (GMMs; Muthén & Muthén, 2000; Muthén & Shedden, 1999) are a combination of latent curve models (LCMs) and finite mixture models to examine the existence of latent classes that follow distinct developmental patterns. GMMs are often fit with linear, latent basis, multiphase, or polynomial change models because of their common use, flexibility in modeling many types of change patterns, the availability of statistical programs to fit such models, and the ease of programming. In this paper, we present additional ways of modeling nonlinear change patterns with GMMs. Specifically, we show how LCMs that follow specific nonlinear functions can be extended to examine the presence of multiple latent classes using the Mplus and OpenMx computer programs. These models are fit to longitudinal reading data from the Early Childhood Longitudinal Study-Kindergarten Cohort to illustrate their use. PMID:25419006

  16. What are the key drivers of MAC curves? A partial-equilibrium modelling approach for the UK

    International Nuclear Information System (INIS)

    Kesicki, Fabian

    2013-01-01

    Marginal abatement cost (MAC) curves are widely used for the assessment of costs related to CO 2 emissions reduction in environmental economics, as well as domestic and international climate policy. Several meta-analyses and model comparisons have previously been performed that aim to identify the causes for the wide range of MAC curves. Most of these concentrate on general equilibrium models with a focus on aspects such as specific model type and technology learning, while other important aspects remain almost unconsidered, including the availability of abatement technologies and level of discount rates. This paper addresses the influence of several key parameters on MAC curves for the United Kingdom and the year 2030. A technology-rich energy system model, UK MARKAL, is used to derive the MAC curves. The results of this study show that MAC curves are robust even to extreme fossil fuel price changes, while uncertainty around the choice of the discount rate, the availability of key abatement technologies and the demand level were singled out as the most important influencing factors. By using a different model type and studying a wider range of influencing factors, this paper contributes to the debate on the sensitivity of MAC curves. - Highlights: ► A partial-equilibrium model is employed to test key sensitivities of MAC curves. ► MAC curves are found to be robust to wide-ranging changes in fossil fuel prices. ► Most influencing factors are the discount rate, availability of key technologies. ► Further important uncertainty in MAC curves is related to demand changes

  17. Impact of Witnessing Violence on Growth Curves for Problem Behaviors among Early Adolescents in Urban and Rural Settings

    Science.gov (United States)

    Farrell, Albert D.; Sullivan, Terri N.

    2004-01-01

    Two studies used latent growth-curve analysis to examine the relation between witnessing violence and changes in problem behaviors (drug use, aggression, and delinquency) and attitudes during early adolescence. In Study 1, six waves of data covering 6th to 8th grades were collected from 731 students in urban schools serving mostly African-American…

  18. Grain nucleation and growth during phase transformations

    DEFF Research Database (Denmark)

    Offerman, S.E.; Dijk, N.H. van; Sietsma, J.

    2002-01-01

    of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally...... different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties....

  19. Exponential models applied to automated processing of radioimmunoassay standard curves

    International Nuclear Information System (INIS)

    Morin, J.F.; Savina, A.; Caroff, J.; Miossec, J.; Legendre, J.M.; Jacolot, G.; Morin, P.P.

    1979-01-01

    An improved computer processing is described for fitting of radio-immunological standard curves by means of an exponential model on a desk-top calculator. This method has been applied to a variety of radioassays and the results are in accordance with those obtained by more sophisticated models [fr

  20. Creep curve modeling of hastelloy-X alloy by using the theta projection method

    International Nuclear Information System (INIS)

    Woo Gon, Kim; Woo-Seog, Ryu; Jong-Hwa, Chang; Song-Nan, Yin

    2007-01-01

    To model the creep curves of the Hastelloy-X alloy which is being considered as a candidate material for the VHTR (Very High Temperature gas-cooled Reactor) components, full creep curves were obtained by constant-load creep tests for different stress levels at 950 C degrees. Using the experimental creep data, the creep curves were modeled by applying the Theta projection method. A number of computing processes of a nonlinear least square fitting (NLSF) analysis was carried out to establish the suitably of the four Theta parameters. The results showed that the Θ 1 and Θ 2 parameters could not be optimized well with a large error during the fitting of the full creep curves. On the other hand, the Θ 3 and Θ 4 parameters were optimized well without an error. For this result, to find a suitable cutoff strain criterion, the NLSF analysis was performed with various cutoff strains for all the creep curves. An optimum cutoff strain range for defining the four Theta parameters accurately was found to be a 3% cutoff strain. At the 3% cutoff strain, the predicted curves coincided well with the experimental ones. The variation of the four Theta parameters as the function of a stress showed a good linearity, and the creep curves were modeled well for the low stress levels. Predicted minimum creep rate showed a good agreement with the experimental data. Also, for a design usage of the Hastelloy-X alloy, the plot of the log stress versus log the time to a 1% strain was predicted, and the creep rate curves with time and a cutoff strain at 950 C degrees were constructed numerically for a wide rang of stresses by using the Theta projection method. (authors)

  1. Multilevel Models for the Analysis of Angle-Specific Torque Curves with Application to Master Athletes

    Directory of Open Access Journals (Sweden)

    Carvalho Humberto M.

    2015-12-01

    Full Text Available The aim of this paper was to outline a multilevel modeling approach to fit individual angle-specific torque curves describing concentric knee extension and flexion isokinetic muscular actions in Master athletes. The potential of the analytical approach to examine between individual differences across the angle-specific torque curves was illustrated including between-individuals variation due to gender differences at a higher level. Torques in concentric muscular actions of knee extension and knee extension at 60°·s-1 were considered within a range of motion between 5°and 85° (only torques “truly” isokinetic. Multilevel time series models with autoregressive covariance structures with standard multilevel models were superior fits compared with standard multilevel models for repeated measures to fit anglespecific torque curves. Third and fourth order polynomial models were the best fits to describe angle-specific torque curves of isokinetic knee flexion and extension concentric actions, respectively. The fixed exponents allow interpretations for initial acceleration, the angle at peak torque and the decrement of torque after peak torque. Also, the multilevel models were flexible to illustrate the influence of gender differences on the shape of torque throughout the range of motion and in the shape of the curves. The presented multilevel regression models may afford a general framework to examine angle-specific moment curves by isokinetic dynamometry, and add to the understanding mechanisms of strength development, particularly the force-length relationship, both related to performance and injury prevention.

  2. Height growth and site index curves for western white pine in the Cascade Range of Washington and Oregon.

    Science.gov (United States)

    Robert O. Curtis; Nancy M. Diaz; Gary W. Clendenen

    1990-01-01

    Height growth and site index curves were constructed from stem analyses of mature western white pine (Pinus monticola Dougl. ex D. Don) growing in high-elevation forests of the Cascade Range in the Mount Hood and Gifford Pinchot National Forests of Oregon and Washington, respectively. Alternate systems using reference ages for site index of 50 and...

  3. Water Stress Scatters Nitrogen Dilution Curves in Wheat

    Directory of Open Access Journals (Sweden)

    Marianne Hoogmoed

    2018-04-01

    Full Text Available Nitrogen dilution curves relate a crop’s critical nitrogen concentration (%Nc to biomass (W according to the allometric model %Nc = a W-b. This model has a strong theoretical foundation, and parameters a and b show little variation for well-watered crops. Here we explore the robustness of this model for water stressed crops. We established experiments to examine the combined effects of water stress, phenology, partitioning of biomass, and water-soluble carbohydrates (WSC, as driven by environment and variety, on the %Nc of wheat crops. We compared models where %Nc was plotted against biomass, growth stage and thermal time. The models were similarly scattered. Residuals of the %Nc - biomass model at anthesis were positively related to biomass, stem:biomass ratio, Δ13C and water supply, and negatively related to ear:biomass ratio and concentration of WSC. These are physiologically meaningful associations explaining the scatter of biomass-based dilution curves. Residuals of the thermal time model showed less consistent associations with these variables. The biomass dilution model developed for well-watered crops overestimates nitrogen deficiency of water-stressed crops, and a biomass-based model is conceptually more justified than developmental models. This has implications for diagnostic and modeling. As theory is lagging, a greater degree of empiricism might be useful to capture environmental, chiefly water, and genotype-dependent traits in the determination of critical nitrogen for diagnostic purposes. Sensitivity analysis would help to decide if scaling nitrogen dilution curves for crop water status, and genotype-dependent parameters are needed.

  4. Adaptive robust polynomial regression for power curve modeling with application to wind power forecasting

    DEFF Research Database (Denmark)

    Xu, Man; Pinson, Pierre; Lu, Zongxiang

    2016-01-01

    of the lack of time adaptivity. In this paper, a refined local polynomial regression algorithm is proposed to yield an adaptive robust model of the time-varying scattered power curve for forecasting applications. The time adaptivity of the algorithm is considered with a new data-driven bandwidth selection......Wind farm power curve modeling, which characterizes the relationship between meteorological variables and power production, is a crucial procedure for wind power forecasting. In many cases, power curve modeling is more impacted by the limited quality of input data rather than the stochastic nature...... of the energy conversion process. Such nature may be due the varying wind conditions, aging and state of the turbines, etc. And, an equivalent steady-state power curve, estimated under normal operating conditions with the intention to filter abnormal data, is not sufficient to solve the problem because...

  5. Urban tree growth modeling

    Science.gov (United States)

    E. Gregory McPherson; Paula J. Peper

    2012-01-01

    This paper describes three long-term tree growth studies conducted to evaluate tree performance because repeated measurements of the same trees produce critical data for growth model calibration and validation. Several empirical and process-based approaches to modeling tree growth are reviewed. Modeling is more advanced in the fields of forestry and...

  6. Simulation-optimization model of reservoir operation based on target storage curves

    Directory of Open Access Journals (Sweden)

    Hong-bin Fang

    2014-10-01

    Full Text Available This paper proposes a new storage allocation rule based on target storage curves. Joint operating rules are also proposed to solve the operation problems of a multi-reservoir system with joint demands and water transfer-supply projects. The joint operating rules include a water diversion rule to determine the amount of diverted water in a period, a hedging rule based on an aggregated reservoir to determine the total release from the system, and a storage allocation rule to specify the release from each reservoir. A simulation-optimization model was established to optimize the key points of the water diversion curves, the hedging rule curves, and the target storage curves using the improved particle swarm optimization (IPSO algorithm. The multi-reservoir water supply system located in Liaoning Province, China, including a water transfer-supply project, was employed as a case study to verify the effectiveness of the proposed join operating rules and target storage curves. The results indicate that the proposed operating rules are suitable for the complex system. The storage allocation rule based on target storage curves shows an improved performance with regard to system storage distribution.

  7. Environmental quality and economic growth: Searching for environmental Kuznets curves for air and water pollutants in Africa

    International Nuclear Information System (INIS)

    Orubu, Christopher O.; Omotor, Douglason G.

    2011-01-01

    This study investigated the relationship between per capita income and environmental degradation in Africa, using longitudinal data on suspended particulate matter and organic water pollutants. The specific objective was to estimate environmental Kuznets curves for two indicators of environmental quality and to establish whether the estimated relationships conform to the inverted U-shape hypothesis. The results of the empirical investigation generally suggest the existence of an environmental Kuznets curve for suspended particulate matter. In the case of organic water pollutants, the evidence weighs more in favor of rising pollution as per capita income increases. The turning point levels of income established for the two indicators of environmental quality were however generally low, when compared to evidence from existing studies. On the face value, this suggests that African countries may be turning the corner of the environmental Kuznets curve, much faster, and at lower levels of income, much in line with the emerging idea of a 'revised environmental Kuznets curve'. The results also suggest that economic growth and rising incomes may matter in African countries in order to curb pollution from these pollutants, but more stringent policy measures, particularly at the industrial level would be required to curb environmental degradation from organic water pollutants. - Highlights: → The specific objective was to establish whether the relationships conform to the inverted U-shape hypothesis. → Evidence suggests the existence of an environmental Kuznets curve for suspended particulate matter. → The turning point levels of income established for the two indicators were however generally low. → We conclude that African countries may be turning the corner of the environmental Kuznets curve, much faster, and at lower levels of income.

  8. Environmental quality and economic growth: Searching for environmental Kuznets curves for air and water pollutants in Africa

    Energy Technology Data Exchange (ETDEWEB)

    Orubu, Christopher O. [Department of Economics, Delta State University, Abraka (Nigeria); Omotor, Douglason G., E-mail: yomotor@yahoo.com [Department of Economics, Delta State University, Abraka (Nigeria)

    2011-07-15

    This study investigated the relationship between per capita income and environmental degradation in Africa, using longitudinal data on suspended particulate matter and organic water pollutants. The specific objective was to estimate environmental Kuznets curves for two indicators of environmental quality and to establish whether the estimated relationships conform to the inverted U-shape hypothesis. The results of the empirical investigation generally suggest the existence of an environmental Kuznets curve for suspended particulate matter. In the case of organic water pollutants, the evidence weighs more in favor of rising pollution as per capita income increases. The turning point levels of income established for the two indicators of environmental quality were however generally low, when compared to evidence from existing studies. On the face value, this suggests that African countries may be turning the corner of the environmental Kuznets curve, much faster, and at lower levels of income, much in line with the emerging idea of a 'revised environmental Kuznets curve'. The results also suggest that economic growth and rising incomes may matter in African countries in order to curb pollution from these pollutants, but more stringent policy measures, particularly at the industrial level would be required to curb environmental degradation from organic water pollutants. - Highlights: > The specific objective was to establish whether the relationships conform to the inverted U-shape hypothesis. > Evidence suggests the existence of an environmental Kuznets curve for suspended particulate matter. > The turning point levels of income established for the two indicators were however generally low. > We conclude that African countries may be turning the corner of the environmental Kuznets curve, much faster, and at lower levels of income.

  9. A void ratio dependent water retention curve model including hydraulic hysteresis

    Directory of Open Access Journals (Sweden)

    Pasha Amin Y.

    2016-01-01

    Full Text Available Past experimental evidence has shown that Water Retention Curve (WRC evolves with mechanical stress and structural changes in soil matrix. Models currently available in the literature for capturing the volume change dependency of WRC are mainly empirical in nature requiring an extensive experimental programme for parameter identification which renders them unsuitable for practical applications. In this paper, an analytical model for the evaluation of the void ratio dependency of WRC in deformable porous media is presented. The approach proposed enables quantification of the dependency of WRC on void ratio solely based on the form of WRC at the reference void ratio and requires no additional parameters. The effect of hydraulic hysteresis on the evolution process is also incorporated in the model, an aspect rarely addressed in the literature. Expressions are presented for the evolution of main and scanning curves due to loading and change in the hydraulic path from scanning to main wetting/drying and vice versa as well as the WRC parameters such as air entry value, air expulsion value, pore size distribution index and slope of the scanning curve. The model is validated using experimental data on compacted and reconstituted soils subjected to various hydro-mechanical paths. Good agreement is obtained between model predictions and experimental data in all the cases considered.

  10. A Composite Light Curve Model of the Symbiotic Nova PU Vul (1979

    Directory of Open Access Journals (Sweden)

    Kato M.

    2012-06-01

    Full Text Available PU Vul (1979 is a symbiotic nova that shows a long-lasting flat optical peak followed by a slow decline. We made a quasi-evolution model for outbursts on a 0.6 M⊙ white dwarf consisting of a series of static solutions with optically-thin winds. Our theoretical models reproduce well the observed visual/UV light curves as well as the new estimates of the temperature and radius of the hot component. We also modeled the light curve of the 1980 and 1994 eclipses as the total eclipse occulted by a pulsating M-giant companion star. In the second eclipse, the visual magnitude is dominated by nebular emission which is possibly ejected from the hot component between 1990 to 2000. We have quantitatively estimated three components of emission, i.e., the white dwarf, companion and nebular, and made a composite light curve that represents well the evolution of the PU Vul outburst.

  11. Growth curves and their implications in hand-fed Monk parrots (Myiopsitta monachus

    Directory of Open Access Journals (Sweden)

    Petzinger C

    2015-10-01

    Full Text Available Christina Petzinger,1,2 J Jill Heatley,3 John E Bauer1,2 1Comparative Animal Nutrition Research Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, 2Intercollegiate Faculty of Nutrition, Texas A&M University, 3Zoological Medicine Service, Department of Small Animal Medicine and Surgery, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA Abstract: Monk parrots (Myiopsitta monachus were hand-fed over two chick seasons spanning of 2010 to 2011. Information from the growth curve of chicks hand-fed in 2010 was used to develop a feeding protocol for the 2011 season (Protocol-2011. This protocol addressed the problems of delayed followed by excessive growth experienced by parrots hand fed in 2010. Monk parrots that were hand-fed in 2011 following the new protocol experienced delayed growth after 20 days of age. However, some Monk parrots were fed in excess of Protocol-2011 and did not experience a major delay in growth. The energy requirement equations used to construct Protocol-2011 were low when compared to adult Monk parrot maintenance energy requirements. The data suggest that growing birds do not require approximately twice their adult maintenance energy requirements, as is the case for growing dogs. Additionally, there appear to be fluctuations in energy needs as Monk parrots grow. A major increase in energy needs occurred between days 18 and 23 posthatching, which corresponds to feather development and growth in Monk parrot chicks. Thus, multiple equations estimating energy requirements, rather than just one equation, are likely needed from hatching to fledging in order to ensure adequate energy is provided to chicks. More research on the energy requirements of growing Monk parrots, especially around the time of fledging and weaning, is needed to improve hand-fed methods and potentially the adult health of hand-fed birds. Keywords

  12. Economic Growth and Environmental Quality in the European Union Countries – Is there Evidence for the Environmental Kuznets Curve?

    Directory of Open Access Journals (Sweden)

    Mazur Anna

    2015-03-01

    Full Text Available This research empirically explores the relation between carbon dioxide emission and economic growth during the period 1992-2010, using panel data on the European Union countries. Both fixed and random effect models are employed to test the Environmental Kuznets Curve (EKC relationship between CO2 emissions and GDP per capita. While no U-shaped EKC was confirmed empirically for all 28 current EU member states, the graphical analysis demonstrates a justified turning point for CO2 emissions as GDP per capita reaches the level of 23,000 USD. Furthermore, there is a firm empirical ground for the EKC hypothesis based on data from 16 older, relatively high-income EU states. Thus, though not empirically confirmed, there is ample data verifying the existence of the EKC in EU economies.

  13. Simulation of a G-tolerance curve using the pulsatile cardiovascular model

    Science.gov (United States)

    Solomon, M.; Srinivasan, R.

    1985-01-01

    A computer simulation study, performed to assess the ability of the cardiovascular model to reproduce the G tolerance curve (G level versus tolerance time) is reported. A composite strength duration curve derived from experimental data obtained in human centrifugation studies was used for comparison. The effects of abolishing automomic control and of blood volume loss on G tolerance were also simulated. The results provide additional validation of the model. The need for the presence of autonomic reflexes even at low levels of G is pointed out. The low margin of safety with a loss of blood volume indicated by the simulation results underscores the necessity for protective measures during Shuttle reentry.

  14. Interpolating Spline Curve-Based Perceptual Encryption for 3D Printing Models

    Directory of Open Access Journals (Sweden)

    Giao N. Pham

    2018-02-01

    Full Text Available With the development of 3D printing technology, 3D printing has recently been applied to many areas of life including healthcare and the automotive industry. Due to the benefit of 3D printing, 3D printing models are often attacked by hackers and distributed without agreement from the original providers. Furthermore, certain special models and anti-weapon models in 3D printing must be protected against unauthorized users. Therefore, in order to prevent attacks and illegal copying and to ensure that all access is authorized, 3D printing models should be encrypted before being transmitted and stored. A novel perceptual encryption algorithm for 3D printing models for secure storage and transmission is presented in this paper. A facet of 3D printing model is extracted to interpolate a spline curve of degree 2 in three-dimensional space that is determined by three control points, the curvature coefficients of degree 2, and an interpolating vector. Three control points, the curvature coefficients, and interpolating vector of the spline curve of degree 2 are encrypted by a secret key. The encrypted features of the spline curve are then used to obtain the encrypted 3D printing model by inverse interpolation and geometric distortion. The results of experiments and evaluations prove that the entire 3D triangle model is altered and deformed after the perceptual encryption process. The proposed algorithm is responsive to the various formats of 3D printing models. The results of the perceptual encryption process is superior to those of previous methods. The proposed algorithm also provides a better method and more security than previous methods.

  15. Modelling of creep curves of Ni3Ge single crystals

    Science.gov (United States)

    Starenchenko, V. A.; Starenchenko, S. V.; Pantyukhova, O. D.; Solov'eva, Yu V.

    2015-01-01

    In this paper the creep model of alloys with L12 superstructure is presented. The creep model is based on the idea of the mechanisms superposition connected with the different elementary deformation processes. Some of them are incident to the ordered structure L12 (anomalous mechanisms), others are typical to pure metals with the fcc structure (normal mechanisms): the accumulation of thermal APBs by means of the intersection of moving dislocations; the formation of APB tubes; the multiplication of superdislocations; the movement of single dislocations; the accumulation of point defects, such as vacancies and interstitial atoms; the accumulation APBs at the climb of edge dislocations. This model takes into account the experimental facts of the wetting antiphase boundaries and emergence of the disordered phase within the ordered phase. The calculations of the creep curves are performed under different conditions. This model describes different kinds of the creep curves and demonstrates the important meaning of the deformation superlocalisation leading to the inverse creep. The experimental and theoretical results coincide rather well.

  16. A location-scale model for non-crossing expectile curves

    NARCIS (Netherlands)

    Schnabel, S.K.; Eilers, P.H.C.

    2013-01-01

    In quantile smoothing, crossing of the estimated curves is a common nuisance, in particular with small data sets and dense sets of quantiles. Similar problems arise in expectile smoothing. We propose a novel method to avoid crossings. It is based on a location-scale model for expectiles and

  17. The development of a curved beam element model applied to finite elements method

    International Nuclear Information System (INIS)

    Bento Filho, A.

    1980-01-01

    A procedure for the evaluation of the stiffness matrix for a thick curved beam element is developed, by means of the minimum potential energy principle, applied to finite elements. The displacement field is prescribed through polynomial expansions, and the interpolation model is determined by comparison of results obtained by the use of a sample of different expansions. As a limiting case of the curved beam, three cases of straight beams, with different dimensional ratios are analised, employing the approach proposed. Finally, an interpolation model is proposed and applied to a curved beam with great curvature. Desplacements and internal stresses are determined and the results are compared with those found in the literature. (Author) [pt

  18. Anterior Overgrowth in Primary Curves, Compensatory Curves and Junctional Segments in Adolescent Idiopathic Scoliosis.

    Science.gov (United States)

    Schlösser, Tom P C; van Stralen, Marijn; Chu, Winnie C W; Lam, Tsz-Ping; Ng, Bobby K W; Vincken, Koen L; Cheng, Jack C Y; Castelein, René M

    2016-01-01

    Although much attention has been given to the global three-dimensional aspect of adolescent idiopathic scoliosis (AIS), the accurate three-dimensional morphology of the primary and compensatory curves, as well as the intervening junctional segments, in the scoliotic spine has not been described before. A unique series of 77 AIS patients with high-resolution CT scans of the spine, acquired for surgical planning purposes, were included and compared to 22 healthy controls. Non-idiopathic curves were excluded. Endplate segmentation and local longitudinal axis in endplate plane enabled semi-automatic geometric analysis of the complete three-dimensional morphology of the spine, taking inter-vertebral rotation, intra-vertebral torsion and coronal and sagittal tilt into account. Intraclass correlation coefficients for interobserver reliability were 0.98-1.00. Coronal deviation, axial rotation and the exact length discrepancies in the reconstructed sagittal plane, as defined per vertebra and disc, were analyzed for each primary and compensatory curve as well as for the junctional segments in-between. The anterior-posterior difference of spinal length, based on "true" anterior and posterior points on endplates, was +3.8% for thoracic and +9.4% for (thoraco)lumbar curves, while the junctional segments were almost straight. This differed significantly from control group thoracic kyphosis (-4.1%; P<0.001) and lumbar lordosis (+7.8%; P<0.001). For all primary as well as compensatory curves, we observed linear correlations between the coronal Cobb angle, axial rotation and the anterior-posterior length difference (r≥0.729 for thoracic curves; r≥0.485 for (thoraco)lumbar curves). Excess anterior length of the spine in AIS has been described as a generalized growth disturbance, causing relative anterior spinal overgrowth. This study is the first to demonstrate that this anterior overgrowth is not a generalized phenomenon. It is confined to the primary as well as the

  19. An experimental and analytical study of ductile fracture and stable crack-growth

    International Nuclear Information System (INIS)

    Rousselier, G.

    1978-01-01

    A study is described, the objectives of which were to define a numerical model for stable crack growth, to calibrate the model by tensile tests, and to obtain agreement between corresponding numerical calculations and experiments on cracked specimens. The model was based on a finite element program with a critical state at the crack tip defined by a ductility curve: equivalent plastic strain versus stress triaxiality. The curve was determined by tests on notched tensile specimens of a low alloy rotor steel. The critical states corresponded to the initiation of a crack at the centre of the specimens. Three point bend tests were also performed and experimental and numerical load displacement curves and crack growth versus displacement curves were compared. Agreement with experiments on cracked specimens was obtained by simple fittings of the 'ductility' curve in the high triaxiality area. Results are discussed and it is indicated where future progress might be made in numerical modelling of cracked bodies. (author)

  20. A Simplified Micromechanical Modeling Approach to Predict the Tensile Flow Curve Behavior of Dual-Phase Steels

    Science.gov (United States)

    Nanda, Tarun; Kumar, B. Ravi; Singh, Vishal

    2017-11-01

    Micromechanical modeling is used to predict material's tensile flow curve behavior based on microstructural characteristics. This research develops a simplified micromechanical modeling approach for predicting flow curve behavior of dual-phase steels. The existing literature reports on two broad approaches for determining tensile flow curve of these steels. The modeling approach developed in this work attempts to overcome specific limitations of the existing two approaches. This approach combines dislocation-based strain-hardening method with rule of mixtures. In the first step of modeling, `dislocation-based strain-hardening method' was employed to predict tensile behavior of individual phases of ferrite and martensite. In the second step, the individual flow curves were combined using `rule of mixtures,' to obtain the composite dual-phase flow behavior. To check accuracy of proposed model, four distinct dual-phase microstructures comprising of different ferrite grain size, martensite fraction, and carbon content in martensite were processed by annealing experiments. The true stress-strain curves for various microstructures were predicted with the newly developed micromechanical model. The results of micromechanical model matched closely with those of actual tensile tests. Thus, this micromechanical modeling approach can be used to predict and optimize the tensile flow behavior of dual-phase steels.

  1. Exploring the link between environmental pollution and economic growth in EU-28 countries: Is there an environmental Kuznets curve?

    Directory of Open Access Journals (Sweden)

    Daniel Armeanu

    Full Text Available This study examines the Environmental Kuznets Curve hypothesis (EKC, considering the primary energy consumption among other country-specific variables, for a panel of the EU-28 countries during the period 1990-2014. By estimating pooled OLS regressions with Driscoll-Kraay standard errors in order to account for cross-sectional dependence, the results confirm the EKC hypothesis in the case of emissions of sulfur oxides and emissions of non-methane volatile organic compounds. In addition to pooled estimations, the output of fixed-effects regressions with Driscoll-Kraay standard errors support the EKC hypothesis for greenhouse gas emissions, greenhouse gas emissions intensity of energy consumption, emissions of nitrogen oxides, emissions of non-methane volatile organic compounds and emissions of ammonia. Additionally, the empirical findings from panel vector error correction model reveal a short-run unidirectional causality from GDP per capita growth to greenhouse gas emissions, as well as a bidirectional causal link between primary energy consumption and greenhouse gas emissions. Furthermore, since there occurred no causal link between economic growth and primary energy consumption, the neo-classical view was confirmed, namely the neutrality hypothesis.

  2. Exploring the link between environmental pollution and economic growth in EU-28 countries: Is there an environmental Kuznets curve?

    Science.gov (United States)

    Armeanu, Daniel; Vintilă, Georgeta; Gherghina, Ştefan Cristian; Drăgoi, Mihaela Cristina; Teodor, Cristian

    2018-01-01

    This study examines the Environmental Kuznets Curve hypothesis (EKC), considering the primary energy consumption among other country-specific variables, for a panel of the EU-28 countries during the period 1990–2014. By estimating pooled OLS regressions with Driscoll-Kraay standard errors in order to account for cross-sectional dependence, the results confirm the EKC hypothesis in the case of emissions of sulfur oxides and emissions of non-methane volatile organic compounds. In addition to pooled estimations, the output of fixed-effects regressions with Driscoll-Kraay standard errors support the EKC hypothesis for greenhouse gas emissions, greenhouse gas emissions intensity of energy consumption, emissions of nitrogen oxides, emissions of non-methane volatile organic compounds and emissions of ammonia. Additionally, the empirical findings from panel vector error correction model reveal a short-run unidirectional causality from GDP per capita growth to greenhouse gas emissions, as well as a bidirectional causal link between primary energy consumption and greenhouse gas emissions. Furthermore, since there occurred no causal link between economic growth and primary energy consumption, the neo-classical view was confirmed, namely the neutrality hypothesis. PMID:29742169

  3. Damage assessment of low-cycle fatigue by crack growth prediction. Development of growth prediction model and its application

    International Nuclear Information System (INIS)

    Kamaya, Masayuki; Kawakubo, Masahiro

    2012-01-01

    In this study, the fatigue damage was assumed to be equivalent to the crack initiation and its growth, and fatigue life was assessed by predicting the crack growth. First, a low-cycle fatigue test was conducted in air at room temperature under constant cyclic strain range of 1.2%. The crack initiation and change in crack size during the test were examined by replica investigation. It was found that a crack of 41.2 μm length was initiated almost at the beginning of the test. The identified crack growth rate was shown to correlate well with the strain intensity factor, whose physical meaning was discussed in this study. The fatigue life prediction model (equation) under constant strain range was derived by integrating the crack growth equation defined using the strain intensity factor, and the predicted fatigue lives were almost identical to those obtained by low-cycle fatigue tests. The change in crack depth predicted by the equation also agreed well with the experimental results. Based on the crack growth prediction model, it was shown that the crack size would be less than 0.1 mm even when the estimated fatigue damage exceeded the critical value of the design fatigue curve, in which a twenty-fold safety margin was used for the assessment. It was revealed that the effect of component size and surface roughness, which have been investigated empirically by fatigue tests, could be reasonably explained by considering the crack initiation and growth. Furthermore, the environmental effect on the fatigue life was shown to be brought about by the acceleration of crack growth. (author)

  4. Theory of the development of curved barbs and their effects on feather morphology.

    Science.gov (United States)

    Feo, Teresa J; Simon, Emma; Prum, Richard O

    2016-08-01

    Feathers exhibit an extraordinary diversity of shapes, which are used by birds to accomplish a diverse set of functions. Pennaceous feathers have a double branched morphology that develops from a tube of epidermis, and variation in branch geometry determines feather shape. Feather development is both complex (i.e., a simple developmental modification can have multiple effects on mature feather shape), and redundant (i.e., different developmental modifications can create the same shape). Due to this, it is not readily apparent how different feather shapes develop. In many feathers, barbs are not straight, but instead curve in toward, or away, from the feather tip. Barb curvature can affect the shape of mature feathers but the development of curved barbs is unknown. Previous research has hypothesized that barb curvature could develop either during the helical growth of barb ridges in the tubular feather germ, or during barb angle expansion as the feather unfurls from the sheath. To better understand the development of curved barbs and their effects on mature feathers we present a theoretical model of curved barb development and test the model with empirical investigations of feathers. We find that curved barbs affect many aspects of feather morphology including vane width, barb length, and barb spacing. In real feathers, curved barbs can develop both during helical barb ridge growth and during barb angle expansion, with most of the observed curvature due to barb angle expansion. Our results demonstrate that barb angle expansion as a feather unfurls from the sheath is a complex and dynamic process that plays an important role in determining the shape and structure of mature feathers. Curved barbs create heterogeneity in barb geometry within the feather vane, which could have important implications for aerodynamic function and the development of within feather pigmentation patterns. J. Morphol. 277:995-1013, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley

  5. Fixing the Phillips curve: The case of downward nominal wage rigidity in the US

    OpenAIRE

    Reitz, Stefan; Slopek, Ulf D.

    2012-01-01

    Whereas microeconomic studies point to pronounced downward rigidity of nominal wages in the US economy, the standard Phillips curve neglects such a feature. Using a stochastic frontier model we find macroeconomic evidence of a strictly nonnegative error in an otherwise standard Phillips curve in post-war data on the US nonfinancial corporate sector. This error depends on growth in the profit ratio, output, and trend productivity, which should all determine the flexibility of wage adjustments....

  6. Patient-specific Distraction Regimen to Avoid Growth-rod Failure.

    Science.gov (United States)

    Agarwal, Aakash; Jayaswal, Arvind; Goel, Vijay K; Agarwal, Anand K

    2018-02-15

    A finite element study to establish the relationship between patient's curve flexibility (determined using curve correction under gravity) in juvenile idiopathic scoliosis and the required distraction frequency to avoid growth rod fracture, as a function of time. To perform a parametric analysis using a juvenile scoliotic spine model (single mid-thoracic curve with the apex at the eighth thoracic vertebra) and establish the relationship between curve flexibility (determined using curve correction under gravity) and the distraction interval that allows a higher factor of safety for the growth rods. Previous studies have shown that frequent distraction with smaller magnitude of distractions are less likely to result in rod failure. However there has not been any methodology or a chart provided to apply this knowledge on to the individual patients that undergo the treatment. This study aims to fill in that gap. The parametric study was performed by varying the material properties of the disc, hence altering the axial stiffness of the scoliotic spine model. The stresses on the rod were found to increase with increased axial stiffness of the spine, and this resulted in the increase of required optimal frequency to achieve a factor of safety of two for growth rods. A relationship between the percentage correction in Cobb's angle due to gravity alone, and the required distraction interval for limiting the maximum von Mises stress to 255 MPa on the growth rods was established. The distraction interval required to limit the stresses to the selected nominal value reduces with increase in stiffness of the spine. Furthermore, the appropriate distraction interval reduces for each model as the spine becomes stiffer with time (autofusion). This points to the fact the optimal distraction frequency is a time-dependent variable that must be achieved to keep the maximum von Mises stress under the specified factor of safety. The current study demonstrates the possibility of

  7. A Pilot Study Verifying How the Curve Information Impacts on the Driver Performance with Cognition Model

    Directory of Open Access Journals (Sweden)

    Xiaohua Zhao

    2013-01-01

    Full Text Available Drivers' misjudgment is a significant issue for the curve safety. It is considered as a more influential factor than other traffic environmental conditions for inducing risk. The research suggested that the cognition theory could explain the process of drivers’ behavior at curves. In this simulator experiment, a principle cognition model was built to examine the rationality of this explanation. The core of this pilot study was using one of the driving decision strategies for braking at curves to verify the accuracy of the cognition model fundamentally. Therefore, the experiment designed three treatments of information providing modes. The result of the experiment presented that the warning information about curves in advance can move the position of first braking away from curves. This phenomenon is consistent with the model’s inference. Thus, the conclusion of this study indicates that the process of the drivers' behavior at curves can be explained by the cognition theory and represented by cognition model. In addition, the model’s characteristics and working parameters can be acquired by doing other research. Then based on the model it can afford the advice for giving the appropriate warning information that may avoid the driver’s mistake.

  8. Time-dependent crack growth and fracture in concrete

    International Nuclear Information System (INIS)

    Zhou Fan Ping.

    1992-02-01

    The objectives of this thesis are to study time-dependent fracture behaviour in concrete. The thesis consists of an experimental study, costitutive modelling and numerical analysis. The experimental study was undertaken to investigate the influences of time on material properties for the fracture process zone and on crack growth and fracture in plain concrete structures. The experiments include tensile relaxation tests, bending tests on notched beams to determine fracture energy at varying deflection rates, and sustained bending and compact tensile tests. From the tensile relaxation tests, the envelope of the σ-w relation does not seem to be influenced by holding periods, though some local detrimental effect does occur. Fracture energy seems to decrease as rates become slower. In the sustained loading tests, deformation (deflection or CMOD) growth curves display three stages, as usually observed in a creep rupture test. The secondary stage dominates the whole failure lifetime, and the secondary deformation rate appears to have good correlation with the failure lifetime. A crack model for time-dependent fracture is proposed, by applying the idea of the Fictitious Crack Model. In this model, a modified Maxwell model is introduced for the fracture process zone incorporated with the static σ-w curve as a failure criterion, based on the observation of the tensile relaxation tests. The time-dependent σ-w curve is expressed in an incremental law. The proposed model has been implemented in a finite element program and applied to simulating sustained flexural and compact tensile tests. Numerical analysis includes simulations of crack growth, load-CMOD curves, stress-failure lifetime curves, size effects on failure life etc. The numerical results indicate that the model seems to be able to properly predict the main features of time-dependent fracture behaviour in concrete, as compared with the experimental results. 97 refs

  9. Triplet ultrasound growth parameters.

    Science.gov (United States)

    Vora, Neeta L; Ruthazer, Robin; House, Michael; Chelmow, David

    2006-03-01

    To create ultrasound growth curves for normal growth of fetal triplets using statistical methodology that properly accounts for similarities of growth of fetuses within a mother as well as repeated measurements over time for each fetus. In this longitudinal study, all triplet pregnancies managed at a single tertiary center from 1992-2004 were reviewed. Fetuses with major anomalies, prior selective reduction, or fetal demise were excluded. Data from early and late gestation in which there were fewer than 30 fetal measurements available for analysis were excluded. We used multilevel models to account for variation in growth within a single fetus over time, variations in growth between multiple fetuses within a single mother, and variations in fetal growth between mothers. Medians (50th), 10th, and 90th percentiles were estimated by the creation of multiple quadratic growth models from bootstrap samples adapting a previously published method to compute prediction intervals. Estimated fetal weight was derived from Hadlock's formula. One hundred fifty triplet pregnancies were identified. Twenty-seven pregnancies were excluded for the following reasons: missing records (23), fetal demise (3), and fetal anomaly (1). The study group consisted of 123 pregnancies. The gestational age range was restricted to 14-34 weeks. Figures and tables were developed showing medians, 10th and 90th percentiles for estimated fetal weight, femur length, biparietal diameter, abdominal circumference, and head circumference. Growth curves for triplet pregnancies were derived. These may be useful for identification of abnormal growth in triplet fetuses. III.

  10. R-curve behaviour of ferroelectric ceramics

    International Nuclear Information System (INIS)

    Egorov, N.Ya.; Kramarov, S.O.

    2004-01-01

    The attempt's made to identify and evaluate the regularities of developing the fractures in the ferroelectric ceramics and also-study the effect of the polishing operation on the strength characteristics of the piezoceramics. The R-curve behaviour in the ferroelectric ceramics is studied on the samples of the barium titanate and lead zirconate-titanate by the four-point bending with controlled surface fractures. It is established that increasing curve of resistance to the fracture growth is observed in the piezoceramics under the conditions of the fracture stable growth. The results obtained on the polished samples prove that the mechanical processing introduces the compression surface stresses into the piezoceramic materials [ru

  11. Effects of growth curve plasticity on size-structured population dynamics

    DEFF Research Database (Denmark)

    Zhang, Lai; Lin, Zhigui; Pedersen, Michael

    2011-01-01

    The physiological-structured population models assume that a fixed fraction of energy intake is utilized for individual growth and maintenance while the remaining for adult fertility. The assumption results in two concerns: energy loss for juveniles and a reproduction dilemma for adults. The dile...

  12. MICA: Multiple interval-based curve alignment

    Science.gov (United States)

    Mann, Martin; Kahle, Hans-Peter; Beck, Matthias; Bender, Bela Johannes; Spiecker, Heinrich; Backofen, Rolf

    2018-01-01

    MICA enables the automatic synchronization of discrete data curves. To this end, characteristic points of the curves' shapes are identified. These landmarks are used within a heuristic curve registration approach to align profile pairs by mapping similar characteristics onto each other. In combination with a progressive alignment scheme, this enables the computation of multiple curve alignments. Multiple curve alignments are needed to derive meaningful representative consensus data of measured time or data series. MICA was already successfully applied to generate representative profiles of tree growth data based on intra-annual wood density profiles or cell formation data. The MICA package provides a command-line and graphical user interface. The R interface enables the direct embedding of multiple curve alignment computation into larger analyses pipelines. Source code, binaries and documentation are freely available at https://github.com/BackofenLab/MICA

  13. Exploring Alternative Characteristic Curve Approaches to Linking Parameter Estimates from the Generalized Partial Credit Model.

    Science.gov (United States)

    Roberts, James S.; Bao, Han; Huang, Chun-Wei; Gagne, Phill

    Characteristic curve approaches for linking parameters from the generalized partial credit model were examined for cases in which common (anchor) items are calibrated separately in two groups. Three of these approaches are simple extensions of the test characteristic curve (TCC), item characteristic curve (ICC), and operating characteristic curve…

  14. The Language Growth of Spanish-Speaking English Language Learners

    Science.gov (United States)

    Rojas, Raul; Iglesias, Aquiles

    2013-01-01

    Although the research literature regarding language growth trajectories is burgeoning, the shape and direction of English Language Learners' (ELLs) language growth trajectories are largely not known. This study used growth curve modeling to determine the shape of ELLs' language growth trajectories across 12,248 oral narrative language samples…

  15. Longitudinal associations between sleep and anxiety during pregnancy, and the moderating effect of resilience, using parallel process latent growth curve models.

    Science.gov (United States)

    van der Zwan, Judith Esi; de Vente, Wieke; Tolvanen, Mimmi; Karlsson, Hasse; Buil, J Marieke; Koot, Hans M; Paavonen, E Juulia; Polo-Kantola, Päivi; Huizink, Anja C; Karlsson, Linnea

    2017-12-01

    For many women, pregnancy-related sleep disturbances and pregnancy-related anxiety change as pregnancy progresses and both are associated with lower maternal quality of life and less favorable birth outcomes. Thus, the interplay between these two problems across pregnancy is of interest. In addition, psychological resilience may explain individual differences in this association, as it may promote coping with both sleep disturbances and anxiety, and thereby reduce their mutual effects. Therefore, the aim of the current study was to examine whether sleep quality and sleep duration, and changes in sleep are associated with the level of and changes in anxiety during pregnancy. Furthermore, the study tested the moderating effect of resilience on these associations. At gestational weeks 14, 24, and 34, 532 pregnant women from the FinnBrain Birth Cohort Study in Finland filled out questionnaires on general sleep quality, sleep duration and pregnancy-related anxiety; resilience was assessed in week 14. Parallel process latent growth curve models showed that shorter initial sleep duration predicted a higher initial level of anxiety, and a higher initial anxiety level predicted a faster shortening of sleep duration. Changes in sleep duration and changes in anxiety over the course of pregnancy were not related. The predicted moderating effect of resilience was not found. The results suggested that pregnant women reporting anxiety problems should also be screened for sleeping problems, and vice versa, because women who experienced one of these pregnancy-related problems were also at risk of experiencing or developing the other problem. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Classical model of the Dirac electron in curved space

    International Nuclear Information System (INIS)

    Barut, A.O.; Pavsic, M.

    1987-01-01

    The action for the classical model of the electron exhibiting Zitterbewegung is generalized to curved space by introducing a spin connection. The dynamical equations and the symplectic structure are given for several different choices of the variables. In particular, we obtain the equation of motion for spin and compare it with the Papapetrou equation. (author)

  17. Lévy-based growth models

    DEFF Research Database (Denmark)

    Jónsdóttir, Kristjana Ýr; Schmiegel, Jürgen; Jensen, Eva Bjørn Vedel

    2008-01-01

    In the present paper, we give a condensed review, for the nonspecialist reader, of a new modelling framework for spatio-temporal processes, based on Lévy theory. We show the potential of the approach in stochastic geometry and spatial statistics by studying Lévy-based growth modelling of planar o...... objects. The growth models considered are spatio-temporal stochastic processes on the circle. As a by product, flexible new models for space–time covariance functions on the circle are provided. An application of the Lévy-based growth models to tumour growth is discussed....

  18. Precipitation extremes on multiple timescales - Bartlett-Lewis rectangular pulse model and intensity-duration-frequency curves

    Science.gov (United States)

    Ritschel, Christoph; Ulbrich, Uwe; Névir, Peter; Rust, Henning W.

    2017-12-01

    For several hydrological modelling tasks, precipitation time series with a high (i.e. sub-daily) resolution are indispensable. The data are, however, not always available, and thus model simulations are used to compensate. A canonical class of stochastic models for sub-daily precipitation are Poisson cluster processes, with the original Bartlett-Lewis (OBL) model as a prominent representative. The OBL model has been shown to well reproduce certain characteristics found in observations. Our focus is on intensity-duration-frequency (IDF) relationships, which are of particular interest in risk assessment. Based on a high-resolution precipitation time series (5 min) from Berlin-Dahlem, OBL model parameters are estimated and IDF curves are obtained on the one hand directly from the observations and on the other hand from OBL model simulations. Comparing the resulting IDF curves suggests that the OBL model is able to reproduce the main features of IDF statistics across several durations but cannot capture rare events (here an event with a return period larger than 1000 years on the hourly timescale). In this paper, IDF curves are estimated based on a parametric model for the duration dependence of the scale parameter in the generalized extreme value distribution; this allows us to obtain a consistent set of curves over all durations. We use the OBL model to investigate the validity of this approach based on simulated long time series.

  19. The Simple Analytics of the Environmental Kuznets Curve

    OpenAIRE

    James Andreoni; Arik Levinson

    1998-01-01

    Evidence suggests that some pollutants follow an inverse-U-shaped pattern relative to countries' incomes. This relationship has been called the out a simple and straight-forward static model of the microfoundations of the pollution-income relationship. We show that the environmental Kuznets curve can be derived directly from the technological link between consumption of a desired good and abatement of its undesirable byproduct. The inverse-U shape does not depend on the dynamics of growth, po...

  20. Analyzing Multiple-Choice Questions by Model Analysis and Item Response Curves

    Science.gov (United States)

    Wattanakasiwich, P.; Ananta, S.

    2010-07-01

    In physics education research, the main goal is to improve physics teaching so that most students understand physics conceptually and be able to apply concepts in solving problems. Therefore many multiple-choice instruments were developed to probe students' conceptual understanding in various topics. Two techniques including model analysis and item response curves were used to analyze students' responses from Force and Motion Conceptual Evaluation (FMCE). For this study FMCE data from more than 1000 students at Chiang Mai University were collected over the past three years. With model analysis, we can obtain students' alternative knowledge and the probabilities for students to use such knowledge in a range of equivalent contexts. The model analysis consists of two algorithms—concentration factor and model estimation. This paper only presents results from using the model estimation algorithm to obtain a model plot. The plot helps to identify a class model state whether it is in the misconception region or not. Item response curve (IRC) derived from item response theory is a plot between percentages of students selecting a particular choice versus their total score. Pros and cons of both techniques are compared and discussed.

  1. A new model describing the curves for repair of both DNA double-strand breaks and chromosome damage

    International Nuclear Information System (INIS)

    Foray, N.; Badie, C.; Alsbeih, G.; Malaise, E.P.; Fertil, B.

    1996-01-01

    A review of reports dealing with fittings of the data for repair of DNA double-strand breaks (DSBs) and excess chromosome fragments (ECFs) shows that several models are used to fit the repair curves. Since DSBs and ECFs are correleated, it is worth developing a model describing both phenomena. The curve-fitting models used most extensively, the two repair half-times model for DSBs and the monoexponential plus residual model for ECFs, appear to be too inflexible to describe the repair curves for both DSBs and ECFs. We have therefore developed a new concept based on a variable repair half-time. According to this concept, the repair curve is continuously bending and dependent on time and probably reflects a continuous spectrum of damage repairability. The fits of the curves for DSB repair to the variable repair half-time and the variable repair half-time plus residual models were compared to those obtained with the two half-times plus residual and two half-times models. Similarly, the fits of the curves for ECF repair to the variable repair half-time and variable half-time plus residual models were compared to that obtained with the monoexponential plus residual model. The quality of fit and the dependence of adjustable parameters on the portion of the curve fitted were used as comparison criteria. We found that: (a) It is useful to postulate the existence of a residual term for unrepairable lesions, regardless of the model adopted. (b) With the two cell lines tested (a normal and a hypersensitive one), data for both DSBs and ECTs are best fitted to the variable repair half-time plus residual model, whatever the repair time range. 47 refs., 3 figs., 3 tabs

  2. Multi-binding site model-based curve-fitting program for the computation of RIA data

    International Nuclear Information System (INIS)

    Malan, P.G.; Ekins, R.P.; Cox, M.G.; Long, E.M.R.

    1977-01-01

    In this paper, a comparison will be made of model-based and empirical curve-fitting procedures. The implementation of a multiple binding-site curve-fitting model which will successfully fit a wide range of assay data, and which can be run on a mini-computer is described. The latter sophisticated model also provides estimates of binding site concentrations and the values of the respective equilibrium constants present: the latter have been used for refining assay conditions using computer optimisation techniques. (orig./AJ) [de

  3. A Parallel Process Growth Model of Avoidant Personality Disorder Symptoms and Personality Traits

    Science.gov (United States)

    Wright, Aidan G. C.; Pincus, Aaron L.; Lenzenweger, Mark F.

    2012-01-01

    Background Avoidant personality disorder (AVPD), like other personality disorders, has historically been construed as a highly stable disorder. However, results from a number of longitudinal studies have found that the symptoms of AVPD demonstrate marked change over time. Little is known about which other psychological systems are related to this change. Although cross-sectional research suggests a strong relationship between AVPD and personality traits, no work has examined the relationship of their change trajectories. The current study sought to establish the longitudinal relationship between AVPD and basic personality traits using parallel process growth curve modeling. Methods Parallel process growth curve modeling was applied to the trajectories of AVPD and basic personality traits from the Longitudinal Study of Personality Disorders (Lenzenweger, 2006), a naturalistic, prospective, multiwave, longitudinal study of personality disorder, temperament, and normal personality. The focus of these analyses is on the relationship between the rates of change in both AVPD symptoms and basic personality traits. Results AVPD symptom trajectories demonstrated significant negative relationships with the trajectories of interpersonal dominance and affiliation, and a significant positive relationship to rates of change in neuroticism. Conclusions These results provide some of the first compelling evidence that trajectories of change in PD symptoms and personality traits are linked. These results have important implications for the ways in which temporal stability is conceptualized in AVPD specifically, and PD in general. PMID:22506627

  4. A comparative study of post-irradiation growth kinetics of spheroids and monolayers

    International Nuclear Information System (INIS)

    Dertinger, J.; Luecke-Huhle, C.

    1975-01-01

    Post-irradiation growth kinetics of γ-irradiated spheroid and monolayer cells in exponential growth phase was investigated by means of dose-response curves based on cell counts after specified time intervals following irradiation. A mathematical model of cell-growth after irradiation was fitted to these curves. The model parameters (related to division delay and growth of non-surviving cells) obtained from this analysis consistently indicated increasing resistance to sub-lethal damage of cells cultured as multicellular spheroids under conditions of increasing three-dimensional contact. In contrast, no indication of an increased radiation-resistance was found with cells cultured on a substratum under a variety of conditions. (author)

  5. Extension of the master sintering curve for constant heating rate modeling

    Science.gov (United States)

    McCoy, Tammy Michelle

    The purpose of this work is to extend the functionality of the Master Sintering Curve (MSC) such that it can be used as a practical tool for predicting sintering schemes that combine both a constant heating rate and an isothermal hold. Rather than just being able to predict a final density for the object of interest, the extension to the MSC will actually be able to model a sintering run from start to finish. Because the Johnson model does not incorporate this capability, the work presented is an extension of what has already been shown in literature to be a valuable resource in many sintering situations. A predicted sintering curve that incorporates a combination of constant heating rate and an isothermal hold is more indicative of what is found in real-life sintering operations. This research offers the possibility of predicting the sintering schedule for a material, thereby having advanced information about the extent of sintering, the time schedule for sintering, and the sintering temperature with a high degree of accuracy and repeatability. The research conducted in this thesis focuses on the development of a working model for predicting the sintering schedules of several stabilized zirconia powders having the compositions YSZ (HSY8), 10Sc1CeSZ, 10Sc1YSZ, and 11ScSZ1A. The compositions of the four powders are first verified using x-ray diffraction (XRD) and the particle size and surface area are verified using a particle size analyzer and BET analysis, respectively. The sintering studies were conducted on powder compacts using a double pushrod dilatometer. Density measurements are obtained both geometrically and using the Archimedes method. Each of the four powders is pressed into ¼" diameter pellets using a manual press with no additives, such as a binder or lubricant. Using a double push-rod dilatometer, shrinkage data for the pellets is obtained over several different heating rates. The shrinkage data is then converted to reflect the change in relative

  6. Power forward curves: a managerial perspective

    International Nuclear Information System (INIS)

    Nagarajan, Shankar

    1999-01-01

    This chapter concentrates on managerial application of power forward curves, and examines the determinants of electricity prices such as transmission constraints, its inability to be stored in a conventional way, its seasonality and weather dependence, the generation stack, and the swing risk. The electricity forward curve, classical arbitrage, constructing a forward curve, volatilities, and electricity forward curve models such as the jump-diffusion model, the mean-reverting heteroscedastic volatility model, and an econometric model of forward prices are examined. A managerial perspective of the applications of the forward curve is presented covering plant valuation, capital budgeting, performance measurement, product pricing and structuring, asset optimisation, valuation of transmission options, and risk management

  7. Model for Spiral Galaxys Rotation Curves

    Science.gov (United States)

    Hodge, John

    2003-11-01

    A model of spiral galaxy dynamics is proposed. An expression describing the rotation velocity of particles v in a galaxy as a function of the distance from the center r (RC) is developed. The resulting, intrinsic RC of a galaxy is Keplerian in the inner bulge and rising in the disk region without modifying the Newtonian gravitational potential (MOND) and without unknown dark matter. The v^2 is linearly related to r of the galaxy in part of the rapidly rising region of the HI RC (RRRC) and to r^2 in another part of the RRRC. The r to discontinuities in the surface brightness versus r curve is related to the 21 cm line width, the measured mass of the central supermassive black hole (SBH), and the maximum v^2 in the RRRC. The distance to spiral galaxies can be calculated from these relationships that tightly correlates with the distance calculated using Cepheid variables. Differing results in measuring the mass of the SBH from differing measurement procedures are explained. This model is consistent with previously unexplained data, has predicted new relationships, and suggests a new model of the universe. Full text: http://web.infoave.net/ ˜scjh.

  8. Revisiting the environmental Kuznets curve hypothesis in a tourism development context.

    Science.gov (United States)

    de Vita, Glauco; Katircioglu, Salih; Altinay, Levent; Fethi, Sami; Mercan, Mehmet

    2015-11-01

    This study investigates empirically an extended version of the Environmental Kuznets Curve model that controls for tourism development. We find that international tourist arrivals into Turkey alongside income, squared income and energy consumption, cointegrate with CO2 emissions. Tourist arrivals, growth, and energy consumption exert a positive and significant impact on CO2 emissions in the long-run. Our results provide empirical support to EKC hypothesis showing that at exponential levels of growth, CO2 emissions decline. The findings suggest that despite the environmental degradation stemming from tourism development, policies aimed at environmental protection should not be pursued at the expense of tourism-led growth.

  9. Modelling of acid-base titration curves of mineral assemblages

    Directory of Open Access Journals (Sweden)

    Stamberg Karel

    2016-01-01

    Full Text Available The modelling of acid-base titration curves of mineral assemblages was studied with respect to basic parameters of their surface sites to be obtained. The known modelling approaches, component additivity (CA and generalized composite (GC, and three types of different assemblages (fucoidic sandstones, sedimentary rock-clay and bentonite-magnetite samples were used. In contrary to GC-approach, application of which was without difficulties, the problem of CA-one consisted in the credibility and accessibility of the parameters characterizing the individual mineralogical components.

  10. Spiral blood flows in an idealized 180-degree curved artery model

    Science.gov (United States)

    Bulusu, Kartik V.; Kulkarni, Varun; Plesniak, Michael W.

    2017-11-01

    Understanding of cardiovascular flows has been greatly advanced by the Magnetic Resonance Velocimetry (MRV) technique and its potential for three-dimensional velocity encoding in regions of anatomic interest. The MRV experiments were performed on a 180-degree curved artery model using a Newtonian blood analog fluid at the Richard M. Lucas Center at Stanford University employing a 3 Tesla General Electric (Discovery 750 MRI system) whole body scanner with an eight-channel cardiac coil. Analysis in two regions of the model-artery was performed for flow with Womersley number=4.2. In the entrance region (or straight-inlet pipe) the unsteady pressure drop per unit length, in-plane vorticity and wall shear stress for the pulsatile, carotid artery-based flow rate waveform were calculated. Along the 180-degree curved pipe (curvature ratio =1/7) the near-wall vorticity and the stretching of the particle paths in the vorticity field are visualized. The resultant flow behavior in the idealized curved artery model is associated with parameters such as Dean number and Womersley number. Additionally, using length scales corresponding to the axial and secondary flow we attempt to understand the mechanisms leading to the formation of various structures observed during the pulsatile flow cycle. Supported by GW Center for Biomimetics and Bioinspired Engineering (COBRE), MRV measurements in collaboration with Prof. John K. Eaton and, Dr. Chris Elkins at Stanford University.

  11. Towards Sustainable Growth Business Models

    Energy Technology Data Exchange (ETDEWEB)

    Kamp-Roelands, N.; Balkenende, J.P.; Van Ommen, P.

    2012-03-15

    The Dutch Sustainable Growth Coalition (DSGC) has the following objectives: The DSGC aims to pro-actively drive sustainable growth business models along three lines: (1) Shape. DSGC member companies aim to connect economic profitability with environmental and social progress on the basis of integrated sustainable growth business models; (2) Share. DSGC member companies aim for joint advocacy of sustainable growth business models both internationally and nationally; and (3) Stimulate. DSGC member companies aim to stimulate and influence the policy debate on enabling sustainable growth - with a view to finding solutions to the environmental and social challenges we are facing. This is their first report. The vision, actions and mission of DSGC are documented in the Manifesto in Chapter 2 of this publication. Chapter 3 contains an overview of key features of an integrated sustainable growth business model and the roadmap towards such a model. In Chapter 4, project examples of DSGC members are presented, providing insight into the hands-on reality of implementing the good practices. Chapter 5 offers an overview of how the Netherlands provides an enabling environment for sustainable growth business models. Chapter 6 offers the key conclusions.

  12. Hierarchical Models for Type Ia Supernova Light Curves in the Optical and Near Infrared

    Science.gov (United States)

    Mandel, Kaisey; Narayan, G.; Kirshner, R. P.

    2011-01-01

    I have constructed a comprehensive statistical model for Type Ia supernova optical and near infrared light curves. Since the near infrared light curves are excellent standard candles and are less sensitive to dust extinction and reddening, the combination of near infrared and optical data better constrains the host galaxy extinction and improves the precision of distance predictions to SN Ia. A hierarchical probabilistic model coherently accounts for multiple random and uncertain effects, including photometric error, intrinsic supernova light curve variations and correlations across phase and wavelength, dust extinction and reddening, peculiar velocity dispersion and distances. An improved BayeSN MCMC code is implemented for computing probabilistic inferences for individual supernovae and the SN Ia and host galaxy dust populations. I use this hierarchical model to analyze nearby Type Ia supernovae with optical and near infared data from the PAIRITEL, CfA3, and CSP samples and the literature. Using cross-validation to test the robustness of the model predictions, I find that the rms Hubble diagram scatter of predicted distance moduli is 0.11 mag for SN with optical and near infrared data versus 0.15 mag for SN with only optical data. Accounting for the dispersion expected from random peculiar velocities, the rms intrinsic prediction error is 0.08-0.10 mag for SN with both optical and near infrared light curves. I discuss results for the inferred intrinsic correlation structures of the optical-NIR SN Ia light curves and the host galaxy dust distribution captured by the hierarchical model. The continued observation and analysis of Type Ia SN in the optical and near infrared is important for improving their utility as precise and accurate cosmological distance indicators.

  13. Light Curve Simulation Using Spacecraft CAD Models and Empirical Material Spectral BRDFS

    Science.gov (United States)

    Willison, A.; Bedard, D.

    This paper presents a Matlab-based light curve simulation software package that uses computer-aided design (CAD) models of spacecraft and the spectral bidirectional reflectance distribution function (sBRDF) of their homogenous surface materials. It represents the overall optical reflectance of objects as a sBRDF, a spectrometric quantity, obtainable during an optical ground truth experiment. The broadband bidirectional reflectance distribution function (BRDF), the basis of a broadband light curve, is produced by integrating the sBRDF over the optical wavelength range. Colour-filtered BRDFs, the basis of colour-filtered light curves, are produced by first multiplying the sBRDF by colour filters, and integrating the products. The software package's validity is established through comparison of simulated reflectance spectra and broadband light curves with those measured of the CanX-1 Engineering Model (EM) nanosatellite, collected during an optical ground truth experiment. It is currently being extended to simulate light curves of spacecraft in Earth orbit, using spacecraft Two-Line-Element (TLE) sets, yaw/pitch/roll angles, and observer coordinates. Measured light curves of the NEOSSat spacecraft will be used to validate simulated quantities. The sBRDF was chosen to represent material reflectance as it is spectrometric and a function of illumination and observation geometry. Homogeneous material sBRDFs were obtained using a goniospectrometer for a range of illumination and observation geometries, collected in a controlled environment. The materials analyzed include aluminum alloy, two types of triple-junction photovoltaic (TJPV) cell, white paint, and multi-layer insulation (MLI). Interpolation and extrapolation methods were used to determine the sBRDF for all possible illumination and observation geometries not measured in the laboratory, resulting in empirical look-up tables. These look-up tables are referenced when calculating the overall sBRDF of objects, where

  14. Water security, risk and economic growth: lessons from a dynamical systems model

    Science.gov (United States)

    Dadson, Simon; Hall, Jim; Garrick, Dustin; Sadoff, Claudia; Grey, David; Whittington, Dale

    2016-04-01

    Investments in the physical infrastructure, human capital, and institutions needed for water resources management have been a noteworthy feature in the development of most civilisations. These investments affect the economy in two distinct ways: (i) by improving the factor productivity of water in multiple sectors of the economy, especially those that are water intensive such as agriculture and energy; and (ii) by reducing the acute and chronic harmful effects of water-related hazards like floods, droughts, and water-related diseases. The need for capital investment to mitigate these risks in order to promote economic growth is widely acknowledged, but prior work to conceptualise the relationship between water-related risks and economic growth has focused on the productive and harmful roles of water in the economy independently. Here the two influences are combined using a simple, dynamical model of water-related investment, risk, and growth at the national level. The model suggests the existence of a context-specific threshold above which growth proceeds along an 'S'-curve. In many cases there is a requirement for initial investment in water-related assets to enable growth. Below the threshold it is possible for a poverty trap to arise. The presence and location of the poverty trap is context-specific and depends on the relative exposure of productive water-related assets to risk, compared with risks faced by assets in the wider economy. Exogenous changes in the level of water-related risk (through, for example, climate and land cover change) can potentially push an economy away from a growth path towards a poverty trap. These results illustrate the value of accounting for environmental risk in models of economic growth and may offer guidance in the design of robust policies for investment in water-related productive assets to manage risk, particularly in the face of global and regional environmental change.

  15. Economic growth and pollutant emissions in Tunisia. An empirical analysis of the environmental Kuznets curve

    Energy Technology Data Exchange (ETDEWEB)

    Fodha, Mouez [Paris School of Economics and CES, University Paris 1 Pantheon-Sorbonne, Maison des Sciences Economiques, 106-112 Bd de l' Hopital, 75647 Paris (France); Zaghdoud, Oussama [CES, University Paris 1 Pantheon-Sorbonne and Department of Economics, High School of Economic and Commercial Sciences of Tunis, 4 Rue Abou Zakaria El Hafsi, 1089 Montfleury (Tunisia)

    2010-02-15

    This paper investigates the relationship between economic growth and pollutant emissions for a small and open developing country, Tunisia, during the period 1961-2004. The investigation is made on the basis of the environmental Kuznets curve hypothesis, using time series data and cointegration analysis. Carbon dioxide (CO{sub 2}) and sulfur dioxide (SO{sub 2}) are used as the environmental indicators, and GDP as the economic indicator. Our results show that there is a long-run cointegrating relationship between the per capita emissions of two pollutants and the per capita GDP. An inverted U relationship between SO{sub 2} emissions and GDP has been found, with income turning point approximately equals to 1200 (constant 2000 prices) or to 3700 (in PPP, constant 2000 prices). However, a monotonically increasing relationship with GDP is found more appropriate for CO{sub 2} emissions. Furthermore, the causality results show that the relationship between income and pollution in Tunisia is one of unidirectional causality with income causing environmental changes and not vice versa, both in the short-run and long-run. This implies that an emission reduction policies and more investment in pollution abatement expense will not hurt economic growth. It could be a feasible policy tool for Tunisia to achieve its sustainable growth in the long-run. (author)

  16. Economic growth and pollutant emissions in Tunisia: An empirical analysis of the environmental Kuznets curve

    Energy Technology Data Exchange (ETDEWEB)

    Fodha, Mouez, E-mail: fodha@univ-paris1.f [Paris School of Economics and CES, University Paris 1 Pantheon-Sorbonne, Maison des Sciences Economiques, 106-112 Bd de l' Hopital, 75647 Paris (France); Zaghdoud, Oussama [CES, University Paris 1 Pantheon-Sorbonne and Department of Economics, High School of Economic and Commercial Sciences of Tunis, 4 Rue Abou Zakaria El Hafsi, 1089 Montfleury (Tunisia)

    2010-02-15

    This paper investigates the relationship between economic growth and pollutant emissions for a small and open developing country, Tunisia, during the period 1961-2004. The investigation is made on the basis of the environmental Kuznets curve hypothesis, using time series data and cointegration analysis. Carbon dioxide (CO{sub 2}) and sulfur dioxide (SO{sub 2}) are used as the environmental indicators, and GDP as the economic indicator. Our results show that there is a long-run cointegrating relationship between the per capita emissions of two pollutants and the per capita GDP. An inverted U relationship between SO{sub 2} emissions and GDP has been found, with income turning point approximately equals to $1200 (constant 2000 prices) or to $3700 (in PPP, constant 2000 prices). However, a monotonically increasing relationship with GDP is found more appropriate for CO{sub 2} emissions. Furthermore, the causality results show that the relationship between income and pollution in Tunisia is one of unidirectional causality with income causing environmental changes and not vice versa, both in the short-run and long-run. This implies that an emission reduction policies and more investment in pollution abatement expense will not hurt economic growth. It could be a feasible policy tool for Tunisia to achieve its sustainable growth in the long-run.

  17. Economic growth and pollutant emissions in Tunisia: An empirical analysis of the environmental Kuznets curve

    International Nuclear Information System (INIS)

    Fodha, Mouez; Zaghdoud, Oussama

    2010-01-01

    This paper investigates the relationship between economic growth and pollutant emissions for a small and open developing country, Tunisia, during the period 1961-2004. The investigation is made on the basis of the environmental Kuznets curve hypothesis, using time series data and cointegration analysis. Carbon dioxide (CO 2 ) and sulfur dioxide (SO 2 ) are used as the environmental indicators, and GDP as the economic indicator. Our results show that there is a long-run cointegrating relationship between the per capita emissions of two pollutants and the per capita GDP. An inverted U relationship between SO 2 emissions and GDP has been found, with income turning point approximately equals to $1200 (constant 2000 prices) or to $3700 (in PPP, constant 2000 prices). However, a monotonically increasing relationship with GDP is found more appropriate for CO 2 emissions. Furthermore, the causality results show that the relationship between income and pollution in Tunisia is one of unidirectional causality with income causing environmental changes and not vice versa, both in the short-run and long-run. This implies that an emission reduction policies and more investment in pollution abatement expense will not hurt economic growth. It could be a feasible policy tool for Tunisia to achieve its sustainable growth in the long-run.

  18. Comparison between two scalar field models using rotation curves of spiral galaxies

    Science.gov (United States)

    Fernández-Hernández, Lizbeth M.; Rodríguez-Meza, Mario A.; Matos, Tonatiuh

    2018-04-01

    Scalar fields have been used as candidates for dark matter in the universe, from axions with masses ∼ 10-5eV until ultra-light scalar fields with masses ∼ Axions behave as cold dark matter while the ultra-light scalar fields galaxies are Bose-Einstein condensate drops. The ultra-light scalar fields are also called scalar field dark matter model. In this work we study rotation curves for low surface brightness spiral galaxies using two scalar field models: the Gross-Pitaevskii Bose-Einstein condensate in the Thomas-Fermi approximation and a scalar field solution of the Klein-Gordon equation. We also used the zero disk approximation galaxy model where photometric data is not considered, only the scalar field dark matter model contribution to rotation curve is taken into account. From the best-fitting analysis of the galaxy catalog we use, we found the range of values of the fitting parameters: the length scale and the central density. The worst fitting results (values of χ red2 much greater than 1, on the average) were for the Thomas-Fermi models, i.e., the scalar field dark matter is better than the Thomas- Fermi approximation model to fit the rotation curves of the analysed galaxies. To complete our analysis we compute from the fitting parameters the mass of the scalar field models and two astrophysical quantities of interest, the dynamical dark matter mass within 300 pc and the characteristic central surface density of the dark matter models. We found that the value of the central mass within 300 pc is in agreement with previous reported results, that this mass is ≈ 107 M ⊙/pc2, independent of the dark matter model. And, on the contrary, the value of the characteristic central surface density do depend on the dark matter model.

  19. Bayesian Model on Fatigue Crack Growth Rate of Type 304 Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sanhae; Yoon, Jae Young; Hwang, Il Soon [Nuclear Materials Laboratory, Seoul National University, Seoul (Korea, Republic of)

    2015-10-15

    The fatigue crack growth rate curve is typically estimated by deterministic methods in accordance with the ASME Boiler and Pressure Vessel Code Sec. XI. The reliability of nuclear materials must also consider the environmental effect. This can be overcome by probabilistic methods that estimate the degradation of materials. In this study, fatigue tests were carried out on Type 304 stainless steel (STS 304) to obtain a fatigue crack growth rate curve and Paris' law constants. Tests were conducted on a constant load and a constant delta K, respectively. The unknown constants of Paris' law were updated probabilistically by Bayesian inference and the method can be used for the probabilistic structural integrity assessment of other nuclear materials. In this paper, Paris' law constants including C and m for Type 304 stainless steel were determined by probabilistic approach with Bayesian Inference. The Bayesian update process is limited in accuracy, because this method should assume initial data distribution. If we select an appropriate distribution, this updating method is powerful enough to get data results considering the environment and materials. Until now, remaining lives of NPPs are estimated by deterministic methods using a priori model to finally assess structural integrity. Bayesian approach can utilize in-service inspection data derived from aged properties.

  20. Bayesian Model on Fatigue Crack Growth Rate of Type 304 Stainless Steel

    International Nuclear Information System (INIS)

    Choi, Sanhae; Yoon, Jae Young; Hwang, Il Soon

    2015-01-01

    The fatigue crack growth rate curve is typically estimated by deterministic methods in accordance with the ASME Boiler and Pressure Vessel Code Sec. XI. The reliability of nuclear materials must also consider the environmental effect. This can be overcome by probabilistic methods that estimate the degradation of materials. In this study, fatigue tests were carried out on Type 304 stainless steel (STS 304) to obtain a fatigue crack growth rate curve and Paris' law constants. Tests were conducted on a constant load and a constant delta K, respectively. The unknown constants of Paris' law were updated probabilistically by Bayesian inference and the method can be used for the probabilistic structural integrity assessment of other nuclear materials. In this paper, Paris' law constants including C and m for Type 304 stainless steel were determined by probabilistic approach with Bayesian Inference. The Bayesian update process is limited in accuracy, because this method should assume initial data distribution. If we select an appropriate distribution, this updating method is powerful enough to get data results considering the environment and materials. Until now, remaining lives of NPPs are estimated by deterministic methods using a priori model to finally assess structural integrity. Bayesian approach can utilize in-service inspection data derived from aged properties

  1. An analysis on the environmental Kuznets curve of Chengdu

    Science.gov (United States)

    Gao, Zijian; Peng, Yue; Zhao, Yue

    2017-12-01

    In this paper based on the environmental and economic data of Chengdu from 2005 to 2014, the measurement models were established to analyze 3 kinds of environmental flow indicators and 4 kinds of environmental stock indicators to obtain their EKC evolution trajectories and characters. The results show that the relationship curve between the discharge of SO2 from industry and the GDP per capita is a positive U shape, just as the curve between discharge of COD from industry and the GDP per person. The relationship curve between the dust discharge from industry and the GDP per capita is an inverted N shape. In the central of the urban the relationship curve between the concentration of SO2 in the air and the GDP per person is a positive U shape. The relationship curves between the concentration of NO2 in the air and the GDP per person, between the concentration of the particulate matters and the GDP per person, and between the concentration of the fallen dusts and the GDP per person are fluctuating. So the EKC curves of the 7 kinds of environmental indicators are not accord with inverted U shape feature. In the development of this urban the environmental problems can’t be resolved only by economic growth. The discharge of industrial pollutants should be controlled to improve the atmospheric environmental quality and reduce the environmental risks.

  2. Predicting the costs of photovoltaic solar modules in 2020 using experience curve models

    International Nuclear Information System (INIS)

    La Tour, Arnaud de; Glachant, Matthieu; Ménière, Yann

    2013-01-01

    Except in few locations, photovoltaic generated electricity remains considerably more expensive than conventional sources. It is however expected that innovation and learning-by-doing will lead to drastic cuts in production cost in the near future. The goal of this paper is to predict the cost of PV modules out to 2020 using experience curve models, and to draw implications about the cost of PV electricity. Using annual data on photovoltaic module prices, cumulative production, R and D knowledge stock and input prices for silicon and silver over the period 1990–2011, we identify a experience curve model which minimizes the difference between predicted and actual module prices. This model predicts a 67% decrease of module price from 2011 to 2020. This rate implies that the cost of PV generated electricity will reach that of conventional electricity by 2020 in the sunniest countries with annual solar irradiation of 2000 kWh/year or more, such as California, Italy, and Spain. - Highlights: • We predict the cost of PV modules out to 2020 using experience curve models. • The model predicts a 67% decrease of module price from 2011 to 2020. • We draw implications about the cost of PV electricity

  3. Growth modeling of Cryptomeria japonica by partial trunk analysis

    Directory of Open Access Journals (Sweden)

    Vinícius Morais Coutinho

    2017-06-01

    Full Text Available This study aimed to evaluate the growth pattern of Cryptomeria japonica increment (L. F. D. Don. and to describe the probability distribution in stands stablished at the municipality of Rio Negro, Paraná State. Twenty trees were sampled in a 34 years-old stand, with 3 m x 2 m spacing. Wood disks were taken from each tree at 1.3 m above the ground (DBH to perform partial stem analysis. Diameter growth series without bark were used to generate the average cumulative growth curves for DBH (cm, mean annual increment (MAI and current annual increment (CAI. From the increment data, the frequency distribution was evaluated by means of probability density functions (pdfs. The mean annual increment for DBH was 0.78 cm year-1 and the age of intersection of CAI and MAI curves was between the 7th and 8th years. It was found that near 43% of the species increments are concentrated bellow 0.5 cm. The results are useful to define appropriate management strategies for the species for sites similar to the studying regions, defining for example ages of silvicultural intervention, such as thinning.

  4. An integrated specification for the nexus of water pollution and economic growth in China: Panel cointegration, long-run causality and environmental Kuznets curve.

    Science.gov (United States)

    Zhang, Chen; Wang, Yuan; Song, Xiaowei; Kubota, Jumpei; He, Yanmin; Tojo, Junji; Zhu, Xiaodong

    2017-12-31

    This paper concentrates on a Chinese context and makes efforts to develop an integrated process to explicitly elucidate the relationship between economic growth and water pollution discharge-chemical oxygen demand (COD) discharge and ammonia nitrogen (NH 3 -N), using two unbalanced panel data sets covering the period separately from 1990 to 2014, and 2001 to 2014. In our present study, the panel unit root tests, cointegration tests, and Granger causality tests allowing for cross-sectional dependence, nonstationary, and heterogeneity are conducted to examine the causal effects of economic growth on COD/NH 3 -N discharge. Further, we simultaneously apply semi-parametric fixed effects estimation and parametric fixed effects estimation to investigate environmental Kuznets curve relationship for COD/NH 3 -N discharge. Our empirical results show a long-term bidirectional causality between economic growth and COD/NH 3 -N discharge in China. Within the Stochastic Impacts by Regression on Population, Affluence and Technology framework, we find evidence in support of an inverted U-shaped curved link between economic growth and COD/NH 3 -N discharge. To the best of our knowledge, there have not been any efforts made in investigating the nexus of economic growth and water pollution in such an integrated manner. Therefore, this study takes a fresh look on this topic. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Quantitative analysis by laser-induced breakdown spectroscopy based on generalized curves of growth

    Energy Technology Data Exchange (ETDEWEB)

    Aragón, C., E-mail: carlos.aragon@unavarra.es; Aguilera, J.A.

    2015-08-01

    A method for quantitative elemental analysis by laser-induced breakdown spectroscopy (LIBS) is proposed. The method (Cσ-LIBS) is based on Cσ graphs, generalized curves of growth which allow including several lines of various elements at different concentrations. A so-called homogeneous double (HD) model of the laser-induced plasma is used, defined by an integration over a single-region of the radiative transfer equation, combined with a separated treatment for neutral atoms (z = 0) and singly-charged ions (z = 1) in Cσ graphs and characteristic parameters. The procedure includes a criterion, based on a model limit, for eliminating data which, due to a high line intensity or concentration, are not well described by the HD model. An initial procedure provides a set of parameters (βA){sup z}, (ηNl){sup z}, T{sup z} and N{sub e}{sup z} (z = 0, 1) which characterize the plasma and the LIBS system. After characterization, two different analytical procedures, resulting in relative and absolute concentrations, may be applied. To test the method, fused glass samples prepared from certified slags and pure compounds are analyzed. We determine concentrations of Ca, Mn, Mg, V, Ti, Si and Al relative to Fe in three samples prepared from slags, and absolute concentrations of Fe, Ca and Mn in three samples prepared from Fe{sub 2}O{sub 3}, CaCO{sub 3} and Mn{sub 2}O{sub 3}. The accuracy obtained is 3.2% on the average for relative concentrations and 9.2% for absolute concentrations. - Highlights: • Method for quantitative analysis by LIBS, based on Csigma graphs • Conventional calibration is replaced with characterization of the LIBS system. • All elements are determined from measurement of one or two Csigma graphs. • The method is tested with fused glass disks prepared from slags and pure compounds. • Accurate results for relative (3.2%) and absolute concentrations (9.2%)

  6. Structural modeling of age specific fertility curves in Peninsular Malaysia: An approach of Lee Carter method

    Science.gov (United States)

    Hanafiah, Hazlenah; Jemain, Abdul Aziz

    2013-11-01

    In recent years, the study of fertility has been getting a lot of attention among research abroad following fear of deterioration of fertility led by the rapid economy development. Hence, this study examines the feasibility of developing fertility forecasts based on age structure. Lee Carter model (1992) is applied in this study as it is an established and widely used model in analysing demographic aspects. A singular value decomposition approach is incorporated with an ARIMA model to estimate age specific fertility rates in Peninsular Malaysia over the period 1958-2007. Residual plots is used to measure the goodness of fit of the model. Fertility index forecast using random walk drift is then utilised to predict the future age specific fertility. Results indicate that the proposed model provides a relatively good and reasonable data fitting. In addition, there is an apparent and continuous decline in age specific fertility curves in the next 10 years, particularly among mothers' in their early 20's and 40's. The study on the fertility is vital in order to maintain a balance between the population growth and the provision of facilities related resources.

  7. Economic Transformation in the Beijing-Tianjin-Hebei Region: Is It Undergoing the Environmental Kuznets Curve?

    Directory of Open Access Journals (Sweden)

    Lichun Xiong

    2017-05-01

    Full Text Available The Beijing-Tianjin-Hebei Region Integration Plan is one of the most important national strategies in China promoting regional economic development. The environmental problems in this region, however, especially air pollution and contaminated groundwater, have enormous influence on the people’s health while also causing economic loss. Therefore, this study aims to analyze the pattern of its environmental and economic development. Panel data in the period 2004–2014 are used to establish an advanced model of the Environmental Kuznets Curve. The results indicate that the economic growth and environmental pollution of Beijing-Tianjin-Hebei region do not completely meet the Environment Kuznets Curve assumptions. The discharge volume of industrial wastewater and economic growth reflect a wave-type relation. The sulfur dioxide discharge volume and economic growth reflect a U-shaped relation; the generated volume of industrial solid wastes and economic growth reflect a reversed N-shaped relation, which is in accordance with the Environmental Kuznets Curve characteristics at the second inflection point. The variables added value of the secondary industry, population size and raw coal consumption volume have a significant positive influence on the discharge of various environmental pollutants in Beijing-Tianjin-Hebei region. The analysis provides policy recommendations for the government to develop regional economic and environmental protection policies.

  8. Stress evolution during growth of InAs on GaAs measured by an in-situ cantilever beam setup

    Energy Technology Data Exchange (ETDEWEB)

    Hu Dongzhi

    2007-02-13

    The influence of stress on the growth of InAs on GaAs(001) by molecular beam epitaxy (MBE) is investigated in this thesis. Film force curves were measured for InAs deposition under As-rich as well as In-rich growth conditions. The growth under As-rich conditions proceeds in the Stranski- Krastanov growth mode, meaning that quantum dots are formed after the initial growth of a wetting layer. During subsequent growth interruptions or intentional annealing at the growth temperature, the quantum dots undergo ripening. This growth mode of InAs films and the subsequent annealing behavior were studied in detail in this thesis. To understand the influence of strain on the growth mechanisms, the film force curves were analyzed and correlated to the morphological evolution of the InAs films during deposition and especially during annealing. Models were developed to fit and explain the relaxation of the film force measured during the annealing of InAs quantum dots. At temperatures lower than 470 C, quantum dots undergo standard Ostwald ripening. Different mechanisms, such as kinetic and diffusion limited, determine the ripening process. Fits of models based on these mechanisms to the film force relaxation curves, show, that although the relaxation curve for annealing at 440 C can be fitted reasonably well with all the models, the model describing ripening limited by the diffusion along dot boundaries yields a slightly better fit. The relaxation curves obtained at 455 C and 470 C can be fitted very well only with the model in which the ripening is controlled by the attachment/detachment of atoms on the dot surface. Annealing of quantum dots at temperatures higher than 500 C shows a very different behavior. Atomic force microscopy images reveal that the quantum dots ripen first and then dissolve after 450 s-600 s annealing. (orig.)

  9. Stress evolution during growth of InAs on GaAs measured by an in-situ cantilever beam setup

    International Nuclear Information System (INIS)

    Hu Dongzhi

    2007-01-01

    The influence of stress on the growth of InAs on GaAs(001) by molecular beam epitaxy (MBE) is investigated in this thesis. Film force curves were measured for InAs deposition under As-rich as well as In-rich growth conditions. The growth under As-rich conditions proceeds in the Stranski- Krastanov growth mode, meaning that quantum dots are formed after the initial growth of a wetting layer. During subsequent growth interruptions or intentional annealing at the growth temperature, the quantum dots undergo ripening. This growth mode of InAs films and the subsequent annealing behavior were studied in detail in this thesis. To understand the influence of strain on the growth mechanisms, the film force curves were analyzed and correlated to the morphological evolution of the InAs films during deposition and especially during annealing. Models were developed to fit and explain the relaxation of the film force measured during the annealing of InAs quantum dots. At temperatures lower than 470 C, quantum dots undergo standard Ostwald ripening. Different mechanisms, such as kinetic and diffusion limited, determine the ripening process. Fits of models based on these mechanisms to the film force relaxation curves, show, that although the relaxation curve for annealing at 440 C can be fitted reasonably well with all the models, the model describing ripening limited by the diffusion along dot boundaries yields a slightly better fit. The relaxation curves obtained at 455 C and 470 C can be fitted very well only with the model in which the ripening is controlled by the attachment/detachment of atoms on the dot surface. Annealing of quantum dots at temperatures higher than 500 C shows a very different behavior. Atomic force microscopy images reveal that the quantum dots ripen first and then dissolve after 450 s-600 s annealing. (orig.)

  10. Computer-aided design of curved surfaces with automatic model generation

    Science.gov (United States)

    Staley, S. M.; Jerard, R. B.; White, P. R.

    1980-01-01

    The design and visualization of three-dimensional objects with curved surfaces have always been difficult. The paper given below describes a computer system which facilitates both the design and visualization of such surfaces. The system enhances the design of these surfaces by virtue of various interactive techniques coupled with the application of B-Spline theory. Visualization is facilitated by including a specially built model-making machine which produces three-dimensional foam models. Thus, the system permits the designer to produce an inexpensive model of the object which is suitable for evaluation and presentation.

  11. Maximum likelihood fitting of FROC curves under an initial-detection-and-candidate-analysis model

    International Nuclear Information System (INIS)

    Edwards, Darrin C.; Kupinski, Matthew A.; Metz, Charles E.; Nishikawa, Robert M.

    2002-01-01

    We have developed a model for FROC curve fitting that relates the observer's FROC performance not to the ROC performance that would be obtained if the observer's responses were scored on a per image basis, but rather to a hypothesized ROC performance that the observer would obtain in the task of classifying a set of 'candidate detections' as positive or negative. We adopt the assumptions of the Bunch FROC model, namely that the observer's detections are all mutually independent, as well as assumptions qualitatively similar to, but different in nature from, those made by Chakraborty in his AFROC scoring methodology. Under the assumptions of our model, we show that the observer's FROC performance is a linearly scaled version of the candidate analysis ROC curve, where the scaling factors are just given by the FROC operating point coordinates for detecting initial candidates. Further, we show that the likelihood function of the model parameters given observational data takes on a simple form, and we develop a maximum likelihood method for fitting a FROC curve to this data. FROC and AFROC curves are produced for computer vision observer datasets and compared with the results of the AFROC scoring method. Although developed primarily with computer vision schemes in mind, we hope that the methodology presented here will prove worthy of further study in other applications as well

  12. The feedback control research on straight and curved road with car-following model

    Science.gov (United States)

    Zheng, Yi-Ming; Cheng, Rong-Jun; Ge, Hong-Xia

    2017-07-01

    Taking account of the road consisting of curved part and straight part, an extended car-following model is proposed in this paper. A control signal including the velocity difference between the considered vehicle and the vehicle in front is taken into account. The control theory method is applied into analysis of the stability condition for the model. Numerical simulations are implemented to prove that the stability of the traffic flow strengthens effectively with an increase of the radius of curved road, and the control signal can suppress the traffic congestion. The results are in good agree with the theoretical analysis.

  13. A theory of economic growth with material/energy resources and dematerialization. Interaction of three growth mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Ayres, Robert U. [Department of Physical Resource Theory, Chalmers Institute, Gothenburg (Sweden); Van den Bergh, Jeroen C.J.M. [Department of Spatial Economics, Faculty of Economics and Business Administration, and Institute for Environmental Studies, Free University, De Boelelaan 1105, Amsterdam 1081 HV (Netherlands)

    2005-10-05

    The nature of energy and material resources in a non-optimizing growth theory framework is clarified. This involves two modifications of the conventional theory. Firstly, multiple feedback mechanisms or 'growth engines' are identified, such that the impact of the cost of production through demand on growth is accounted for. Secondly, a production function distinguishes between resource use, technical efficiency, and value creation. The resulting model is analytically solved under the condition of a constant growth rate. Given model complexity, numerical experiments are performed as well, providing relevant insights to the academic and political debates on 'environmental Kuznets curves' and 'dematerialization.'.

  14. Modeling growth of three bakery product spoilage molds as a function of water activity, temperature and pH.

    Science.gov (United States)

    Dagnas, Stéphane; Onno, Bernard; Membré, Jeanne-Marie

    2014-09-01

    The objective of this study was to quantify the effect of water activity, pH and storage temperature on the growth of Eurotium repens, Aspergillus niger and Penicillium corylophilum, isolated from spoiled bakery products. Moreover, the behaviors of these three mold species were compared to assess whether a general modeling framework may be set and re-used in future research on bakery spoilage molds. The mold growth was modeled by building two distinct Gamma-type secondary models: one on the lag time for growth and another one on the radial growth rate. A set of 428 experimental growth curves was generated. The effect of temperature (15-35 °C), water activity (0.80-0.98) and pH (3-7) was assessed. Results showed that it was not possible to apply the same set of secondary model equations to the three mold species given that the growth rate varied significantly with the factors pH and water activity. In contrast, the temperature effect on both growth rate and lag time of the three mold species was described by the same equation. The equation structure and model parameter values of the Gamma models were also compared per mold species to assess whether a relationship between lag time and growth rate existed. There was no correlation between the two growth responses for E. repens, but a slight one for A. niger and P. corylophilum. These findings will help in determining bakery product shelf-life and guiding future work in the predictive mycology field. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. THE LATITUDINAL COMPENSATION HYPOTHESIS: GROWTH DATA AND A MODEL OF LATITUDINAL GROWTH DIFFERENTIATION BASED UPON ENERGY BUDGETS. I. INTERSPECIFIC COMPARISON OF OPHRYOTROCHA (POLYCHAETA: DORVILLEIDAE).

    Science.gov (United States)

    Levinton, Jeffrey S

    1983-12-01

    A northern (North Carolina) sibling species of Ophryotrocha grew more rapidly than a southern sibling species (Florida); this presumed advantage, however, diminished to zero as temperature increased from 15 to 30°C. Survival of the northern sibling species was low at 30°C. The differential response probably had a genetic basis since both species had been reared for 2-3 generations under the same conditions. The effect lasted in laboratory populations reared for a year in the laboratory at 25°C (ca. 10 generations). My results are consistent with a graphical model that suggests an evolutionary shift of metabolism-temperature curves and feeding efficiency curves for the two sibling species. These shifts predict a changing advantage of growth of one species relative to the other as temperature increases.

  16. MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

    Directory of Open Access Journals (Sweden)

    Grzegorz SZALA

    2014-03-01

    Full Text Available In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF, high cycle fatigue (HCF, fatigue limit (FL and giga cycle fatigue (GCF appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys.

  17. A New Model of Stopping Sight Distance of Curve Braking Based on Vehicle Dynamics

    Directory of Open Access Journals (Sweden)

    Rong-xia Xia

    2016-01-01

    Full Text Available Compared with straight-line braking, cornering brake has longer braking distance and poorer stability. Therefore, drivers are more prone to making mistakes. The braking process and the dynamics of vehicles in emergency situations on curves were analyzed. A biaxial four-wheel vehicle was simplified to a single model. Considering the braking process, dynamics, force distribution, and stability, a stopping sight distance of the curve braking calculation model was built. Then a driver-vehicle-road simulation platform was built using multibody dynamic software. The vehicle test of brake-in-turn was realized in this platform. The comparison of experimental and calculated values verified the reliability of the computational model. Eventually, the experimental values and calculated values were compared with the stopping sight distance recommended by the Highway Route Design Specification (JTGD20-2006; the current specification of stopping sight distance does not apply to cornering brake sight distance requirements. In this paper, the general values and limits of the curve stopping sight distance are presented.

  18. Establishment of Uropygial Gland Growth Curves for White, Three-Way Crossed Mule Ducklings

    Directory of Open Access Journals (Sweden)

    YH Chen

    2015-06-01

    Full Text Available Growth curves for the uropygial gland (UG of white, 3-way crossed mule ducklings were established using the Gompertz function. In total, 144 ducklings were fed in 12 floor pens with 12 birds in each pen. Each pen contained an equal number of animals of each sex. Feed and water were supplied ad libitumthroughout the entire experimental period. The weekly change in UG weight was recorded in males and females from hatch to 8 weeks of age. The weight and length of the UG, the width of the lobus glandulae uropygialis, the length and width of the pluma of the circulus uropygialis, and the index of the papilla uropygialis were measured once a week in individual ducklings in one pen. The average UG weight gain observed in white, 3-way crossed drakes was significantly higher than that of ducks of 21-56 days of age (P< 0.05. The UG length was 1.64-2.23 times the width of the left or right lobe, and the development of the UG was delayed from 3-4 weeks of age. The morphology of the UG changed from elliptical to elongated-elliptical with age. The right and left lobus glandulae uropygialis were symmetrical. The Gompertz growth functions of the UG in drakes and ducks were W=5.49e-e-0.675(t-1.955 and W=4.76e-e-0.685(t-1.936, respectively, where t represents age in weeks. These equations indicated that the maximum growth rate for drakes occurred at 14.1 days of age and for ducks at 13.6 days of age.

  19. SPIDERMAN: an open-source code to model phase curves and secondary eclipses

    Science.gov (United States)

    Louden, Tom; Kreidberg, Laura

    2018-03-01

    We present SPIDERMAN (Secondary eclipse and Phase curve Integrator for 2D tempERature MAppiNg), a fast code for calculating exoplanet phase curves and secondary eclipses with arbitrary surface brightness distributions in two dimensions. Using a geometrical algorithm, the code solves exactly the area of sections of the disc of the planet that are occulted by the star. The code is written in C with a user-friendly Python interface, and is optimised to run quickly, with no loss in numerical precision. Approximately 1000 models can be generated per second in typical use, making Markov Chain Monte Carlo analyses practicable. The modular nature of the code allows easy comparison of the effect of multiple different brightness distributions for the dataset. As a test case we apply the code to archival data on the phase curve of WASP-43b using a physically motivated analytical model for the two dimensional brightness map. The model provides a good fit to the data; however, it overpredicts the temperature of the nightside. We speculate that this could be due to the presence of clouds on the nightside of the planet, or additional reflected light from the dayside. When testing a simple cloud model we find that the best fitting model has a geometric albedo of 0.32 ± 0.02 and does not require a hot nightside. We also test for variation of the map parameters as a function of wavelength and find no statistically significant correlations. SPIDERMAN is available for download at https://github.com/tomlouden/spiderman.

  20. SPIDERMAN: an open-source code to model phase curves and secondary eclipses

    Science.gov (United States)

    Louden, Tom; Kreidberg, Laura

    2018-06-01

    We present SPIDERMAN (Secondary eclipse and Phase curve Integrator for 2D tempERature MAppiNg), a fast code for calculating exoplanet phase curves and secondary eclipses with arbitrary surface brightness distributions in two dimensions. Using a geometrical algorithm, the code solves exactly the area of sections of the disc of the planet that are occulted by the star. The code is written in C with a user-friendly Python interface, and is optimized to run quickly, with no loss in numerical precision. Approximately 1000 models can be generated per second in typical use, making Markov Chain Monte Carlo analyses practicable. The modular nature of the code allows easy comparison of the effect of multiple different brightness distributions for the data set. As a test case, we apply the code to archival data on the phase curve of WASP-43b using a physically motivated analytical model for the two-dimensional brightness map. The model provides a good fit to the data; however, it overpredicts the temperature of the nightside. We speculate that this could be due to the presence of clouds on the nightside of the planet, or additional reflected light from the dayside. When testing a simple cloud model, we find that the best-fitting model has a geometric albedo of 0.32 ± 0.02 and does not require a hot nightside. We also test for variation of the map parameters as a function of wavelength and find no statistically significant correlations. SPIDERMAN is available for download at https://github.com/tomlouden/spiderman.

  1. Dependence on supernovae light-curve processing in void models

    Energy Technology Data Exchange (ETDEWEB)

    Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); De Rossi, Maria E., E-mail: derossi@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2014-06-02

    In this work, we show that when supernova Ia (SN Ia) data sets are used to put constraints on the free parameters of inhomogeneous models, certain extra information regarding the light-curve fitter used in the supernovae Ia luminosity fluxes processing should be taken into account. We found that the size of the void as well as other parameters of these models might be suffering extra degenerations or additional systematic errors due to the fitter. A recent proposal to relieve the tension between the results from Planck satellite and SNe Ia is re-analyzed in the framework of these subjects.

  2. Gender and Facebook motives as predictors of specific types of Facebook use: A latent growth curve analysis in adolescence.

    Science.gov (United States)

    Frison, Eline; Eggermont, Steven

    2016-10-01

    Despite increasing evidence that specific types of Facebook use (i.e., active private, active public, and passive Facebook use) are differently related to adolescents' well-being, little is known how these types function over the course of adolescence and whether gender and Facebook motives may predict the initial level and changes in these types over time. To address these gaps, Flemish adolescents (ages 12-19) were questioned at three different time points, with six months in between (NTime1 = 1866). Latent growth curve models revealed that active private Facebook use increased over the course of adolescence, whereas public Facebook use decreased. Passive Facebook use, however, remained stable. In addition, gender and Facebook motives were related to initial levels of specific types of Facebook use, and predictive of dynamic change in specific types of Facebook use over time. The discussion focuses on the understanding and implications of these findings. Copyright © 2016. Published by Elsevier Ltd.

  3. Application of different models to the lactation curves of unimproved ...

    African Journals Online (AJOL)

    The objective of this study was to investigate the use of four different mathematical functions (Wood, Inverse Polynomial, Quadratic and Cubic models) for describing the lactation curve of unimproved Awassi ewes. Data were collected from 136 ewes from the same flock raised on the State Farm of Gözlü in the Konya ...

  4. Can Low-Resolution Airborne Laser Scanning Data Be Used to Model Stream Rating Curves?

    Directory of Open Access Journals (Sweden)

    Steve W. Lyon

    2015-03-01

    Full Text Available This pilot study explores the potential of using low-resolution (0.2 points/m2 airborne laser scanning (ALS-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2 ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries. This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.

  5. Can low-resolution airborne laser scanning data be used to model stream rating curves?

    Science.gov (United States)

    Lyon, Steve; Nathanson, Marcus; Lam, Norris; Dahlke, Helen; Rutzinger, Martin; Kean, Jason W.; Laudon, Hjalmar

    2015-01-01

    This pilot study explores the potential of using low-resolution (0.2 points/m2) airborne laser scanning (ALS)-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2) ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries). This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.

  6. Curved-space classical solutions of a massive supermatrix model

    International Nuclear Information System (INIS)

    Azuma, Takehiro; Bagnoud, Maxime

    2003-01-01

    We investigate here a supermatrix model with a mass term and a cubic interaction. It is based on the super Lie algebra osp(1 vertical bar 32,R), which could play a role in the construction of the eleven-dimensional M-theory. This model contains a massive version of the IIB matrix model, where some fields have a tachyonic mass term. Therefore, the trivial vacuum of this theory is unstable. However, this model possesses several classical solutions where these fields build noncommutative curved spaces and these solutions are shown to be energetically more favorable than the trivial vacuum. In particular, we describe in details two cases, the SO(3)xSO(3)xSO(3) (three fuzzy 2-spheres) and the SO(9) (fuzzy 8-sphere) classical backgrounds

  7. A formulation of multidimensional growth models for the assessment and forecast of technology attributes

    Science.gov (United States)

    Danner, Travis W.

    modeling technique begins to diminish. With the introduction of multiple objectives, researchers often abandon technology growth models for scoring models and technology frontiers. While both approaches possess advantages over current growth models for the assessment of multi-objective technologies, each lacks a necessary dimension for comprehensive technology assessment. By collapsing multiple system metrics into a single, non-intuitive technology measure, scoring models provide a succinct framework for multi-objective technology assessment and forecasting. Yet, with no consideration of physical limits, scoring models provide no insight as to the feasibility of a particular combination of system capabilities. They only indicate that a given combination of system capabilities yields a particular score. Conversely, technology frontiers are constructed with the distinct objective of providing insight into the feasibility of system capability combinations. Yet again, upper limits to overall system performance are ignored. Furthermore, the data required to forecast subsequent technology frontiers is often inhibitive. In an attempt to reincorporate the fundamental nature of technology advancement as bound by physical principles, researchers have sought to normalize multi-objective systems whereby the variability of a single system objective is eliminated as a result of changes in the remaining objectives. This drastically limits the applicability of the resulting technology model because it is only applicable for a single setting of all other system attributes. Attempts to maintain the interaction between the growth curves of each technical objective of a complex system have thus far been limited to qualitative and subjective consideration. This research proposes the formulation of multidimensional growth models as an approach to simulating the advancement of multi-objective technologies towards their upper limits. Multidimensional growth models were formulated by noticing and

  8. Modelling and assessment of urban flood hazards based on rainfall intensity-duration-frequency curves reformation

    OpenAIRE

    Ghazavi, Reza; Moafi Rabori, Ali; Ahadnejad Reveshty, Mohsen

    2016-01-01

    Estimate design storm based on rainfall intensity–duration–frequency (IDF) curves is an important parameter for hydrologic planning of urban areas. The main aim of this study was to estimate rainfall intensities of Zanjan city watershed based on overall relationship of rainfall IDF curves and appropriate model of hourly rainfall estimation (Sherman method, Ghahreman and Abkhezr method). Hydrologic and hydraulic impacts of rainfall IDF curves change in flood properties was evaluated via Stormw...

  9. Spatially varying dispersion to model breakthrough curves.

    Science.gov (United States)

    Li, Guangquan

    2011-01-01

    Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

  10. C-Curves for Lengthening of Widmanstätten and Bainitic Ferrite

    Science.gov (United States)

    Yin, Jiaqing; Leach, Lindsay; Hillert, Mats; Borgenstam, Annika

    2017-09-01

    Widmanstätten ferrite and bainitic ferrite are both acicular and their lengthening rate in binary Fe-C alloys and low-alloyed steels under isothermal conditions is studied by searching the literature and through new measurements. As a function of temperature, the lengthening rate can be represented by a common curve for both kinds of acicular ferrite in contrast to the separate C-curves often presented in time-temperature-transformation (TTT) diagrams. The curves for Fe-C alloys with low carbon content show no obvious decrease in rate at low temperatures down to 623 K (350 °C). For alloys with higher carbon content, the expected decrease of rate as a function of temperature below a nose was observed. An attempt to explain the absence of a nose for low carbon contents by an increasing deviation from local equilibrium at high growth rates is presented. This explanation is based on a simple kinetic model, which predicts that the growth rates for Fe-C alloys with less than 0.3 mass pct carbon are high enough at low temperatures to make the carbon pileup, in front of the advancing tip of a ferrite plate, shrink below atomic dimensions, starting at about 600 K (323 °C).

  11. Development of the curve of Spee.

    Science.gov (United States)

    Marshall, Steven D; Caspersen, Matthew; Hardinger, Rachel R; Franciscus, Robert G; Aquilino, Steven A; Southard, Thomas E

    2008-09-01

    Ferdinand Graf von Spee is credited with characterizing human occlusal curvature viewed in the sagittal plane. This naturally occurring phenomenon has clinical importance in orthodontics and restorative dentistry, yet we have little understanding of when, how, or why it develops. The purpose of this study was to expand our understanding by examining the development of the curve of Spee longitudinally in a sample of untreated subjects with normal occlusion from the deciduous dentition to adulthood. Records of 16 male and 17 female subjects from the Iowa Facial Growth Study were selected and examined. The depth of the curve of Spee was measured on their study models at 7 time points from ages 4 (deciduous dentition) to 26 (adult dentition) years. The Wilcoxon signed rank test was used to compare changes in the curve of Spee depth between time points. For each subject, the relative eruption of the mandibular teeth was measured from corresponding cephalometric radiographs, and its contribution to the developing curve of Spee was ascertained. In the deciduous dentition, the curve of Spee is minimal. At mean ages of 4.05 and 5.27 years, the average curve of Spee depths are 0.24 and 0.25 mm, respectively. With change to the transitional dentition, corresponding to the eruption of the mandibular permanent first molars and central incisors (mean age, 6.91 years), the curve of Spee depth increases significantly (P < 0.0001) to a mean maximum depth of 1.32 mm. The curve of Spee then remains essentially unchanged until eruption of the second molars (mean age, 12.38 years), when the depth increases (P < 0.0001) to a mean maximum depth of 2.17 mm. In the adolescent dentition (mean age, 16.21 years), the depth decreases slightly (P = 0.0009) to a mean maximum depth of 1.98 mm, and, in the adult dentition (mean age 26.98 years), the curve remains unchanged (P = 0.66), with a mean maximum depth of 2.02 mm. No significant differences in curve of Spee development were found between

  12. Longitudinal associations between body mass index, physical activity, and healthy dietary behaviors in adults: A parallel latent growth curve modeling approach.

    Directory of Open Access Journals (Sweden)

    Youngdeok Kim

    Full Text Available Physical activity (PA and healthy dietary behaviors (HDB are two well-documented lifestyle factors influencing body mass index (BMI. This study examined 7-year longitudinal associations between changes in PA, HDB, and BMI among adults using a parallel latent growth curve modeling (LGCM.We used prospective cohort data collected by a private company (SimplyWell LLC, Omaha, NE, USA implementing a workplace health screening program. Data from a total of 2,579 adults who provided valid BMI, PA, and HDB information for at least 5 out of 7 follow-up years from the time they entered the program were analyzed. PA and HDB were subjectively measured during an annual online health survey. Height and weight measured during an annual onsite health screening were used to calculate BMI (kg·m2. The parallel LGCMs stratified by gender and baseline weight status (normal: BMI30 were fitted to examine the longitudinal associations of changes in PA and HDB with change in BMI over years.On average, BMI gradually increased over years, at rates ranging from 0.06 to 0.20 kg·m2·year, with larger increases observed among those of normal baseline weight status across genders. The increases in PA and HDB were independently associated with a smaller increase in BMI for obese males (b = -1.70 and -1.98, respectively, and overweight females (b = -1.85 and -2.46, respectively and obese females (b = -2.78 and -3.08, respectively. However, no significant associations of baseline PA and HDB with changes in BMI were observed.Our study suggests that gradual increases in PA and HDB are independently associated with smaller increases in BMI in overweight and obese adults, but not in normal weight individuals. Further study is warranted to address factors that check increases in BMI in normal weight adults.

  13. Modelling lactation curve for milk fat to protein ratio in Iranian buffaloes (Bubalus bubalis) using non-linear mixed models.

    Science.gov (United States)

    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.

  14. Survival curves and cell restoration of gamma irradiated chlorella

    International Nuclear Information System (INIS)

    Gilet, Roland

    1970-01-01

    The characteristics of the living material used and the cultures developed are defined. The irradiation techniques and the dosimetry methods used are described. The clonal growth in a gelified nutrient solution was studied and the survival curves, which are very reproducible when anoxic conditions are eliminated, were established. It is shown that the radiosensitivity of Chlorella decreases with the age of the culture when the plateau of the growth curve is reached, and that for synchronous cells it varies slightly with the phase in the cycle at which the radiation is received. The restoration from sublethal damage occurs quickly and does not depend upon the continuation of the cell cycle when no multiplication occurs during the experiments and is not modified by anoxic conditions. The restoration rate is reduced at 0 deg. C. It explains the variations in the apparent radiosensitivity with the dose rate. In contrast with the results published for many cells, the restoration is incomplete. The problem of the elimination of sublethal damage during clonal development is posed. A model summarizing the experimental results and suggesting future work is given. (author) [fr

  15. Regional pressure volume curves by electrical impedance tomography in a model of acute lung injury

    NARCIS (Netherlands)

    Kunst, P. W.; Böhm, S. H.; Vazquez de Anda, G.; Amato, M. B.; Lachmann, B.; Postmus, P. E.; de Vries, P. M.

    2000-01-01

    OBJECTIVE: A new noninvasive method, electrical impedance tomography (EIT), was used to make pressure-impedance (PI) curves in a lung lavage model of acute lung injury in pigs. The lower inflection point (LIP) and the upper deflection point (UDP) were determined from these curves and from the

  16. Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

    Science.gov (United States)

    Griebeler, Eva Maria; Klein, Nicole; Sander, P Martin

    2013-01-01

    Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but

  17. Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

    Directory of Open Access Journals (Sweden)

    Eva Maria Griebeler

    Full Text Available Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp. and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti. Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM, all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average

  18. Method of construction spatial transition curve

    Directory of Open Access Journals (Sweden)

    S.V. Didanov

    2013-04-01

    Full Text Available Purpose. The movement of rail transport (speed rolling stock, traffic safety, etc. is largely dependent on the quality of the track. In this case, a special role is the transition curve, which ensures smooth insertion of the transition from linear to circular section of road. The article deals with modeling of spatial transition curve based on the parabolic distribution of the curvature and torsion. This is a continuation of research conducted by the authors regarding the spatial modeling of curved contours. Methodology. Construction of the spatial transition curve is numerical methods for solving nonlinear integral equations, where the initial data are taken coordinate the starting and ending points of the curve of the future, and the inclination of the tangent and the deviation of the curve from the tangent plane at these points. System solutions for the numerical method are the partial derivatives of the equations of the unknown parameters of the law of change of torsion and length of the transition curve. Findings. The parametric equations of the spatial transition curve are calculated by finding the unknown coefficients of the parabolic distribution of the curvature and torsion, as well as the spatial length of the transition curve. Originality. A method for constructing the spatial transition curve is devised, and based on this software geometric modeling spatial transition curves of railway track with specified deviations of the curve from the tangent plane. Practical value. The resulting curve can be applied in any sector of the economy, where it is necessary to ensure a smooth transition from linear to circular section of the curved space bypass. An example is the transition curve in the construction of the railway line, road, pipe, profile, flat section of the working blades of the turbine and compressor, the ship, plane, car, etc.

  19. Thermodynamic and mechanical properties of curved interfaces : a discussion of models

    NARCIS (Netherlands)

    Oversteegen, M.

    2000-01-01

    Although relatively much is known about the physics of curved interfaces, several models for these kind of systems seem conflicting or internally inconsistent. It is the aim of this thesis to derive a rigorous framework of thermodynamic and mechanical expressions and study their relation to

  20. The Ising model: from elliptic curves to modular forms and Calabi-Yau equations

    International Nuclear Information System (INIS)

    Bostan, A; Boukraa, S; Hassani, S; Zenine, N; Van Hoeij, M; Maillard, J-M; Weil, J-A

    2011-01-01

    We show that almost all the linear differential operators factors obtained in the analysis of the n-particle contributions of the susceptibility of the Ising model for n ≤ 6 are linear differential operators associated with elliptic curves. Beyond the simplest differential operators factors which are homomorphic to symmetric powers of the second order operator associated with the complete elliptic integral E, the second and third order differential operators Z 2 , F 2 , F 3 , L-tilde 3 can actually be interpreted as modular forms of the elliptic curve of the Ising model. A last order-4 globally nilpotent linear differential operator is not reducible to this elliptic curve, modular form scheme. This operator is shown to actually correspond to a natural generalization of this elliptic curve, modular form scheme, with the emergence of a Calabi-Yau equation, corresponding to a selected 4 F 3 hypergeometric function. This hypergeometric function can also be seen as a Hadamard product of the complete elliptic integral K, with a remarkably simple algebraic pull-back (square root extension), the corresponding Calabi-Yau fourth order differential operator having a symplectic differential Galois group SP(4,C). The mirror maps and higher order Schwarzian ODEs, associated with this Calabi-Yau ODE, present all the nice physical and mathematical ingredients we had with elliptic curves and modular forms, in particular an exact (isogenies) representation of the generators of the renormalization group, extending the modular group SL(2,Z) to a GL(2,Z) symmetry group.

  1. Some fundamental questions about R-curves

    International Nuclear Information System (INIS)

    Kolednik, O.

    1992-01-01

    With the help of two simple thought experiments it is demonstrated that there exist two physically different types of fracture toughness. The crack-growth toughness, which is identical to the Griffith crack growth resistance, R, is a measure of the non-reversible energy which is needed to produce an increment of new crack area. The size of R is reflected by the slopes of the R-curves commonly used. So an increasing J-Δa-curve does not mean that the crack-growth resistance increases. The fracture initiation toughness, J i , is a normalized total energy (related to the ligament area) which must be put into the specimen up to fracture initiation. Only for ideally brittle materials R and J i have equal sizes. For small-scale yielding a relationship exists between R and J i , ao a one-parameter description of fracture processes is applicable. For large-scale yielding R and J i are not strictly related and both parameters are necessary to describe the fracture process. (orig.) [de

  2. The Value of Hydrograph Partitioning Curves for Calibrating Hydrological Models in Glacierized Basins

    Science.gov (United States)

    He, Zhihua; Vorogushyn, Sergiy; Unger-Shayesteh, Katy; Gafurov, Abror; Kalashnikova, Olga; Omorova, Elvira; Merz, Bruno

    2018-03-01

    This study refines the method for calibrating a glacio-hydrological model based on Hydrograph Partitioning Curves (HPCs), and evaluates its value in comparison to multidata set optimization approaches which use glacier mass balance, satellite snow cover images, and discharge. The HPCs are extracted from the observed flow hydrograph using catchment precipitation and temperature gradients. They indicate the periods when the various runoff processes, such as glacier melt or snow melt, dominate the basin hydrograph. The annual cumulative curve of the difference between average daily temperature and melt threshold temperature over the basin, as well as the annual cumulative curve of average daily snowfall on the glacierized areas are used to identify the starting and end dates of snow and glacier ablation periods. Model parameters characterizing different runoff processes are calibrated on different HPCs in a stepwise and iterative way. Results show that the HPC-based method (1) delivers model-internal consistency comparably to the tri-data set calibration method; (2) improves the stability of calibrated parameter values across various calibration periods; and (3) estimates the contributions of runoff components similarly to the tri-data set calibration method. Our findings indicate the potential of the HPC-based approach as an alternative for hydrological model calibration in glacierized basins where other calibration data sets than discharge are often not available or very costly to obtain.

  3. Curvas de crescimento na produção animal Growth curves in animal production

    Directory of Open Access Journals (Sweden)

    Alfredo Ribeiro de Freitas

    2005-06-01

    Full Text Available Foram discutidas as propriedades de sete modelos não-lineares, considerando-se o ajuste de curvas de crescimento na produção animal. Os modelos utilizados: Brody, Richards, Von Bertalanffy e duas alternativas de Gompertz e de Logístico foram ajustados, pelo método de Gauss Newton por meio do procedimento NLIN do SAS, a dados peso-idade de oito espécies: camarão-d'água-doce, rã-pimenta, coelho, frango, ovino, caprino, suíno e bovino. Considerando-se os critérios como: convergência ou não, coeficiente de determinação e interpretabilidade biológica dos parâmetros, concluiu-se que: a o modelo Logístico y= A/(1 + e-ktm estimou o peso em todas as espécies animais, enquanto o de Von Bertalanffy apenas não foi adequado para camarão; b os dois modelos Gompertz foram adequados para camarão, rã, frango, suíno e bovino; c em cada espécie, pelo menos dois dos sete modelos mostraram-se adequados para estimar o crescimento corporal das espécies animais estudadas, pois os coeficientes de determinação foram superiores a 92,0%.The properties of seven nonlinear models were discussed concerning its applications in the fitting of growth curves in animal production. The models used: Brody, Richards, Von Bertalanffy and two alternatives of Gompertz and Logistic models, were fitted by Gauss Newton method to weight-age data from eight animal species: freshwater prawn Macrobrachium rosenbergi, pepper frog, rabbit, poultry, sheep, goat, swine and cattle. Considering results of the fitted models such as convergence or not, coefficient of determination and biological interpretation of parameters, it was concluded that: a the Logisticmethod y = A/(1 + e-ktm estimated body weight in all species, while the Von Bertalanffy model was not adequate only for freshwater prawn Macrobrachium rosenbergi; b both Gompertz models were adequate for freshwater prawn Macrobrachium rosenbergi, pepper frog, poultry, swine and cattle; c for each specie, at least two

  4. Otolith reading and multi-model inference for improved estimation of age and growth in the gilthead seabream Sparus aurata (L.)

    Science.gov (United States)

    Mercier, Lény; Panfili, Jacques; Paillon, Christelle; N'diaye, Awa; Mouillot, David; Darnaude, Audrey M.

    2011-05-01

    Accurate knowledge of fish age and growth is crucial for species conservation and management of exploited marine stocks. In exploited species, age estimation based on otolith reading is routinely used for building growth curves that are used to implement fishery management models. However, the universal fit of the von Bertalanffy growth function (VBGF) on data from commercial landings can lead to uncertainty in growth parameter inference, preventing accurate comparison of growth-based history traits between fish populations. In the present paper, we used a comprehensive annual sample of wild gilthead seabream ( Sparus aurata L.) in the Gulf of Lions (France, NW Mediterranean) to test a methodology improving growth modelling for exploited fish populations. After validating the timing for otolith annual increment formation for all life stages, a comprehensive set of growth models (including VBGF) were fitted to the obtained age-length data, used as a whole or sub-divided between group 0 individuals and those coming from commercial landings (ages 1-6). Comparisons in growth model accuracy based on Akaike Information Criterion allowed assessment of the best model for each dataset and, when no model correctly fitted the data, a multi-model inference (MMI) based on model averaging was carried out. The results provided evidence that growth parameters inferred with VBGF must be used with high caution. Hence, VBGF turned to be among the less accurate for growth prediction irrespective of the dataset and its fit to the whole population, the juvenile or the adult datasets provided different growth parameters. The best models for growth prediction were the Tanaka model, for group 0 juveniles, and the MMI, for the older fish, confirming that growth differs substantially between juveniles and adults. All asymptotic models failed to correctly describe the growth of adult S. aurata, probably because of the poor representation of old individuals in the dataset. Multi-model

  5. Gamma-ray pulsar physics: gap-model populations and light-curve analyses in the Fermi era

    International Nuclear Information System (INIS)

    Pierbattista, M.

    2010-01-01

    This thesis research focusses on the study of the young and energetic isolated ordinary pulsar population detected by the Fermi gamma-ray space telescope. We compared the model expectations of four emission models and the LAT data. We found that all the models fail to reproduce the LAT detections, in particular the large number of high E objects observed. This inconsistency is not model dependent. A discrepancy between the radio-loud/radio-quiet objects ratio was also found between the observed and predicted samples. The L γ α E 0.5 relation is robustly confirmed by all the assumed models with particular agreement in the slot gap (SG) case. On luminosity bases, the intermediate altitude emission of the two pole caustic SG model is favoured. The beaming factor f Ω shows an E dependency that is slightly visible in the SG case. Estimates of the pulsar orientations have been obtained to explain the simultaneous gamma and radio light-curves. By analysing the solutions we found a relation between the observed energy cutoff and the width of the emission slot gap. This relation has been theoretically predicted. A possible magnetic obliquity α alignment with time is rejected -for all the models- on timescale of the order of 10 6 years. The light-curve morphology study shows that the outer magnetosphere gap emission (OGs) are favoured to explain the observed radio-gamma lag. The light curve moment studies (symmetry and sharpness) on the contrary favour a two pole caustic SG emission. All the model predictions suggest a different magnetic field layout with an hybrid two pole caustic and intermediate altitude emission to explain both the pulsar luminosity and light curve morphology. The low magnetosphere emission mechanism of the polar cap model, is systematically rejected by all the tests done. (author) [fr

  6. A model of economic growth with physical and human capital: The role of time delays.

    Science.gov (United States)

    Gori, Luca; Guerrini, Luca; Sodini, Mauro

    2016-09-01

    This article aims at analysing a two-sector economic growth model with discrete delays. The focus is on the dynamic properties of the emerging system. In particular, this study concentrates on the stability properties of the stationary solution, characterised by analytical results and geometrical techniques (stability crossing curves), and the conditions under which oscillatory dynamics emerge (through Hopf bifurcations). In addition, this article proposes some numerical simulations to illustrate the behaviour of the system when the stationary equilibrium is unstable.

  7. Results of Casting in Severe Curves in Infantile Scoliosis.

    Science.gov (United States)

    Stasikelis, Peter J; Carpenter, Ashley M

    2018-04-01

    Previous work has demonstrated best results for casting in infantile scoliosis when the curves are small and the child begins casting under 2 years of age. This study examines if casting can delay the need for growth friendly instrumentation in severe curves (50 to 106 degrees) and how the comorbidities of syrinx or genetic syndromes affected outcomes. All children undergoing casting for scoliosis at a single institution over an 8-year period were examined. Inclusion criteria included initial curve at first casting of ≥50 degrees, age ≤3 years at the start of casting, and a minimum follow-up of 3 years. Of 148 children undergoing casting during this period, 44 met our inclusion criteria. All children underwent magnetic resonance imaging. Ten children with a syrinx were identified. Ten children had known genetic syndromes (2 who also had a syrinx). The 26 children without these comorbidities were considered idiopathic. Curve magnitude ranged from 50 to 106 degrees. Nine of the 26 (35%) children in the children with idiopathic curves demonstrated resolution of their curves, while only 3 of the remaining 18 (17%) did. Of the children that did not have resolution of their curves, 14 were maintained over the entire follow-up period to within 15 degrees of their initial curve and 13 were improved 15 degrees or more. Only 5 children had an increase of 15 degrees or more over the follow-up period and 4 of these have undergone growth friendly instrumentation after a mean delay from initial cast of 71 months (range, 18 to 100 mo). This study demonstrates that even in severe curves, casting was effective in delaying instrumentation in all cases, and led to curve resolution of the curves in 12 of 44 children. Level III-case control study.

  8. A parallel process growth model of avoidant personality disorder symptoms and personality traits.

    Science.gov (United States)

    Wright, Aidan G C; Pincus, Aaron L; Lenzenweger, Mark F

    2013-07-01

    Avoidant personality disorder (AVPD), like other personality disorders, has historically been construed as a highly stable disorder. However, results from a number of longitudinal studies have found that the symptoms of AVPD demonstrate marked change over time. Little is known about which other psychological systems are related to this change. Although cross-sectional research suggests a strong relationship between AVPD and personality traits, no work has examined the relationship of their change trajectories. The current study sought to establish the longitudinal relationship between AVPD and basic personality traits using parallel process growth curve modeling. Parallel process growth curve modeling was applied to the trajectories of AVPD and basic personality traits from the Longitudinal Study of Personality Disorders (Lenzenweger, M. F., 2006, The longitudinal study of personality disorders: History, design considerations, and initial findings. Journal of Personality Disorders, 20, 645-670. doi:10.1521/pedi.2006.20.6.645), a naturalistic, prospective, multiwave, longitudinal study of personality disorder, temperament, and normal personality. The focus of these analyses is on the relationship between the rates of change in both AVPD symptoms and basic personality traits. AVPD symptom trajectories demonstrated significant negative relationships with the trajectories of interpersonal dominance and affiliation, and a significant positive relationship to rates of change in neuroticism. These results provide some of the first compelling evidence that trajectories of change in PD symptoms and personality traits are linked. These results have important implications for the ways in which temporal stability is conceptualized in AVPD specifically, and PD in general.

  9. Neck Muscle Moment Arms Obtained In-Vivo from MRI: Effect of Curved and Straight Modeled Paths.

    Science.gov (United States)

    Suderman, Bethany L; Vasavada, Anita N

    2017-08-01

    Musculoskeletal models of the cervical spine commonly represent neck muscles with straight paths. However, straight lines do not best represent the natural curvature of muscle paths in the neck, because the paths are constrained by bone and soft tissue. The purpose of this study was to estimate moment arms of curved and straight neck muscle paths using different moment arm calculation methods: tendon excursion, geometric, and effective torque. Curved and straight muscle paths were defined for two subject-specific cervical spine models derived from in vivo magnetic resonance images (MRI). Modeling neck muscle paths with curvature provides significantly different moment arm estimates than straight paths for 10 of 15 neck muscles (p straight lines to model muscle paths can lead to overestimating neck extension moment. However, moment arm methods for curved paths should be investigated further, as different methods of calculating moment arm can provide different estimates.

  10. Consistent Valuation across Curves Using Pricing Kernels

    Directory of Open Access Journals (Sweden)

    Andrea Macrina

    2018-03-01

    Full Text Available The general problem of asset pricing when the discount rate differs from the rate at which an asset’s cash flows accrue is considered. A pricing kernel framework is used to model an economy that is segmented into distinct markets, each identified by a yield curve having its own market, credit and liquidity risk characteristics. The proposed framework precludes arbitrage within each market, while the definition of a curve-conversion factor process links all markets in a consistent arbitrage-free manner. A pricing formula is then derived, referred to as the across-curve pricing formula, which enables consistent valuation and hedging of financial instruments across curves (and markets. As a natural application, a consistent multi-curve framework is formulated for emerging and developed inter-bank swap markets, which highlights an important dual feature of the curve-conversion factor process. Given this multi-curve framework, existing multi-curve approaches based on HJM and rational pricing kernel models are recovered, reviewed and generalised and single-curve models extended. In another application, inflation-linked, currency-based and fixed-income hybrid securities are shown to be consistently valued using the across-curve valuation method.

  11. Mathematical modeling improves EC50 estimations from classical dose-response curves.

    Science.gov (United States)

    Nyman, Elin; Lindgren, Isa; Lövfors, William; Lundengård, Karin; Cervin, Ida; Sjöström, Theresia Arbring; Altimiras, Jordi; Cedersund, Gunnar

    2015-03-01

    The β-adrenergic response is impaired in failing hearts. When studying β-adrenergic function in vitro, the half-maximal effective concentration (EC50 ) is an important measure of ligand response. We previously measured the in vitro contraction force response of chicken heart tissue to increasing concentrations of adrenaline, and observed a decreasing response at high concentrations. The classical interpretation of such data is to assume a maximal response before the decrease, and to fit a sigmoid curve to the remaining data to determine EC50 . Instead, we have applied a mathematical modeling approach to interpret the full dose-response curve in a new way. The developed model predicts a non-steady-state caused by a short resting time between increased concentrations of agonist, which affect the dose-response characterization. Therefore, an improved estimate of EC50 may be calculated using steady-state simulations of the model. The model-based estimation of EC50 is further refined using additional time-resolved data to decrease the uncertainty of the prediction. The resulting model-based EC50 (180-525 nm) is higher than the classically interpreted EC50 (46-191 nm). Mathematical modeling thus makes it possible to re-interpret previously obtained datasets, and to make accurate estimates of EC50 even when steady-state measurements are not experimentally feasible. The mathematical models described here have been submitted to the JWS Online Cellular Systems Modelling Database, and may be accessed at http://jjj.bio.vu.nl/database/nyman. © 2015 FEBS.

  12. Modeling Soil Water Retention Curves in the Dry Range Using the Hygroscopic Water Content

    DEFF Research Database (Denmark)

    Chen, Chong; Hu, Kelin; Arthur, Emmanuel

    2014-01-01

    Accurate information on the dry end (matric potential less than −1500 kPa) of soil water retention curves (SWRCs) is crucial for studying water vapor transport and evaporation in soils. The objectives of this study were to assess the potential of the Oswin model for describing the water adsorption...... curves of soils and to predict SWRCs at the dry end using the hygroscopic water content at a relative humidity of 50% (θRH50). The Oswin model yielded satisfactory fits to dry-end SWRCs for soils dominated by both 2:1 and 1:1 clay minerals. Compared with the Oswin model, the Campbell and Shiozawa model...... for soils dominated by 2:1 and 1:1 clays, respectively. Comparison of the Oswin model combined with the Kelvin equation, with water potential estimated from θRH50 (Oswin-KRH50), CS model combined with the Arthur equation (CS-A), and CS-K model, with water potential obtained from θRH50 (CS-KRH50) indicated...

  13. Comparison of parametric, orthogonal, and spline functions to model individual lactation curves for milk yield in Canadian Holsteins

    Directory of Open Access Journals (Sweden)

    Corrado Dimauro

    2010-11-01

    Full Text Available Test day records for milk yield of 57,390 first lactation Canadian Holsteins were analyzed with a linear model that included the fixed effects of herd-test date and days in milk (DIM interval nested within age and calving season. Residuals from this model were analyzed as a new variable and fitted with a five parameter model, fourth-order Legendre polynomials, with linear, quadratic and cubic spline models with three knots. The fit of the models was rather poor, with about 30-40% of the curves showing an adjusted R-square lower than 0.20 across all models. Results underline a great difficulty in modelling individual deviations around the mean curve for milk yield. However, the Ali and Schaeffer (5 parameter model and the fourth-order Legendre polynomials were able to detect two basic shapes of individual deviations among the mean curve. Quadratic and, especially, cubic spline functions had better fitting performances but a poor predictive ability due to their great flexibility that results in an abrupt change of the estimated curve when data are missing. Parametric and orthogonal polynomials seem to be robust and affordable under this standpoint.

  14. Stochastic models for tumoral growth

    Science.gov (United States)

    Escudero, Carlos

    2006-02-01

    Strong experimental evidence has indicated that tumor growth belongs to the molecular beam epitaxy universality class. This type of growth is characterized by the constraint of cell proliferation to the tumor border and the surface diffusion of cells at the growing edge. Tumor growth is thus conceived as a competition for space between the tumor and the host, and cell diffusion at the tumor border is an optimal strategy adopted for minimizing the pressure and helping tumor development. Two stochastic partial differential equations are reported in this paper in order to correctly model the physical properties of tumoral growth in (1+1) and (2+1) dimensions. The advantage of these models is that they reproduce the correct geometry of the tumor and are defined in terms of polar variables. An analysis of these models allows us to quantitatively estimate the response of the tumor to an unfavorable perturbation during growth.

  15. Latent Growth and Dynamic Structural Equation Models.

    Science.gov (United States)

    Grimm, Kevin J; Ram, Nilam

    2018-05-07

    Latent growth models make up a class of methods to study within-person change-how it progresses, how it differs across individuals, what are its determinants, and what are its consequences. Latent growth methods have been applied in many domains to examine average and differential responses to interventions and treatments. In this review, we introduce the growth modeling approach to studying change by presenting different models of change and interpretations of their model parameters. We then apply these methods to examining sex differences in the development of binge drinking behavior through adolescence and into adulthood. Advances in growth modeling methods are then discussed and include inherently nonlinear growth models, derivative specification of growth models, and latent change score models to study stochastic change processes. We conclude with relevant design issues of longitudinal studies and considerations for the analysis of longitudinal data.

  16. Cosmological parameter uncertainties from SALT-II type Ia supernova light curve models

    International Nuclear Information System (INIS)

    Mosher, J.; Sako, M.; Guy, J.; Astier, P.; Betoule, M.; El-Hage, P.; Pain, R.; Regnault, N.; Kessler, R.; Frieman, J. A.; Marriner, J.; Biswas, R.; Kuhlmann, S.; Schneider, D. P.

    2014-01-01

    We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ∼120 low-redshift (z < 0.1) SNe Ia, ∼255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ∼290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w input – w recovered ) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty; the average bias on w is –0.014 ± 0.007.

  17. Cosmological Parameter Uncertainties from SALT-II Type Ia Supernova Light Curve Models

    Energy Technology Data Exchange (ETDEWEB)

    Mosher, J. [Pennsylvania U.; Guy, J. [LBL, Berkeley; Kessler, R. [Chicago U., KICP; Astier, P. [Paris U., VI-VII; Marriner, J. [Fermilab; Betoule, M. [Paris U., VI-VII; Sako, M. [Pennsylvania U.; El-Hage, P. [Paris U., VI-VII; Biswas, R. [Argonne; Pain, R. [Paris U., VI-VII; Kuhlmann, S. [Argonne; Regnault, N. [Paris U., VI-VII; Frieman, J. A. [Fermilab; Schneider, D. P. [Penn State U.

    2014-08-29

    We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ~120 low-redshift (z < 0.1) SNe Ia, ~255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ~290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w (input) – w (recovered)) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty, the average bias on w is –0.014 ± 0.007.

  18. Curve Boxplot: Generalization of Boxplot for Ensembles of Curves.

    Science.gov (United States)

    Mirzargar, Mahsa; Whitaker, Ross T; Kirby, Robert M

    2014-12-01

    In simulation science, computational scientists often study the behavior of their simulations by repeated solutions with variations in parameters and/or boundary values or initial conditions. Through such simulation ensembles, one can try to understand or quantify the variability or uncertainty in a solution as a function of the various inputs or model assumptions. In response to a growing interest in simulation ensembles, the visualization community has developed a suite of methods for allowing users to observe and understand the properties of these ensembles in an efficient and effective manner. An important aspect of visualizing simulations is the analysis of derived features, often represented as points, surfaces, or curves. In this paper, we present a novel, nonparametric method for summarizing ensembles of 2D and 3D curves. We propose an extension of a method from descriptive statistics, data depth, to curves. We also demonstrate a set of rendering and visualization strategies for showing rank statistics of an ensemble of curves, which is a generalization of traditional whisker plots or boxplots to multidimensional curves. Results are presented for applications in neuroimaging, hurricane forecasting and fluid dynamics.

  19. Theoretical melting curve of caesium

    International Nuclear Information System (INIS)

    Simozar, S.; Girifalco, L.A.; Pennsylvania Univ., Philadelphia

    1983-01-01

    A statistical-mechanical model is developed to account for the complex melting curve of caesium. The model assumes the existence of three different species of caesium defined by three different electronic states. On the basis of this model, the free energy of melting and the melting curve are computed up to 60 kbar, using the solid-state data and the initial slope of the fusion curve as input parameters. The calculated phase diagram agrees with experiment to within the experimental error. Other thermodynamic properties including the entropy and volume of melting were also computed, and they agree with experiment. Since the theory requires only one adjustable constant, this is taken as strong evidence that the three-species model is satisfactory for caesium. (author)

  20. Environmental Kuznets Curve for carbon emissions in Pakistan: An empirical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, Muhammad, E-mail: nasirawan84@yahoo.co [Staff Economist, Pakistan Institute of Development Economics, 44000 Islamabad (Pakistan); Ur Rehman, Faiz, E-mail: faizeconomist@yahoo.co [Department of Economics, Quaid-i-Azam University, Islamabad (Pakistan)

    2011-03-15

    This study investigates the relationship between carbon emissions, income, energy consumption, and foreign trade in Pakistan for the period 1972-2008. By employing the Johansen method of cointegration, the study finds that there is a quadratic long-run relationship between carbon emissions and income, confirming the existence of Environmental Kuznets Curve for Pakistan. Moreover, both energy consumption and foreign trade are found to have positive effects on emissions. The short-run results have, however, denied the existence of the Environmental Kuznets Curve. The short-run results are unique to the existing literature in the sense that none of the long-run determinants of emissions is significant. The contradictory results of short- and long-run give policy makers the opportunity to formulate different types of growth policies for the two terms taking environmental issues into consideration. In addition, the uni-directional causality from growth to energy consumption suggests that the policy makers should not only focus on forecasting future demand for energy with different growth scenarios but also on obtaining the least cost energy. Furthermore, the absence of causality from emissions to growth suggests that Pakistan can curb its carbon emissions without disturbing its economic growth. - Research highlights: {yields} Environmental Kuznets Curve exists only in the long-run in Pakistan. {yields} Both energy consumption and trade openness also affect carbon emissions positively in the long run. {yields} The short-run results have, however, denied the existence of the Environmental Kuznets Curve. {yields} None of the explanatory variables affect emissions in short-run. {yields} There is uni-directional causality from growth to energy consumption. {yields} There is uni-directional causality from growth to emissions.

  1. Environmental Kuznets Curve for carbon emissions in Pakistan: An empirical investigation

    International Nuclear Information System (INIS)

    Nasir, Muhammad; Ur Rehman, Faiz

    2011-01-01

    This study investigates the relationship between carbon emissions, income, energy consumption, and foreign trade in Pakistan for the period 1972-2008. By employing the Johansen method of cointegration, the study finds that there is a quadratic long-run relationship between carbon emissions and income, confirming the existence of Environmental Kuznets Curve for Pakistan. Moreover, both energy consumption and foreign trade are found to have positive effects on emissions. The short-run results have, however, denied the existence of the Environmental Kuznets Curve. The short-run results are unique to the existing literature in the sense that none of the long-run determinants of emissions is significant. The contradictory results of short- and long-run give policy makers the opportunity to formulate different types of growth policies for the two terms taking environmental issues into consideration. In addition, the uni-directional causality from growth to energy consumption suggests that the policy makers should not only focus on forecasting future demand for energy with different growth scenarios but also on obtaining the least cost energy. Furthermore, the absence of causality from emissions to growth suggests that Pakistan can curb its carbon emissions without disturbing its economic growth. - Research highlights: → Environmental Kuznets Curve exists only in the long-run in Pakistan. → Both energy consumption and trade openness also affect carbon emissions positively in the long run. → The short-run results have, however, denied the existence of the Environmental Kuznets Curve. → None of the explanatory variables affect emissions in short-run. → There is uni-directional causality from growth to energy consumption. → There is uni-directional causality from growth to emissions.

  2. Exactly solvable string models of curved space-time backgrounds

    International Nuclear Information System (INIS)

    Russo, J.G.

    1995-01-01

    We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the ''dilatonic'' (a=1) and ''Kaluza-Klein'' (a=√(3)) Melvin solutions and the uniform magnetic field solution, as well as some singular space-times. Solvability of the string σ-model is related to its connection via duality to a simpler model which is a ''twisted'' product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model (tachyonic instabilities in the spectrum, gyromagnetic ratio, issue of singularities, etc.). It provides one of the first examples of a consistent solvable conformal string model with explicit D=4 curved space-time interpretation. (orig.)

  3. Testing mechanistic models of growth in insects.

    Science.gov (United States)

    Maino, James L; Kearney, Michael R

    2015-11-22

    Insects are typified by their small size, large numbers, impressive reproductive output and rapid growth. However, insect growth is not simply rapid; rather, insects follow a qualitatively distinct trajectory to many other animals. Here we present a mechanistic growth model for insects and show that increasing specific assimilation during the growth phase can explain the near-exponential growth trajectory of insects. The presented model is tested against growth data on 50 insects, and compared against other mechanistic growth models. Unlike the other mechanistic models, our growth model predicts energy reserves per biomass to increase with age, which implies a higher production efficiency and energy density of biomass in later instars. These predictions are tested against data compiled from the literature whereby it is confirmed that insects increase their production efficiency (by 24 percentage points) and energy density (by 4 J mg(-1)) between hatching and the attainment of full size. The model suggests that insects achieve greater production efficiencies and enhanced growth rates by increasing specific assimilation and increasing energy reserves per biomass, which are less costly to maintain than structural biomass. Our findings illustrate how the explanatory and predictive power of mechanistic growth models comes from their grounding in underlying biological processes. © 2015 The Author(s).

  4. Growth Modeling with Non-Ignorable Dropout: Alternative Analyses of the STAR*D Antidepressant Trial

    Science.gov (United States)

    Muthén, Bengt; Asparouhov, Tihomir; Hunter, Aimee; Leuchter, Andrew

    2011-01-01

    This paper uses a general latent variable framework to study a series of models for non-ignorable missingness due to dropout. Non-ignorable missing data modeling acknowledges that missingness may depend on not only covariates and observed outcomes at previous time points as with the standard missing at random (MAR) assumption, but also on latent variables such as values that would have been observed (missing outcomes), developmental trends (growth factors), and qualitatively different types of development (latent trajectory classes). These alternative predictors of missing data can be explored in a general latent variable framework using the Mplus program. A flexible new model uses an extended pattern-mixture approach where missingness is a function of latent dropout classes in combination with growth mixture modeling using latent trajectory classes. A new selection model allows not only an influence of the outcomes on missingness, but allows this influence to vary across latent trajectory classes. Recommendations are given for choosing models. The missing data models are applied to longitudinal data from STAR*D, the largest antidepressant clinical trial in the U.S. to date. Despite the importance of this trial, STAR*D growth model analyses using non-ignorable missing data techniques have not been explored until now. The STAR*D data are shown to feature distinct trajectory classes, including a low class corresponding to substantial improvement in depression, a minority class with a U-shaped curve corresponding to transient improvement, and a high class corresponding to no improvement. The analyses provide a new way to assess drug efficiency in the presence of dropout. PMID:21381817

  5. Standardized Percentile Curves of Body Mass Index of Northeast Iranian Children Aged 25 to 60 Months

    Science.gov (United States)

    Emdadi, Maryam; Safarian, Mohammad; Doosti, Hassan

    2011-01-01

    Objective Growth charts are widely used to assess children's growth status and can provide a trajectory of growth during early important months of life. Racial differences necessitate using local growth charts. This study aimed to provide standardized growth curves of body mass index (BMI) for children living in northeast Iran. Methods A total of 23730 apparently healthy boys and girls aged 25 to 60 months recruited for 20 days from those attending community clinics for routine health checks. Anthropometric measurements were done by trained health staff using WHO methodology. The LMSP method with maximum penalized likelihood, the Generalized Additive Models, the Box-Cox power exponential distribution distribution, Akaike Information Criteria and Generalized Akaike Criteria with penalty equal to 3 [GAIC(3)], and Worm plot and Q-tests as goodness of fit tests were used to construct the centile reference charts. Findings The BMI centile curves for boys and girls aged 25 to 60 months were drawn utilizing a population of children living in northeast Iran. Conclusion The results of the current study demonstrate the possibility of preparation of local growth charts and their importance in evaluating children's growth. Also their differences, relative to those prepared by global references, reflect the necessity of preparing local charts in future studies using longitudinal data. PMID:23056770

  6. Suppression of elongation and growth of tomato seedlings by auxin biosynthesis inhibitors and modeling of the growth and environmental response.

    Science.gov (United States)

    Higashide, Tadahisa; Narukawa, Megumi; Shimada, Yukihisa; Soeno, Kazuo

    2014-04-02

    To develop a growth inhibitor, the effects of auxin inhibitors were investigated. Application of 30 μM L-α-aminooxy-β-phenylpropionic acid (AOPP) or (S)-methyl 2-((1,3-dioxoisoindolin-2-yl)oxy)-3-phenylpropanoate (KOK1101), decreased the endogenous IAA levels in tomato seedlings at 8 days after sowing. Then, 10-1200 μM AOPP or KOK1101 were sprayed on the leaves and stem of 2-3 leaf stage tomato plants grown under a range of environmental conditions. We predicted plant growth and environmental response using a model based on the observed suppression of leaf enlargement. Spraying AOPP or KOK1101 decreased stem length and leaf area. Concentration-dependent inhibitions and dose response curves were observed. Although the effects of the inhibitors on dry weight varied according to the environmental conditions, the net assimilation rate was not influenced by the inhibitors. Accordingly, the observed decrease in dry weight caused by the inhibitors may result from decreased leaf area. Validation of the model based on observed data independent of the dataset showed good correlations between the observed and predicted values of dry weight and leaf area index.

  7. Modelling the Load Curve of Aggregate Electricity Consumption Using Principal Components

    OpenAIRE

    Matteo Manera; Angelo Marzullo

    2003-01-01

    Since oil is a non-renewable resource with a high environmental impact, and its most common use is to produce combustibles for electricity, reliable methods for modelling electricity consumption can contribute to a more rational employment of this hydrocarbon fuel. In this paper we apply the Principal Components (PC) method to modelling the load curves of Italy, France and Greece on hourly data of aggregate electricity consumption. The empirical results obtained with the PC approach are compa...

  8. Phase response curves for models of earthquake fault dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Franović, Igor, E-mail: franovic@ipb.ac.rs [Scientific Computing Laboratory, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kostić, Srdjan [Institute for the Development of Water Resources “Jaroslav Černi,” Jaroslava Černog 80, 11226 Belgrade (Serbia); Perc, Matjaž [Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor (Slovenia); CAMTP—Center for Applied Mathematics and Theoretical Physics, University of Maribor, Krekova 2, SI-2000 Maribor (Slovenia); Klinshov, Vladimir [Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); Nekorkin, Vladimir [Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); University of Nizhny Novgorod, 23 Prospekt Gagarina, 603950 Nizhny Novgorod (Russian Federation); Kurths, Jürgen [Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); Potsdam Institute for Climate Impact Research, 14412 Potsdam (Germany); Institute of Physics, Humboldt University Berlin, 12489 Berlin (Germany)

    2016-06-15

    We systematically study effects of external perturbations on models describing earthquake fault dynamics. The latter are based on the framework of the Burridge-Knopoff spring-block system, including the cases of a simple mono-block fault, as well as the paradigmatic complex faults made up of two identical or distinct blocks. The blocks exhibit relaxation oscillations, which are representative for the stick-slip behavior typical for earthquake dynamics. Our analysis is carried out by determining the phase response curves of first and second order. For a mono-block fault, we consider the impact of a single and two successive pulse perturbations, further demonstrating how the profile of phase response curves depends on the fault parameters. For a homogeneous two-block fault, our focus is on the scenario where each of the blocks is influenced by a single pulse, whereas for heterogeneous faults, we analyze how the response of the system depends on whether the stimulus is applied to the block having a shorter or a longer oscillation period.

  9. Phase response curves for models of earthquake fault dynamics

    International Nuclear Information System (INIS)

    Franović, Igor; Kostić, Srdjan; Perc, Matjaž; Klinshov, Vladimir; Nekorkin, Vladimir; Kurths, Jürgen

    2016-01-01

    We systematically study effects of external perturbations on models describing earthquake fault dynamics. The latter are based on the framework of the Burridge-Knopoff spring-block system, including the cases of a simple mono-block fault, as well as the paradigmatic complex faults made up of two identical or distinct blocks. The blocks exhibit relaxation oscillations, which are representative for the stick-slip behavior typical for earthquake dynamics. Our analysis is carried out by determining the phase response curves of first and second order. For a mono-block fault, we consider the impact of a single and two successive pulse perturbations, further demonstrating how the profile of phase response curves depends on the fault parameters. For a homogeneous two-block fault, our focus is on the scenario where each of the blocks is influenced by a single pulse, whereas for heterogeneous faults, we analyze how the response of the system depends on whether the stimulus is applied to the block having a shorter or a longer oscillation period.

  10. Comparison of two models of intrauterine growth restriction for early catch-up growth and later development of glucose intolerance and obesity in rats.

    Science.gov (United States)

    Shahkhalili, Yasaman; Moulin, Julie; Zbinden, Irene; Aprikian, Olivier; Macé, Katherine

    2010-01-01

    Two models of intrauterine growth restriction, maternal food restriction (FR), and dexamethasone (DEX) exposure were compared for early postnatal catch-up growth and later development of glucose intolerance and obesity in Sprague-Dawley rats. Mated dams were randomly divided into three groups at 10 days gestational age. Group FR was food restricted (50% of nongestating rats) during the last 11 days of gestation; Group DEX received DEX injections during the last week of gestation, and Group CON, the control group, had no intervention. Birth weight, catch-up growth, body weight, and food intake were measured in male offspring for 22 wk. Body composition, blood glucose, and plasma insulin in response to a glucose load were assessed at 8, 16, and 22 wk. Pups from both FR and DEX dams had similarly lower birth weights than CON (22% and 25%, P growth, which occurred during the suckling period, was much more rapid in FR than DEX offspring (6 vs. 25 days, 95% CI). Postweaning, there were no significant differences between groups in food intake, body weight, body fat, and plasma insulin, but baseline plasma glucose at 22 wk and 2-h glucose area-under-the-curve at 8 and 22 wk were greater only in FR vs. CON offspring (P restriction is a more sensitive model than DEX exposure for studies aimed at investigating the link between low birth weight, early postnatal catch-up growth, and later development of glucose intolerance.

  11. An integral parametrization of the bacterial growth curve experimental demonstration with E. coli C{sub 6}00 bacteria; Parametrizacion integrada de la curva de crecimiento bacteriano. Comprobacion experimental para E. coli C{sub 6}00

    Energy Technology Data Exchange (ETDEWEB)

    Garces, F; Vidania, R de

    1984-07-01

    In this work an integral parametrization of the bacterial growth curve is presented. The values of the parameters are obtained by fitting to the experimental data. Those parameters, with allow to describe the growth in its different phases, are the followings: slopes of the curve in its three parts and the time which divides the last two phases of the bacterial growth. The experimental data are bacterial densities measured by optical methods. The bacteria used was the E. coli C{sub 6}00. (Author)

  12. Uncertainty in urban flood damage assessment due to urban drainage modelling and depth-damage curve estimation.

    Science.gov (United States)

    Freni, G; La Loggia, G; Notaro, V

    2010-01-01

    Due to the increased occurrence of flooding events in urban areas, many procedures for flood damage quantification have been defined in recent decades. The lack of large databases in most cases is overcome by combining the output of urban drainage models and damage curves linking flooding to expected damage. The application of advanced hydraulic models as diagnostic, design and decision-making support tools has become a standard practice in hydraulic research and application. Flooding damage functions are usually evaluated by a priori estimation of potential damage (based on the value of exposed goods) or by interpolating real damage data (recorded during historical flooding events). Hydraulic models have undergone continuous advancements, pushed forward by increasing computer capacity. The details of the flooding propagation process on the surface and the details of the interconnections between underground and surface drainage systems have been studied extensively in recent years, resulting in progressively more reliable models. The same level of was advancement has not been reached with regard to damage curves, for which improvements are highly connected to data availability; this remains the main bottleneck in the expected flooding damage estimation. Such functions are usually affected by significant uncertainty intrinsically related to the collected data and to the simplified structure of the adopted functional relationships. The present paper aimed to evaluate this uncertainty by comparing the intrinsic uncertainty connected to the construction of the damage-depth function to the hydraulic model uncertainty. In this way, the paper sought to evaluate the role of hydraulic model detail level in the wider context of flood damage estimation. This paper demonstrated that the use of detailed hydraulic models might not be justified because of the higher computational cost and the significant uncertainty in damage estimation curves. This uncertainty occurs mainly

  13. Modeling of Continuum Manipulators Using Pythagorean Hodograph Curves.

    Science.gov (United States)

    Singh, Inderjeet; Amara, Yacine; Melingui, Achille; Mani Pathak, Pushparaj; Merzouki, Rochdi

    2018-05-10

    Research on continuum manipulators is increasingly developing in the context of bionic robotics because of their many advantages over conventional rigid manipulators. Due to their soft structure, they have inherent flexibility, which makes it a huge challenge to control them with high performances. Before elaborating a control strategy of such robots, it is essential to reconstruct first the behavior of the robot through development of an approximate behavioral model. This can be kinematic or dynamic depending on the conditions of operation of the robot itself. Kinematically, two types of modeling methods exist to describe the robot behavior; quantitative methods describe a model-based method, and qualitative methods describe a learning-based method. In kinematic modeling of continuum manipulator, the assumption of constant curvature is often considered to simplify the model formulation. In this work, a quantitative modeling method is proposed, based on the Pythagorean hodograph (PH) curves. The aim is to obtain a three-dimensional reconstruction of the shape of the continuum manipulator with variable curvature, allowing the calculation of its inverse kinematic model (IKM). It is noticed that the performances of the PH-based kinematic modeling of continuum manipulators are considerable regarding position accuracy, shape reconstruction, and time/cost of the model calculation, than other kinematic modeling methods, for two cases: free load manipulation and variable load manipulation. This modeling method is applied to the compact bionic handling assistant (CBHA) manipulator for validation. The results are compared with other IKMs developed in case of CBHA manipulator.

  14. Structural Change, Economic Growth and the Environmental Kuznets Curve. A Theoretical Perspective

    International Nuclear Information System (INIS)

    De Groot, H.L.F.

    1999-01-01

    The question of whether economic growth will ultimately resolve environmental problems has recently been discussed in a mainly empirical literature. One of the mechanisms that can explain the finding of an inverted U-shaped relationship between income and emissions relies on the changes in the sectoral composition of economies associated with economic growth. This paper develops a multi-sector general-equilibrium model to study the dynamic relationships between technological progress, economic development, the sectoral composition of economies and emissions. In the model, structural change is the outcome of a complex interplay between factors of demand and supply, and results from both differences in technological progress on a sectoral level and from differences in income elasticities of demand for different goods. We will derive under what conditions such changes can give rise to a hump-shaped relationship between per capita income and emissions. 39 refs

  15. Layered growth model and epitaxial growth structures for SiCAlN alloys

    International Nuclear Information System (INIS)

    Liu Zhaoqing; Ni Jun; Su Xiaoao; Dai Zhenhong

    2009-01-01

    Epitaxial growth structures for (SiC) 1-x (AlN) x alloys are studied using a layered growth model. First-principle calculations are used to determine the parameters in the layered growth model. The phase diagrams of epitaxial growth are given. There is a rich variety of the new metastable polytype structures at x=1/6 ,1/5 ,1/4 ,1/3 , and 1/2 in the layered growth phase diagrams. We have also calculated the electronic properties of the short periodical SiCAlN alloys predicted by our layered growth model. The results show that various ordered structures of (SiC) 1-x (AlN) x alloys with the band gaps over a wide range are possible to be synthesized by epitaxial growth.

  16. A Method for Formulizing Disaster Evacuation Demand Curves Based on SI Model

    Directory of Open Access Journals (Sweden)

    Yulei Song

    2016-10-01

    Full Text Available The prediction of evacuation demand curves is a crucial step in the disaster evacuation plan making, which directly affects the performance of the disaster evacuation. In this paper, we discuss the factors influencing individual evacuation decision making (whether and when to leave and summarize them into four kinds: individual characteristics, social influence, geographic location, and warning degree. In the view of social contagion of decision making, a method based on Susceptible-Infective (SI model is proposed to formulize the disaster evacuation demand curves to address both social influence and other factors’ effects. The disaster event of the “Tianjin Explosions” is used as a case study to illustrate the modeling results influenced by the four factors and perform the sensitivity analyses of the key parameters of the model. Some interesting phenomena are found and discussed, which is meaningful for authorities to make specific evacuation plans. For example, due to the lower social influence in isolated communities, extra actions might be taken to accelerate evacuation process in those communities.

  17. Modeling of a Robust Confidence Band for the Power Curve of a Wind Turbine.

    Science.gov (United States)

    Hernandez, Wilmar; Méndez, Alfredo; Maldonado-Correa, Jorge L; Balleteros, Francisco

    2016-12-07

    Having an accurate model of the power curve of a wind turbine allows us to better monitor its operation and planning of storage capacity. Since wind speed and direction is of a highly stochastic nature, the forecasting of the power generated by the wind turbine is of the same nature as well. In this paper, a method for obtaining a robust confidence band containing the power curve of a wind turbine under test conditions is presented. Here, the confidence band is bound by two curves which are estimated using parametric statistical inference techniques. However, the observations that are used for carrying out the statistical analysis are obtained by using the binning method, and in each bin, the outliers are eliminated by using a censorship process based on robust statistical techniques. Then, the observations that are not outliers are divided into observation sets. Finally, both the power curve of the wind turbine and the two curves that define the robust confidence band are estimated using each of the previously mentioned observation sets.

  18. Stochastic ontogenetic growth model

    Science.gov (United States)

    West, B. J.; West, D.

    2012-02-01

    An ontogenetic growth model (OGM) for a thermodynamically closed system is generalized to satisfy both the first and second law of thermodynamics. The hypothesized stochastic ontogenetic growth model (SOGM) is shown to entail the interspecies allometry relation by explicitly averaging the basal metabolic rate and the total body mass over the steady-state probability density for the total body mass (TBM). This is the first derivation of the interspecies metabolic allometric relation from a dynamical model and the asymptotic steady-state distribution of the TBM is fit to data and shown to be inverse power law.

  19. A Hierarchical Modeling for Reactive Power Optimization With Joint Transmission and Distribution Networks by Curve Fitting

    DEFF Research Database (Denmark)

    Ding, Tao; Li, Cheng; Huang, Can

    2018-01-01

    –slave structure and improves traditional centralized modeling methods by alleviating the big data problem in a control center. Specifically, the transmission-distribution-network coordination issue of the hierarchical modeling method is investigated. First, a curve-fitting approach is developed to provide a cost......In order to solve the reactive power optimization with joint transmission and distribution networks, a hierarchical modeling method is proposed in this paper. It allows the reactive power optimization of transmission and distribution networks to be performed separately, leading to a master...... optimality. Numerical results on two test systems verify the effectiveness of the proposed hierarchical modeling and curve-fitting methods....

  20. Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

    International Nuclear Information System (INIS)

    Glenn, Autumn L.; Bulusu, Kartik V.; Shu Fangjun; Plesniak, Michael W.

    2012-01-01

    Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T ≈ 0.20–0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

  1. Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

    Energy Technology Data Exchange (ETDEWEB)

    Glenn, Autumn L.; Bulusu, Kartik V. [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States); Shu Fangjun [Department of Mechanical and Aerospace Engineering, New Mexico State University, MSC 3450, P.O. Box 30001, Las Cruces, NM 88003-8001 (United States); Plesniak, Michael W., E-mail: plesniak@gwu.edu [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States)

    2012-06-15

    Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T Almost-Equal-To 0.20-0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

  2. Prediction of ttt curves of cold working tool steels using support vector machine model

    Science.gov (United States)

    Pillai, Nandakumar; Karthikeyan, R., Dr.

    2018-04-01

    The cold working tool steels are of high carbon steels with metallic alloy additions which impart higher hardenability, abrasion resistance and less distortion in quenching. The microstructure changes occurring in tool steel during heat treatment is of very much importance as the final properties of the steel depends upon these changes occurred during the process. In order to obtain the desired performance the alloy constituents and its ratio plays a vital role as the steel transformation itself is complex in nature and depends very much upon the time and temperature. The proper treatment can deliver satisfactory results, at the same time process deviation can completely spoil the results. So knowing time temperature transformation (TTT) of phases is very critical which varies for each type depending upon its constituents and proportion range. To obtain adequate post heat treatment properties the percentage of retained austenite should be lower and metallic carbides obtained should be fine in nature. Support vector machine is a computational model which can learn from the observed data and use these to predict or solve using mathematical model. Back propagation feedback network will be created and trained for further solutions. The points on the TTT curve for the known transformations curves are used to plot the curves for different materials. These data will be trained to predict TTT curves for other steels having similar alloying constituents but with different proportion range. The proposed methodology can be used for prediction of TTT curves for cold working steels and can be used for prediction of phases for different heat treatment methods.

  3. Retiring the Short-Run Aggregate Supply Curve

    Science.gov (United States)

    Elwood, S. Kirk

    2010-01-01

    The author argues that the aggregate demand/aggregate supply (AD/AS) model is significantly improved--although certainly not perfected--by trimming it of the short-run aggregate supply (SRAS) curve. Problems with the SRAS curve are shown first for the AD/AS model that casts the AD curve as identifying the equilibrium level of output associated…

  4. Abordagem Bayesiana das curvas de crescimento de duas cultivares de feijoeiro Bayesian approach in the growth curves of two cultivars of common bean

    Directory of Open Access Journals (Sweden)

    Sebastião Martins Filho

    2008-09-01

    Full Text Available Neste trabalho foi utilizada a metodologia Bayesiana para ajustar o modelo não-linear logístico para dados de crescimento de duas cultivares de feijoeiro, "Neguinho" e "Carioca". O delineamento experimental utilizado foi o inteiramente casualizado, com vinte repetições, no esquema de parcelas subdivididas, sendo que os tratamentos principais foram constituídos pelas cultivares e as subparcelas foram constituídas por 17 períodos de avaliações, do plantio até aos 85 dias. A metodologia permitiu comparar as curvas de crescimentos sem utilizar a teoria assintótica e estes resultados mostraram um maior incremento em altura para a cultivar "Carioca".In this paper the Bayesian methodology was used to fit the logistic nonlinear model to growth data of two common bean cultivars, 'Neguinho' and 'Carioca'. The experiment was a split plot under a completely randomized design with twenty replicates, being the main treatments constituted by cultivars and the sub plots constituted by seventeen periods of evaluations, from planting to 85 days. The methodology allowed comparing the growth curves without using the asymptotic theory, and these results showed a larger height increment for the 'Carioca' cultivar.

  5. A residual life prediction model based on the generalized σ -N curved surface

    Directory of Open Access Journals (Sweden)

    Zongwen AN

    2016-06-01

    Full Text Available In order to investigate change rule of the residual life of structure under random repeated load, firstly, starting from the statistic meaning of random repeated load, the joint probability density function of maximum stress and minimum stress is derived based on the characteristics of order statistic (maximum order statistic and minimum order statistic; then, based on the equation of generalized σ -N curved surface, considering the influence of load cycles number on fatigue life, a relationship among minimum stress, maximum stress and residual life, that is the σmin(n- σmax(n-Nr(n curved surface model, is established; finally, the validity of the proposed model is demonstrated by a practical case. The result shows that the proposed model can reflect the influence of maximum stress and minimum stress on residual life of structure under random repeated load, which can provide a theoretical basis for life prediction and reliability assessment of structure.

  6. Incorporating Measurement Non-Equivalence in a Cross-Study Latent Growth Curve Analysis.

    Science.gov (United States)

    Flora, David B; Curran, Patrick J; Hussong, Andrea M; Edwards, Michael C

    2008-10-01

    A large literature emphasizes the importance of testing for measurement equivalence in scales that may be used as observed variables in structural equation modeling applications. When the same construct is measured across more than one developmental period, as in a longitudinal study, it can be especially critical to establish measurement equivalence, or invariance, across the developmental periods. Similarly, when data from more than one study are combined into a single analysis, it is again important to assess measurement equivalence across the data sources. Yet, how to incorporate non-equivalence when it is discovered is not well described for applied researchers. Here, we present an item response theory approach that can be used to create scale scores from measures while explicitly accounting for non-equivalence. We demonstrate these methods in the context of a latent curve analysis in which data from two separate studies are combined to create a single longitudinal model spanning several developmental periods.

  7. An extended CFD model to predict the pumping curve in low pressure plasma etch chamber

    Science.gov (United States)

    Zhou, Ning; Wu, Yuanhao; Han, Wenbin; Pan, Shaowu

    2014-12-01

    Continuum based CFD model is extended with slip wall approximation and rarefaction effect on viscosity, in an attempt to predict the pumping flow characteristics in low pressure plasma etch chambers. The flow regime inside the chamber ranges from slip wall (Kn ˜ 0.01), and up to free molecular (Kn = 10). Momentum accommodation coefficient and parameters for Kn-modified viscosity are first calibrated against one set of measured pumping curve. Then the validity of this calibrated CFD models are demonstrated in comparison with additional pumping curves measured in chambers of different geometry configurations. More detailed comparison against DSMC model for flow conductance over slits with contraction and expansion sections is also discussed.

  8. Reflected Light Curves of Extrasolar Planets

    Science.gov (United States)

    Green, D.; Matthews, J.; Kuschnig, R.; Seager, S.

    The planned launches of ultra-precise photometric satellites such as MOST, COROT and MONS should provide the first opportunity to study the reflected light curves from extrasolar planets. To predict the capabilities of these missions, we have constructed a series of models of such light curves, improving upon the Monte Carlo simulations by Seager et al. (2000). These models include more realistic features such limb darkening of the star and broad band photometry. For specific models, the resulting planet light curves exhibit unique behavior with the variation of radius, inclination and presence or absence of clouds.

  9. Image Analysis of a Negatively Curved Graphitic Sheet Model for Amorphous Carbon

    Science.gov (United States)

    Bursill, L. A.; Bourgeois, Laure N.

    High-resolution electron micrographs are presented which show essentially curved single sheets of graphitic carbon. Image calculations are then presented for the random surface schwarzite-related model of Townsend et al. (Phys. Rev. Lett. 69, 921-924, 1992). Comparison with experimental images does not rule out the contention that such models, containing surfaces of negative curvature, may be useful for predicting some physical properties of specific forms of nanoporous carbon. Some difficulties of the model predictions, when compared with the experimental images, are pointed out. The range of application of this model, as well as competing models, is discussed briefly.

  10. Correction of Flow Curves and Constitutive Modelling of a Ti-6Al-4V Alloy

    Directory of Open Access Journals (Sweden)

    Ming Hu

    2018-04-01

    Full Text Available Isothermal uniaxial compressions of a Ti-6Al-4V alloy were carried out in the temperature range of 800–1050 °C and strain rate range of 0.001–1 s−1. The effects of friction between the specimen and anvils as well as the increase in temperature caused by the high strain rate deformation were considered, and flow curves were corrected as a result. Constitutive models were discussed based on the corrected flow curves. The correlation coefficient and average absolute relative error for the strain compensated Arrhenius-type constitutive model are 0.986 and 9.168%, respectively, while the values for a modified Johnson-Cook constitutive model are 0.924 and 22.673%, respectively. Therefore, the strain compensated Arrhenius-type constitutive model has a better prediction capability than a modified Johnson-Cook constitutive model.

  11. Comparison of power curve monitoring methods

    Directory of Open Access Journals (Sweden)

    Cambron Philippe

    2017-01-01

    Full Text Available Performance monitoring is an important aspect of operating wind farms. This can be done through the power curve monitoring (PCM of wind turbines (WT. In the past years, important work has been conducted on PCM. Various methodologies have been proposed, each one with interesting results. However, it is difficult to compare these methods because they have been developed using their respective data sets. The objective of this actual work is to compare some of the proposed PCM methods using common data sets. The metric used to compare the PCM methods is the time needed to detect a change in the power curve. Two power curve models will be covered to establish the effect the model type has on the monitoring outcomes. Each model was tested with two control charts. Other methodologies and metrics proposed in the literature for power curve monitoring such as areas under the power curve and the use of statistical copulas have also been covered. Results demonstrate that model-based PCM methods are more reliable at the detecting a performance change than other methodologies and that the effectiveness of the control chart depends on the types of shift observed.

  12. Principal Curves on Riemannian Manifolds.

    Science.gov (United States)

    Hauberg, Soren

    2016-09-01

    Euclidean statistics are often generalized to Riemannian manifolds by replacing straight-line interpolations with geodesic ones. While these Riemannian models are familiar-looking, they are restricted by the inflexibility of geodesics, and they rely on constructions which are optimal only in Euclidean domains. We consider extensions of Principal Component Analysis (PCA) to Riemannian manifolds. Classic Riemannian approaches seek a geodesic curve passing through the mean that optimizes a criteria of interest. The requirements that the solution both is geodesic and must pass through the mean tend to imply that the methods only work well when the manifold is mostly flat within the support of the generating distribution. We argue that instead of generalizing linear Euclidean models, it is more fruitful to generalize non-linear Euclidean models. Specifically, we extend the classic Principal Curves from Hastie & Stuetzle to data residing on a complete Riemannian manifold. We show that for elliptical distributions in the tangent of spaces of constant curvature, the standard principal geodesic is a principal curve. The proposed model is simple to compute and avoids many of the pitfalls of traditional geodesic approaches. We empirically demonstrate the effectiveness of the Riemannian principal curves on several manifolds and datasets.

  13. An analytical model of stand dynamics as a function of tree growth, mortality and recruitment: the shade tolerance-stand structure hypothesis revisited.

    Science.gov (United States)

    Zavala, Miguel A; Angulo, Oscar; Bravo de la Parra, Rafael; López-Marcos, Juan C

    2007-02-07

    Light competition and interspecific differences in shade tolerance are considered key determinants of forest stand structure and dynamics. Specifically two main stand diameter distribution types as a function of shade tolerance have been proposed based on empirical observations. All-aged stands of shade tolerant species tend to have steeply descending, monotonic diameter distributions (inverse J-shaped curves). Shade intolerant species in contrast typically exhibit normal (unimodal) tree diameter distributions due to high mortality rates of smaller suppressed trees. In this study we explore the generality of this hypothesis which implies a causal relationship between light competition or shade tolerance and stand structure. For this purpose we formulate a partial differential equation system of stand dynamics as a function of individual tree growth, recruitment and mortality which allows us to explore possible individual-based mechanisms--e.g. light competition-underlying observed patterns of stand structure--e.g. unimodal or inverse J-shaped equilibrium diameter curves. We find that contrary to expectations interspecific differences in growth patterns can result alone in any of the two diameter distributions types observed in the field. In particular, slow growing species can present unimodal equilibrium curves even in the absence of light competition. Moreover, light competition and shade intolerance evaluated both at the tree growth and mortality stages did not have a significant impact on stand structure that tended to converge systematically towards an inverse J-shaped curves for most tree growth scenarios. Realistic transient stand dynamics for even aged stands of shade intolerant species (unimodal curves) were only obtained when recruitment was completely suppressed, providing further evidence on the critical role played by juvenile stages of tree development (e.g. the sampling stage) on final forest structure and composition. The results also point out the

  14. Environmental Kuznets Curve Hypothesis: A Perspective of Sustainable Development in Indonesia

    Directory of Open Access Journals (Sweden)

    Galuh Nuansa Citrasmara

    2018-01-01

    Full Text Available Sustainable development with three main pillars, namely environmental, economic, and social, is the concept of country’s development to achieve inclusive economic growth, good environmental quality, and improvement of people's welfare. However, the dominance of economic factors cause various environmental problem. This phenomenon occurs in most of developing countries, including in Indonesia. The relationship between economic activity and environmental quality has been widely discussed and empirically tested by scholars. This descriptive research analysed the hypothesis called Environmental Kuznets Curve (EKC from a perspective of sustainable development in Indonesia. EKC hypothesis illustrates the relationship between economic growth and environmental degradation forming an inverted U-curve, indicating that at the beginning of development, environmental quality will decrease along with increasing economic growth, and then reached a certain point the environmental quality will gradually improve. In this paper will be discussed how the relationship between environmental quality and economic growth in Indonesia was investigated. The preliminary results show that most of the empirical studies use the conventional approach, in which the CO2 emission used as the proxy of environmental degradation. The existence of inverted U-curve is also inconclusive. Therefore, the extension research on the relationship between economic growth and environmental quality in Indonesia using the EKC hypothesis is required.

  15. Environmental Kuznets Curve Hypothesis: A Perspective of Sustainable Development in Indonesia

    Science.gov (United States)

    Nuansa, Citrasmara Galuh; Widodo, Wahyu

    2018-02-01

    Sustainable development with three main pillars, namely environmental, economic, and social, is the concept of country's development to achieve inclusive economic growth, good environmental quality, and improvement of people's welfare. However, the dominance of economic factors cause various environmental problem. This phenomenon occurs in most of developing countries, including in Indonesia. The relationship between economic activity and environmental quality has been widely discussed and empirically tested by scholars. This descriptive research analysed the hypothesis called Environmental Kuznets Curve (EKC) from a perspective of sustainable development in Indonesia. EKC hypothesis illustrates the relationship between economic growth and environmental degradation forming an inverted U-curve, indicating that at the beginning of development, environmental quality will decrease along with increasing economic growth, and then reached a certain point the environmental quality will gradually improve. In this paper will be discussed how the relationship between environmental quality and economic growth in Indonesia was investigated. The preliminary results show that most of the empirical studies use the conventional approach, in which the CO2 emission used as the proxy of environmental degradation. The existence of inverted U-curve is also inconclusive. Therefore, the extension research on the relationship between economic growth and environmental quality in Indonesia using the EKC hypothesis is required.

  16. Theoretical foundations for environmental Kuznets curve analysis

    Science.gov (United States)

    Lantz, Van

    This thesis provides a dynamic theory for analyzing the paths of aggregate output and pollution in a country over time. An infinite horizon, competitive growth-pollution model is explored in order to determine the role that economic scale, production techniques, and pollution regulations play in explaining the inverted U-shaped relationship between output and some forms of pollution (otherwise known as the Environmental Kuznets Curve, or EKC). Results indicate that the output-pollution relationship may follow a strictly increasing, strictly decreasing (but bounded), inverted U-shaped, or some combination of curves. While the 'scale' effect may cause output and pollution to exhibit a monotonic relationship, 'technique' and 'regulation' effects may ultimately cause a de-linking of these two variables. Pollution-minimizing energy regulation policies are also investigated within this framework. It is found that the EKC may be 'flattened' or even eliminated moving from a poorly-regulated economy to one that minimizes pollution. The model is calibrated to the US economy for output (gross national product, GNP) and two pollutants (sulfur dioxide, SO2, and carbon dioxide, CO2) over the period 1900 to 1990. Results indicate that the model replicates the observations quite well. The predominance of 'scale' effects cause aggregate SO2 and CO2 levels to increase with GNP in the early stages of development. Then, in the case of SO 2, 'technique' and 'regulation' effects may be the cause of falling SO2 levels with continued economic growth (establishing the EKC). CO2 continues to monotonically increase as output levels increase over time. The positive relationship may be due to the lack of regulations on this pollutant. If stricter regulation policies were instituted in the two case studies, an improved allocation of resources may result. While GNP may be 2.596 to 20% lower than what has been realized in the US economy (depending on the pollution variable analyzed), individual

  17. On a Versatile Stochastic Growth Model

    Directory of Open Access Journals (Sweden)

    Samiur Arif

    2012-06-01

    Full Text Available Growth phenomena are ubiquitous and pervasive not only in biology and the medical sciences, but also in economics, marketing and the computer and social sciences. We introduce a three-parameter version of the classic pure-birth process growth model when suitably instantiated, can be used to model growth phenomena in many seemingly unrelated application domains. We point out that the model is computationally attractive since it admits of conceptually simple, closed form solutions for the time-dependent probabilities.

  18. A random matrix model for elliptic curve L-functions of finite conductor

    International Nuclear Information System (INIS)

    Dueñez, E; Huynh, D K; Keating, J P; Snaith, N C; Miller, S J

    2012-01-01

    We propose a random-matrix model for families of elliptic curve L-functions of finite conductor. A repulsion of the critical zeros of these L-functions away from the centre of the critical strip was observed numerically by Miller (2006 Exp. Math. 15 257–79); such behaviour deviates qualitatively from the conjectural limiting distribution of the zeros (for large conductors this distribution is expected to approach the one-level density of eigenvalues of orthogonal matrices after appropriate rescaling). Our purpose here is to provide a random-matrix model for Miller’s surprising discovery. We consider the family of even quadratic twists of a given elliptic curve. The main ingredient in our model is a calculation of the eigenvalue distribution of random orthogonal matrices whose characteristic polynomials are larger than some given value at the symmetry point in the spectra. We call this sub-ensemble of SO(2N) the excised orthogonal ensemble. The sieving-off of matrices with small values of the characteristic polynomial is akin to the discretization of the central values of L-functions implied by the formulae of Waldspurger and Kohnen–Zagier. The cut-off scale appropriate to modelling elliptic curve L-functions is exponentially small relative to the matrix size N. The one-level density of the excised ensemble can be expressed in terms of that of the well-known Jacobi ensemble, enabling the former to be explicitly calculated. It exhibits an exponentially small (on the scale of the mean spacing) hard gap determined by the cut-off value, followed by soft repulsion on a much larger scale. Neither of these features is present in the one-level density of SO(2N). When N → ∞ we recover the limiting orthogonal behaviour. Our results agree qualitatively with Miller’s discrepancy. Choosing the cut-off appropriately gives a model in good quantitative agreement with the number-theoretical data. (paper)

  19. Viscoelastic model of tungsten 'fuzz' growth

    International Nuclear Information System (INIS)

    Krasheninnikov, S I

    2011-01-01

    A viscoelastic model of fuzz growth is presented. The model describes the main features of tungsten fuzz observed in experiments. It gives estimates of fuzz growth rate and temperature range close to experimental ones.

  20. The Forecasting Power of the Yield Curve, a Supervised Factor Model Approach

    DEFF Research Database (Denmark)

    Boldrini, Lorenzo; Hillebrand, Eric Tobias

    loadings have the Nelson and Siegel (1987) structure and we consider one forecast target at a time. We compare the forecasting performance of our specification to benchmark models such as principal components regression, partial least squares, and ARMA(p,q) processes. We use the yield curve data from G...

  1. Technological change in energy systems. Learning curves, logistic curves and input-output coefficients

    International Nuclear Information System (INIS)

    Pan, Haoran; Koehler, Jonathan

    2007-01-01

    Learning curves have recently been widely adopted in climate-economy models to incorporate endogenous change of energy technologies, replacing the conventional assumption of an autonomous energy efficiency improvement. However, there has been little consideration of the credibility of the learning curve. The current trend that many important energy and climate change policy analyses rely on the learning curve means that it is of great importance to critically examine the basis for learning curves. Here, we analyse the use of learning curves in energy technology, usually implemented as a simple power function. We find that the learning curve cannot separate the effects of price and technological change, cannot reflect continuous and qualitative change of both conventional and emerging energy technologies, cannot help to determine the time paths of technological investment, and misses the central role of R and D activity in driving technological change. We argue that a logistic curve of improving performance modified to include R and D activity as a driving variable can better describe the cost reductions in energy technologies. Furthermore, we demonstrate that the top-down Leontief technology can incorporate the bottom-up technologies that improve along either the learning curve or the logistic curve, through changing input-output coefficients. An application to UK wind power illustrates that the logistic curve fits the observed data better and implies greater potential for cost reduction than the learning curve does. (author)

  2. The i-V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

    KAUST Repository

    Han, Jie

    2016-07-17

    The i-V curve describes the current drawn from a flame as a function of the voltage difference applied across the reaction zone. Since combustion diagnostics and flame control strategies based on electric fields depend on the amount of current drawn from flames, there is significant interest in modeling and understanding i-V curves. We implement and apply a detailed model for the simulation of the production and transport of ions and electrons in one-dimensional premixed flames. An analytical reduced model is developed based on the detailed one, and analytical expressions are used to gain insight into the characteristics of the i-Vcurve for various flame configurations. In order for the reduced model to capture the spatial distribution of the electric field accurately, the concept of a dead zone region, where voltage is constant, is introduced, and a suitable closure for the spatial extent of the dead zone is proposed and validated. The results from the reduced modeling framework are found to be in good agreement with those from the detailed simulations. The saturation voltage is found to depend significantly on the flame location relative to the electrodes, and on the sign of the voltage difference applied. Furthermore, at sub-saturation conditions, the current is shown to increase linearly or quadratically with the applied voltage, depending on the flame location. These limiting behaviors exhibited by the reduced model elucidate the features of i-V curves observed experimentally. The reduced model relies on the existence of a thin layer where charges are produced, corresponding to the reaction zone of a flame. Consequently, the analytical model we propose is not limited to the study of premixed flames, and may be applied easily to others configurations, e.g.~nonpremixed counterflow flames.

  3. Calculation of accurate small angle X-ray scattering curves from coarse-grained protein models

    Directory of Open Access Journals (Sweden)

    Stovgaard Kasper

    2010-08-01

    Full Text Available Abstract Background Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference. Results We present a method for the efficient calculation of accurate SAXS curves based on the Debye formula and a set of scattering form factors for dummy atom representations of amino acids. Such a method avoids the computationally costly iteration over all atoms. We estimated the form factors using generated data from a set of high quality protein structures. No ad hoc scaling or correction factors are applied in the calculation of the curves. Two coarse-grained representations of protein structure were investigated; two scattering bodies per amino acid led to significantly better results than a single scattering body. Conclusion We show that the obtained point estimates allow the calculation of accurate SAXS curves from coarse-grained protein models. The resulting curves are on par with the current state-of-the-art program CRYSOL, which requires full atomic detail. Our method was also comparable to CRYSOL in recognizing native structures among native-like decoys. As a proof-of-concept, we combined the coarse-grained Debye calculation with a previously described probabilistic model of protein structure, TorusDBN. This resulted in a significant improvement in the decoy recognition performance. In conclusion, the presented method shows great promise for

  4. Mathematical modeling of microbial growth in milk

    Directory of Open Access Journals (Sweden)

    Jhony Tiago Teleken

    2011-12-01

    Full Text Available A mathematical model to predict microbial growth in milk was developed and analyzed. The model consists of a system of two differential equations of first order. The equations are based on physical hypotheses of population growth. The model was applied to five different sets of data of microbial growth in dairy products selected from Combase, which is the most important database in the area with thousands of datasets from around the world, and the results showed a good fit. In addition, the model provides equations for the evaluation of the maximum specific growth rate and the duration of the lag phase which may provide useful information about microbial growth.

  5. Water security, risk, and economic growth: Insights from a dynamical systems model

    Science.gov (United States)

    Dadson, Simon; Hall, Jim W.; Garrick, Dustin; Sadoff, Claudia; Grey, David; Whittington, Dale

    2017-08-01

    Investments in the physical infrastructure, human capital, and institutions needed for water resources management have been noteworthy in the development of most civilizations. These investments affect the economy in two distinct ways: (i) by improving the factor productivity of water in multiple economic sectors, especially those that are water intensive such as agriculture and energy and (ii) by reducing acute and chronic harmful effects of water-related hazards like floods, droughts, and water-related diseases. The need for capital investment to mitigate risks and promote economic growth is widely acknowledged, but prior conceptual work on the relationship between water-related investments and economic growth has focused on the productive and harmful roles of water in the economy independently. Here the two influences are combined using a simple, dynamical systems model of water-related investment, risk, and growth. In cases where initial water security is low, initial investment in water-related assets enables growth. Without such investment, losses due to water-related hazards exert a drag on economic growth and may create a poverty trap. The presence and location of the poverty trap is context-specific and depends on the exposure of productive water-related assets to water-related risk. Exogenous changes in water-related risk can potentially push an economy away from a growth path toward a poverty trap. Our investigation shows that an inverted-U-shaped investment relation between the level of investment in water security and the current level of water security leads to faster rates of growth than the alternatives that we consider here, and that this relation is responsible for the "S"-curve that is posited in the literature. These results illustrate the importance of accounting for environmental and health risks in economic models and offer insights for the design of robust policies for investment in water-related productive assets to manage risk, in the face

  6. Dynamics of curved fronts

    CERN Document Server

    Pelce, Pierre

    1989-01-01

    In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.

  7. Real-Time Exponential Curve Fits Using Discrete Calculus

    Science.gov (United States)

    Rowe, Geoffrey

    2010-01-01

    An improved solution for curve fitting data to an exponential equation (y = Ae(exp Bt) + C) has been developed. This improvement is in four areas -- speed, stability, determinant processing time, and the removal of limits. The solution presented avoids iterative techniques and their stability errors by using three mathematical ideas: discrete calculus, a special relationship (be tween exponential curves and the Mean Value Theorem for Derivatives), and a simple linear curve fit algorithm. This method can also be applied to fitting data to the general power law equation y = Ax(exp B) + C and the general geometric growth equation y = Ak(exp Bt) + C.

  8. Learning Curve? Which One?

    Directory of Open Access Journals (Sweden)

    Paulo Prochno

    2004-07-01

    Full Text Available Learning curves have been studied for a long time. These studies provided strong support to the hypothesis that, as organizations produce more of a product, unit costs of production decrease at a decreasing rate (see Argote, 1999 for a comprehensive review of learning curve studies. But the organizational mechanisms that lead to these results are still underexplored. We know some drivers of learning curves (ADLER; CLARK, 1991; LAPRE et al., 2000, but we still lack a more detailed view of the organizational processes behind those curves. Through an ethnographic study, I bring a comprehensive account of the first year of operations of a new automotive plant, describing what was taking place on in the assembly area during the most relevant shifts of the learning curve. The emphasis is then on how learning occurs in that setting. My analysis suggests that the overall learning curve is in fact the result of an integration process that puts together several individual ongoing learning curves in different areas throughout the organization. In the end, I propose a model to understand the evolution of these learning processes and their supporting organizational mechanisms.

  9. Data driven modelling of vertical atmospheric radiation

    International Nuclear Information System (INIS)

    Antoch, Jaromir; Hlubinka, Daniel

    2011-01-01

    In the Czech Hydrometeorological Institute (CHMI) there exists a unique set of meteorological measurements consisting of the values of vertical atmospheric levels of beta and gamma radiation. In this paper a stochastic data-driven model based on nonlinear regression and on nonhomogeneous Poisson process is suggested. In the first part of the paper, growth curves were used to establish an appropriate nonlinear regression model. For comparison we considered a nonhomogeneous Poisson process with its intensity based on growth curves. In the second part both approaches were applied to the real data and compared. Computational aspects are briefly discussed as well. The primary goal of this paper is to present an improved understanding of the distribution of environmental radiation as obtained from the measurements of the vertical radioactivity profiles by the radioactivity sonde system. - Highlights: → We model vertical atmospheric levels of beta and gamma radiation. → We suggest appropriate nonlinear regression model based on growth curves. → We compare nonlinear regression modelling with Poisson process based modeling. → We apply both models to the real data.

  10. Comparison and evaluation of mathematical lactation curve ...

    African Journals Online (AJOL)

    p2492989

    A mathematical model of the lactation curve provides summary information about culling and milking strategies ..... Table 2 Statistics of the edited data for first lactation Holstein cows ..... Application of different models to the lactation curves of.

  11. Universality in stochastic exponential growth.

    Science.gov (United States)

    Iyer-Biswas, Srividya; Crooks, Gavin E; Scherer, Norbert F; Dinner, Aaron R

    2014-07-11

    Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

  12. Stochastic process corrosion growth models for pipeline reliability

    International Nuclear Information System (INIS)

    Bazán, Felipe Alexander Vargas; Beck, André Teófilo

    2013-01-01

    Highlights: •Novel non-linear stochastic process corrosion growth model is proposed. •Corrosion rate modeled as random Poisson pulses. •Time to corrosion initiation and inherent time-variability properly represented. •Continuous corrosion growth histories obtained. •Model is shown to precisely fit actual corrosion data at two time points. -- Abstract: Linear random variable corrosion models are extensively employed in reliability analysis of pipelines. However, linear models grossly neglect well-known characteristics of the corrosion process. Herein, a non-linear model is proposed, where corrosion rate is represented as a Poisson square wave process. The resulting model represents inherent time-variability of corrosion growth, produces continuous growth and leads to mean growth at less-than-one power of time. Different corrosion models are adjusted to the same set of actual corrosion data for two inspections. The proposed non-linear random process corrosion growth model leads to the best fit to the data, while better representing problem physics

  13. One Curve Embedded Full-Bridge MMC Modeling Method with Detailed Representation of IGBT Characteristics

    Science.gov (United States)

    Hongyang, Yu; Zhengang, Lu; Xi, Yang

    2017-05-01

    Modular Multilevel Converter is more and more widely used in high voltage DC transmission system and high power motor drive system. It is a major topological structure for high power AC-DC converter. Due to the large module number, the complex control algorithm, and the high power user’s back ground, the MMC model used for simulation should be as accurate as possible to simulate the details of how MMC works for the dynamic testing of the MMC controller. But so far, there is no sample simulation MMC model which can simulate the switching dynamic process. In this paper, one curve embedded full-bridge MMC modeling method with detailed representation of IGBT characteristics is proposed. This method is based on the switching curve referring and sample circuit calculation, and it is sample for implementation. Based on the simulation comparison test under Matlab/Simulink, the proposed method is proved to be correct.

  14. Simulating Supernova Light Curves

    Energy Technology Data Exchange (ETDEWEB)

    Even, Wesley Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dolence, Joshua C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-05

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.

  15. Simulating Supernova Light Curves

    International Nuclear Information System (INIS)

    Even, Wesley Paul; Dolence, Joshua C.

    2016-01-01

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth's atmosphere.

  16. The Predicting Model of E-commerce Site Based on the Ideas of Curve Fitting

    Science.gov (United States)

    Tao, Zhang; Li, Zhang; Dingjun, Chen

    On the basis of the idea of the second multiplication curve fitting, the number and scale of Chinese E-commerce site is analyzed. A preventing increase model is introduced in this paper, and the model parameters are solved by the software of Matlab. The validity of the preventing increase model is confirmed though the numerical experiment. The experimental results show that the precision of preventing increase model is ideal.

  17. Ultraviolet Light Curves of Gaia16apd in Superluminous Supernova Models

    Energy Technology Data Exchange (ETDEWEB)

    Tolstov, Alexey; Zhiglo, Andrey; Nomoto, Ken’ichi; Blinnikov, Sergei [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Sorokina, Elena [Sternberg Astronomical Institute, M.V.Lomonosov Moscow State University, 119234 Moscow (Russian Federation); Kozyreva, Alexandra, E-mail: alexey.tolstov@ipmu.jp [The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

    2017-08-10

    Observations of Gaia16apd revealed extremely luminous ultraviolet emission among superluminous supernovae (SLSNe). Using radiation hydrodynamics simulations, we perform a comparison of UV light curves, color temperatures, and photospheric velocities between the most popular SLSN models: pair-instability supernova, magnetar, and interaction with circumstellar medium. We find that the interaction model is the most promising to explain the extreme UV luminosity of Gaia16apd. The differences in late-time UV emission and in color evolution found between the models can be used to link an observed SLSN event to the most appropriate model. Observations at UV wavelengths can be used to clarify the nature of SLSNe and more attention should be paid to them in future follow-up observations.

  18. Improving 3d Spatial Queries Search: Newfangled Technique of Space Filling Curves in 3d City Modeling

    Science.gov (United States)

    Uznir, U.; Anton, F.; Suhaibah, A.; Rahman, A. A.; Mioc, D.

    2013-09-01

    The advantages of three dimensional (3D) city models can be seen in various applications including photogrammetry, urban and regional planning, computer games, etc.. They expand the visualization and analysis capabilities of Geographic Information Systems on cities, and they can be developed using web standards. However, these 3D city models consume much more storage compared to two dimensional (2D) spatial data. They involve extra geometrical and topological information together with semantic data. Without a proper spatial data clustering method and its corresponding spatial data access method, retrieving portions of and especially searching these 3D city models, will not be done optimally. Even though current developments are based on an open data model allotted by the Open Geospatial Consortium (OGC) called CityGML, its XML-based structure makes it challenging to cluster the 3D urban objects. In this research, we propose an opponent data constellation technique of space-filling curves (3D Hilbert curves) for 3D city model data representation. Unlike previous methods, that try to project 3D or n-dimensional data down to 2D or 3D using Principal Component Analysis (PCA) or Hilbert mappings, in this research, we extend the Hilbert space-filling curve to one higher dimension for 3D city model data implementations. The query performance was tested using a CityGML dataset of 1,000 building blocks and the results are presented in this paper. The advantages of implementing space-filling curves in 3D city modeling will improve data retrieval time by means of optimized 3D adjacency, nearest neighbor information and 3D indexing. The Hilbert mapping, which maps a subinterval of the [0, 1] interval to the corresponding portion of the d-dimensional Hilbert's curve, preserves the Lebesgue measure and is Lipschitz continuous. Depending on the applications, several alternatives are possible in order to cluster spatial data together in the third dimension compared to its

  19. Nonconvex Model of Material Growth: Mathematical Theory

    Science.gov (United States)

    Ganghoffer, J. F.; Plotnikov, P. I.; Sokolowski, J.

    2018-06-01

    The model of volumetric material growth is introduced in the framework of finite elasticity. The new results obtained for the model are presented with complete proofs. The state variables include the deformations, temperature and the growth factor matrix function. The existence of global in time solutions for the quasistatic deformations boundary value problem coupled with the energy balance and the evolution of the growth factor is shown. The mathematical results can be applied to a wide class of growth models in mechanics and biology.

  20. Development of hot and cool executive functions in middle childhood: Three-year growth curves of decision making and working memory updating.

    Science.gov (United States)

    Lensing, Nele; Elsner, Birgit

    2018-05-07

    Although middle childhood is an important period for the development of hot and cool executive functions (EFs), longitudinal studies investigating trajectories of childhood EF development are still limited and little is known about predictors for individual developmental trajectories. The current study examined the development of two typical facets of cool and hot EFs over a 3-year period during middle childhood, comparing a younger cohort (6- and 7-year-olds at the first wave [T1]; n = 621) and an older cohort (8- and 9-year-olds at T1; n = 975) of children. "Cool" working memory updating (WM) was assessed using a backward digit span task, and "hot" decision making (DM) was assessed using a child variant of the Iowa Gambling Task. Linear latent growth curve analyses revealed evidence for developmental growth as well as interindividual variance in the initial level and rate of change in both EF facets. Initial level of WM was positively associated with age (both between and within cohorts), socioeconomic status, verbal ability, and processing speed, whereas initial levels of DM were, in addition to a (potentially age-related) cohort effect, exclusively predicted by gender, with boys outperforming girls. None of the variables predicted the rate of change, that is, the developmental trajectories. However, younger children, as compared with older children, had slightly steeper WM growth curves over time, hinting at a leveling off in the development of WM during middle childhood. In sum, these data add important evidence to the understanding of hot and cool EF development during middle childhood. Copyright © 2018 Elsevier Inc. All rights reserved.

  1. Modeling Root Growth, Crop Growth and N Uptake of Winter Wheat Based on SWMS_2D: Model and Validation

    Directory of Open Access Journals (Sweden)

    Dejun Yang

    Full Text Available ABSTRACT Simulations for root growth, crop growth, and N uptake in agro-hydrological models are of significant concern to researchers. SWMS_2D is one of the most widely used physical hydrologically related models. This model solves equations that govern soil-water movement by the finite element method, and has a public access source code. Incorporating key agricultural components into the SWMS_2D model is of practical importance, especially for modeling some critical cereal crops such as winter wheat. We added root growth, crop growth, and N uptake modules into SWMS_2D. The root growth model had two sub-models, one for root penetration and the other for root length distribution. The crop growth model used was adapted from EU-ROTATE_N, linked to the N uptake model. Soil-water limitation, nitrogen limitation, and temperature effects were all considered in dry-weight modeling. Field experiments for winter wheat in Bouwing, the Netherlands, in 1983-1984 were selected for validation. Good agreements were achieved between simulations and measurements, including soil water content at different depths, normalized root length distribution, dry weight and nitrogen uptake. This indicated that the proposed new modules used in the SWMS_2D model are robust and reliable. In the future, more rigorous validation should be carried out, ideally under 2D situations, and attention should be paid to improve some modules, including the module simulating soil N mineralization.

  2. Explaining environmental Kuznets curves. How pollution induces policy and new technology

    International Nuclear Information System (INIS)

    Smulders, S.; Bretschger, L.

    2000-01-01

    Production often causes pollution as a by-product. Once pollution problems become too severe, regulation is introduced by political authorities which forces the economy to make a transition to cleaner production processes. We model this transition as a change in 'general purpose technology' (GPT) and investigate how it interferes with economic growth driven by quality-improvements. The model gives an explanation for the inverted U-shaped relationship found in empirical research for many pollutants, often referred to as the Environmental Kuznets Curve (EKC). We provide an analytical foundation for the claim that the rise and decline of pollution can be explained by policy-induced technology shifts. 19 refs

  3. Type Ia Supernova Light Curve Inference: Hierarchical Models for Nearby SN Ia in the Optical and Near Infrared

    Science.gov (United States)

    Mandel, Kaisey; Kirshner, R. P.; Narayan, G.; Wood-Vasey, W. M.; Friedman, A. S.; Hicken, M.

    2010-01-01

    I have constructed a comprehensive statistical model for Type Ia supernova light curves spanning optical through near infrared data simultaneously. The near infrared light curves are found to be excellent standard candles (sigma(MH) = 0.11 +/- 0.03 mag) that are less vulnerable to systematic error from dust extinction, a major confounding factor for cosmological studies. A hierarchical statistical framework incorporates coherently multiple sources of randomness and uncertainty, including photometric error, intrinsic supernova light curve variations and correlations, dust extinction and reddening, peculiar velocity dispersion and distances, for probabilistic inference with Type Ia SN light curves. Inferences are drawn from the full probability density over individual supernovae and the SN Ia and dust populations, conditioned on a dataset of SN Ia light curves and redshifts. To compute probabilistic inferences with hierarchical models, I have developed BayeSN, a Markov Chain Monte Carlo algorithm based on Gibbs sampling. This code explores and samples the global probability density of parameters describing individual supernovae and the population. I have applied this hierarchical model to optical and near infrared data of over 100 nearby Type Ia SN from PAIRITEL, the CfA3 sample, and the literature. Using this statistical model, I find that SN with optical and NIR data have a smaller residual scatter in the Hubble diagram than SN with only optical data. The continued study of Type Ia SN in the near infrared will be important for improving their utility as precise and accurate cosmological distance indicators.

  4. Testing R&D-Based Endogenous Growth Models

    DEFF Research Database (Denmark)

    Kruse-Andersen, Peter Kjær

    2017-01-01

    R&D-based growth models are tested using US data for the period 1953-2014. A general growth model is developed which nests the model varieties of interest. The model implies a cointegrating relationship between multifactor productivity, research intensity, and employment. This relationship...... is estimated using cointegrated VAR models. The results provide evidence against the widely used fully endogenous variety and in favor of the semi-endogenous variety. Forecasts based on the empirical estimates suggest that the slowdown in US productivity growth will continue. Particularly, the annual long...

  5. Numerical modeling of the effect of surface topology on the saturated pool nucleate boiling curve

    International Nuclear Information System (INIS)

    Unal, C.; Pasamehmetoglu, K.O.

    1993-01-01

    A numerical study of saturated pool nucleate boiling with an emphasis on the effect of surface topography is presented. The numerical model consisted of solving the three-dimensional transient heat conduction equation within the heater subjected to nucleate boiling over its upper surface. The surface topography model considered the distribution of the cavity and cavity angles based on exponential and normal probability functions. Parametric results showed that the saturated nucleate boiling curve shifted left and became steeper with an increase in the mean cavity radius. The boiling curve was found to be sensitive to the selection of how many cavities were selected for each octagonal cell. A small variation in the statistical parameters, especially cavity radii for smooth surfaces, resulted in noticeable differences in wall superheat for a given heat flux. This result indicated that while the heat transfer coefficient increased with cavity radii, the cavity radii or height alone was not sufficient to characterize the boiling curve. It also suggested that statistical experimental data should consider large samples to characterize the surface topology. The boiling curve shifted to the right when the cavity angle was obtained using a normal distribution. This effect became less important when the number of cavities for each cell was increasing because the probability of the potential cavity with a larger radius in each cell was increased. When the contact angle of the fluid decreased for a given mean cavity radii, the boiling curve shifted to the right. This shift was more pronounced at smaller mean cavity radii and decreased with increasing mean cavity radii

  6. 3D Hilbert Space Filling Curves in 3D City Modeling for Faster Spatial Queries

    DEFF Research Database (Denmark)

    Ujang, Uznir; Antón Castro, Francesc/François; Azri, Suhaibah

    2014-01-01

    The advantages of three dimensional (3D) city models can be seen in various applications including photogrammetry, urban and regional planning, computer games, etc. They expand the visualization and analysis capabilities of Geographic Information Systems on cities, and they can be developed using...... method, retrieving portions of and especially searching these 3D city models, will not be done optimally. Even though current developments are based on an open data model allotted by the Open Geospatial Consortium (OGC) called CityGML, its XML-based structure makes it challenging to cluster the 3D urban...... objects. In this research, the authors propose an opponent data constellation technique of space-filling curves (3D Hilbert curves) for 3D city model data representation. Unlike previous methods, that try to project 3D or n-dimensional data down to 2D or 3D using Principal Component Analysis (PCA...

  7. Comprehensive computational model for combining fluid hydrodynamics, light transport and biomass growth in a Taylor vortex algal photobioreactor: Lagrangian approach.

    Science.gov (United States)

    Gao, Xi; Kong, Bo; Vigil, R Dennis

    2017-01-01

    A comprehensive quantitative model incorporating the effects of fluid flow patterns, light distribution, and algal growth kinetics on biomass growth rate is developed in order to predict the performance of a Taylor vortex algal photobioreactor for culturing Chlorella vulgaris. A commonly used Lagrangian strategy for coupling the various factors influencing algal growth was employed whereby results from computational fluid dynamics and radiation transport simulations were used to compute numerous microorganism light exposure histories, and this information in turn was used to estimate the global biomass specific growth rate. The simulations provide good quantitative agreement with experimental data and correctly predict the trend in reactor performance as a key reactor operating parameter is varied (inner cylinder rotation speed). However, biomass growth curves are consistently over-predicted and potential causes for these over-predictions and drawbacks of the Lagrangian approach are addressed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Characterization of subcritical water oxidation with in situ monitoring and self-modeling curve resolution

    International Nuclear Information System (INIS)

    Gemperline, Paul J.; Yang Yu; Bian Zhihui

    2003-01-01

    In this paper, a subcritical water oxidation (SBWO) process was monitored using self-modeling curve resolution (SMCR) of in situ UV-Vis measurements to estimate time-dependant composition profiles of reactants, intermediates and products. A small laboratory scale reactor with UV-Vis fiber-optic probes and a flow cell was used to demonstrate the usefulness of SMCR for monitoring the destruction of model compounds phenol, benzoic acid, and aniline in a dilute aqueous solutions. Hydrogen peroxide was used as the oxidizing reagent at moderate temperature (150-250 deg. C) and pressure (60-90 atm) in a single phase. By use of in situ monitoring, reaction times were easily determined and conditions for efficient oxidations were easily diagnosed without the need for time consuming off-line reference measurements. For selected runs, the destruction of the model compound was confirmed by gas chromatography and chemical oxygen demand (COD) measurements. Suspected intermediate oxidation products were easily detected by the use of UV-Vis spectrometry and self-modeling curve resolution, but could not be detected by gas chromatography

  9. Curves of growth of spectral lines emitted by a laser-induced plasma: influence of the temporal evolution and spatial inhomogeneity of the plasma

    Energy Technology Data Exchange (ETDEWEB)

    Aguilera, J.A.; Bengoechea, J.; Aragon, C. E-mail: carlos.aragon@unavarra.es

    2003-02-03

    The curves of growth (COG) of five Fe I lines emitted from a laser-induced plasma, generated with Fe-Ni alloys in air at atmospheric pressure, have been investigated. Spectral lines with different energy levels and line widths, emitted with a broad range of optical depths, have been included in the study in order to check the validity of theoretical models proposed for COG generation, based in the radiative transfer within a plasma in local thermodynamic equilibrium. The COGs have been measured at time windows of 4-5 {mu}s and 15-18 {mu}s. The Stark widths of the Fe I lines have been obtained, and the line widths have been determined by measuring the plasma electron density at the time windows selected. It is shown that at a time window of 4-5 {mu}s, the inhomogeneity of the plasma magnitudes has an important influence on the COGs of intense lines. For this time window, a two-region model of the plasma has been used to generate theoretical COGs that describe satisfactorily the experimental curves of all the lines using a single set of plasma parameters. The results reveal the existence of considerable gradients between the inner and the outer plasma regions in the temperature (9400-7800 K) and in the density of Fe atoms (4x10{sup 16}-0.02x10{sup 16} cm{sup -3} for a sample with 100% Fe). On the contrary, at the time window 15-18 {mu}s, at which the plasma has suffered most of its expansion and cooling process, the COGs of all the lines may be described by a single-region model, corresponding to a plasma with uniform temperature (6700 K) and density of Fe atoms (0.06x10{sup 16} cm{sup -3} for a sample with 100% Fe). It is also shown that at initial times, the plasma inhomogeneity has an important effect in the line profiles of intense spectral lines, which are described by using the two-region model of the laser-induced plasma.

  10. Implementation of a correction factor for the Pohlhausen laminar boundary layer applied on the CEVA curved wall jet model

    Directory of Open Access Journals (Sweden)

    Valeriu DRAGAN

    2013-09-01

    Full Text Available Curved wall jets have many technical applications, ranging from aeronautical circulation controlled wings to micro-fluidics and cryogenics. This paper addresses the issue of correctly estimating the boundary layer separation for laminar curved wall jets. For this, the Pohlhausen model was used in conjunction with the CEVA wall jet model with a semi-empirical modification which increases the accuracy for very thin jets. The method is therefore a mix of analytical equations with curve fitted experimental data in order to produce a simple yet effective way of estimating the boundary layer velocity profile along the curved wall. In order to cross-check the results, Newman’s empirical equation – which only provides a separation location but no information regarding the velocity profile - for boundary layer separation was used with good results. The hereby model could be used as a pre-design tool for rapid assessment of aeronautical high-lift applications such as Upper Surface Blown (USB or entrainment wings.

  11. [Application of decision curve on evaluation of MRI predictive model for early assessing pathological complete response to neoadjuvant therapy in breast cancer].

    Science.gov (United States)

    He, Y J; Li, X T; Fan, Z Q; Li, Y L; Cao, K; Sun, Y S; Ouyang, T

    2018-01-23

    Objective: To construct a dynamic enhanced MR based predictive model for early assessing pathological complete response (pCR) to neoadjuvant therapy in breast cancer, and to evaluate the clinical benefit of the model by using decision curve. Methods: From December 2005 to December 2007, 170 patients with breast cancer treated with neoadjuvant therapy were identified and their MR images before neoadjuvant therapy and at the end of the first cycle of neoadjuvant therapy were collected. Logistic regression model was used to detect independent factors for predicting pCR and construct the predictive model accordingly, then receiver operating characteristic (ROC) curve and decision curve were used to evaluate the predictive model. Results: ΔArea(max) and Δslope(max) were independent predictive factors for pCR, OR =0.942 (95% CI : 0.918-0.967) and 0.961 (95% CI : 0.940-0.987), respectively. The area under ROC curve (AUC) for the constructed model was 0.886 (95% CI : 0.820-0.951). Decision curve showed that in the range of the threshold probability above 0.4, the predictive model presented increased net benefit as the threshold probability increased. Conclusions: The constructed predictive model for pCR is of potential clinical value, with an AUC>0.85. Meanwhile, decision curve analysis indicates the constructed predictive model has net benefit from 3 to 8 percent in the likely range of probability threshold from 80% to 90%.

  12. Kinetic Model of Growth of Arthropoda Populations

    Science.gov (United States)

    Ershov, Yu. A.; Kuznetsov, M. A.

    2018-05-01

    Kinetic equations were derived for calculating the growth of crustacean populations ( Crustacea) based on the biological growth model suggested earlier using shrimp ( Caridea) populations as an example. The development cycle of successive stages for populations can be represented in the form of quasi-chemical equations. The kinetic equations that describe the development cycle of crustaceans allow quantitative prediction of the development of populations depending on conditions. In contrast to extrapolation-simulation models, in the developed kinetic model of biological growth the kinetic parameters are the experimental characteristics of population growth. Verification and parametric identification of the developed model on the basis of the experimental data showed agreement with experiment within the error of the measurement technique.

  13. Modelling critical NDVI curves in perennial ryegrass

    DEFF Research Database (Denmark)

    Gislum, R; Boelt, B

    2010-01-01

      The use of optical sensors to measure canopy reflectance and calculate crop index as e.g. normalized difference vegetation index (NDVI) is widely used in agricultural crops, but has so far not been implemented in herbage seed production. The present study has the purpose to develop a critical...... NDVI curve where the critical NDVI, defined as the minimum NDVI obtained to achieve a high seed yield, will be modelled during the growing season. NDVI measurements were made at different growing degree days (GDD) in a three year field experiment where different N application rates were applied....... There was a clear maximum in the correlation coefficient between seed yield and NDVI in the period from approximately 700 to 900 GDD. At this time there was an exponential relationship between NDVI and seed yield where highest seed yield were at NDVI ~0.9. Theoretically the farmers should aim for an NDVI of 0...

  14. An analytic model of pool boiling critical heat flux on an immerged downward facing curved surface

    International Nuclear Information System (INIS)

    He, Hui; Pan, Liang-ming; Wu, Yao; Chen, De-qi

    2015-01-01

    Highlights: • Thin liquid film and supplement of liquid contribute to the CHF. • CHF increases from the bottom to the upper of the lowerhead. • Evaporation of thin liquid film is dominant nearby bottom region. • The subcooling has significant effects on the CHF. - Abstract: In this paper, an analytical model of the critical heat flux (CHF) on the downward facing curved surface for pool boiling has been proposed, which hypothesizes that the CHF on the downward facing curved is composed of two parts, i.e. the evaporation of the thin liquid film underneath the elongated bubble adhering to the lower head outer surface and the depletion of supplement of liquid due to the relative motion of vapor bubbles along with the downward facing curved. The former adopts the Kelvin–Helmholtz instability analysis of vapor–liquid interface of the vapor jets which penetrating in the thin liquid film. When the heat flux closing to the CHF point, the vapor–liquid interface becomes highly distorted, which block liquid to feed the thin liquid film and the thin liquid film will dry out gradually. While the latter considers that the vapor bubbles move along with the downward facing curved surface, and the liquid in two-phase boundary layer enter the liquid film that will be exhausted when the CHF occurs. Based on the aforementioned mechanism and the energy balance between the thin liquid film evaporation and water feeding, and taking the subcooling of the bulk water into account, the mathematic model about the downward facing curved surface CHF has been proposed. The CHF of the downward facing curved surface for pool boiling increases along with the downward facing orientation except in the vicinity of bottom center region, because in this region the vapor bubble almost stagnates and the evaporation of the thin liquid film is dominant. In addition, the subcooling has significant effect on the CHF. Comparing the result of this model with the published experimental results show

  15. Differential model of macroeconomic growth with endogenic cyclicity

    Directory of Open Access Journals (Sweden)

    Mikhail I. Geraskin

    2017-09-01

    Full Text Available Objective to elaborate a mathematical model of economic growth taking into account the cyclical nature of macroeconomic dynamics with the model parameters based on the Russian economy statistics. Methods economic and mathematical modeling system analysis regression factor analysis econometric time series analysis. Results the article states that under unstable economic growth in Russia forecasting of strategic prospects of the Russian economy is one of the topical directions of scientific studies. Furthermore construction of predictive models should be based on multiple factors taking into account such basic concepts as the neoKeynesian HarrodDomar model Ramsey ndash Cass ndash Koopmans model S. V. Dubovskiyrsquos concept as well as the neoclassical growth model by R. Solow. They served as the basis for developing a multifactor differential economic growth model which is a modification of the neoclassical growth model by R. Solow taking into account the laborsaving and capitalsaving forms of scientifictechnical progress and the Keynesian concept of investment. The model parameters are determined based on the dynamics of actual GDP employment fixed assets and investments in fixed assets for 19652016 in Russia on the basis of official statistics. The generalized model showed the presence of longwave fluctuations that are not detected during the individual periods modeling. The cyclical nature of macroeconomic dynamics with a period of 54 years was found which corresponds to the parameters of long waves by N. D. Kondratiev. Basing on the model the macroeconomic growth forecast was generated which shows that after 2020 the increase of scientifictechnical progress will be negative. Scientific novelty a model is proposed of the scientifictechnical progress indicator showing the growth rate of the capital productivity ratio to the saving rate a differential model of macroeconomic growth is obtained which endogenously takes cyclicity into account

  16. Herdabilidades de parâmetros de curvas de crescimento não-lineares em zebuínos, no estado de Pernambuco Heritabilities of nonlinear growth curve parameters in zebu breeds, in Pernambuco State, Northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Kleber Régis Santoro

    2005-12-01

    Full Text Available Objetivou-se estimar parâmetros genéticos e fenotípicos de curvas de crescimento de modelos não-lineares. Foram analisados dados de pesagem constantes no banco de dados de Controle de Desenvolvimento Ponderal da Associação Brasileira de Criadores de Zebu (ABCZ, referentes a 24.028 animais Zebu, nascidos entre 1960 e 2000, das raças Guzerá, Nelore e Nelore Mocho. As pesagens ocorreram ao nascimento e em intervalos de 90 dias até dois anos de idade. Os seguintes modelos não-lineares foram utilizados na análise dos dados de peso-idade: Brody, Gompertz, Logístico, von Bertalanffy e Richards. Os efeitos fixos estudados no modelo misto foram sexo, rebanho, ano e mês de nascimento e regime de criação. As herdabilidades para os parâmetros foram de baixa a alta magnitude, em geral, para todos os modelos. As correlações genéticas entre peso assintótico e taxa de maturidade e entre peso assintótico e velocidade de crescimento foram negativas, enquanto aquelas entre taxa de maturidade e velocidade de crescimento foram positivas. As correlações fenotípicas foram negativas entre peso assintótico e taxa de crescimento e entre peso assintótico e velocidade de crescimento e positivas entre taxa e velocidade de crescimento. Encontrou-se variabilidade possível de ser explorada em um programa de melhoramento genético, especialmente para a raça Nelore, que apresentou amostra de dados e resultados mais consistentes.Weight records of 24.028 zebu animals from Guzerá, Nelore, and Polled Nelore breeds available from Brazilian Association of Zebu Breeders (ABCZ database were used to estimate heritabilities of growth curve parameters. Non-linear Brody, Gompertz, Logistic, Mitscherlich, von Bertalanffy, Richards, and Double Logistic models including sex, farm, year of birth, month of birth, raising system, and interaction sex*raising system as fixed effects and sire and dam, as random effects were adjusted using weight-age records of animals

  17. Model-based Approach for Long-term Creep Curves of Alloy 617 for a High Temperature Gas-cooled Reactor

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Yin, Song Nan; Kim, Yong Wan

    2008-01-01

    Alloy 617 is a principal candidate alloy for the high temperature gas-cooled reactor (HTGR) components, because of its high creep rupture strength coupled with its good corrosion behavior in simulated HTGR-helium and its sufficient workability. To describe a creep strain-time curve well, various constitutive equations have been proposed by Kachanov-Rabotnov, Andrade, Garofalo, Evans and Maruyama, et al.. Among them, the K-R model has been used frequently, because a secondary creep resulting from a balance between a softening and a hardening of materials and a tertiary creep resulting from an appearance and acceleration of the internal or external damage processes are adequately considered. In the case of nickel-base alloys, it has been reported that a tertiary creep at a low strain range may be generated, and this tertiary stage may govern the total creep deformation. Therefore, a creep curve for nickel-based Alloy 617 will be predicted appropriately by using the K-R model that can reflect a tertiary creep. In this paper, the long-term creep curves for Alloy 617 were predicted by using the nonlinear least square fitting (NLSF) method in the K-R model. The modified K-R model was introduced to fit the full creep curves well. The values for the λ and K parameters in the modified K-R model were obtained with stresses

  18. Estimating regional centile curves from mixed data sources and countries.

    Science.gov (United States)

    van Buuren, Stef; Hayes, Daniel J; Stasinopoulos, D Mikis; Rigby, Robert A; ter Kuile, Feiko O; Terlouw, Dianne J

    2009-10-15

    Regional or national growth distributions can provide vital information on the health status of populations. In most resource poor countries, however, the required anthropometric data from purpose-designed growth surveys are not readily available. We propose a practical method for estimating regional (multi-country) age-conditional weight distributions based on existing survey data from different countries. We developed a two-step method by which one is able to model data with widely different age ranges and sample sizes. The method produces references both at the country level and at the regional (multi-country) level. The first step models country-specific centile curves by Box-Cox t and Box-Cox power exponential distributions implemented in generalized additive model for location, scale and shape through a common model. Individual countries may vary in location and spread. The second step defines the regional reference from a finite mixture of the country distributions, weighted by population size. To demonstrate the method we fitted the weight-for-age distribution of 12 countries in South East Asia and the Western Pacific, based on 273 270 observations. We modeled both the raw body weight and the corresponding Z score, and obtained a good fit between the final models and the original data for both solutions. We briefly discuss an application of the generated regional references to obtain appropriate, region specific, age-based dosing regimens of drugs used in the tropics. The method is an affordable and efficient strategy to estimate regional growth distributions where the standard costly alternatives are not an option. Copyright (c) 2009 John Wiley & Sons, Ltd.

  19. Prediction of fire growth on furniture using CFD

    Science.gov (United States)

    Pehrson, Richard David

    A fire growth calculation method has been developed that couples a computational fluid dynamics (CFD) model with bench scale cone calorimeter test data for predicting the rate of flame spread on compartment contents such as furniture. The commercial CFD code TASCflow has been applied to solve time averaged conservation equations using an algebraic multigrid solver with mass weighted skewed upstream differencing for advection. Closure models include k-e for turbulence, eddy breakup for combustion following a single step irreversible reaction with Arrhenius rate constant, finite difference radiation transfer, and conjugate heat transfer. Radiation properties are determined from concentrations of soot, CO2 and H2O using the narrow band model of Grosshandler and exponential wide band curve fit model of Modak. The growth in pyrolyzing area is predicted by treating flame spread as a series of piloted ignitions based on coupled gas-fluid boundary conditions. The mass loss rate from a given surface element follows the bench scale test data for input to the combustion prediction. The fire growth model has been tested against foam-fabric mattresses and chairs burned in the furniture calorimeter. In general, agreement between model and experiment for peak heat release rate (HRR), time to peak HRR, and total energy lost is within +/-20%. Used as a proxy for the flame spread velocity, the slope of the HRR curve predicted by model agreed with experiment within +/-20% for all but one case.

  20. Shaking Table Tests of Curved Bridge considering Bearing Friction Sliding Isolation

    Directory of Open Access Journals (Sweden)

    Lei Yan

    2016-01-01

    Full Text Available Specific to severe damage to curved bridges in earthquakes caused by the excessive force of the fixed bearings and piers, a new seismic design method on curved bridges considering bearing friction sliding isolation is proposed in this paper. Seismic model bridge and isolation model bridge with similarity ratio of 1/20 were made and the shaking table comparison test was conducted. The experimental results show that the isolation model curved bridge suffered less seismic damage than the seismic model curved bridge. The fundamental frequencies of the seismic model bridge and isolation model bridge decreased and the damping ratio increased with the increase of seismic intensity. Compared with seismic curved bridge, the maximum reduction rates of peak acceleration along the radial and tangential directions on the top of pier of the isolation model curved bridge were 47.3% and 55.5%, respectively, and the maximum reduction rate of the peak strain on the bottom of pier of the isolation model curved bridge was 43.4%. For the isolation model curved bridge, the maximum reduction rate of peak acceleration on the top of pier was 24.6% compared with that on the bottom of pier. The study results can provide experimental basis for the seismic design of curved bridges.

  1. ON THE R-CURVE BEHAVIOR OF HUMAN TOOTH ENAMEL

    OpenAIRE

    Bajaj, Devendra; Arola, Dwayne

    2009-01-01

    In this study the crack growth resistance behavior and fracture toughness of human tooth enamel were quantified using incremental crack growth measures and conventional fracture mechanics. Results showed that enamel undergoes an increase in crack growth resistance (i.e. rising R-curve) with crack extension from the outer to the inner enamel, and that the rise in toughness is function of distance from the Dentin Enamel Junction (DEJ). The outer enamel exhibited the lowest apparent toughness (0...

  2. Environment and Economic Growth. Is Technical Change the Key to Decoupling?

    Energy Technology Data Exchange (ETDEWEB)

    Galeotti, M. [Universita di Milano, Milan (Italy)

    2003-09-01

    The relationship between economic growth and pollution is very complex, depending upon a host of different factors. Thus the study of this phenomenon represents a challenging endeavor. While most economics papers begin with theory and support that theory with econometric evidence, the literature on Environmental Kuznets Curves has proceeded in the opposite direction: first developing an empirical observation about the world, and then attempting to supply appropriate theories. A number of papers have aimed at providing the theoretical underpinnings to the Environmental Kuznets Curve. Prominent here is the class of optimal growth models. These are usually studied from the point of view of the analytical conditions that must hold in order to obtain an inverted-U functional relationship between pollution and growth. These models are however seldom confronted with the data. In this paper we take one popular optimal growth model designed for climate change policy analysis and carry out a few simulation exercises with the purpose of characterizing the relationship between economic growth and emissions. In particular, we try to assess the relative contribution of the ingredients of the well-known decomposition of the environment-growth relationship put forth by Grossman (1995): according to it, the presumed inverted-U pattern results from the joint effect of scale, composition, and technology components. We do this focusing on the developed regions of the world and on a global pollutant, CO2 emissions.

  3. Modelling growth of five different colour types of mink | Liu | South ...

    African Journals Online (AJOL)

    The objective of this study was to estimate and compare the growth curve parameters for live weight of standard black, brown, mahogany, Hedlund white and sapphire minks. The data were collected from five colour types in the period from seven days to 24 weeks of age. Three hundred mink (about 60 of each colour types) ...

  4. Analysis of variation in calibration curves for Kodak XV radiographic film using model-based parameters.

    Science.gov (United States)

    Hsu, Shu-Hui; Kulasekere, Ravi; Roberson, Peter L

    2010-08-05

    Film calibration is time-consuming work when dose accuracy is essential while working in a range of photon scatter environments. This study uses the single-target single-hit model of film response to fit the calibration curves as a function of calibration method, processor condition, field size and depth. Kodak XV film was irradiated perpendicular to the beam axis in a solid water phantom. Standard calibration films (one dose point per film) were irradiated at 90 cm source-to-surface distance (SSD) for various doses (16-128 cGy), depths (0.2, 0.5, 1.5, 5, 10 cm) and field sizes (5 × 5, 10 × 10 and 20 × 20 cm²). The 8-field calibration method (eight dose points per film) was used as a reference for each experiment, taken at 95 cm SSD and 5 cm depth. The delivered doses were measured using an Attix parallel plate chamber for improved accuracy of dose estimation in the buildup region. Three fitting methods with one to three dose points per calibration curve were investigated for the field sizes of 5 × 5, 10 × 10 and 20 × 20 cm². The inter-day variation of model parameters (background, saturation and slope) were 1.8%, 5.7%, and 7.7% (1 σ) using the 8-field method. The saturation parameter ratio of standard to 8-field curves was 1.083 ± 0.005. The slope parameter ratio of standard to 8-field curves ranged from 0.99 to 1.05, depending on field size and depth. The slope parameter ratio decreases with increasing depth below 0.5 cm for the three field sizes. It increases with increasing depths above 0.5 cm. A calibration curve with one to three dose points fitted with the model is possible with 2% accuracy in film dosimetry for various irradiation conditions. The proposed fitting methods may reduce workload while providing energy dependence correction in radiographic film dosimetry. This study is limited to radiographic XV film with a Lumisys scanner.

  5. Testing linear growth rate formulas of non-scale endogenous growth models

    NARCIS (Netherlands)

    Ziesemer, Thomas

    2017-01-01

    Endogenous growth theory has produced formulas for steady-state growth rates of income per capita which are linear in the growth rate of the population. Depending on the details of the models, slopes and intercepts are positive, zero or negative. Empirical tests have taken over the assumption of

  6. Patterns and sources of adult personality development: growth curve analyses of the NEO PI-R scales in a longitudinal twin study.

    Science.gov (United States)

    Bleidorn, Wiebke; Kandler, Christian; Riemann, Rainer; Spinath, Frank M; Angleitner, Alois

    2009-07-01

    The present study examined the patterns and sources of 10-year stability and change of adult personality assessed by the 5 domains and 30 facets of the Revised NEO Personality Inventory. Phenotypic and biometric analyses were performed on data from 126 identical and 61 fraternal twins from the Bielefeld Longitudinal Study of Adult Twins (BiLSAT). Consistent with previous research, LGM analyses revealed significant mean-level changes in domains and facets suggesting maturation of personality. There were also substantial individual differences in the change trajectories of both domain and facet scales. Correlations between age and trait changes were modest and there were no significant associations between change and gender. Biometric extensions of growth curve models showed that 10-year stability and change of personality were influenced by both genetic as well as environmental factors. Regarding the etiology of change, the analyses uncovered a more complex picture than originally stated, as findings suggest noticeable differences between traits with respect to the magnitude of genetic and environmental effects. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

  7. Lagrangian Curves on Spectral Curves of Monopoles

    International Nuclear Information System (INIS)

    Guilfoyle, Brendan; Khalid, Madeeha; Ramon Mari, Jose J.

    2010-01-01

    We study Lagrangian points on smooth holomorphic curves in TP 1 equipped with a natural neutral Kaehler structure, and prove that they must form real curves. By virtue of the identification of TP 1 with the space LE 3 of oriented affine lines in Euclidean 3-space, these Lagrangian curves give rise to ruled surfaces in E 3 , which we prove have zero Gauss curvature. Each ruled surface is shown to be the tangent lines to a curve in E 3 , called the edge of regression of the ruled surface. We give an alternative characterization of these curves as the points in E 3 where the number of oriented lines in the complex curve Σ that pass through the point is less than the degree of Σ. We then apply these results to the spectral curves of certain monopoles and construct the ruled surfaces and edges of regression generated by the Lagrangian curves.

  8. Stress strain flow curves for Cu-OFP

    International Nuclear Information System (INIS)

    Sandstroem, Rolf; Hallgren, Josefin

    2009-04-01

    Stress strain curves of oxygen free copper alloyed with phosphorus Cu-OFP have been determined in compression and tension. The compression tests were performed at room temperature for strain rates between 10 -5 and 10 -3 1/s. The tests in tension covered the temperature range 20 to 175 deg C for strain rates between 10 -7 and 5x10 -3 1/s. The results in compression and tension were close for similar strain rates. A model for stress strain curves has been formulated using basic dislocation mechanisms. The model has been set up in such a way that fitting of parameters to the curves is avoided. By using a fundamental creep model as a basis a direct relation to creep data has been established. The maximum engineering flow stress in tension is related to the creep stress giving the same strain rate. The model reproduces the measured flow curves as function of temperature and strain rate in the investigated interval. The model is suitable to use in finite-element computations of structures in Cu-OFP

  9. Species-area curves revised: the effects of model choise on parameter sensitivity to environmental, community, and individual plant characteristics

    Czech Academy of Sciences Publication Activity Database

    Horník, J.; Janeček, Štěpán; Klimešová, Jitka; Doležal, Jiří; Janečková, Petra; Jiráská, Š.; Lanta, V.

    2012-01-01

    Roč. 213, č. 10 (2012), s. 1675-1686 ISSN 1385-0237 R&D Projects: GA ČR GA526/07/0808; GA ČR GAP505/12/1296 Institutional research plan: CEZ:AV0Z60050516 Institutional support: RVO:67985939 Keywords : species-area curve * wet meadows * clonal growth Subject RIV: EF - Botanics Impact factor: 1.534, year: 2012

  10. TELECOMMUNICATIONS INFRASTRUCTURE AND GDP /JIPP CURVE/

    Directory of Open Access Journals (Sweden)

    Mariana Kaneva

    2016-07-01

    Full Text Available The relationship between telecommunications infrastructure and economic activity is under discussion in many scientific papers. Most of the authors use for research and analysis the Jipp curve. A lot of doubts about the correctness of the Jipp curve appear in terms of applying econometric models. The aim of this study is a review of the Jipp curve, refining the possibility of its application in modern conditions. The methodology used in the study is based on dynamic econometric models, including tests for nonstationarity and tests for causality. The focus of this study is directed to methodological problems in measuring the local density types of telecommunication networks. This study offers a specific methodology for assessing the Jipp law, through VAR-approach and Granger causality tests. It is proved that mechanical substitution of momentary aggregated variables (such as the number of subscribers of a telecommunication network at the end of the year and periodically aggregated variables (such as GDP per capita in the Jipp�s curve is methodologically wrong. Researchers have to reconsider the relationship set in the Jipp�s curve by including additional variables that characterize the Telecommunications sector and the economic activity in a particular country within a specified time period. GDP per capita should not be regarded as a single factor for the local density of telecommunications infrastructure. New econometric models studying the relationship between the investments in telecommunications infrastructure and economic development may be not only linear regression models, but also other econometric models. New econometric models should be proposed after testing and validating with sound economic theory and econometric methodology.

  11. Verification of a model for the detection of intrauterine growth restriction (IUGR) by receiver operating characteristics (ROC)

    Science.gov (United States)

    Liu, Pengbo; Mongelli, Max; Mondry, Adrian

    2004-07-01

    The purpose of this study is to verify by Receiver Operating Characteristics (ROC) a mathematical model supporting the hypothesis that IUGR can be diagnosed by estimating growth velocity. The ROC compare computerized simulation results with clinical data from 325 pregnant British women. Each patient had 6 consecutive ultrasound examinations for fetal abdominal circumference (fac). Customized and un-customized fetal weights were calculated according to Hadlock"s formula. IUGR was diagnosed by the clinical standard, i.e. estimated weight below the tenth percentile. Growth velocity was estimated by calculating the changes of fac (Dzfac/dt) at various time intervals from 3 to 10 weeks. Finally, ROC was used to compare the methods. At 3~4 weeks scan interval, the area under the ROC curve is 0.68 for customized data and 0.66 for the uncustomized data with 95% confidence interval. Comparison between simulation data and real pregnancies verified that the model is clinically acceptable.

  12. Efficacy of the Frame and Hu mathematical model for the quantitative analysis of agents influencing growth of chick embryo fibroblasts

    International Nuclear Information System (INIS)

    Korohoda, K.; Czyz, J.

    1994-01-01

    The experiments on the effect of various sera and substratum surface area upon growth of chick embryo fibroblasts-like in secondary cultures are described and discussed on the grounds of a mathematical model for growth of anchorage-dependent cells proposed by Frame and Hu. The model and presented results demonstrate the mutual independence of the effects of agent influencing of rate of cell proliferation (i.e. accelerating or retarding growth) and the agents that modify the limitation of cell proliferation (i.e. maximum cell density at confluence). The model proposed by Frame and Hu due to its relative simplicity offers and easy mode of description and quantitative evaluation of experiments concerning cell growth regulation. It is shown that various sera added at constant concentration significantly modify the rate of cell proliferation with little effect upon the maximum cell density attainable. The cells grew much more slowly in the presence of calf serum than in the presence of chick serum and the addition of iron and zinc complexes to calf serum significantly accelerated cell growth. An increase in the substratum surface area by the addition of glass wool to culture vessels significantly increased cell density per constant volume of medium even when retardation of growth was observed. The results presented point to the need of direct cell counting for estimation of cell growth curves and discussion of effects of agents influencing parameters characterizing cell proliferation. (author). 34 refs, 5 figs, 2 tabs

  13. p-Curve and p-Hacking in Observational Research.

    Science.gov (United States)

    Bruns, Stephan B; Ioannidis, John P A

    2016-01-01

    The p-curve, the distribution of statistically significant p-values of published studies, has been used to make inferences on the proportion of true effects and on the presence of p-hacking in the published literature. We analyze the p-curve for observational research in the presence of p-hacking. We show by means of simulations that even with minimal omitted-variable bias (e.g., unaccounted confounding) p-curves based on true effects and p-curves based on null-effects with p-hacking cannot be reliably distinguished. We also demonstrate this problem using as practical example the evaluation of the effect of malaria prevalence on economic growth between 1960 and 1996. These findings call recent studies into question that use the p-curve to infer that most published research findings are based on true effects in the medical literature and in a wide range of disciplines. p-values in observational research may need to be empirically calibrated to be interpretable with respect to the commonly used significance threshold of 0.05. Violations of randomization in experimental studies may also result in situations where the use of p-curves is similarly unreliable.

  14. Analysis of Mode I and Mode II Crack Growth Arrest Mechanism with Z-Fibre Pins in Composite Laminated Joint

    Science.gov (United States)

    Jeevan Kumar, N.; Ramesh Babu, P.

    2018-04-01

    This paper presents the numerical study of the mode I and mode II interlaminar crack growth arrest in hybrid laminated curved composite stiffened joint with Z-fibre reinforcement. A FE model of hybrid laminated skin-stiffener joint reinforced with Z-pins is developed to investigate the effect of Z- fibre pins on mode I and mode II crack growth where the delamination is embedded inbetween the skin and stiffener interface. A finite element model was developed using S4R element of a 4-node doubly curved thick shell elements to model the composite laminates and non linear interface elements to simulate the reinforcements. The numerical analyses revealed that Z-fibre pinning were effective in suppressing the delamination growth when propagated due to applied loads. Therefore, the Z-fibre technique effectively improves the crack growth resistance and hence arrests or delays crack growth extension.

  15. Three-dimensional flow analysis and improvement of slip factor model for forward-curved blades centrifugal fan

    International Nuclear Information System (INIS)

    Guo, En Min; Kim, Kwang Yong

    2004-01-01

    This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient

  16. A Lévy HJM Multiple-Curve Model with Application to CVA Computation

    DEFF Research Database (Denmark)

    Crépey, Stéphane; Grbac, Zorana; Ngor, Nathalie

    2015-01-01

    , the calibration to OTM swaptions guaranteeing that the model correctly captures volatility smile effects and the calibration to co-terminal ATM swaptions ensuring an appropriate term structure of the volatility in the model. To account for counterparty risk and funding issues, we use the calibrated multiple......-curve model as an underlying model for CVA computation. We follow a reduced-form methodology through which the problem of pricing the counterparty risk and funding costs can be reduced to a pre-default Markovian BSDE, or an equivalent semi-linear PDE. As an illustration, we study the case of a basis swap...... and a related swaption, for which we compute the counterparty risk and funding adjustments...

  17. IGMtransmission: Transmission curve computation

    Science.gov (United States)

    Harrison, Christopher M.; Meiksin, Avery; Stock, David

    2015-04-01

    IGMtransmission is a Java graphical user interface that implements Monte Carlo simulations to compute the corrections to colors of high-redshift galaxies due to intergalactic attenuation based on current models of the Intergalactic Medium. The effects of absorption due to neutral hydrogen are considered, with particular attention to the stochastic effects of Lyman Limit Systems. Attenuation curves are produced, as well as colors for a wide range of filter responses and model galaxy spectra. Photometric filters are included for the Hubble Space Telescope, the Keck telescope, the Mt. Palomar 200-inch, the SUBARU telescope and UKIRT; alternative filter response curves and spectra may be readily uploaded.

  18. Inferring the temperature dependence of Beremin cleavage model parameters from the Master Curve

    International Nuclear Information System (INIS)

    Cao Yupeng; Hui Hu; Wang Guozhen; Xuan Fuzhen

    2011-01-01

    Research highlights: → Temperature dependence of Beremin model parameters is inferred by Master Curve approach. → Weibull modulus decreases while Weibull stress scale parameter increases with increasing the temperature. → Estimation of Weibull stress parameters in terms of small amounts of specimens leads to a considerable uncertainty. - Abstract: The temperature dependence of Beremin model parameters in the ductile-to-brittle transition region was addressed by employing the Master Curve. Monte Carlo simulation was performed to produce a large number of 1T fracture toughness data randomly drawn from the scatter band at a temperature of interest and thus to determine Beremin model parameters. In terms of the experimental data of a C-Mn steel (the 16MnR steel in China), results revealed that the Weibull modulus, m, decreases with temperature over the lower transition range and remains a constant in the lower-to-mid transition region. The Weibull scale parameter, σ u , increases with temperature over the temperature range of investigated. A small sample may lead to a considerable uncertainty in estimates of the Weibull stress parameters. However, no significant difference was observed for the average of Weibull stress parameters from different sample sizes.

  19. Computational Tools for Probing Interactions in Multiple Linear Regression, Multilevel Modeling, and Latent Curve Analysis

    Science.gov (United States)

    Preacher, Kristopher J.; Curran, Patrick J.; Bauer, Daniel J.

    2006-01-01

    Simple slopes, regions of significance, and confidence bands are commonly used to evaluate interactions in multiple linear regression (MLR) models, and the use of these techniques has recently been extended to multilevel or hierarchical linear modeling (HLM) and latent curve analysis (LCA). However, conducting these tests and plotting the…

  20. Growth curve and diet density affect eating motivation, behavior, and body composition of broiler breeders during rearing.

    Science.gov (United States)

    de Los Mozos, J; García-Ruiz, A I; den Hartog, L A; Villamide, M J

    2017-08-01

    The aim of this work has been to assess the effect of diet density [control (CON) or 15% diluted (DIL)] and growth curve [recommended by the genetic line (RBW) or 15% heavier (HBW)] and their interaction on BW uniformity, feeding motivation, behavior, and body composition of broiler breeder pullets. A total of 3,000 one-day-old female breeders Ross 308, distributed in 20 pens, was randomly assigned to each treatment. Feed allowance was weekly adjusted to reach the desired BW. Feed was provided as pelleted (zero to 3 wk) and crumble (4 to 19 wk). Time eating was measured at 7, 11, and 19 weeks. A feeding rate test was performed after 11 weeks. Behavior was observed at 9 and 15 wk, by visual scan. At 6, 13, and 19 wk of age, one bird/pen was slaughtered for weighing different organs and analyzing the composition of empty whole bodies. Treatments did not affect BW uniformity; relative weights of the ovary, oviduct, or gizzard; or protein content of empty BW. Time eating varied with the growth curve at 19 wk (P motivation. Behavior was affected by the age and by the time of the d measured, but it did not change with the treatments. Birds spent most time pecking objects (50%), feeding (28%), and drinking (17%). Pullets fed DIL had 8% lower breast yield at different ages and higher empty digestive tracts at 6 weeks. Body composition varied with age; fat content increased from 12.7 to 15.9 to 19.8% for 6, 13, and 19 wk, respectively. The lowest body fat was observed for RBW pullets fed DIL (P = 0.003) at 19 weeks. Feeding DIL diets to HBW pullets could be done to increase the time spent eating and reduce their feeling of hunger without negative effects on body composition. However, its influence on behavior and BW uniformity was not proved. © The Author 2017. Published by Oxford University Press on behalf of Poultry Science Association.

  1. Dose-response curve estimation: a semiparametric mixture approach.

    Science.gov (United States)

    Yuan, Ying; Yin, Guosheng

    2011-12-01

    In the estimation of a dose-response curve, parametric models are straightforward and efficient but subject to model misspecifications; nonparametric methods are robust but less efficient. As a compromise, we propose a semiparametric approach that combines the advantages of parametric and nonparametric curve estimates. In a mixture form, our estimator takes a weighted average of the parametric and nonparametric curve estimates, in which a higher weight is assigned to the estimate with a better model fit. When the parametric model assumption holds, the semiparametric curve estimate converges to the parametric estimate and thus achieves high efficiency; when the parametric model is misspecified, the semiparametric estimate converges to the nonparametric estimate and remains consistent. We also consider an adaptive weighting scheme to allow the weight to vary according to the local fit of the models. We conduct extensive simulation studies to investigate the performance of the proposed methods and illustrate them with two real examples. © 2011, The International Biometric Society.

  2. Graphene growth process modeling: a physical-statistical approach

    Science.gov (United States)

    Wu, Jian; Huang, Qiang

    2014-09-01

    As a zero-band semiconductor, graphene is an attractive material for a wide variety of applications such as optoelectronics. Among various techniques developed for graphene synthesis, chemical vapor deposition on copper foils shows high potential for producing few-layer and large-area graphene. Since fabrication of high-quality graphene sheets requires the understanding of growth mechanisms, and methods of characterization and control of grain size of graphene flakes, analytical modeling of graphene growth process is therefore essential for controlled fabrication. The graphene growth process starts with randomly nucleated islands that gradually develop into complex shapes, grow in size, and eventually connect together to cover the copper foil. To model this complex process, we develop a physical-statistical approach under the assumption of self-similarity during graphene growth. The growth kinetics is uncovered by separating island shapes from area growth rate. We propose to characterize the area growth velocity using a confined exponential model, which not only has clear physical explanation, but also fits the real data well. For the shape modeling, we develop a parametric shape model which can be well explained by the angular-dependent growth rate. This work can provide useful information for the control and optimization of graphene growth process on Cu foil.

  3. Physical growth of the shuar: Height, Weight, and BMI references for an indigenous amazonian population.

    Science.gov (United States)

    Urlacher, Samuel S; Blackwell, Aaron D; Liebert, Melissa A; Madimenos, Felicia C; Cepon-Robins, Tara J; Gildner, Theresa E; Snodgrass, J Josh; Sugiyama, Lawrence S

    2016-01-01

    Information concerning physical growth among small-scale populations remains limited, yet such data are critical to local health efforts and to foster basic understandings of human life history and variation in childhood development. Using a large dataset and robust modeling methods, this study aims to describe growth from birth to adulthood among the indigenous Shuar of Amazonian Ecuador. Mixed-longitudinal measures of height, weight, and body mass index (BMI) were collected from Shuar participants (n = 2,463; age: 0-29 years). Centile growth curves and tables were created for each anthropometric variable of interest using Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Pseudo-velocity and Lambda-Mu-Sigma curves were generated to further investigate Shuar patterns of growth and to facilitate comparison with United States Center for Disease Control and Prevention and multinational World Health Organization growth references. The Shuar are small throughout life and exhibit complex patterns of growth that differ substantially from those of international references. Similar to other Amazonians, Shuar growth in weight compares more favorably to references than growth in height, resulting in BMI curves that approximate international medians. Several additional characteristics of Shuar development are noteworthy, including large observed variation in body size early in life, significant infant growth faltering, extended male growth into adulthood, and a markedly early female pubertal growth spurt in height. Phenotypic plasticity and genetic selection in response to local environmental factors may explain many of these patterns. Providing a detailed reference of growth for the Shuar and other Amazonian populations, this study possesses direct clinical application and affords valuable insight into childhood health and the ecology of human growth. © 2015 Wiley Periodicals, Inc.

  4. Observational constraints on interstellar depletion mechanisms in lines of sight exhibiting peculiar extinction curves

    International Nuclear Information System (INIS)

    Joseph, C.L.

    1985-01-01

    The nature of dust-gas interactions, which are capable of modifying the size distribution of the grains and thus causing changes in the selective extinction curve, are investigated through depletion studies. The gaseous abundances of 16 elements were determined for several lines of sight toward moderately reddened stars, each having a so called anomalous extinction curve. Four lines of sight in the rho Ophiuchi dark cloud complexes as well as several lines of sight through the diffuse interstellar medium were also analyzed for comparison. Two approaches are used to assess the strength of density dependent depletion processes. First, the depletion pattern from element-to-element for each integrated line of sight is studied with particular emphasis being given to those species that are potential discriminators between the two major competing models of grain formation and growth. In the second approach, the relative abundancies of neutral atoms, which are thought to form primarily in the densest portions of interstellar clouds, are studied. Both of these constraints are then compared to a theoretical extinction curve derived from a simple model for the size distribution of the grains based on the degree of mantling

  5. A Primer on the Statistical Modelling of Learning Curves in Health Professions Education

    Science.gov (United States)

    Pusic, Martin V.; Boutis, Kathy; Pecaric, Martin R.; Savenkov, Oleksander; Beckstead, Jason W.; Jaber, Mohamad Y.

    2017-01-01

    Learning curves are a useful way of representing the rate of learning over time. Features include an index of baseline performance (y-intercept), the efficiency of learning over time (slope parameter) and the maximal theoretical performance achievable (upper asymptote). Each of these parameters can be statistically modelled on an individual and…

  6. Prediction of Accurate Mixed Mode Fatigue Crack Growth Curves using the Paris' Law

    Science.gov (United States)

    Sajith, S.; Krishna Murthy, K. S. R.; Robi, P. S.

    2017-12-01

    Accurate information regarding crack growth times and structural strength as a function of the crack size is mandatory in damage tolerance analysis. Various equivalent stress intensity factor (SIF) models are available for prediction of mixed mode fatigue life using the Paris' law. In the present investigation these models have been compared to assess their efficacy in prediction of the life close to the experimental findings as there are no guidelines/suggestions available on selection of these models for accurate and/or conservative predictions of fatigue life. Within the limitations of availability of experimental data and currently available numerical simulation techniques, the results of present study attempts to outline models that would provide accurate and conservative life predictions.

  7. Kinetics of slow domain growth in complex systems

    International Nuclear Information System (INIS)

    Lindgard, P.-A.; Castan, T.

    1989-01-01

    The domain growth after a quench to very low and to finite temperatures T is analyzed by scaling theory and Monte Carlo simulation. The model studied has continuous variables, non-conserved order parameter and has two kinds of domain walls: sharp, straight stacking faults and broad curved soliton-like walls. For quenches to higher temperatures the growth exponent is found to approach the classical Allen-Cahn exponent n = 1/2. (A.C.A.S.) [pt

  8. Sensitivity analysis for linear structural equation models, longitudinal mediation with latent growth models and blended learning in biostatistics education

    Science.gov (United States)

    Sullivan, Adam John

    In chapter 1, we consider the biases that may arise when an unmeasured confounder is omitted from a structural equation model (SEM) and sensitivity analysis techniques to correct for such biases. We give an analysis of which effects in an SEM are and are not biased by an unmeasured confounder. It is shown that a single unmeasured confounder will bias not just one but numerous effects in an SEM. We present sensitivity analysis techniques to correct for biases in total, direct, and indirect effects when using SEM analyses, and illustrate these techniques with a study of aging and cognitive function. In chapter 2, we consider longitudinal mediation with latent growth curves. We define the direct and indirect effects using counterfactuals and consider the assumptions needed for identifiability of those effects. We develop models with a binary treatment/exposure followed by a model where treatment/exposure changes with time allowing for treatment/exposure-mediator interaction. We thus formalize mediation analysis with latent growth curve models using counterfactuals, makes clear the assumptions and extends these methods to allow for exposure mediator interactions. We present and illustrate the techniques with a study on Multiple Sclerosis(MS) and depression. In chapter 3, we report on a pilot study in blended learning that took place during the Fall 2013 and Summer 2014 semesters here at Harvard. We blended the traditional BIO 200: Principles of Biostatistics and created ID 200: Principles of Biostatistics and epidemiology. We used materials from the edX course PH207x: Health in Numbers: Quantitative Methods in Clinical & Public Health Research and used. These materials were used as a video textbook in which students would watch a given number of these videos prior to class. Using surveys as well as exam data we informally assess these blended classes from the student's perspective as well as a comparison of these students with students in another course, BIO 201

  9. Simulation of uranium oxides reduction kinetics by hydrogen. Reactivities of germination and growth

    International Nuclear Information System (INIS)

    Brun, C.

    1997-01-01

    The aim of this work is to simulate the reduction by hydrogen of the tri-uranium octo-oxide U 3 O 8 (obtained by uranium trioxide calcination) into uranium dioxide. The kinetics curves have been obtained by thermal gravimetric analysis, the hydrogen and steam pressures being defined. The geometrical modeling which has allowed to explain the trend of the kinetics curves and of the velocity curves is an anisotropic germination-growth modeling. The powder is supposed to be formed of spherical grains with the same radius. The germs of the new UO 2 phase appear at the surface of the U 3 O 8 grains with a specific germination frequency. The growth reactivity is anisotropic and is very large in the tangential direction to the grains surface. Then, the uranium dioxide growths inside the grain and the limiting step is the grain surface. The variations of the growth reactivity and of the germination specific frequency in terms of the gases partial pressures and of the temperature have been explained by two different mechanisms. The limiting step of the growth mechanism is the desorption of water in the uranium dioxide surface. Concerning the germination mechanism the limiting step is a water desorption too but in the tri-uranium octo-oxide surface. The same geometrical modeling and the same germination and growth mechanisms have been applied to the reduction of a tri-uranium octo-oxide obtained by calcination of hydrated uranium trioxide. The values of the germination specific frequency of this solid are nevertheless weaker than those of the solid obtained by direct calcination of the uranium trioxide. (O.M.)

  10. Research on the Integration of Bionic Geometry Modeling and Simulation of Robot Foot Based on Characteristic Curve

    Science.gov (United States)

    He, G.; Zhu, H.; Xu, J.; Gao, K.; Zhu, D.

    2017-09-01

    The bionic research of shape is an important aspect of the research on bionic robot, and its implementation cannot be separated from the shape modeling and numerical simulation of the bionic object, which is tedious and time-consuming. In order to improve the efficiency of shape bionic design, the feet of animals living in soft soil and swamp environment are taken as bionic objects, and characteristic skeleton curve, section curve, joint rotation variable, position and other parameters are used to describe the shape and position information of bionic object’s sole, toes and flipper. The geometry modeling of the bionic object is established by using the parameterization of characteristic curves and variables. Based on this, the integration framework of parametric modeling and finite element modeling, dynamic analysis and post-processing of sinking process in soil is proposed in this paper. The examples of bionic ostrich foot and bionic duck foot are also given. The parametric modeling and integration technique can achieve rapid improved design based on bionic object, and it can also greatly improve the efficiency and quality of robot foot bionic design, and has important practical significance to improve the level of bionic design of robot foot’s shape and structure.

  11. Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

    Science.gov (United States)

    Harding, A. K.; Kalapotharakos, C.; Kazanas, D.; Contopoulos, I.

    2012-01-01

    The Fermi Large Area Telescope has provided an unprecedented database for pulsar emission studies that includes gamma-ray light curves for over 100 pulsars. Modeling these light curves can reveal and constrain the geometry of the particle accelerator, as well as the pulsar magnetic field structure. We have constructed 3D magnetosphere models with finite conductivity, that bridge the extreme vacuum and force-free solutions used in previous light curves modeling. We are investigating the shapes of pulsar gamma-ray light curves using these dissipative solutions with two different approaches: (l) assuming geometric emission patterns of the slot gap and outer gap, and (2) using the parallel electric field provided by the resistive models to compute the trajectories and . emission of the radiating particles. The light curves using geometric emission patterns show a systematic increase in gamma-ray peak phase with increasing conductivity, introducing a new diagnostic of these solutions. The light curves using the model electric fields are very sensitive to the conductivity but do not resemble the observed Fermi light curves, suggesting that some screening of the parallel electric field, by pair cascades not included in the models, is necessary

  12. Nanoimprint Lithography on curved surfaces prepared by fused deposition modelling

    International Nuclear Information System (INIS)

    Köpplmayr, Thomas; Häusler, Lukas; Bergmair, Iris; Mühlberger, Michael

    2015-01-01

    Fused deposition modelling (FDM) is an additive manufacturing technology commonly used for modelling, prototyping and production applications. The achievable surface roughness is one of its most limiting aspects. It is however of great interest to create well-defined (nanosized) patterns on the surface for functional applications such as optical effects, electronics or bio-medical devices. We used UV-curable polymers of different viscosities and flexible stamps made of poly(dimethylsiloxane) (PDMS) to perform Nanoimprint Lithography (NIL) on FDM-printed curved parts. Substrates with different roughness and curvature were prepared using a commercially available 3D printer. The nanoimprint results were characterized by optical light microscopy, profilometry and atomic force microscopy (AFM). Our experiments show promising results in creating well-defined microstructures on the 3D-printed parts. (paper)

  13. Developments in Interpreting Learning Curves and Applications to Energy Technology Policy

    International Nuclear Information System (INIS)

    Van der Zwaan, B.C.C.; Wene, C.O.

    2011-01-01

    The book 'Learning Curves: Theory, Models, and Applications' first draws a learning map that shows where learning is involved within organizations, then examines how it can be sustained, perfected, and accelerated. The book reviews empirical findings in the literature in terms of different sources for learning and partial assessments of the steps that make up the actual learning process inside the learning curve. Chapter 23 on 'Developments in Interpreting Learning Curves and Applications to Energy Technology Policy' is written by Bob van der Zwaan and Clas-Otto Wene. In this chapter they provide some interpretations of experience and learning curves starting from three different theoretical platforms. These interpretations are aimed at explaining learning rates for different energy technologies. The ultimate purpose is to find the role that experience and learning curves can legitimately play in designing efficient government deployment programs and in analyzing the implications of different energy scenarios. The 'Component Learning' section summarizes recent work by the authors that focuses on the disaggregation of technologies in their respective components and argues that traditional learning for overall technology should perhaps be replaced by a phenomenology that recognizes learning for individual components. The 'Learning and Time' section presents an approach that departs more strongly from the conventional learning curve methodology, by suggesting that exponential growth and progress may be the deeper underlying processes behind observed learning-by-doing. Contrary to this view, the cybernetic approach presented in the 'Cybernetic Approach' section sees learning curves as expressing a fundamental property of organizations in competitive markets and applies the findings from second order cybernetics to calculate the learning rates for operationally closed systems. All three interpretations find empirical support. The 'Conclusions' section summarizes the

  14. Developments in Interpreting Learning Curves and Applications to Energy Technology Policy

    Energy Technology Data Exchange (ETDEWEB)

    Van der Zwaan, B.C.C. [Energy research Centre of the Netherlands, ECN Policy Studies, Petten (Netherlands); Wene, C.O. [Wenergy, Lund (Sweden)

    2011-06-15

    The book 'Learning Curves: Theory, Models, and Applications' first draws a learning map that shows where learning is involved within organizations, then examines how it can be sustained, perfected, and accelerated. The book reviews empirical findings in the literature in terms of different sources for learning and partial assessments of the steps that make up the actual learning process inside the learning curve. Chapter 23 on 'Developments in Interpreting Learning Curves and Applications to Energy Technology Policy' is written by Bob van der Zwaan and Clas-Otto Wene. In this chapter they provide some interpretations of experience and learning curves starting from three different theoretical platforms. These interpretations are aimed at explaining learning rates for different energy technologies. The ultimate purpose is to find the role that experience and learning curves can legitimately play in designing efficient government deployment programs and in analyzing the implications of different energy scenarios. The 'Component Learning' section summarizes recent work by the authors that focuses on the disaggregation of technologies in their respective components and argues that traditional learning for overall technology should perhaps be replaced by a phenomenology that recognizes learning for individual components. The 'Learning and Time' section presents an approach that departs more strongly from the conventional learning curve methodology, by suggesting that exponential growth and progress may be the deeper underlying processes behind observed learning-by-doing. Contrary to this view, the cybernetic approach presented in the 'Cybernetic Approach' section sees learning curves as expressing a fundamental property of organizations in competitive markets and applies the findings from second order cybernetics to calculate the learning rates for operationally closed systems. All three interpretations find empirical

  15. Constructing forward price curves in electricity markets

    DEFF Research Database (Denmark)

    Fleten, S.-E.; Lemming, Jørgen Kjærgaard

    2003-01-01

    We present and analyze a method for constructing approximated high-resolution forward price curves in electricity markets. Because a limited number of forward or futures contracts are traded in the market, only a limited picture of the theoretical continuous forward price curve is available...... to the analyst. Our method combines the information contained in observed bid and ask prices with information from the forecasts generated by bottom-up models. As an example, we use information concerning the shape of the seasonal variation from a bottom-up model to improve the forward price curve quoted...

  16. Two-peaked dose curves for irradiated pollen growth

    International Nuclear Information System (INIS)

    Andrejchenko, S.V.; Grodzinskij, D.M.

    1992-01-01

    The effect of γ-radiation on growth activity of bicellular pollen of hybrid petunia has been investigated. Irradiation of pollen with doses of 5 to 70 Gy increases the pollen tube growth in an artificial culture medium. As the radiation dose increases the germination ability of pollen gradually decreases and the mean pollen tube length shortens, which is accompanied by the suppression of the generative cell division into spermia and inhibition of the unscheduled incorporation of labelled thymidine into DNA. With radiation doses of 1200 to 1700 Gy some pollen tubes grow intensively. It is suggested that the phenomenon observed lays the basis for the gametic transformation

  17. A fluid dynamical flow model for the central peak in the rotation curve of disk galaxies

    International Nuclear Information System (INIS)

    Bhattacharyya, T.; Basu, B.

    1980-01-01

    The rotation curve of the central region in some disk galaxies shows a linear rise, terminating at a peak (primary peak) which is then vollowed by a deep minimum. The curve then again rises to another peak at more or less half-way across the galactic radius. This latter peak is considered as the peak of the rotation curve in all large-scale analysis of galactic structure. The primary peak is usually ignored for the purpose. In this work an attempt has been made to look at the primary peak as the manifestation of the post-explosion flow pattern of gas in the deep central region of galaxies. Solving hydrodynamical equations of motion, a flow model has been derived which imitates very closely the actually observed linear rotational velocity, followed by the falling branch of the curve to minimum. The theoretical flow model has been compared with observed results for nine galaxies. The agreement obtained is extremely encouraging. The distance of the primary peak from the galactic centre has been shown to be correlated with the angular velocity in the linear part of the rotation curve. Here also, agreement is very good between theoretical and observed results. It is concluded that the distance of the primary peak from the centre not only speaks of the time that has elapsed since the explosion occurred in the nucleus, it also speaks of the potential capability of the nucleus of the galaxy for repeating explosions through some efficient process of mass replenishment at the core. (orig.)

  18. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size......-asymmetric growth part, where growth is assumed to be proportional to a power function of the size of the individual, and a term that reduces the relative growth rate as a decreasing function of the individual plant size and the competitive interactions from other plants in the neighbourhood....

  19. Decline curve based models for predicting natural gas well performance

    Directory of Open Access Journals (Sweden)

    Arash Kamari

    2017-06-01

    Full Text Available The productivity of a gas well declines over its production life as cannot cover economic policies. To overcome such problems, the production performance of gas wells should be predicted by applying reliable methods to analyse the decline trend. Therefore, reliable models are developed in this study on the basis of powerful artificial intelligence techniques viz. the artificial neural network (ANN modelling strategy, least square support vector machine (LSSVM approach, adaptive neuro-fuzzy inference system (ANFIS, and decision tree (DT method for the prediction of cumulative gas production as well as initial decline rate multiplied by time as a function of the Arps' decline curve exponent and ratio of initial gas flow rate over total gas flow rate. It was concluded that the results obtained based on the models developed in current study are in satisfactory agreement with the actual gas well production data. Furthermore, the results of comparative study performed demonstrates that the LSSVM strategy is superior to the other models investigated for the prediction of both cumulative gas production, and initial decline rate multiplied by time.

  20. A new model for simulating growth in fish

    Directory of Open Access Journals (Sweden)

    Johannes Hamre

    2014-01-01

    Full Text Available A real dynamic population model calculates change in population sizes independent of time. The Beverton & Holt (B&H model commonly used in fish assessment includes the von Bertalanffy growth function which has age or accumulated time as an independent variable. As a result the B&H model has to assume constant fish growth. However, growth in fish is highly variable depending on food availability and environmental conditions. We propose a new growth model where the length increment of fish living under constant conditions and unlimited food supply, decreases linearly with increasing fish length until it reaches zero at a maximal fish length. The model is independent of time and includes a term which accounts for the environmental variation. In the present study, the model was validated in zebrafish held at constant conditions. There was a good fit of the model to data on observed growth in Norwegian spring spawning herring, capelin from the Barents Sea, North Sea herring and in farmed coastal cod. Growth data from Walleye Pollock from the Eastern Bering Sea and blue whiting from the Norwegian Sea also fitted reasonably well to the model, whereas data from cod from the North Sea showed a good fit to the model only above a length of 70 cm. Cod from the Barents Sea did not grow according to the model. The last results can be explained by environmental factors and variable food availability in the time under study. The model implicates that the efficiency of energy conversion from food decreases as the individual animal approaches its maximal length and is postulated to represent a natural law of fish growth.

  1. Modeling Population Growth and Extinction

    Science.gov (United States)

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  2. Modeling of Hybrid Growth Wastewater Bio-reactor

    International Nuclear Information System (INIS)

    EI Nashaei, S.; Garhyan, P.; Prasad, P.; Abdel Halim, H.S.; Ibrahim, G.

    2004-01-01

    The attached/suspended growth mixed reactors are considered one of the recently tried approaches to improve the performance of the biological treatment by increasing the volume of the accumulated biomass in terms of attached growth as well as suspended growth. Moreover, the domestic WW can be easily mixed with a high strength non-hazardous industrial wastewater and treated together in these bio-reactors if the need arises. Modeling of Hybrid hybrid growth wastewater reactor addresses the need of understanding the rational of such system in order to achieve better design and operation parameters. This paper aims at developing a heterogeneous mathematical model for hybrid growth system considering the effect of diffusion, external mass transfer, and power input to the system in a rational manner. The model will be based on distinguishing between liquid/solid phase (bio-film and bio-floc). This model would be a step ahead to the fine tuning the design of hybrid systems based on the experimental data of a pilot plant to be implemented in near future

  3. A Practical Anodic and Cathodic Curve Intersection Model to Understand Multiple Corrosion Potentials of Fe-Based Glassy Alloys in OH- Contained Solutions.

    Science.gov (United States)

    Li, Y J; Wang, Y G; An, B; Xu, H; Liu, Y; Zhang, L C; Ma, H Y; Wang, W M

    2016-01-01

    A practical anodic and cathodic curve intersection model, which consisted of an apparent anodic curve and an imaginary cathodic line, was proposed to explain multiple corrosion potentials occurred in potentiodynamic polarization curves of Fe-based glassy alloys in alkaline solution. The apparent anodic curve was selected from the measured anodic curves. The imaginary cathodic line was obtained by linearly fitting the differences of anodic curves and can be moved evenly or rotated to predict the number and value of corrosion potentials.

  4. The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model

    Energy Technology Data Exchange (ETDEWEB)

    Penn, James; Vallis, Geoffrey K, E-mail: jp492@exeter.ac.uk, E-mail: g.vallis@exeter.ac.uk [University of Exeter, Exeter, Devon (United Kingdom)

    2017-06-20

    Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension of the well-studied Matsuno–Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet’s surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.

  5. Statistical study of clone survival curves after irradiation in one or two stages. Comparison and generalization of different models

    International Nuclear Information System (INIS)

    Lachet, Bernard.

    1975-01-01

    A statistical study was carried out on 208 survival curves for chlorella subjected to γ or particle radiations. The computing programmes used were written in Fortran. The different experimental causes contributing to the variance of a survival rate are analyzed and consequently the experiments can be planned. Each curve was fitted to four models by the weighted least squares method applied to non-linear functions. The validity of the fits obtained can be checked by the F test. It was possible to define the confidence and prediction zones around an adjusted curve by weighting of the residual variance, in spite of error on the doses delivered; the confidence limits can them be fixed for a dose estimated from an exact or measured survival. The four models adopted were compared for the precision of their fit (by a non-parametric simultaneous comparison test) and the scattering of their adjusted parameters: Wideroe's model gives a very good fit with the experimental points in return for a scattering of its parameters, which robs them of their presumed meaning. The principal component analysis showed the statistical equivalence of the 1 and 2 hit target models. Division of the irradiation into two doses, the first fixed by the investigator, leads to families of curves for which the equation was established from that of any basic model expressing the dose survival relationship in one-stage irradiation [fr

  6. Dynamic Analysis of Recalescence Process and Interface Growth of Eutectic Fe82B17Si1 Alloy

    Science.gov (United States)

    Fan, Y.; Liu, A. M.; Chen, Z.; Li, P. Z.; Zhang, C. H.

    2018-03-01

    By employing the glass fluxing technique in combination with cyclical superheating, the microstructural evolution of the undercooled Fe82B17Si1 alloy in the obtained undercooling range was studied. With increase in undercooling, a transition of cooling curves was detected from one recalescence to two recalescences, followed by one recalescence. The two types of cooling curves were fitted by the break equation and the Johnson-Mehl-Avrami-Kolmogorov model. Based on the cooling curves at different undercoolings, the recalescence rate was calculated by the multi-logistic growth model and the Boettinger-Coriel-Trivedi model. Both the recalescence features and the interface growth kinetics of the eutectic Fe82B17Si1 alloy were explored. The fitting results that were obtained using TEM (SAED), SEM and XRD were consistent with the changing rule of microstructures. Finally, the relationship between the microstructure and hardness was also investigated.

  7. Economic Growth Models Transition

    Directory of Open Access Journals (Sweden)

    Coralia Angelescu

    2006-03-01

    Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations. Over the past few years, most candidate countries have made progress in the transition to a competitive market economy, macroeconomic stabilization and structural reform. However their income levels have remained far below those in the Member States. Measured by per capita income in purchasing power standards, there has been a very limited amount of catching up over the past fourteen years. Prior, the distinctions between Solow-Swan model and endogenous growth model. The interdependence between transition and integration are stated in this study. Finally, some measures of macroeconomic policy for sustainable growth are proposed in correlation with real macroeconomic situation of the Romanian economy. Our study would be considered the real convergence for the Romanian economy and the recommendations for the adequate policies to achieve a fast real convergence and sustainable growth.

  8. Economic Growth Models Transition

    Directory of Open Access Journals (Sweden)

    Coralia Angelescu

    2006-01-01

    Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations