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Letteratura scientifica selezionata sul tema "Variance components testing"

Autore: Grafiati

Pubblicato: 25 gennaio 2025

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Articoli di riviste sul tema "Variance components testing"

Li, Zaixing, Fei Chen e Lixing Zhu. "Variance Components Testing inANOVA-Type Mixed Models". Scandinavian Journal of Statistics 41, n. 2 (20 novembre 2013): 482–96. http://dx.doi.org/10.1111/sjos.12044.

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Johansson, Anders S., Thomas B. Whitaker, Winston M. Hagler, Francis G. Giesbrecht, James H. Young e Daryl T. Bowman. "Testing Shelled Corn for Aflatoxin, Part I: Estimation of Variance Components". Journal of AOAC INTERNATIONAL 83, n. 5 (1 settembre 2000): 1264–69. http://dx.doi.org/10.1093/jaoac/83.5.1264.

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Abstract The variability associated with testing lots of shelled corn for aflatoxin was investigated. Eighteen lots of shelled corn were tested for aflatoxin contamination. The total variance associated with testing shelled corn was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances increased as aflatoxin concentration increased. With the use of regression analysis, mathematical expressions were developed to model the relationship between aflatoxin concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific aflatoxin concentration. Test results on a lot with 20 parts per billion aflatoxin using a 1.13 kg sample, a Romer mill, 50 g subsamples, and liquid chromatographic analysis showed that the total, sampling, sample preparation, and analytical variances were 274.9 (CV = 82.9%), 214.0 (CV = 73.1%), 56.3 (CV = 37.5%), and 4.6 (CV = 10.7%), respectively. The percentage of the total variance for sampling, sample preparation, and analytical was 77.8, 20.5, and 1.7, respectively.

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Weerahandi, Samaradasa. "Testing Variance Components in Mixed Models with GeneralizedpValues". Journal of the American Statistical Association 86, n. 413 (marzo 1991): 151–53. http://dx.doi.org/10.1080/01621459.1991.10475013.

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Vargas, Eugenia A., Thomas B. Whitaker, Eliene A. Santos, Andrew B. Slate, Francisco B. Lima e Regina C. A. França. "Testing Green Coffee for Ochratoxin A, Part I: Estimation of Variance Components". Journal of AOAC INTERNATIONAL 87, n. 4 (1 luglio 2004): 884–91. http://dx.doi.org/10.1093/jaoac/87.4.884.

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Abstract The variability associated with testing lots of green coffee beans for ochratoxin A (OTA) was investigated. Twenty-five lots of green coffee were tested for OTA contamination. The total variance associated with testing green coffee was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances increased with an increase in OTA concentration. Using regression analysis, mathematical expressions were developed to model the relationship between OTA concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific OTA concentration. Testing a lot with 5 μg/kg OTA using a 1 kg sample, Romer RAS mill, 25 g subsamples, and liquid chromatography analysis, the total, sampling, sample preparation, and analytical variances were 10.75 (coefficient of variation [CV] = 65.6%), 7.80 (CV = 55.8%), 2.84 (CV = 33.7%), and 0.11 (CV = 6.6%), respectively. The total variance for sampling, sample preparation, and analytical were 73, 26, and 1%, respectively.

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Stram, Daniel O., e Jae Won Lee. "Variance Components Testing in the Longitudinal Mixed Effects Model". Biometrics 50, n. 4 (dicembre 1994): 1171. http://dx.doi.org/10.2307/2533455.

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Michalski, Andrzej, e Roman Zmyślony. "Testing Hypotheses for Variance Components in Mixed Linear Models". Statistics 27, n. 3-4 (gennaio 1996): 297–310. http://dx.doi.org/10.1080/02331889708802533.

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Sirkova, Lydia, e Viktor Witkovsky. "On Testing Variance Components in Unbalanced Mixed Linear Model". Applications of Mathematics 46, n. 3 (giugno 2001): 191–213. http://dx.doi.org/10.1023/a:1013739907119.

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Du, Han, e Lijuan Wang. "Testing Variance Components in Linear Mixed Modeling Using Permutation". Multivariate Behavioral Research 55, n. 1 (27 giugno 2019): 120–36. http://dx.doi.org/10.1080/00273171.2019.1627513.

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Drikvandi, R., G. Verbeke, A. Khodadadi e V. Partovi Nia. "Testing multiple variance components in linear mixed-effects models". Biostatistics 14, n. 1 (28 agosto 2012): 144–59. http://dx.doi.org/10.1093/biostatistics/kxs028.

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Drikvandi, Reza, Ahmad Khodadadi e Geert Verbeke. "Testing variance components in balanced linear growth curve models". Journal of Applied Statistics 39, n. 3 (marzo 2012): 563–72. http://dx.doi.org/10.1080/02664763.2011.603294.

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Più fonti

Tesi sul tema "Variance components testing"

Guédon, Tom. "Tests des composantes de la variance dans les modèles à effets mixtes pour des petits échantillons. Application à l'étude de la variabilité génotypique chez Arabidopsis thaliana". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASM046.

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Les modèles à effets mixtes permettent d'analyser des données présentant une structure hiérarchique, telles que les données longitudinales qui sont des mesures collectées sur un même individu au cours du temps. Ces modèles prennent en compte la variabilité au sein des mesures effectuées sur chaque individu (variabilité intra-individuelle) et entre différents individus (variabilité inter-individuelle), grâce à deux types d'effets : les effets fixes, communs à tous les individus de la population, et les effets aléatoires, variables d'un individu à l'autre. Ces derniers sont modélisés par des variables latentes non observées, qui portent la variabilité inter-individuelle de la population. Identifier les paramètres du modèle à la source de cette variabilité est une question importante, en particulier pour l'étude de la variabilité génotypique en amélioration des plantes. Cet objectif peut être formulé comme un test statistique de nullité des variances des effets aléatoires et la statistique du rapport de vraisemblances peut être considérée. Dans ce contexte, ce test présente cependant plusieurs défis. Théoriquement, la nullité des variances testées pose problème car ces variances se trouvent à la frontière de l'espace des paramètres. Les résultats classiques des méthodes basées sur le maximum de vraisemblance ne sont pas valides. Par ailleurs, la matrice d'information de Fisher est singulière dans ce cadre. De plus, si des variances non testées sont nulles, les tests asymptotiques ne sont plus applicables. Dans ce travail de thèse, une procédure de test du rapport de vraisemblances de nullité des composantes de la variance dans les modèles à effets mixtes est proposée, basée sur le Bootstrap paramétrique. La consistance de cette procédure de test sous l'hypothèse nulle est démontrée, pour un choix judicieux du paramètre utilisé pour simuler les échantillons Bootstrap. Une étape de seuillage de ce paramètre est proposée pour pallier les problèmes de frontière et de singularité de la matrice d'Information de Fisher. D'un point de vue computationnel, les modèles à effets mixtes étant des modèles à variables latentes, leur vraisemblance est la plupart du temps non explicite, ce qui rend difficile l'estimation de la statistique du rapport de vraisemblances. Estimer cette statistique revient à estimer un ratio de constantes de normalisation de densités de probabilité. Une nouvelle procédure d'estimation de ce ratio, basée sur une approximation stochastique, est proposée. Elle consiste à trouver le zéro d'une fonction définie par une espérance. Ce nouvel estimateur est consistant et asymptotiquement gaussien. Il présente de très bonnes performances théoriques et pratiques et peut s'intégrer dans une procédure d'estimation de paramètres dans un modèle à variables latentes. Pour finir, motivé par l'analyse de la variabilité génotypique pour l'amélioration des plantes, une étude de 48 génotypes d'Arabidopsis thaliana est présentée. Un modèle mécaniste complexe décrivant les échanges de carbone et d'azote entre la plante et son environnement est intégré à un modèle à effets mixtes afin d'identifier des paramètres biologiques portant une partie de la variabilité génotypique observée
Mixed-effects models allow for the analysis of data with a hierarchical structure, such as longitudinal data which are measurements collected on the same individual over time. These models take into account variability within measurements for each individual (intra-individual variability) and between different individuals (inter-individual variability) through two types of effects: fixed effects, which are common to all individuals in the population, and random effects, which vary from one individual to another. The latter are modeled by unobserved latent variables that account for the inter-individual variability in the population. Identifying the model parameters that are the source of this variability is an important issue, especially for studying genotypic variability in plant breeding. This objective can be formulated as a statistical test of the nullity of the random effects variances and the likelihood ratio statistic can be considered. In this context, however, the test presents several challenges. Theoretically, the nullity of the tested variances is problematic because these variances are on the boundary of the parameter space. Classical results of methods based on maximum likelihood are not valid anymore. Moreover, the Fisher information matrix is singular in this context. Additionally, if non-tested variances are null, asymptotic tests are no longer applicable. In this thesis work, a likelihood ratio test procedure for the nullity of variance components in mixed-effects models is proposed, based on parametric Bootstrap. The consistency of this test procedure under the null hypothesis are demonstrated, provided that a judicious choice is made for the parameter used for simulating the Bootstrap samples. A shrinkage step for this parameter is proposed to address boundary issues and the singularity of the Fisher Information matrix. From a computational perspective, since mixed-effects models are latent variable models, their likelihood is often not explicit, making the estimation of the likelihood ratio statistic challenging. Estimating this statistic amounts to estimating a ratio of normalization constants of probability densities. A new estimation procedure for this ratio, based on stochastic approximation, is proposed. It involves finding the zero of a function defined by an expectation. This new estimator is consistent and asymptotically Gaussian. It demonstrates very good theoretical and practical performances and can be integrated into a parameter estimation procedure in a latent variable model. Finally, motivated by the analysis of genotypic variability for plant breeding, a study of 48 genotypes of Arabidopsis thaliana is presented. A complex mechanistic model describing carbon and nitrogen exchanges between the plant and its environment is integrated into a mixed-effects model to identify which biological parameters are responsible for the observed genotypic variability

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Balasubramanian, Vijay. "Variance reduction and outlier identification for IDDQ testing of integrated chips using principal component analysis". Texas A&M University, 2006. http://hdl.handle.net/1969.1/4766.

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Integrated circuits manufactured in current technology consist of millions of transistors with dimensions shrinking into the nanometer range. These small transistors have quiescent (leakage) currents that are increasingly sensitive to process variations, which have increased the variation in good-chip quiescent current and consequently reduced the effectiveness of IDDQ testing. This research proposes the use of a multivariate statistical technique known as principal component analysis for the purpose of variance reduction. Outlier analysis is applied to the reduced leakage current values as well as the good chip leakage current estimate, to identify defective chips. The proposed idea is evaluated using IDDQ values from multiple wafers of an industrial chip fabricated in 130 nm technology. It is shown that the proposed method achieves significant variance reduction and identifies many outliers that escape identification by other established techniques. For example, it identifies many of the absolute outliers in bad neighborhoods, which are not detected by Nearest Neighbor Residual and Nearest Current Ratio. It also identifies many of the spatial outliers that pass when using Current Ratio. The proposed method also identifies both active and passive defects.

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Zhang, Angang. "Some Advances in Classifying and Modeling Complex Data". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77958.

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In statistical methodology of analyzing data, two of the most commonly used techniques are classification and regression modeling. As scientific technology progresses rapidly, complex data often occurs and requires novel classification and regression modeling methodologies according to the data structure. In this dissertation, I mainly focus on developing a few approaches for analyzing the data with complex structures. Classification problems commonly occur in many areas such as biomedical, marketing, sociology and image recognition. Among various classification methods, linear classifiers have been widely used because of computational advantages, ease of implementation and interpretation compared with non-linear classifiers. Specifically, linear discriminant analysis (LDA) is one of the most important methods in the family of linear classifiers. For high dimensional data with number of variables p larger than the number of observations n occurs more frequently, it calls for advanced classification techniques. In Chapter 2, I proposed a novel sparse LDA method which generalizes LDA through a regularized approach for the two-class classification problem. The proposed method can obtain an accurate classification accuracy with attractive computation, which is suitable for high dimensional data with p>n. In Chapter 3, I deal with the classification when the data complexity lies in the non-random missing responses in the training data set. Appropriate classification method needs to be developed accordingly. Specifically, I considered the "reject inference problem'' for the application of fraud detection for online business. For online business, to prevent fraud transactions, suspicious transactions are rejected with unknown fraud status, yielding a training data with selective missing response. A two-stage modeling approach using logistic regression is proposed to enhance the efficiency and accuracy of fraud detection. Besides the classification problem, data from designed experiments in scientific areas often have complex structures. Many experiments are conducted with multiple variance sources. To increase the accuracy of the statistical modeling, the model need to be able to accommodate more than one error terms. In Chapter 4, I propose a variance component mixed model for a nano material experiment data to address the between group, within group and within subject variance components into a single model. To adjust possible systematic error introduced during the experiment, adjustment terms can be added. Specifically a group adaptive forward and backward selection (GFoBa) procedure is designed to select the significant adjustment terms.
Ph. D.

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Kramlinger, Peter. "Essays on Inference in Linear Mixed Models". Doctoral thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-1396-C.

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Roy, Soumya. "Bayesian Accelerated Life Testing of Series Systems". Thesis, 2014. http://etd.iisc.ac.in/handle/2005/3021.

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Consider life testing of J-component series systems that are subjected to stress levels that are steeper than that at normal usage condition. The objective of performing such life tests, commonly known as Accelerated Life Testing (ALT) in the literature, is to collect observations on system failure times within a limited time frame. The accelerated observations are then used to infer on the component and system reliability metrics at usage stress. In this thesis, the existing literature is first extended by considering the general case of K stress variables, as opposed to the usual consideration of a single stress variable. Next, a general model assuming that the component log-lifetimes belong to an arbitrary location-scale family of distributions, is formulated. The location parameters are assumed to depend on the stress variables through a general stress translation function, while the scale parameters are assumed to be independent of the stress variables. This formulation covers the standard lifetime distributions as well as well-known stress translation functions as special cases. Bayesian methodologies are then developed for four special cases of the proposed general model, viz., exponentials, Weibulls with equal shape parameter, Weibulls with distinct shape parameters and log-normals with distinct scale parameters. For exponential and Weibull models, the priors on lifetime parameters are assumed to be log-concave and independent of each other. The resulting univariate conditional posterior of each lifetime parameter given the rest, is shown to be log-concave. This facilitates Gibbs sampling from the joint posterior of lifetime parameters. Propriety of the joint posteriors with Laplacian uniform priors on stress coefficients are also proved under a suitable set of sufficient conditions. For the log-normal model, the observed data is first augmented with log-lifetimes of un-failed components to form complete data. A Gibbs sampling scheme is then developed to generate observations from the joint posterior of lifetime parameters, through the augmented data and a conjugate prior for the complete data. In all four cases, Bayesian predictive inference techniques are used to study component and system reliability metrics at usage stress. Though this thesis mainly deals with Bayesian inference of accelerated data of series systems, maximum likelihood analysis for the log-normal component lifetimes is also performed via an expectation-maximization (EM) algorithm and bootstrap, which are not available in the literature. The last part of this thesis deals with construction of optimal Bayesian designs for accelerated life tests of J-component series systems under Type-I censoring scheme. Optimal ALT plans for a single stress variable are obtained using two different Bayesian D-optimality criteria for exponentially distributed component lives. A detailed sensitivity analysis is carried out to investigate the effect of different planning inputs on the optimal designs as well.

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Roy, Soumya. "Bayesian Accelerated Life Testing of Series Systems". Thesis, 2014. http://hdl.handle.net/2005/3021.

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Libri sul tema "Variance components testing"

Brennan, Robert L. The bootstrap and other procedures for examining the variability of estimated variance components in testing contexts. Iowa City, Iowa: American College Testing Program, 1987.

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Lejeune, Bernard. Error components models and variable heterogeneity: Modelisation, second order pseudo-maximum likelihood estimation and specification testing. Grenoble: A.N.R.T, Université Pierre Mendes France (Grenoble II), 1998.

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Commercial Vehicles 2021. VDI Verlag, 2021. http://dx.doi.org/10.51202/9783181023808.

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Contents Ways to achieve Zero Emission ZF E-Mobility products and software for commercial vehicles ..... 1 Thermoelectric generators for heavy-duty vehicles as an economical waste heat recovery system ..... 17 Hybridization of heavy duty trucks – Market analysis and technology for high voltage as well as low voltage solutions ..... 33 Development processes and methods Lightweight construction and cost reduction – a lean, agile MSCDPS® product development process ..... 43 eDrive & Fuel Cell powertrain systems engineering for commercial vehicles ..... 55 Fatigue development of a 10x10 commercial vehicle frame using dynamic and/or strength simulation, virtual iteration and component testing together with measurement data acquisition ..... 73 Data-driven selection of vehicle variants for the E/E integration test – Increasing variants and complex technology versus test coverage ..... 81 Hydrogen propulsion High performance and efficiency hydrogen engine using westport fuel systems’ Commercially available HPDI fuel system ..... 97 E/E architecture and operating strategy for fuel-cell trucks – Challenges...

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Capitoli di libri sul tema "Variance components testing"

Hartung, Joachim, e Bernard Voet. "Some Variants for Testing Linear Hypotheses on Variance Components". In Mathematische Methoden der Wirtschaftswissenschaften, 130–40. Heidelberg: Physica-Verlag HD, 1999. http://dx.doi.org/10.1007/978-3-662-12433-8_13.

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El-Bassiouni, Mohamed Y. "Testing Variance Components in Mixed Linear Models". In International Encyclopedia of Statistical Science, 1590–92. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-04898-2_588.

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Crainiceanu, Ciprian M. "Likelihood Ratio Testing for Zero Variance Components in Linear Mixed Models". In Random Effect and Latent Variable Model Selection, 3–17. New York, NY: Springer New York, 2008. http://dx.doi.org/10.1007/978-0-387-76721-5_1.

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Moder, Karl. "Testing Interaction and Estimating Variance Components in Block Designs - Based on a Linear Model". In Mindful Topics on Risk Analysis and Design of Experiments, 135–46. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-06685-6_10.

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Navarro, Danielle, e David Foxcroft. "13. Comparing several means (one-way ANOVA)". In Learning Statistics with jamovi, 295–324. Cambridge, UK: Open Book Publishers, 2025. https://doi.org/10.11647/obp.0333.13.

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This chapter delves into the foundational principles and applications of one-way ANOVA (Analysis of Variance), a pivotal statistical tool introduced by Sir Ronald Fisher in the early 20th century. Despite its name suggesting a focus on variances, ANOVA primarily investigates differences in means across multiple groups. Through the use of a clinical trial example involving three drugs—placebo, Anxifree, and Joyzepam—the chapter illustrates the mechanics of one-way ANOVA, highlighting its ability to discern whether observed differences in outcomes, such as mood improvements, are statistically significant. Readers are guided through the calculations underpinning the F-statistic, including between-group and within-group variability, and how these components inform hypothesis testing. The chapter also explores the practicalities of conducting ANOVA using jamovi, ensuring accessibility for researchers and students. Building on the core functionality of one-way ANOVA, the chapter addresses essential topics like effect size computation, post hoc testing for multiple comparisons, and adjustments for violations of assumptions. Key assumptions such as homogeneity of variance, normality, and independence are discussed alongside diagnostic methods and remedies, such as the Welch ANOVA and non-parametric alternatives like the Kruskal-Wallis test. For designs involving repeated measures, the chapter introduces the Friedman test. Emphasis is placed on the practical interpretation of results, including effect sizes and adjusted p-values, fostering a comprehensive understanding of ANOVA's capabilities and limitations in real-world research contexts.

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Noller, Yannic. "Hybrid Differential Software Testing". In Ernst Denert Award for Software Engineering 2020, 167–95. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-83128-8_9.

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AbstractDifferential software testing is important for software quality assurance as it aims to automatically generate test inputs that reveal behavioral differences in software. Detecting regression bugs in software evolution, analyzing side-channels in programs, maximizing the execution cost of a program over multiple executions, and evaluating the robustness of neural networks are instances of differential software analysis to generate diverging executions of program paths. The key challenge thereby is to simultaneously reason about multiple program paths, often across program variants, in an efficient way. Existing work in differential testing is often not (specifically) directed to reveal a different behavior or is limited to a subset of the search space. This work proposes the concept of Hybrid Differential Software Testing (HyDiff) as a hybrid analysis technique to generate difference revealing inputs. HyDiff consists of two components that operate in a parallel setup: (1) a search-based technique that inexpensively generates inputs and (2) a systematic exploration technique to also exercise deeper program behaviors. HyDiff’s search-based component uses differential fuzzing directed by differential heuristics. HyDiff’s systematic exploration component is based on differential dynamic symbolic execution that allows to incorporate concrete inputs in its analysis. HyDiff is evaluated experimentally with applications specific for differential testing. The results show that HyDiff is effective in all considered categories and outperforms its components in isolation.

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Evans, R. W., e B. Wilshire. "Computer Modelling of Creep Damage in Components with Variable Metallurgical Structure". In Techniques for Multiaxial Creep Testing, 209–21. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-3415-3_12.

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Tomaselli, Venera, e Giulio Giacomo Cantone. "Multipoint vs slider: a protocol for experiments". In Proceedings e report, 91–96. Florence: Firenze University Press, 2021. http://dx.doi.org/10.36253/978-88-5518-304-8.19.

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Since the broad diffusion of Computer-Assisted survey tools (i.e. web surveys), a lively debate about innovative scales of measure arose among social scientists and practitioners. Implications are relevant for applied Statistics and evaluation research since while traditional scales collect ordinal observations, data from sliders can be interpreted as continuous. Literature, however, report excessive times of completion of the task from sliders in web surveys. This experimental protocol is aimed at testing hypotheses on the accuracy in prediction and dispersion of estimates from anonymous participants who are recruited online and randomly assigned into tasks in recognition of shades of colour. The treatment variable is two scales: a traditional multipoint 0-10 multipoint vs a slider 0-100. Shades have a unique parametrisation (true value) and participants have to guess the true value through the scale. These tasks are designed to recreate situations of uncertainty among participants while minimizing the subjective component of a perceptual assessment and maximizing information about scale-driven differences and biases. We propose to test statistical differences in the treatment variable: (i) mean absolute error from the true value (ii), time of completion of the task. To correct biases due to the variance in the number of completed tasks among participants, data about participants can be collected through both pre-tasks acceptance of web cookies and post-tasks explicit questions.

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Zhang, Daowen, e Xihong Lin. "Variance Component Testing in Generalized Linear Mixed Models for Longitudinal/Clustered Data and other Related Topics". In Random Effect and Latent Variable Model Selection, 19–36. New York, NY: Springer New York, 2008. http://dx.doi.org/10.1007/978-0-387-76721-5_2.

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Stütz, Leon, Timo König, Roman Bader e Markus Kley. "Improvement of the Scheduling of Automotive Testing Processes Based on Production Scheduling Methods". In Advances in Automotive Production Technology – Towards Software-Defined Manufacturing and Resilient Supply Chains, 59–67. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27933-1_6.

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AbstractIncreasing challenges in the automotive industry are caused by shorter development times for products, greater diversity of variants and increasing cost pressure. Testing plays an elementary role within the product development process (PDP). There are already many publications that deal with the early phases of the PDP, but relatively few that address testing. Inefficient scheduling leads to suboptimal use of development and testing resources.Automotive testing is characterized by high momentum and process complexity. The complexity of testing is determined, among other things, by the number of test rigs in a test field, the number and diversity of test objects, the type of testing and the preparatory setups. In addition, complex testing processes at the component and system level require a large number of human and material resources, whose time availability and sequence must be coordinated with the testing process. The sequence planning is subject to a high inherent dynamic because unexpected changes and disturbances of the process can occur during the testing. These changes require a rescheduling of the testing process. If done manually, the rescheduling results in high costs.Based on known production planning methods, a solution approach is derived for improved utilization of test field resources for the automotive sector. The planning is optimized with a multitude of product - and process-related dependencies and restrictions using mixed-integer linear programming, a standardized method from operations research. The test field is simulated via a discrete event simulation. The proposed method considers the availability of essential resources.

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Atti di convegni sul tema "Variance components testing"

David, Matthew, Rodney Thomson, Tiansong Hou, Gangadhara Prusty, Garth Pearce e Don Kelly. "Impact Tests and Simulations of Crashworthy Composite Structures Using Variable Load Concept". In Vertical Flight Society 70th Annual Forum & Technology Display, 1–12. The Vertical Flight Society, 2014. http://dx.doi.org/10.4050/f-0070-2014-9477.

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Composite materials are used extensively in modern helicopter structures to reduce weight. Applications include energy absorption components necessary to meet crashworthiness requirements, where composite material can offer higher Specific Energy Absorption (SEA) than traditional metallic materials. However, the constant force energy absorbers that are currently used exhibit some limitations, such as under-utilisation of the crushing stroke leading to inefficient material usage and therefore higher than necessary decelerations to the occupants in some crash scenarios. This paper describes the results of a project to develop an improved system for crashworthiness. As part of this project, a novel Variable Load Concept (VLC) has been introduced to improve the performance of the energy absorption components. The crushing force can be controlled through the radius size of trigger mechanism and the use of pressurised composite tubes. The concept and the system were developed and further validated by crush testing at speeds of quasi-static, 2 m/s and 8 m/s. The results established that the VLC with pressurised composite tube system can be used in crashworthiness applications, and that the significant improvement in energy absorption characteristics is possible. Finally, an explicit finite element study was carried out using software PAM-CRASH, where very good agreement with experiment was demonstrated.

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Suder, Kenneth, Kenneth Durbin, Paul Giel, Douglas Thurman, Ali Ameri e Phil Poinsatte. "Variable Speed Turbine Technology Development and Demonstration". In Vertical Flight Society 74th Annual Forum & Technology Display, 1–14. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12870.

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The objective of this technical report is to provide a summary of the research performed under the NASA Revolutionary Vertical Lift (RVLT) Project to develop and demonstrate required engine technologies and designs for achieving a 50% reduction in rotor rotational speed via engine speed changes alone with a fixed ratio drive system while maintaining high engine efficiency over the wide operational speed range. This research culminated in a joint effort between the ARMY and NASA to develop and demonstrate a Variable Speed Power Turbine (VSPT) with an efficiency of 1) 92% or better at the Maximum Rated Power (MRP) condition corresponding to operation at sea-level conditions to hover at 100% rotational speed and 2) Efficiency of 90% or better at the Maximum Continuous Power (MCP) corresponding to cruise at 25000ft at Mach 0.5 at 55% rotational speed. NASA VSPT blade cascade testing at high and low inlet turbulence levels over a large range of Mach numbers, Reynolds numbers, and incidence provided a benchmark data base to validate the ability of CFD analysis codes to predict the VSPT losses over the entire flight operating envelope. These test results were also used to validate the ability of models to predict flow separation and laminar-to-turbulent flow transition. To demonstrate the VSPT technology, a notional engine was developed and the power turbine was designed to meet the NASA/Army performance requirements under the Army's Advanced Variable Speed Power Turbine (AVSPOT) program. Based on the notional engine a VSPT component test rig was designed, fabricated, and tested to demonstrate that their design would meet the performance requirements. The tested VSPT exceeded the efficiency goals of the design. Furthermore, the lapse between the MCP and MRP conditions was closely matched by CFD predictions, providing confidence in using these predictive tools in future applications. The technology development work completed on this contract is expected to transition to a viable engine demonstration in the future.

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Scheu, Thomas, Agnes Poks, Michael Weigand e Jonas Koch. "Dynamic Behaviour of a Rotorcraft Main Rotor System with Variable Speed". In Vertical Flight Society 80th Annual Forum & Technology Display, 1–10. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0080-2024-1368.

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Current Rotorcraft Developments like under the Future Vertical Lift Program in the USA (e.g. Bell V-280, see figure 1) respectively RACER (Airbus Helicopters, see figure 2) and NextGENCivil Tiltrotor (Leonardo, see figure 3) in Europe deal with High-Speed Rotorcraft or Tiltrotor-/Tiltwing Aircraft. They can expand and optimize their performance by using a variable rotor speed either to adopt the rotor speed to high forward speed or to meet the different requirements of a rotor in Hover and Aircraft Mode of a Tiltrotor-/Tiltwing Aircraft. As the required speed range can not be covered by the turbine, TU Munich (Germany), TU Wien (Vienna, Austria), ADT - Advanced Drivetrain Technologies (Austria) and Zoerkler Gears (Austria) work in the transnational project "VARI-SPEED II" on a rotor system that can change the rotor speed via change of the ratio of the transmission (variable rotor speed with constant turbine speed). The project is based on the results of "VARI-SPEED" and the direct follow-up project. VARI-SPEED showed that a rotor speed variation performed by a transmission system is possible. The efficiency and the flight envelope of the rotorcraft can be improved by this technology. Furthermore, a method for rotor blade design in a RPM range was invented. VARI-SPEED II now has built up a model of the complete dynamic system from engine to rotor of a helicopter with a variable speed rotor. This model is used for dynamic simulations of the components and the whole system. A scaled model of the module that changes the speed will be developed and pilot studies in a simulator are planned to find out the characteristics of such a system. Aim of the project is to reach TRL 3 as basis for further development of the technology with interested OEM's. This paper deals with the dynamic behaviour of the components and the whole drive train. The Bell V-280 is in the flight testing phase, RACER has recently conducted its maiden sortie and for the NextGENCtr the first flight is announced for the first half of 2024. All mentioned aircraft use transmission systems with a fixed gearbox ratio; this is feasible as a new technology like Vari-Speed normally is not added to completely new rotorcraft. However as the OEM's rate Vari-Speed positive, variable rotor speed can be integrated in a later development stage of the rotorcraft and thus development timelines of the rotorcrafts and Vari-Speed match quite well.

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Hooi, Chin. "Design, Rapid Prototyping and Testing of a Ducted Fan Micro-Quadcopter". In Vertical Flight Society 70th Annual Forum & Technology Display, 1–10. The Vertical Flight Society, 2014. http://dx.doi.org/10.4050/f-0070-2014-9429.

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This paper discusses recent results toward the design, rapid prototyping and testing of a ducted microquadcopter. Mobility and convenience objectives of this work dictate that the quadcopter must fit into a pocket, be capable of shooting high-definition videos and pictures, be controllable through a smartphone application, have a rotor diameter of 7cm and weigh approximately 300 g. Previous designs have rotor dimensions of 25 cm or more as well as airframe width and length of 75 cm and above. Aerodynamically, the ducted fan design is analyzed through Momentum Theory and Blade Element Momentum Theory (BEMT) to determine its contribution toward improved performance in hover, axial climb, axial descent and forward flight. The ducted fan design can be optimized for lower power consumption of up to 30% or smaller diameter than an open rotor and improves hover performance most significantly. Individual components, including the upper ducted and lower airframe were fabricated using composite layup methods. Microrotors as well as ducted fan molds were designed and built through three-dimensional (3D) Printing methods, including the Fused Deposit Modeling (FDM) and the PolyJet (PJ) method. Careful attention was taken to patch the duct lips with composites and sanding them to ensure smoothness. It was found that microrotors have to have at least a 4% thickness-to-chord ratio in order to be structurally sound. For the FDM method, the microrotors have to be printed with the blade plane perpendicular to the print bed and the blades oriented such that the blades have the strongest structural layout possible. For four and two blades, the best configurations are having the blades at having the blades at 60° and 0° (horizontal) to the print bed respectively. The PJ method, is capable of printing highly accurate microrotors flat on the print bed. However, they are less stiff and tend to flap more and structurally deform under exposure to ultraviolet (UV) and heat sources, hence making them more suitable for short term usage. Test results indicate that the FDM rotors produce more thrust than PJ rotors and have a lower torque-to-thrust ratio due to the fact that PJ rotors are less stiff. This in turn leads to excessive flapping and more susceptibility to flutter, which requires thicker blades at the expense of higher profile drag. Likewise, PJ rotors can be designed for higher thrust and lower torque-to-thrust ratio by incorporating constant chord blades at lower pitch angles, yet maintaining the same diameter and solidity as their variable chord counterparts.

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Walsh, Kenneth F. "Optical Shop Specifications". In Optical Fabrication and Testing. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oft.1990.owa1.

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This tutorial will explore the process of establishing the specifications for optical components. It is intended to help the Optical Shop Supervisor or Process Engineer gain a better understanding of the reasons behind the specifications sent to the shop by the designers. The factors considered by the Optical Designer and Engineer in selecting materials, finishes, and tolerances, as well as the consequence of excessive variance from specification.

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Deardorff, Arthur F., Dilip Dedhia, Stan T. Rosinski e David O. Harris. "Probabilistic Analysis of 60-Year Environmental Fatigue Effects for Reactor Components". In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1779.

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In NUREG/CR-6674, a probabilistic fracture mechanics analysis was conducted to assess the effects of light water reactor environmental effects on the probability of fatigue initiation and subsequent crack growth leading to leakage and possible core damage. The results were based on stresses for typical locations in BWR and PWR reactors as determined from an analysis reported in NUREG/CR-6260. Although environmental effects were shown to have an insignificant effect on core damage frequency, the study concluded that there could be a significant increase in probability of leakage. A detailed review of the methodology and input conditions used in NUREG/CR-6674 has been completed, including use of an altered probabilistic fatigue curve with more representative high-cycle stress variance and consideration of results from more recent environmental fatigue testing. This revised analysis indicates that environmental effects on the probability of leakage and core damage frequency in an extended nuclear plant operating period are significantly less than previously reported in NUREG/CR-6674. This paper summarizes the analysis performed and the results obtained.

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Ealy, Brandon, Luisana Calderon, Wenping Wang, Jay Kapat, Ilya Mingareev, Martin Richardson e Ranier Valentin. "Characterization of LAM-Fabricated Porous Superalloys for Turbine Components". In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-58080.

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The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel alloys remain the material of choice for most hot gas path components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings (TBC). Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiency capabilities. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Various cooling features were incorporated in the design, consisting of internal impingement cooling, internal lattice structures, and external showerhead or transpiration cooling. The internal structure was designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Through a non-destructive approach, the presented geometry is further analyzed against the departure of the design by utilizing x-ray computed tomography (CT). Employing this non-destructive evaluation (NDE) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Flow testing was performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficient of internal impingement arrays and porous structure are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for manufacture of micro-features in current turbine blade production.

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Sugumar, Suresh, Gopinath Dhamodaran, Pradeepkumar Seetharaman e Rajkamal Sivakumar. "Study of Hardness and Compression Strength of Carbon Fibre Reinforced Poly-Lactic Acid Composites Fabricated by Fused Deposition Modelling". In Automotive Technical Papers. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2024. https://doi.org/10.4271/2024-01-5227.

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<div class="section abstract"><div class="htmlview paragraph">3-Dimensional (3D) printing is an additive manufacturing technology that deposits materials in layers to build a three-dimensional component. Fused Deposition Modelling (FDM) is the most widely used 3D printing technique to produce the thermoplastic components. In FDM, the printing process parameters have a major role in controlling the performance of fabricated components. In this study, carbon fibre reinforced polymer composites were fabricated using FDM technique based on Taguchi's Design of experimental approach. The matrix and reinforcement materials were poly-lactic acid (PLA) and short carbon fibre, respectively. The goal of this study is to optimize the FDM process parameters in order to obtain the carbon fibre reinforced PLA composites with enhanced hardness and compressive strength values. Shore-D hardness and compression tests were carried out as per American Society for Testing and Materials (ASTM) D2240 and ASTM D695 standards respectively, to measure the output responses. The FDM process parameters considered in this study are layer height, infill density and infill pattern. The grey relational analysis (GRA) based multi-response optimization technique is used to optimize the process parameters. Analysis of variance is used to determine the most influential process parameter. The results showed that 3D printed components with improved performance characteristics could be achieved at 0.1mm layer height, Grid shaped infill pattern, and 75g/cm<sup>3</sup> infill density with a Shore-D hardness value of 76 and compressive strength of 42 N/mm<sup>2</sup>. It was identified that for multi-response optimization of equal weightage condition, the layer height contributed 44.44% followed by the contribution of Infill pattern and Infill density by 25.93% and 18.04% respectively. The developed regression model predicted the grade value at 90% confidence interval.</div></div>

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Dixit, Y., P. Begeman, G. S. Dhaliwal, G. Newaz, D. Board, Y. Chen e O. Faruque. "Full Frontal Crashworthiness of Carbon Fiber Composite Front Bumper Crush Can (FBCC) Structures". In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70354.

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This research study highlights the testing method and relevant results for assessing impact performance of a carbon fiber composite front bumper crush can (FBCC) assembly subjected to full frontal crash loading. It becomes extremely important to study the behavior of lightweight composite components under a crash scenario in order to apply them to automotive structures to reduce the overall weight of the vehicle. Computer-aided engineering (CAE) models are extremely important tools to virtually validate the physical testing by assessing the performances of these structures. Due to lack of available studies on carbon fiber composite FBCCs assemblies under the frontal crash scenario, a new component-level test approach would provide assistance to CAE models and better correlation between results can be made. In this study, all the tests were performed by utilizing a sled-on-sled testing method. An extreme care was taken to ensure that there is no bottoming-out force for this type of test while adjusting the impact speed of sled. Full frontal tests on FBCC structures were conducted by utilizing five high-speed cameras (HSCs), several accelerometers and a load wall. Excellent correlation was achieved between video tracking and accelerometers results for time histories of displacement and velocity. The standard deviation and coefficient of variance for the energy absorbed were very low suggesting the repeatability of the full frontal tests. The impact histories of FBCC specimens were consistent and in excellent agreement with respect to each other. Post-impact photographs showed the consistent crushing of composite crush cans and breakage of the bumper beam from middle due to the production of tensile stresses stretched caused by straightening of the bumper curvature after hitting the load wall.

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SAUVÉ, JAMES A., e KEVIN M. JAANSALU. "TOWARDS A DROP-IN REPLACEMENT SUBSONIC CAPABILITY FOR NATO SMALL ARMS". In 32ND INTERNATIONAL SYMPOSIUM ON BALLISTICS. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/ballistics22/36094.

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While subsonic ammunition has been of military interest for years, particularly for covert operations, significant limitations of current offerings have prevented its adoption including the inability to cycle an automatic action. This and other limitations were investigated through a design exercise to establish the feasibility of a drop-in replacement relevant to the Canadian Armed Forces using commercial off the shelf components. A survey and stability analysis of commercially available 5.56 mm projectiles led to the selection of the 90 grain Sierra Matchking for this design. Three different cartridge configurations were investigated in order to evaluate the effect of reducing cartridge volume on key internal ballistic variables. A cycling impulse model was developed in order to rank candidate designs on their ability to cycle a prescribed automatic weapon. Cartridge volume, in terms of standard cartridge, straight internal bore, and custom internal diameter to realize 95% load density, was explored as a means of increasing the load density of subsonic ammunition in order to reduce muzzle velocity variance and thus increase accuracy. However, the accuracy gained by reducing cartridge volume is shown to cause significant tradeoffs in cycling impulse. Live fire testing was performed in order to determine the minimum cycling impulse required to cycle the test weapon. The results also indicate that there may exist a threshold load density above which load density does not play a significant role in muzzle velocity variance. Thus, an objective of maximizing load density may overconstrain the design for minimal benefit.

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Rapporti di organizzazioni sul tema "Variance components testing"

Zareian, Farzin, e Joel Lanning. Development of Testing Protocol for Cripple Wall Components (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/olpv6741.

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Schiller, Brandon, Tara Hutchinson e Kelly Cobeen. Comparison of the Response of Small- and Large-Component Cripple Wall Specimens Tested under Simulated Seismic Loading (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/iyca1674.

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This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 4: Testing, whose central focus was to experimentally investigate the seismic performance of retrofitted and existing cripple walls. Two testing programs were conducted; the University of California, Berkeley (UC Berkeley) focused on large-component tests; and the University of California San Diego (UC San Diego) focused on small-component tests. The primary objectives of the tests were to develop descriptions of the load-deflection behavior of components and connections for use by Working Group 5 in developing numerical models and collect descriptions of damage at varying levels of drift for use by Working Group 6 in developing fragility functions. This report considers two large-component cripple wall tests performed at UC Berkeley and several small-component tests performed at UC San Diego that resembled the testing details of the large-component tests. Experiments involved imposition of combined vertical loading and quasi-static reversed cyclic lateral load on cripple wall assemblies. The details of the tests are representative of era-specific construction, specifically the most vulnerable pre-1945 construction. All cripple walls tested were 2 ft high and finished with stucco over horizontal lumber sheathing. Specimens were tested in both the retrofitted and unretrofitted condition. The large-component tests were constructed as three-dimensional components (with a 20-ft  4-ft floor plan) and included the cripple wall and a single-story superstructure above. The small-component tests were constructed as 12-ft-long two-dimensional components and included only the cripple wall. The pairing of small- and large-component tests was considered to make a direct comparison to determine the following: (1) how closely small-component specimen response could emulate the response of the large-component specimens; and (2) what boundary conditions in the small-component specimens led to the best match the response of the large-component specimens. The answers to these questions are intended to help identify best practices for the future design of cripple walls in residential housing, with particular interest in: (1) supporting the realistic design of small-component specimens that may capture the response large-component specimen response; and (2) to qualitatively determine where the small-component tests fall in the range of lower- to upper-bound estimation of strength and deformation capacity for the purposes of numerical modelling. Through these comparisons, the experiments will ultimately advance numerical modeling tools, which will in turn help generate seismic loss models capable of quantifying the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings. To this end, details of the test specimens, measured as well as physical observations, and comparisons between the two test programs are summarized in this report.

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Cobeen, Kelly, Vahid Mahdavifar, Tara Hutchinson, Brandon Schiller, David Welch, Grace Kang e Yousef Bozorgnia. Large-Component Seismic Testing for Existing and Retrofitted Single-Family Wood-Frame Dwellings (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/hxyx5257.

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Schiller, Brandon, Tara Hutchinson e Kelly Cobeen. Cripple Wall Small-Component Test Program: Wet Specimens I (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/dqhf2112.

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This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 4: Testing and focuses on the first phase of an experimental investigation to study the seismic performance of retrofitted and existing cripple walls with sill anchorage. Paralleled by a large-component test program conducted at the University of California [Cobeen et al. 2020], the present study involves the first of multiple phases of small-component tests conducted at the UC San Diego. Details representative of era-specific construction, specifically the most vulnerable pre-1960s construction, are of predominant focus in the present effort. Parameters examined are cripple wall height, finish materials, gravity load, boundary conditions, anchorage, and deterioration. This report addresses the first phase of testing, which consisted of six specimens. Phase 1 including quasi-static reversed cyclic lateral load testing of six 12-ft-long, 2-ft high cripple walls. All specimens in this phase were finished on their exterior with stucco over horizontal sheathing (referred to as a “wet” finish), a finish noted to be common of dwellings built in California before 1945. Parameters addressed in this first phase include: boundary conditions on the top, bottom, and corners of the walls, attachment of the sill to the foundation, and the retrofitted condition. Details of the test specimens, testing protocol, instrumentation; and measured as well as physical observations are summarized in this report. In addition, this report discusses the rationale and scope of subsequent small-component test phases. Companion reports present these test phases considering, amongst other variables, the impacts of dry finishes and cripple wall height (Phases 2–4). Results from these experiments are intended to provide an experimental basis to support numerical modeling used to develop loss models, which are intended to quantify the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100, Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings.

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Schiller, Brandon, Tara Hutchinson e Kelly Cobeen. Cripple Wall Small-Component Test Program: Wet Specimens II (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/ldbn4070.

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This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 4 (WG4): Testing, whose central focus was to experimentally investigate the seismic performance of retrofitted and existing cripple walls. This report focuses stucco or “wet” exterior finishes. Paralleled by a large-component test program conducted at the University of California, Berkeley (UC Berkeley) [Cobeen et al. 2020], the present study involves two of multiple phases of small-component tests conducted at the University of California San Diego (UC San Diego). Details representative of era-specific construction, specifically the most vulnerable pre-1960s construction, are of predominant focus in the present effort. Parameters examined are cripple wall height, finish style, gravity load, boundary conditions, anchorage, and deterioration. This report addresses the third phase of testing, which consisted of eight specimens, as well as half of the fourth phase of testing, which consisted of six specimens where three will be discussed. Although conducted in different phases, their results are combined here to co-locate observations regarding the behavior of the second phase the wet (stucco) finished specimens. The results of first phase of wet specimen tests were presented in Schiller et al. [2020(a)]. Experiments involved imposition of combined vertical loading and quasi-static reversed cyclic lateral load onto ten cripple walls of 12 ft long and 2 or 6 ft high. One cripple wall was tested with a monotonic loading protocol. All specimens in this report were constructed with the same boundary conditions on the top and corners of the walls as well as being tested with the same vertical load. Parameters addressed in this report include: wet exterior finishes (stucco over framing, stucco over horizontal lumber sheathing, and stucco over diagonal lumber sheathing), cripple wall height, loading protocol, anchorage condition, boundary condition at the bottom of the walls, and the retrofitted condition. Details of the test specimens, testing protocol, including instrumentation; and measured as well as physical observations are summarized in this report. Companion reports present phases of the tests considering, amongst other variables, impacts of various boundary conditions, stucco (wet) and non-stucco (dry) finishes, vertical load, cripple wall height, and anchorage condition. Results from these experiments are intended to support advancement of numerical modeling tools, which ultimately will inform seismic loss models capable of quantifying the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100,Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings.

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Schiller, Brandon, Tara Hutchinson e Kelly Cobeen. Cripple Wall Small-Component - Test Program: Comparisons (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/lohh5109.

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Jury, William A., e David Russo. Characterization of Field-Scale Solute Transport in Spatially Variable Unsaturated Field Soils. United States Department of Agriculture, gennaio 1994. http://dx.doi.org/10.32747/1994.7568772.bard.

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This report describes activity conducted in several lines of research associated with field-scale water and solute processes. A major effort was put forth developing a stochastic continuum analysis for an important class of problems involving flow of reactive and non reactive chemicals under steady unsaturated flow. The field-scale velocity covariance tensor has been derived from local soil properties and their variability, producing a large-scale description of the medium that embodies all of the local variability in a statistical sense. Special cases of anisotropic medium properties not aligned along the flow direction of spatially variable solute sorption were analysed in detail, revealing a dependence of solute spreading on subtle features of the variability of the medium, such as cross-correlations between sorption and conductivity. A novel method was developed and tested for measuring hydraulic conductivity at the scale of observation through the interpretation of a solute transport outflow curve as a stochastic-convective process. This undertaking provided a host of new K(q) relationships for existing solute experiments and also laid the foundation for future work developing a self-consistent description of flow and transport under these conditions. Numerical codes were developed for calculating K(q) functions for a variety of solute pulse outflow shapes, including lognormal, Fickian, Mobile-Immobile water, and bimodal. Testing of this new approach against conventional methodology was mixed, and agreed most closely when the assumptions of the new method were met. We conclude that this procedure offers a valuable alternative to conventional methods of measuring K(q), particularly when the application of the method is at a scale (e.g. and agricultural field) that is large compared to the common scale at which conventional K(q) devices operate. The same problem was approached from a numerical perspective, by studying the feasibility of inverting a solute outflow signal to yield the hydraulic parameters of the medium that housed the experiment. We found that the inverse problem was solvable under certain conditions, depending on the amount of noise in the signal and the degree of heterogeneity in the medium. A realistic three dimensional model of transient water and solute movement in a heterogeneous medium that contains plant roots was developed and tested. The approach taken was to generate a single realization of this complex flow event, and examine the results to see whether features were present that might be overlooked in less sophisticated model efforts. One such feature revealed is transverse dispersion, which is a critically important component in the development of macrodispersion in the longitudinal direction. The lateral mixing that was observed greatly exceeded that predicted from simpler approaches, suggesting that at least part of the important physics of the mixing process is embedded in the complexity of three dimensional flow. Another important finding was the observation that variability can produce a pseudo-kinetic behavior for solute adsorption, even when the local models used are equilibrium.

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Korobeinikova, Tetiana I., Nataliia P. Volkova, Svitlana P. Kozhushko, Daryna O. Holub, Nataliia V. Zinukova, Tetyana L. Kozhushkina e Sergei B. Vakarchuk. Google cloud services as a way to enhance learning and teaching at university. [б. в.], luglio 2020. http://dx.doi.org/10.31812/123456789/3854.

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The article is devoted to the issue of a cloud-based learning system implementation as a powerful strategy for future specialists’ training at higher educational establishments. Using cloud computing in self-work management of the university courses is essential to equip students with a workload of appropriate educational materials and variable activities for professional training. Theoretical and empirical research methods were applied to select the appropriate services and tools for organizing students’ self-work at university. Critical analysis of scientific literature, synthesis of the data, didactic observation of the educational process, designing of the skeleton for university courses, questionnaires enabled to facilitate the study of the issue. G Suite has been chosen to enhance the quality of training of prospective specialists at a higher educational establishment. This paper introduces the outcomes of the project on applying Google Classroom in the management of students’ self-work while studying university courses. The focus of the first stage of the project was on testing pilot versions of the courses with the aim to work out the requirements and recommendations for incorporation general blended learning model of university courses. Particular attention is drawn to the designed model of the university course based on the curriculum with the necessary components of blended learning in the G Suite virtual environment. Cloud-based higher education is considered as a prospective tool for design of university courses with the need for further research and implementation.

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Reis, Evan. Development of Index Buildings, (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/fudb2072.

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McElwain, Terry F., Eugene Pipano, Guy H. Palmer, Varda Shkap, Stephn A. Hines e Wendy C. Brown. Protection of Cattle against Babesiosis: Immunization against Babesia bovis with an Optimized RAP-1/Apical Complex Construct. United States Department of Agriculture, settembre 1999. http://dx.doi.org/10.32747/1999.7573063.bard.

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Previous research and current efforts at control of babesiosis fall short of meeting the needs of countries where the disease is endemic, such as Israel, as well as the needs of exporting countries and countries bordering on endemic areas, such as the U.S. Our long-term goal is to develop improved methods of immunization against bovine babesiosis based on an understanding of the molecular mechanisms of immune protection and parasite targets of a protective immune response. In our previous BARD project, we established the basis for focusing on rhoptry antigens as components of a subunit vaccine against bovine babesiosis, and for additional research to better characterize rhoptry associated protein-1 (RAP-1) as a target of protective immunity. In this continuation BARD project, our objectives were to [1] optimize the immune response against RAP-1, and [2] identify additional rhoptry candidate vaccine antigens. The entire locus encoding B. bovis RAP-1 was sequenced, and the rap-1 open reading frame compared among several strains. Unlike B. bigemina, in which multiple gene copies with variant domains encode RAP-1, the B. bovis RAP-1 locus contains only two identical genes which are conserved among strains. Through testing of multiple truncated constructs of rRAP-1, one or more immunodominant T cell epitopes were mapped to the amino terminal half of RAP-1. At least one linear and one conformational B cell epitope have been demonstrated in the same amino terminal construct, which in B. bigemina RAP-1 also contains an epitope recognized by neutralizing antibody. The amine terminal half of the molecule represents the most highly conserved part of the gene family and contains motifs conserved broadly among the apicomplexa. In contrast, the carboxy terminal half of B. bovis RAP-1 is less well conserved and contains multiple repeats encoding a linear B cell epitope potentially capable of inducing an ineffective, T cell independent, type 2 immune response. Therefore, we are testing an amino terminal fragment of RAP-1 (RAP-1N) in an immunization trial in cattle. Cattle have beer immunized with RAP-1N or control antigen, and IL-12 with Ribi adjuvant. Evaluation of the immune response is ongoing, and challenge with virulent B. bovis will occur in the near future. While no new rhoptry antigens were identified, our studies did identify and characterize a new spherical body antigen (SBP3), and several heat shock proteins (HSP's). The SBP3 and HSP21 antigens stimulate T cells from immune cattle and are considered new vaccine candidates worthy of further testing. Overall, we conclude that a single RAP-1 vaccine construct representing the conserved amino terminal region of the molecule should be sufficient for immunization against all strains of B. bovis. While results of the ongoing immunization trial will direct our next research steps, results at this time are consistent with our long term goal of designing a subunit vaccine which contains only the epitopes relevant to induction of protective immunity. Parallel studies are defining the mechanisms of protective immunity. Apicomplexan protozoa, including babesiosis and malaria, cause persistent diseases for which control is inadequate. The apical organelles are defining features of these complex protozoa, and have been conserved through the evolutionary process, Past and current BARD projects on babesiosis have established the validity and potential of exploiting these conserved organelles in developing improved control methods applicable to all apicomplexan diseases.

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