Academic literature on the topic 'Uniform prior'
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Journal articles on the topic "Uniform prior"
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Hartigan, J. A. "Locally uniform prior distributions." Annals of Statistics 24, no. 1 (February 1996): 160–73. http://dx.doi.org/10.1214/aos/1033066204.
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Shulman, N., and M. Feder. "The Uniform Distribution as a Universal Prior." IEEE Transactions on Information Theory 50, no. 6 (June 2004): 1356–62. http://dx.doi.org/10.1109/tit.2004.828152.
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van Zwet, Erik. "A default prior for regression coefficients." Statistical Methods in Medical Research 28, no. 12 (December 13, 2018): 3799–807. http://dx.doi.org/10.1177/0962280218817792.
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When the sample size is not too small, M-estimators of regression coefficients are approximately normal and unbiased. This leads to the familiar frequentist inference in terms of normality-based confidence intervals and p-values. From a Bayesian perspective, use of the (improper) uniform prior yields matching results in the sense that posterior quantiles agree with one-sided confidence bounds. For this, and various other reasons, the uniform prior is often considered objective or non-informative. In spite of this, we argue that the uniform prior is not suitable as a default prior for inference about a regression coefficient in the context of the bio-medical and social sciences. We propose that a more suitable default choice is the normal distribution with mean zero and standard deviation equal to the standard error of the M-estimator. We base this recommendation on two arguments. First, we show that this prior is non-informative for inference about the sign of the regression coefficient. Second, we show that this prior agrees well with a meta-analysis of 50 articles from the MEDLINE database.
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Kulawik, S. S., K. W. Bowman, M. Luo, C. D. Rodgers, and L. Jourdain. "Impact of nonlinearity on changing the a priori of trace gas profile estimates from the Tropospheric Emission Spectrometer (TES)." Atmospheric Chemistry and Physics 8, no. 12 (June 20, 2008): 3081–92. http://dx.doi.org/10.5194/acp-8-3081-2008.
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Abstract. Non-linear maximum a posteriori (MAP) estimates of atmospheric profiles from the Tropospheric Emission Spectrometer (TES) contains a priori information that may vary geographically, which is a confounding factor in the analysis and physical interpretation of an ensemble of profiles. One mitigation strategy is to transform profile estimates to a common prior using a linear operation thereby facilitating the interpretation of profile variability. However, this operation is dependent on the assumption of not worse than moderate non-linearity near the solution of the non-linear estimate. The robustness of this assumption is tested by comparing atmospheric retrievals from the Tropospheric Emission Spectrometer processed with a uniform prior with those processed with a variable prior and converted to a uniform prior following the non-linear retrieval. Linearly converting the prior following a non-linear retrieval is shown to have a minor effect on the results as compared to a non-linear retrieval using a uniform prior when compared to the expected total error, with less than 10% of the change in the prior ending up as unbiased fluctuations in the profile estimate results.
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Mukhopadhyay, S., and M. Ghosh. "On the Uniform Approximation of Laplace′s Prior by t-Priors in Location Problems." Journal of Multivariate Analysis 54, no. 2 (August 1995): 284–94. http://dx.doi.org/10.1006/jmva.1995.1057.
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Kulawik, S. S., K. W. Bowman, M. Luo, C. D. Rodgers, and L. Jourdain. "Technical Note: Impact of nonlinearity on changing the a priori of trace gas profiles estimates from the Tropospheric Emission Spectrometer (TES)." Atmospheric Chemistry and Physics Discussions 8, no. 1 (January 25, 2008): 1261–89. http://dx.doi.org/10.5194/acpd-8-1261-2008.
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Abstract. Non-linear optimal estimates of atmospheric profiles from the Tropospheric Emission Spectrometer (TES) may contain a priori information that varies geographically, which is a confounding factor in the analysis and physical interpretation of an ensemble of profiles. A common strategy is to transform these profile estimates to a common prior using a linear operation thereby facilitating the interpretation of profile variability. However, this operation is dependent on the assumption of not worse than moderate non-linearity near the solution of the non-linear estimate. We examines the robustness of this assumption when exchanging the prior by comparing atmospheric retrievals from the Tropospheric Emission Spectrometer processed with a uniform prior with those processed with a variable prior and converted to a uniform prior following the non-linear retrieval. We find that linearly converting the prior following a non-linear retrieval is shown to have a minor effect on the results as compared to a non-linear retrieval using a uniform prior when compared to the expected total error, with less than 10% of the change in the prior ending up as unbiased fluctuations in the profile estimate results.
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Tak, H. "Frequency coverage properties of a uniform shrinkage prior distribution." Journal of Statistical Computation and Simulation 87, no. 15 (July 8, 2017): 2929–39. http://dx.doi.org/10.1080/00949655.2017.1349769.
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Di, Ruohai, Peng Wang, Chuchao He, and Zhigao Guo. "Constrained Adjusted Maximum a Posteriori Estimation of Bayesian Network Parameters." Entropy 23, no. 10 (September 30, 2021): 1283. http://dx.doi.org/10.3390/e23101283.
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Maximum a posteriori estimation (MAP) with Dirichlet prior has been shown to be effective in improving the parameter learning of Bayesian networks when the available data are insufficient. Given no extra domain knowledge, uniform prior is often considered for regularization. However, when the underlying parameter distribution is non-uniform or skewed, uniform prior does not work well, and a more informative prior is required. In reality, unless the domain experts are extremely unfamiliar with the network, they would be able to provide some reliable knowledge on the studied network. With that knowledge, we can automatically refine informative priors and select reasonable equivalent sample size (ESS). In this paper, considering the parameter constraints that are transformed from the domain knowledge, we propose a Constrained adjusted Maximum a Posteriori (CaMAP) estimation method, which is featured by two novel techniques. First, to draw an informative prior distribution (or prior shape), we present a novel sampling method that can construct the prior distribution from the constraints. Then, to find the optimal ESS (or prior strength), we derive constraints on the ESS from the parameter constraints and select the optimal ESS by cross-validation. Numerical experiments show that the proposed method is superior to other learning algorithms.
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Cunanan, Kristen M., Alexia Iasonos, Ronglai Shen, and Mithat Gönen. "Variance prior specification for a basket trial design using Bayesian hierarchical modeling." Clinical Trials 16, no. 2 (December 7, 2018): 142–53. http://dx.doi.org/10.1177/1740774518812779.
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Background: In the era of targeted therapies, clinical trials in oncology are rapidly evolving, wherein patients from multiple diseases are now enrolled and treated according to their genomic mutation(s). In such trials, known as basket trials, the different disease cohorts form the different baskets for inference. Several approaches have been proposed in the literature to efficiently use information from all baskets while simultaneously screening to find individual baskets where the drug works. Most proposed methods are developed in a Bayesian paradigm that requires specifying a prior distribution for a variance parameter, which controls the degree to which information is shared across baskets. Methods: A common approach used to capture the correlated binary endpoints across baskets is Bayesian hierarchical modeling. We evaluate a Bayesian adaptive design in the context of a non-randomized basket trial and investigate three popular prior specifications: an inverse-gamma prior on the basket-level variance, a uniform prior and half-t prior on the basket-level standard deviation. Results: From our simulation study, we can see that the inverse-gamma prior is highly sensitive to the input hyperparameters. When the prior mean value of the variance parameter is set to be near zero [Formula: see text], this can lead to unacceptably high false-positive rates [Formula: see text] in some scenarios. Thus, use of this prior requires a fully comprehensive sensitivity analysis before implementation. Alternatively, we see that a prior that places sufficient mass in the tail, such as the uniform or half-t prior, displays desirable and robust operating characteristics over a wide range of prior specifications, with the caveat that the upper bound of the uniform prior and the scale parameter of the half-t prior must be larger than 1. Conclusion: Based on the simulation results, we recommend that those involved in designing basket trials that implement hierarchical modeling avoid using a prior distribution that places a majority of the density mass near zero for the variance parameter. Priors with this property force the model to share information regardless of the true efficacy configuration of the baskets. Many commonly used inverse-gamma prior specifications have this undesirable property. We recommend to instead consider the more robust uniform prior or half-t prior on the standard deviation.
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Zhu, Hai, Xia Luo, Yanjin Li, Ying Zhu, and Qian Huang. "Comparing the efficiency and robustness of state-of-the-art experimental designs for stated choice modeling: A simulation analysis." Advances in Mechanical Engineering 9, no. 2 (February 2017): 168781401769189. http://dx.doi.org/10.1177/1687814017691894.
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Among the ways to construct experimental designs having been proposed, orthogonal design, uniform design, and D-efficient design are state-of-the-art methods. This article provides detailed comparisons on the efficiency and robustness among these methods with three case studies in multinomial logit and mixed multinomial logit models. ND-error values and the departures of D-errors corresponding to misspecification of prior information are used as measurements of design efficiency and design robustness, respectively. Design methods are described, and designs with various numbers of runs are constructed. The results indicate that (a) when parameter priors are available, D-efficient design method outperforms the other two methods, in terms of design efficiency, while uniform design and orthogonal design methods are comparable with each other; (b) there will be efficiency loss when D-efficient design that constructed for specific model is implemented in other ones; (c) all three methods have comparable robustness against misspecifications in parameter prior values; however, the effect of misspecification in prior distribution is massive when D-efficient design is used in mixed multinomial logit model; and (d) when parameter priors are unknown, uniform design is suggested to be used in the construction of experimental designs.
Dissertations / Theses on the topic "Uniform prior"
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Righi, Ali. "Sur l'estimation de densités prédictives et l'estimation d'un coût." Rouen, 2011. http://www.theses.fr/2011ROUES002.
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Cette thèse est composée de deux parties. Dans la première partie, nous étudions l’estimation des densités prédictives, sous le coût de Kullback-Leibler, pour le modèle gaussien multidimensionnel de dimension p. Nous nous focalisons sur le lien qui existe entre ce problème d’estimation et l’estimation de la moyenne correspondante sous coût quadratique. Nous exhibons plusieurs résultats parallèles. Nous prouvons des résultats de minimaxité et d’amélioration des estimateurs sous contrainte pour la moyenne inconnue. Notamment, nous établissons, au travers deux méthodes, que la densité prédictive bayésienne associée à la loi a priori uniforme sur un convexe C domine la meilleure densité invariante sous la contrainte μ 2 C. Ceci constitue un résultat parallèle à celui de Hartigan en 2004 pour l’estimation de la moyenne sous coût quadratique. A la fin de cette partie, nous donnons des simulations numériques pour visualiser les gains réalisés par quelques nouveaux estimateurs proposés. Dans la seconde partie, pour le modèle gaussien de dimension p, nous traitons le problème de l’estimation du coût quadratique de l’estimateur standard de la moyenne (soit #0(X) = X). Nous proposons des estimateurs de coût bayésiens généralisés qui dominent l’estimateur standard du coût (soit #0(X) = p), en donnant des conditions suffisantes sur la loi a priori afin d’obtenir cette domination pour p # 5. Nous illustrons nos résultats par des exemples. Ensuite nous réalisons une étude technique et des simulations numériques du gain obtenu par un de nos estimateurs bayésiens généralisés proposésThis thesis is divided in two parts. In the first part, we investigate predictive density estimation for a multivariate Gaussian model under the Kullback-Leibler loss. We focus on the link with the problem of estimation of the mean under quadratic loss. We obtain several parallel results. We prove minimaxity and improved estimation results under restriction for the unknown mean. In particular, we show, via two different paths, that the Bayesian predictive density associated to the uniform prior on a convex C dominates the best invariant predictive density when μ 2 C. This is a parallel result to Hartigan’s result in 2004, for the estimation of the mean under quadratic loss. At the end of this part, we give numerical simulations to visualize the gain obtained by some of our new proposed estimators. In the second part, for the Gaussian model of dimension p, we treat the problem of estimating the loss of the standard estimator of the mean (that is, #0(X) = X). We give generalized Bayes estimators which dominate the unbiased estimator of loss (that is, #0(X) = p), through sufficient conditions for p # 5. Examples illustrate the theory. Then we carry on a technical study and numerical simulations on the gain reached by one of our proposed minimax generalized Bayes estimators of loss
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Floropoulos, Theodore C. "A Bayesian method to improve sampling in weapons testing." Thesis, 1988. http://hdl.handle.net/10945/22930.
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Approved for public release; distribution is unlimitedThis thesis describes a Bayesian method to determine the number of samples needed to estimate a proportion or probability with 95% confidence when prior bounds are placed on that proportion. It uses the Uniform [a,b] distribution as the prior, and develops a computer program and tables to find the sample size. Tables and examples are also given to compare these results with other approaches for finding sample size. The improvement that can be obtained with this method is fewer samples, and consequently less cost in Weapons Testing is required to meet a desired confidence size for a proportion or probability.
http://archive.org/details/bayesianmethodto00flor
Lieutenant Commander, Hellenic Navy
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Yu, Ting-Ta, and 余庭達. "On the Optimum Quantum Detection for the Ternary Geometrically Uniform Pure State Signal with Unequal Prior Probability." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/85178959322928165739.
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碩士國立清華大學
電機工程學系
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This thesis concerns the quantum detection problem for ternary pure state signals. We first review the relevant study on the quantum signal detection problem in the manner determined in Eldar's paper. We verify her result with the ternary geometrically uniform (GU) pure state signal having the uniform prior probability distribution, in which we have used the matrix-form expression of the optimum detection operators. Next, we consider the optimum detection problem for the ternary GU pure state signal under the condition that one prior probability is given and the others are unknown. In this situation, we formulate our optimization problem and derive the necessary and sufficient conditions for the solution of the problem. To seek the closed-form expression for the optimum detection operators, we perform the numerical simulation. As a result, we make a conjecture on the closed-form expression of the optimum measurement operators and on the optimum prior distribution for our problem.
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Tuyl, Frank Adrianus Wilhelmus Maria. "Estimation of the Binomial parameter: in defence of Bayes (1763)." Thesis, 2007. http://hdl.handle.net/1959.13/25730.
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Research Doctorate - Doctor of Philosophy (PhD)Interval estimation of the Binomial parameter è, representing the true probability of a success, is a problem of long standing in statistical inference. The landmark work is by Bayes (1763) who applied the uniform prior to derive the Beta posterior that is the normalised Binomial likelihood function. It is not well known that Bayes favoured this ‘noninformative’ prior as a result of considering the observable random variable x as opposed to the unknown parameter è, which is an important difference. In this thesis we develop additional arguments in favour of the uniform prior for estimation of è. We start by describing the frequentist and Bayesian approaches to interval estimation. It is well known that for common continuous models, while different in interpretation, frequentist and Bayesian intervals are often identical, which is directly related to the existence of a pivotal quantity. The Binomial model, and its Poisson sister also, lack a pivotal quantity, despite having sufficient statistics. Lack of a pivotal quantity is the reason why there is no consensus on one particular estimation method, more so than its discreteness: frequentist (unconditional) coverage depends on è. Exact methods guarantee minimum coverage to be at least equal to nominal and approximate methods aim for mean coverage to be close to nominal. We agree with what seems like the majority of frequentists, that exact methods are too conservative in practice, and show additional undesirable properties. This includes more recent ‘short’ exact intervals. We argue that Bayesian intervals based on noninformative priors are preferable to the family of frequentist approximate intervals, some of which are wider than exact intervals for particular data values. A particular property of the interval based on the uniform prior is that its mean coverage is exactly equal to nominal. However, once committed to the Bayesian approach there is no denying that the current preferred choice, by ‘objective’ Bayesians, is the U-shaped Jeffreys prior which results from various methods aimed at finding noninformative priors. The most successful such method seems to be reference analysis which has led to sensible priors in previously unsolved problems, concerning multiparameter models that include ‘nuisance’ parameters. However, we argue that there is a class of models for which the Jeffreys/reference prior may be suboptimal and that in the case of the Binomial distribution the requirement of a uniform prior predictive distribution leads to a more reasonable ‘consensus’ prior.
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Tuyl, Frank Adrianus Wilhelmus Maria. "Estimation of the Binomial parameter: in defence of Bayes (1763)." 2007. http://hdl.handle.net/1959.13/25730.
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Research Doctorate - Doctor of Philosophy (PhD)Interval estimation of the Binomial parameter è, representing the true probability of a success, is a problem of long standing in statistical inference. The landmark work is by Bayes (1763) who applied the uniform prior to derive the Beta posterior that is the normalised Binomial likelihood function. It is not well known that Bayes favoured this ‘noninformative’ prior as a result of considering the observable random variable x as opposed to the unknown parameter è, which is an important difference. In this thesis we develop additional arguments in favour of the uniform prior for estimation of è. We start by describing the frequentist and Bayesian approaches to interval estimation. It is well known that for common continuous models, while different in interpretation, frequentist and Bayesian intervals are often identical, which is directly related to the existence of a pivotal quantity. The Binomial model, and its Poisson sister also, lack a pivotal quantity, despite having sufficient statistics. Lack of a pivotal quantity is the reason why there is no consensus on one particular estimation method, more so than its discreteness: frequentist (unconditional) coverage depends on è. Exact methods guarantee minimum coverage to be at least equal to nominal and approximate methods aim for mean coverage to be close to nominal. We agree with what seems like the majority of frequentists, that exact methods are too conservative in practice, and show additional undesirable properties. This includes more recent ‘short’ exact intervals. We argue that Bayesian intervals based on noninformative priors are preferable to the family of frequentist approximate intervals, some of which are wider than exact intervals for particular data values. A particular property of the interval based on the uniform prior is that its mean coverage is exactly equal to nominal. However, once committed to the Bayesian approach there is no denying that the current preferred choice, by ‘objective’ Bayesians, is the U-shaped Jeffreys prior which results from various methods aimed at finding noninformative priors. The most successful such method seems to be reference analysis which has led to sensible priors in previously unsolved problems, concerning multiparameter models that include ‘nuisance’ parameters. However, we argue that there is a class of models for which the Jeffreys/reference prior may be suboptimal and that in the case of the Binomial distribution the requirement of a uniform prior predictive distribution leads to a more reasonable ‘consensus’ prior.
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Chen, Hsiang-Chun. "Inference for Clustered Mixed Outcomes from a Multivariate Generalized Linear Mixed Model." Thesis, 2013. http://hdl.handle.net/1969.1/151145.
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Multivariate generalized linear mixed models (MGLMM) are used for jointly modeling the clustered mixed outcomes obtained when there are two or more responses repeatedly measured on each individual in scientific studies. The relationship among these responses is often of interest. In the clustered mixed data, the correlation could be present between repeated measurements either within the same observer or between different observers on the same subjects. This study proposes a series of in- dices, namely, intra, inter and total correlation coefficients, to measure the correlation under various circumstances of observations from a multivariate generalized linear model, especially for joint modeling of clustered count and continuous outcomes.
Bayesian methods are widely used techniques for analyzing MGLMM. The need for noninformative priors arises when there is insufficient prior information on the model parameters. Another aim of this study is to propose an approximate uniform shrinkage prior for the random effect variance components in the Bayesian analysis for the MGLMM. This prior is an extension of the approximate uniform shrinkage prior. This prior is easy to apply and is shown to possess several nice properties. The methods are illustrated in terms of both a simulation study and a case example.
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Huang, Cheng-Jyun, and 黃程鈞. "A priori uniform estimates for an interface problem from composite media with anisotropic periodic fibres." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/06585777399663562634.
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碩士國立交通大學
應用數學系所
104
我們關心非均勻橢圓方程在介面附近的解的均勻估計。這個方程式描述了 在異質媒介中電流 (熱、速度等) 的行為。其中，異質媒介是具各向異性的傳導 纖維嵌入的各向同性的方陣。詳細的說，我們考慮的是嵌入了具我們所關心的 各向異性傳導纖維 (通過介面方向的傳導系數與在沿纖維方向的傳導系數的比值 小於 1) 的雙面多孔類型區域 (見 Figure 3)。在通過介面的方向上，纖維對於方 陣的傳導系數比值記作 ϵ ∈ (0,1)。我們得到在介面附近的解的先驗均勻 Hölder 估計，還有在介面附近的梯度 Hölder 估計。但是在估計中的係數與 ε^(-1) 有關。 為了凸顯出 ϵ −1 的作用，我們精確的寫出在 Hölder 估計中 ε^(-1) 的次方數。
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Gueye, N'deye Rokhaya. "Problèmes d'estimation de paramètres avec restriction sur l'espace des paramètres." Thèse, 2003. http://hdl.handle.net/1866/14587.
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Perret, Stéphane. "Localisation, reconstruction et mosaïque appliquées aux peintures sur cylindres généralisés à axe droit en vision monoculaire." Phd thesis, 1997. http://tel.archives-ouvertes.fr/tel-00004961.
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Ces travaux concernent la localisation et la reconstruction de surfaces cylindriques sur lesquelles sont projetées ou plaquées des scènes que le capteur perçoit comme des images. Du fait d'une étude limitée à la vision monoculaire, l'utilisation de connaissances a priori est nécessaire. On se propose d'approfondir des méthodes intégrant des contours contenus dans l'image, qui sont supposés être des projections de sections de Cylindres Généralisés Homogènes à axe Droit (CGHD). Les résultats sont appliqués principalement au domaine des oeuvres d'art comme les peintures sur voutes ou les fresques sur colonnes. Compte tenu de la limitation du champ d'observation des capteurs, nous sommes aussi amenés à aborder le problème de mosaïque de surfaces. Dans un premier temps nous présentons un ensemble de définitions concernant le modèle d'une caméra et les surfaces cylindriques généralisées, nous développons les connaissances a priori utilisées et le contexte d'application reliant le traitement d'images et les oeuvres d'art. Nous décrivons alors des mèthodes de localisation de Cylindres Généralisés Uniformes à axe Droit (CGUD) dans le repère de la caméra. Nous présentons deux mèthodes de détection de la projection de l'axe d'un CGUD, puis nous décrivons comment obtenir un deuxième axe dans l'image. Nous interprétons alors la signification de ces deux axes. Nous décrivons ensuite une méthode de reconstruction 3D de CGUD pouvant être étendue aux CGHD de sections fermées circulaires ou elliptiques, ou de sections ouvertes paraboliques ou elliptiques. Dans un premier temps, nous démontrons que l'évolution des courbures des ellipses dans l'image, projections de sections du CGUD de sections circulaires, est fonction linéaire de l'altitude de la section dans l'espace 3D. Nous étendons ces travaux aux problèmes de mosaïques de surfaces cylindriques. Nous analysons les distorsions dues à la projection perspective sur le plan image d'une scène issue d'une surface cylindrique. Nous présentons aussi une estimation du nombre de vues d'un CGUD nécessaire pour obtenir une scène complète. Tout au long de ces travaux, des résultats issus d'images synthètiques ou de peintures illustrent les méthodes développées.
Book chapters on the topic "Uniform prior"
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Wang, Guodong, Bin Wei, Zhenkuan Pan, Jingge Lu, and Zhaojing Diao. "Non-uniform Motion Deblurring Using Normalized Hyper Laplacian Prior." In Communications in Computer and Information Science, 103–13. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-48558-3_11.
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Lekdee, Krisada, Chao Yang, Lily Ingsrisawang, and Yisheng Li. "A Uniform Shrinkage Prior in Spatiotemporal Poisson Models for Count Data." In Emerging Topics in Statistics and Biostatistics, 83–102. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-72437-5_4.
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Tamaki, Mitsushi, and Qi Wang. "A Random Arrival Time Best-Choice Problem with Uniform Prior on the Number of Arrivals." In Springer Optimization and Its Applications, 499–510. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-0-387-89496-6_24.
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Cheng, Yougan, Ronny Straube, Abed E. Alnaif, Lu Huang, Tarek A. Leil, and Brian J. Schmidt. "Virtual Populations for Quantitative Systems Pharmacology Models." In Methods in Molecular Biology, 129–79. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2265-0_8.
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AbstractQuantitative systems pharmacology (QSP) places an emphasis on dynamic systems modeling, incorporating considerations from systems biology modeling and pharmacodynamics. The goal of QSP is often to quantitatively predict the effects of clinical therapeutics, their combinations, and their doses on clinical biomarkers and endpoints. In order to achieve this goal, strategies for incorporating clinical data into model calibration are critical. Virtual population (VPop) approaches facilitate model calibration while faced with challenges encountered in QSP model application, including modeling a breadth of clinical therapies, biomarkers, endpoints, utilizing data of varying structure and source, capturing observed clinical variability, and simulating with models that may require more substantial computational time and resources than often found in pharmacometrics applications. VPops are frequently developed in a process that may involve parameterization of isolated pathway models, integration into a larger QSP model, incorporation of clinical data, calibration, and quantitative validation that the model with the accompanying, calibrated VPop is suitable to address the intended question or help with the intended decision. Here, we introduce previous strategies for developing VPops in the context of a variety of therapeutic and safety areas: metabolic disorders, drug-induced liver injury, autoimmune diseases, and cancer. We introduce methodological considerations, prior work for sensitivity analysis and VPop algorithm design, and potential areas for future advancement. Finally, we give a more detailed application example of a VPop calibration algorithm that illustrates recent progress and many of the methodological considerations. In conclusion, although methodologies have varied, VPop strategies have been successfully applied to give valid clinical insights and predictions with the assistance of carefully defined and designed calibration and validation strategies. While a uniform VPop approach for all potential QSP applications may be challenging given the heterogeneity in use considerations, we anticipate continued innovation will help to drive VPop application for more challenging cases of greater scale while developing new rigorous methodologies and metrics.
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Pettigrew, Richard. "Priors that Allow You to Learn Inductively." In Epistemic Risk and the Demands of Rationality, 175–82. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192864352.003.0011.
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Abstract In this chapter, I consider an objection that is inspired by a worry that Wayne Myrvold (2019) raised to my earlier work on epistemic risk. This notes that our account permits priors, such as the uniform prior, that do not allow you to learn from experience in the ways we think you should. In the end, I think these priors, and the inductive scepticism they embody, must be permitted, however little we like the consequences of adopting them. But, unlike in my earlier work, they are not now mandated, which was the central focus of Myrvold's original objection.
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Donovan, Therese M., and Ruth M. Mickey. "Probability Density Functions." In Bayesian Statistics for Beginners, 108–30. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198841296.003.0009.
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This chapter builds on probability distributions. Its focus is on general concepts associated with probability density functions (pdf’s), which are distributions associated with continuous random variables. The continuous uniform and normal distributions are highlighted as examples of pdf’s. These and other pdf’s can be used to specify prior distributions, likelihoods, and/or posterior distributions in Bayesian inference. Although this chapter specifically focuses on the continuous uniform and normal distributions, the concepts discussed in this chapter will apply to other continuous probability distributions. By the end of the chapter, the reader should be able to define and use the following terms for a continuous random variable: random variable, probability distribution, parameter, probability density, likelihood, and likelihood profile.
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Ahranjani, Maryam. "Erecting a Virtual Schoolhouse Gate." In Advances in Electronic Government, Digital Divide, and Regional Development, 73–89. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8350-9.ch004.
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The very first amendment to the United States Constitution protects the freedom of speech. While the Supreme Court held in 1969 that students “do not shed their constitutional rights at the schoolhouse gate,” since then the Court has limited students' freedom of speech, stopping short of considering the boundaries of off-campus, online speech. Lower court holdings vary, meaning that a student engaging in certain online speech may not be punished at all in one state but would face harsh criminal punishments in another. The lack of a uniform standard leads to dangerously inconsistent punishments and poses the ultimate threat to constitutional knowledge and citizenship exercise: chilling of speech. Recent interest in technology-related cases and the presence of a new justice may reverse the Court's prior unwillingness to address this issue. In the meantime, this chapter argues that school districts should erect a virtual schoolhouse gate by implementing a uniform standard.
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Ricketson, Sam, and Jane C. Ginsburg. "Origins of the Berne Convention." In International Copyright and Neighbouring Rights, 38–76. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198801986.003.0002.
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This chapter discusses the origins of the Berne Convention. Although the network of bilateral copyright arrangements in force prior to 1886 was extensive, the protection which this offered to authors in countries other than their own was far from comprehensive or systematic. Apart from the early treaties with the German and Italian states, multilateral copyright agreements in the true sense took time to emerge. Of these, the Berne Convention was to be the first, and the most important. However, the need for a more uniform and broader-based kind of international protection had been recognized some time before this by authors and artists. The chapter deals with this development, and the different stages by which this early recognition was eventually transformed into the Berne Convention.
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Ostwald, Kai, and Tun Myint. "Myanmar: Pandemic in a Time of Transition." In Covid-19 in Asia, 335–48. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197553831.003.0023.
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This chapter examines how Myanmar faced distinct disadvantages in its ability to respond to the Covid-19 pandemic relative to regional neighbours. This is due to its continued grappling with simultaneous political, economic, and conflict-related transitions: Myanmar was a largely closed-off military dictatorship for nearly fifty years prior to its partial opening in 2011. In conjunction with structural factors, the triple transition had several important implications for Myanmar’s response to the pandemic. First, many of the aggressive approaches to countering Covid-19 that were effective in other contexts were infeasible for Myanmar, as the state lacked the capacity to enforce comprehensive population movement controls and large-scale testing and contact tracing. Second, Myanmar’s structural conditions prevented a uniform response to the pandemic. Third, Myanmar has several high-risk subgroups that complicated responses to the pandemic.
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Lenka, Rasmita, Asimananda Khandual, Koustav Dutta, and Soumya Ranjan Nayak. "Image Enhancement." In Examining Fractal Image Processing and Analysis, 211–23. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-0066-8.ch011.
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This chapter describes a novel method to enhance degraded nighttime images by dehazing and color correction method. In the first part of this chapter, the authors focus on filtering process for low illumination images. Secondly, they propose an efficient dehazing model for removing haziness Thirdly, a color correction method proposed for color consistency approach. Removing nighttime haze technique is an important and necessary procedure to avoid ill-condition visibility of human eyes. Scattering and color distortion are two major problems of distortion in case of hazy image. To increase the visibility of the scene, the authors compute the preprocessing using WLS filter. Then the airlight component for the non-uniform illumination presents in nighttime scenes is improved by using a modified well-known dark-channel prior algorithm for removing nighttime haze, and then it uses α-automatic color equalization as post-processing for color correction over the entire image for getting a better enhanced output image free from haze with improved color constancy.
Conference papers on the topic "Uniform prior"
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Rademacher, Paul, and Milos Doroslovacki. "Bayesian Learning for Classification using a Uniform Dirichlet Prior." In 2019 IEEE Global Conference on Signal and Information Processing (GlobalSIP). IEEE, 2019. http://dx.doi.org/10.1109/globalsip45357.2019.8969120.
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Liu, Guang, Shikang Wu, Yu Shi, Yuerui Zhang, Junxiong Fei, and Xia Hua. "Underwater Non-uniform Illumination Image Correction Method Based on Dark Channel and Frequency Distribution Prior." In 2021 China Automation Congress (CAC). IEEE, 2021. http://dx.doi.org/10.1109/cac53003.2021.9728308.
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Nezhad, Hamed Yazdani, Noel P. O’Dowd, Catrin M. Davies, Ali N. Mehmanparast, and Kamran M. Nikbin. "Influence of Prior Deformation on Creep Crack Growth Behaviour of 316H Austenitic Steels." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78680.
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The influence of pre-strain and pre-stress on creep crack growth behaviour of 316H austenitic steels is studied experimentally and numerically in this paper. Compact tension, C(T), specimens (25mm thickness) have been extracted from two steam headers, one as-received and one uniformly compressed to the strain value of 8%. The C(T) specimen extracted from the as-received header was compressed, introducing a non-uniform strain field. Creep crack growth (CCG) tests were performed at 550°C. Comparisons have been provided with the results from as-received C(T) specimens. Finite element (FE) analysis has been carried out to simulate the CCG behaviour of the C(T) specimens. By choosing the problem parameters appropriately, good agreement may be achieved between the FE predictions and the creep data.
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Zur, Richard M., Lorenzo L. Pesce, Yulei Jiang, and Charles E. Metz. "A Bayesian interpretation of the "proper" binormal ROC model using a uniform prior distribution for the area under the curve." In Medical Imaging, edited by Yulei Jiang and Berkman Sahiner. SPIE, 2007. http://dx.doi.org/10.1117/12.711689.
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Hermanson, K. S., and K. A. Thole. "Effect of Non-Uniform Inlet Conditions on Endwall Secondary Flows." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30188.
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Exit combustor flow and thermal fields entering downstream stator vane passages in a gas turbine engine are highly non-uniform. These flow and thermal fields can significantly affect the development of the secondary flows in the turbine passages contributing to high platform heat transfer and large aerodynamic losses. The flow and thermal fields combine to give non-uniform total pressure profiles entering the turbine passage which, along with the airfoil geometry, dictate the secondary flow field. This paper presents an analysis of the effects of varying total pressure profiles in both the radial and combined radial and circumferential directions on the secondary flow fields in a first stage stator vane. These inlet conditions used for the first vane simulations are based on the exit conditions predicted for a combustor. Prior to using the predictions, these CFD simulations were benchmarked against flow field data measured in a large-scale, linear, turbine vane cascade. Good agreement occurred between the computational predictions and experimentally measured secondary flows. Analyses of the results for several different cases indicate variations in the secondary flow pattern from pitch to pitch, which attributes to the rationale as to why some airfoils quickly degrade while others remain intact over time.
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Pham, Quang N., Youngjoon Suh, Bowen Shao, and Yoonjin Won. "Boiling Heat Transfer Using Spatially-Variant and Uniform Microporous Coatings." In ASME 2019 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipack2019-6307.
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Abstract Two-phase thermal management offers cooling performance enhancement by an order of magnitude higher than single-phase flow due to the latent heat associated with phase change. Among the modes of phase-change, boiling can effectively remove massive amounts of heat flux from the surface by employing structured or 3D microporous coatings to significantly enlarge the interfacial surface area for improved heat transfer rate as well as increase the number of potential sites for bubble nucleation and departure. The bubble dynamics during pool boiling are often considered to be essential in predicting heat transfer performance, causing it to be a field of significant interest. While prior investigations seek to modulate the bubble dynamics through either active (e.g., surfactants, electricity) or passive means (e.g., surface wettability, microstructures), the utilization of an ordered microporous architecture to instigate desirable liquid and vapor flow field has been limited. Here, we investigate the bubble dynamics using various spatial patterns of inverse opal channels to induce preferential heat and mass flow site in highly-interconnected microporous media. A fully-coated inverse opal surface demonstrates the intrinsic boiling effects of a uniform microporous coating, which exhibits 156% enhancement in heat transfer coefficient in comparison to the polished silicon surface. The boiling heat transfer performances of spatially-variant inverse opal channels significantly differ based on the pitch spacings between the microporous channels, which dictate the bubble coalescent behaviors and bubble departure characteristics. The elucidated boiling heat transfer performances will provide engineering guidance toward designing optimal two-phase thermal management devices.
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Hellum, Aren M., Ranjan Mukherjee, and Andrew J. Hull. "Dynamics of Pipes Conveying Fluid With a Non-Uniform Velocity Profile." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12858.
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Previous work on stability of fluid-conveying cantilever pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces drop out of the system’s dynamics since the force of fluid shear on the wall is precisely balanced by pressure drop in the conveyed fluid. The effect of shear has therefore not been ignored in these studies. However, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed non-uniform profile such as would be encountered in real fluid flows. A modified equation of motion was derived to account for the reduced momentum carried by the sheared fluid. Numerical analysis was carried out to determine a number of velocity profiles over the Reynolds number range of interest and a simple set of curve fits was used when finer discretization was required. Stability analysis of a pipe conveying fluid with these profiles was performed, and the results were compared to a uniform profile. The mass ratio, β, is the ratio of the fluid mass to the total system mass. At β = 0.2, the non-uniform case becomes unstable at a critical velocity, ucr, that is 5.4% lower than the uniform case. The critical frequency, fcr, is 0.36% higher than the uniform case. A more sensitive region exists near β = 0.32. There, the nonuniform velocity ucr is 23% lower than the uniform case and the non-uniform critical frequency fcr is 49% of the uniform case.
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Tian, Jie, Xiaopu Zhang, Yong Chen, Peter Russhard, and Hua Ouyang. "Sparse Reconstruction Method of Non-Uniform Sampling and its Application in Blade Tip Timing System." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14753.
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Abstract Based on the blade vibration theory of turbomachinery and the basic principle of blade timing systems, a sparse reconstruction model is derived for the tip timing signal under an arbitrary sensor circumferential placement distribution. The proposed approach uses the sparsity of the tip timing signal in the frequency domain. The application of compressive sensing in reconstructing the blade tip timing signal and monitoring multi-mode blade vibrations is explored. To improve the reconstruction effect, a number of numerical experiments are conducted to examine the effects of various factors on synchronous and non-synchronous signals. This enables the specific steps involved in the compressive sensing reconstruction of tip timing signals to be determined. The proposed method is then applied to the tip timing data of a 27-blade rotor. The results show that the method accurately identifies the multi-mode blade vibrations at different rotation speeds. The proposed method has the advantages of low dependence on prior information, insensitivity to environmental noise, and simultaneous identification of synchronous and non-synchronous signals. The experimental results validate the effectiveness of the proposed approach in engineering applications.
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Hellum, Aren M., Ranjan Mukherjee, and Andrew J. Hull. "Dynamics of Pipes Conveying Fluid With Non-Uniform Turbulent and Laminar Velocity Profiles." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30866.
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Previous analytical work on stability of fluid-conveying pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces do not affect the dynamics of the system since these forces are balanced by pressure drop in the conveyed fluid. Although viscous shear has not been ignored in these studies, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed nonuniform profile such as would be encountered in real fluid flows. A modified, highly tractable equation of motion was derived, which includes a single additional parameter to account for the true momentum of the fluid. This empirical parameter was determined by numerical analysis over the Reynolds number range of interest. The stability of cantilever pipes conveying fluid with two types of non-uniform velocity profile was assessed. In the first case, the profile was a function of Reynolds number and transition to turbulence occurred before the onset of flutter instability. This case had stability properties similar to the uniform velocity case except in specific narrow regions of the parameter space. The second case required that the Reynolds number be such that the flow was always laminar. For this case, lower fluid velocity was required to achieve instability, and the oscillation frequency at instability was considerably lower over much of the parameter space, compared to the uniform case.
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Diez, F. J., L. P. Bernal, and G. M. Faeth. "Self-Preserving Properties of Steady Round Nonbuoyant Turbulent Jets in Uniform Crossflows." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56110.
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The properties of steady round nonbuoyant turbulent jets in uniform crossflows were studied, motivated by applications to the dispersion of heat and potentially harmful substances from steady exhaust flows. Emphasis was placed on self-preserving conditions far from the source where source disturbances have been lost and where jet properties are largely controlled by the conserved properties of the flow. The experiments involved steady round nonbuoyant fresh water jet sources injected into uniform and steady fresh water crossflows within the windowed test section of a water channel facility. Flow visualization was carried out by photographing dye-containing source jets. Mean and fluctuating concentrations of source fluid were measured over cross sections of the flow using Planar Laser-Induced Fluorescence (PLIF). The self-preserving properties of the flow were correlated successfully based on scaling analysis due to Fischer et al. (1979) which involves assumptions of no-slip convection in the cross stream direction (parallel to the crossflow) and a self-preserving nonbuoyant turbulent line puff having a conserved momentum force per unit length that moves in the streamwise direction (parallel to the initial source flow). The flow structure consisted of two counterrotating vortices, with their axes nearly aligned with the crossflow direction, that move away from the source in the streamwise direction due to the action of source momentum. Present measurements extended up to 160 source diameters from the source in the streamwise direction and yielded the following results: jet motion in the cross stream direction satisfied the no-slip convection approximation; geometrical features, such as the penetration of flow boundaries and the trajectories of the axes of the counter-rotating vortices, reached self-preserving behavior at streamwise distances greater than 40–50 source diameters from the source; parameters associated with the structure of the flow, e.g., contours and profiles of mean and fluctuating concentrations of source fluid, however, did not reach self-preserving behavior prior to reaching streamwise (vertical) distances greater than 70–80 source diameters from the source.
Reports on the topic "Uniform prior"
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Wüthrich, Annik. L’expression de la filiation à la XXIe dynastie: reflet d’une réalité historique ou simple effet de mode? L’exemple du Livre des Morts. Verlag der Österreichischen Akademie der Wissenschaften, August 2021. http://dx.doi.org/10.1553/erc_stg_757951_a.wuethrich_l_expression_de_la_filiation_a_la_xxie_dynastie:_reflet_d_une_realit_historique_ou_simple_effet_de_mode_l_exemple_du_livre_des_morts.
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The study of expressions of filiation has already been the subject of several articles, which were limited to periods prior to the Third Intermediate Period. The aim of this article is to evaluate these expressions within the specific framework of the Books of the Dead from the 21st and 22nd Dynasties. These periods are marked by a significant increase in the variety of expressions employed, whereas the New Kingdom manuscripts expressed filiation according to a more uniform and rigid scheme. Similarly to what happens with titles and despite the diversity of expressions, one observes a progressive decrease in the mention of filiation which almost disappears from funerary papyri, while long genealogies on temple statues are developing. This contribution attempts to understand the motivations behind the use of these expressions and more generally to grasp their purpose in expressing the identity of the deceased.
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Clausen, Jay, Susan Frankenstein, Jason Dorvee, Austin Workman, Blaine Morriss, Keran Claffey, Terrance Sobecki, et al. Spatial and temporal variance of soil and meteorological properties affecting sensor performance—Phase 2. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/41780.
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An approach to increasing sensor performance and detection reliability for buried objects is to better understand which physical processes are dominant under certain environmental conditions. The present effort (Phase 2) builds on our previously published prior effort (Phase 1), which examined methods of determining the probability of detection and false alarm rates using thermal infrared for buried-object detection. The study utilized a 3.05 × 3.05 m test plot in Hanover, New Hampshire. Unlike Phase 1, the current effort involved removing the soil from the test plot area, homogenizing the material, then reapplying it into eight discrete layers along with buried sensors and objects representing targets of inter-est. Each layer was compacted to a uniform density consistent with the background undisturbed density. Homogenization greatly reduced the microscale soil temperature variability, simplifying data analysis. The Phase 2 study spanned May–November 2018. Simultaneous measurements of soil temperature and moisture (as well as air temperature and humidity, cloud cover, and incoming solar radiation) were obtained daily and recorded at 15-minute intervals and coupled with thermal infrared and electro-optical image collection at 5-minute intervals.
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Wolfenson, David, William W. Thatcher, and James E. Kinder. Regulation of LH Secretion in the Periovulatory Period as a Strategy to Enhance Ovarian Function and Fertility in Dairy and Beef Cows. United States Department of Agriculture, December 2003. http://dx.doi.org/10.32747/2003.7586458.bard.
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The general research objective was to increase herd pregnancy rates by enhancing corpus luteum (CL) function and optimizing follicle development, in order to increase conception rate and embryo survival. The specific objectives were: to determine the effect of the duration of the preovulatory LH surge on CL function; to determine the function of LH during the postovulatory period on CL development; to optimize CL differentiation and follicle development by means of a biodegradable GnRH implant; to test whether optimization of CL development and follicle dynamics in timed- insemination protocols would improve fertility in high-yielding dairy cows. Low fertility in cattle results in losses of hundreds of millions of dollars in the USA and Israel. Two major causes of low fertility are formation of a functionally impaired CL, and subsequent enhanced ovarian follicle development. A functionally impaired CL may result from suboptimal LH secretion. The two major causes of low fertility in dairy cattle in US and Israel are negative energy status and summer heat stress; in both situations, low fertility is associated with reductions in LH secretion and impaired development of the ovulatory follicle and of the CL. In Florida, the use of 450-mg deslorelin (GnRH analogue) implants to induce ovulation, under the Ovsynch protocol resulted in a higher pregnancy rates than use of 750-mg implants, and pregnancy losses tended to decrease compared to controls, due probably to decrease in follicular development and estradiol secretion at the time of conceptus signaling to maintain the CL. An alternative strategy to enhance progesterone concentrations involved induction of an accessory CL by injection of hCG on day 5 after the cows were inseminated. Treatment with hCG resulted in 86% of the cows having two CLs, compared with 23% of the control cows. Conception rates were higher among the hCG-treated cows than among the controls. Another approach was to replace the second injection of GnRH analogue, in a timed-insemination protocol, with estradiol cypionate (ECP) injected 24 h after the injection of PGF₂ₐ Pregnancy rates were comparable with those obtained under the regular Ovsynch (timed- AI) program. Use of ECP induced estrus, and cows inseminated at detected estrus are indeed more fertile than those not in estrus at the time of insemination. Collectively, the BARD-supported programs at the University of Florida have improved timed insemination programs. In Ohio, the importance of the frequency of LH episodes during the early stages of the estrous cycle of cattle, when the corpus luteum is developing, was studied in an in vivo experiment in which cows were subjected to various episodic exposures to exogenous bovine LH. Results indicate that the frequent LH episodes immediately following the time of ovulation are important in development of the corpus luteum, from the points of view of both size and functionality. In another study, rates of cell proliferation and numbers of endothelial cells were examined in vitro in CLs collected from cows that received post-ovulation pulsatile LH treatment at various frequencies. The results indicate that the corpora lutea growth that results from luteal cell proliferation is enhanced by the episodes of LH release that occur immediately after the time of ovulation in cattle. The results also show that luteal endothelial cell numbers did not differ among cows treated with different LH doses. In Israel. a longer duration of the preovulatory LH surge stimulated the steroidogenic capacity of granulosa-derived luteal cells, and might, thereby, contribute to a higher progesterone output from the bovine corpus luteum. In an in vivo study, a subgroup of high-yielding dairy cows with extended estrus to ovulation interval was identified. Associated with this extended interval were: low plasma progesterone and estradiol concentrations and a low preovulatory LH surge prior to ovulation, as well as low post- ovulation progesterone concentration. In experiments based on the above results, we found that injection of GnRH at the onset of estrus increased the LHpeak, prevented late ovulation, decreased the variability between cows and elicited high and uniform progesterone levels after ovulation. GnRH at estrus onset increased conception rates, especially in the summer, and among primiparous cows and those with low body condition. Another study compared ovarian functions in multiparous lactating cows with those in nulliparous non-lactating heifers. The results revealed differences in ovarian follicular dynamics, and in plasma concentrations of steroids and gonadotropins that may account for the differences in fertility between heifers and cows.