Search results for "model uncertainty"
showing 6 items of 6 documents
Sensitivity and uncertainty analysis of an integrated ASM2d MBR model for wastewater treatment
2018
Abstract An integrated membrane bioreactor (MBR) model was previously proposed and tested. The model provides a comprehensive and detailed description of the nitrogen biological removal processes with respect to up-to-date literature. This paper presents a sensitivity and uncertainty analysis aimed at identifying the key factors affecting the variability of the model predictions. The Standardized Regression Coefficients (SRC) method was adopted for the sensitivity analysis. The uncertainty analysis was employed by running Monte Carlo simulations by varying only the value of the key factors affecting the model outputs. The sensitivity analysis combined with the uncertainty analysis applied h…
Deep and Proximate Determinants of the World Income Distribution
2019
This paper studies the deep and proximate determinants of the evolution of the cross-country distribution of GDP per worker in the period 1960–2008 by a novel method based on an information criterion. We find that countries of our sample follow three distinctive growth regimes identified by two deep determinants, namely life expectancy at birth in 1960 and the share of Catholics in 1965, and that each regime is characterized by non-linearities. Growth regimes appear to be the main cause of the increased inequality and polarization, while technological catch-up, proxied by the initial level of GDP per worker, acts in the opposite direction. Finally, human capital marginally reduces polarizat…
Unawareness, Priors and Posteriors
2008
Abstract. This note contains first thoughts on awareness of unawareness in a simple dynamic context where a decision situation is repeated over time. The main consequence of increasing awareness is that the model the decision maker uses, and the prior which it contains, becomes richer over time. The decision maker is prepared to this change, and we show that if a projection-consistency axiom is satisfied unawareness does not affect the value of her estimate of a payoff-relevant conditional probability (although it may weaken confidence in such estimate). Probability-zero events however pose a challenge to this axiom, and if that fails, even estimate values will be different if the decision …
A new integrated MBR model for wastewater treatment: sensitivity and uncertainty analysis
2017
In this study a new integrated membrane bioreactor (MBR) model is proposed. The model is able to describe the main biological processes aimed at the carbon and the nutrients (nitrogen, N and phosphorus, P) removal coupled with the soluble microbial products (SMP) formation/degradation. Furthermore, the model describes the key physical processes and the interconnection between SMP and membrane fouling. The model was calibrated by adopting data measured during the monitoring of a University Cape Town (UCT) MBR pilot plant. A sensitivity analysis allowed the reduction of the number of model FACTORs to be calibrated from 122 to 45. A good correlation between measured and simulated data was obta…
Bayesian model averaging and weighted-average least squares: Equivariance, stability, and numerical issues
2011
In this article, we describe the estimation of linear regression models with uncertainty about the choice of the explanatory variables. We introduce the Stata commands bma and wals, which implement, respectively, the exact Bayesian model-averaging estimator and the weighted-average least-squares estimator developed by Magnus, Powell, and Prüfer (2010, Journal of Econometrics 154: 139–153). Unlike standard pretest estimators that are based on some preliminary diagnostic test, these model-averaging estimators provide a coherent way of making inference on the regression parameters of interest by taking into account the uncertainty due to both the estimation and the model selection steps. Spec…
A comprehensive analysis for N2O mechanisms by advanced mathematical techniques
2018
Recent evaluation of the existing activated sludge models, incorporating nitrous oxide (N2O) formation, is only based on the capabilities and inabilities in describing experimental data under different conditions. This paper will present an advanced mathematical modeling framework (i.e. coupling global sensitivity, identifiability and uncertainty analysis) for a comprehensive analysis on the evaluation of the structural differences among three ammonia oxidizing bacteria (AOB) two-pathway models in combination with two heterotrophic denitrification models. The analysis will be performed based on experimental data from a lab-scale deammonification granular sequencing batch reactor operated un…