Search results for " Sensitivity analysis"

Sensitivity analysis: fundamentals

2015

Sensitivity analysis (SA) is a valuable tool to support the use of mathematical models for environmental systems. Local or global SA (namely, LSA and GSA) are performed in order to better understand processes and to select the most influential factors affecting processes. The main objective of this extended abstract is to provide an informed problem statement of the issues surrounding LSA and GSA applications in the environmental water quality modelling field. Specifically, this paper aims at identifying, for the most popular methods, their potential use, the critical issues to be solved and the limits identified in a comprehensive literature review.

Global sensitivity analysis in ASM applications: comparison of the SRC and Extended-FAST method for a UCT-MBR model

2011

In this study global sensitivity analysis is performed to identify influential as well as non-influential parameters in a model of a University Cape Town Membrane Bioreactor (UCT-MBR). In particular, the Standardised Regression Coefficients (SRC) and Extended-FAST sensitivity analysis methods are applied. The sensitivity of model variables towards parameter variation is analysed for CODTOT, SNH4, SNO3, SPO, and MLSS along five reactor compartments. Both methods indicate that the parameters identified as being influential differ from section to section due to the different processes involved. Moreover, the relevant influence of the membrane filtration parameters is detected in the first plan…

The GSA-GLUE approach for uncertainty assessment of an integrated MBR model

2012

In the recent literature, the uncertainty of wastewater treatment plant (WWTP) modelling has had relevant interest both for designers and operators. Indeed, the frequent data lacking and the need to improve process knowledge, in case of innovative technologies, make the use of mathematical models more uncertain. Therefore, the need to make model uncertainty more explicit is warmly recommended. However, only few applications of uncertainty analysis in the wastewater field have been carried out. In this work, the combination of the global sensitivity analysis (GSA) and the Generalized Likelihood Uncertainty Estimation (GLUE) is applied for the uncertainty assessment of a WWTP model, in order …

An intelligent way to predict the building thermal needs: ANNs and optimization

2022

The evaluation of the energy performance of existing or new buildings is a fundamental action to guarantee the feasibility of a project and the achievement of the minimum efficiency requirements. In general, the determination of the thermal loads of a building is carried out via software but their use requires adequate knowledge of physical phenomena and therefore the presence of an expert user. Furthermore, the resolution can be difficult to implement and can require high computational costs; all conditions that can influence the success of a project. Based on these considerations, this work proposes an alternative solution to traditional calculation tools, which in a simple and effective …

River water quality modelling: a parsimonious model approach

2009

Change-points detection for variance piecewise constant models

2011

A new approach based on the fit of a generalized linear regression model is introduced for detecting change-points in the variance of heteroscedastic Gaussian variables, with piecewise constant variance function. This approach overcome some limitations of both exact and approximate well-known methods that are based on successive application of search and tend to overestimate the real number of changes in the variance of the series. The proposed method just requires the computation of a gamma GLM with log-link, resulting in a very efficient algorithm even with large sample size and many change points to be estimated.

A macroeconomic analysis of the public investments in European combined transport

2009

Intermodal transport has been recognized as a priority by the European Union, that has defined different budget allocations of investments to improve the shifting from road to intermodal transport, which is more sustainable. In this context, the main aim of the paper is to discuss the macroeconomic effects, in terms of economic growth, welfare and trade, of these public investments for combined transport, which aspects have been neglected in literature. A multi-country computable general equilibrium model has been used. The main results have been that the European Union benefits from these investments, but at international level, USA and Japan would lose in terms of welfare. Furthermore, th…

Power sensitivity analysis of multi-frequency, multi-polarized, multi-temporal SAR data for soil-vegetation system variables characterization

2017

Abstract: The knowledge of spatial and temporal variability of soil water content and others soil-vegetation variables (leaf area index, fractional cover) assumes high importance in crop management. Where and when the cloudiness limits the use of optical and thermal remote sensing techniques, synthetic aperture radar (SAR) imagery has proven to have several advantages (cloud penetration, day/night acquisitions and high spatial resolution). However, measured backscattering is controlled by several factors including SAR configuration (acquisition geometry, frequency and polarization), and target dielectric and geometric properties. Thus, uncertainties arise about the more suitable configurati…

A practical methodology to perform global sensitivity analysis for 2D hydrodynamic computationally intensive simulations

2021

Sensitivity analysis is a commonly used technique in hydrological modeling for different purposes, including identifying the influential parameters and ranking them. This paper proposes a simplified sensitivity analysis approach by applying the Taguchi design and the ANOVA technique to 2D hydrodynamic flood simulations, which are computationally intensive. This approach offers an effective and practical way to rank the influencing parameters, quantify the contribution of each parameter to the variability of the outputs, and investigate the possible interaction between the input parameters. A number of 2D flood simulations have been carried out using the proposed combinations by Taguchi (L27…

Calcul des contributions des incertitudes dans un modèle complexe de qualité de l'eau

2010

The quantification of uncertainty in integrated urban drainage water quality models is of paramount interest. Indeed, the assessment of the reliability of the model results for complex water quality models is useful for understanding the significance of the results. However, the state of knowledge regarding uncertainties in urban drainage models is poor. In the case of integrated urban drainage water quality models, due to the fact that integrated approaches are basically a cascade of sub-models (simulating sewer system, wastewater treatment plant and receiving water body), the uncertainty produced in one sub-model propagates to the following ones depending on the model structure, the estim…