Search results for "uncertainty."
showing 10 items of 972 documents
Approaches to evaluate the virtual instrumentation measurement uncertainties
2002
This paper deals with the metrological characterization of virtual instruments. After a brief description of the features, the components and the working principle of the virtual instruments and the various uncertainty sources are analyzed. Then, two methods to evaluate the uncertainty of the measurement results are presented: a numerical method simulating the physical process of the A/D conversion, and an approximated theoretical method applying the "uncertainty propagation law" of the "guide to the expression of uncertainty in measurement." With both methods, the combined standard uncertainty of the measurement result is obtained, starting from the standard uncertainty generated by each s…
Measurement uncertainty estimation of a virtual instrument
2002
The law of uncertainty propagation is applied to a PC-based virtual instrument. According to the "guide to the expression of uncertainty in measurement", the measuring model and the various sources of uncertainty have been taken into account. The expressions of the combined output uncertainty in various basic digital signal processing blocks, are obtained starting from each input sample absolute accuracy, without taking into account the parameters which regard the overall behavior of an acquisition board, such as the effective number of bits. In order to verify this procedure, the results obtained by means of the theoretical analysis, are compared with the ones obtained from numerical simul…
Assessment of virtual instruments measurement uncertainty
2001
Abstract In this paper, two methods to evaluate the measurement uncertainty of a virtual instrument are presented: a numerical method simulating the physical process of the A/D conversion, and an approximated theoretical method applying the “uncertainty propagation law” of the “guide to the expression of uncertainty in measurement”. After a brief description of the features, the constitution and the working principle of the virtual instruments, the various uncertainty sources, are analyzed. With both methods, the combined standard uncertainty of the measurement result is obtained, starting from the standard uncertainty generated by each single source and without taking into account the para…
Propagation of errors due to incorrect positions of sources and detectors in wave-field tomography
2004
Tomographic data processed by 2D inversion programs can produce fairly large distortions due to incorrect source and/or detector positions. This problem is very serious in high-frequency electromagnetic tomography (GPR), due to the dimensions of the transmitter and receiver antennae. The errors can even be larger when coupled antennae are used (receiver and transmitter inside the same box) whose positions are not clearly known. Similar errors can be involved in seismic tomography, for instance when the mechanical connection between transducers and sample is defective. In this paper the problem has been studied using synthetic data which were calculated for different acquisition geometries. …
Data Treatment and Error Analysis in Kinetics
2000
Methods of data treatment in kinetics are reviewed from a practical viewpoint. The equations to describe the kinetics of chemical reactions and the methodology to obtain the models are presented. Moreover, the integration methods that are needed for the simulation of complex reactions are explained, from the simple first-order reaction to the complex general mechanism. However, it is essential to know the main sources of error in data treatment in order to reduce their effects on the results. Stress is put on the analysis of the errors due to the simplification of complex models. The different factors that influence the kinetics of the reaction are reviewed. How to take advantage of the kin…
Near-Real-Time Estimation of Water Vapor Column From MSG-SEVIRI Thermal Infrared Bands: Implications for Land Surface Temperature Retrieval
2015
The Meteosat Second Generation-Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI) instrument provides observations of half the globe every 15 min, at low spatial resolution. These data are an invaluable tool to observe daily to yearly cycle of land surface temperature (LST), as well as for various early warning systems. However, advanced algorithms for LST estimation requires a previous estimation of the water vapor (WV) column above the observed pixel, for which no instantaneous retrieval methods are yet available, and therefore hinders their implementation in a near-real-time processing chain for MSG-SEVIRI data. This work analyzes three different formulations for such WV retrieva…
A C1-generic dichotomy for diffeomorphisms: Weak forms of hyperbolicity or infinitely many sinks or sources
2003
We show that, for every compact n-dimensional manifold, n > 1, there is a residual subset of Diff (M) of diffeomorphisms for which the homoclinic class of any periodic saddle of f verifies one of the following two possibilities: Either it is contained in the closure of an infinite set of sinks or sources (Newhouse phenomenon), or it presents some weak form of hyperbolicity called dominated splitting (this is a generalization of a bidimensional result of Mafine [Ma3]). In particular, we show that any Cl-robustly transitive diffeomorphism admits a dominated splitting.
A proof of Carleson's $\varepsilon^2$-conjecture
2019
In this paper we provide a proof of the Carleson $\varepsilon^2$-conjecture. This result yields a characterization (up to exceptional sets of zero length) of the tangent points of a Jordan curve in terms of the finiteness of the associated Carleson $\varepsilon^2$-square function.
Receiving water quality assessment: comparison between simplified and detailed integrated urban modelling approaches
2010
Urban water quality management often requires use of numerical models allowing the evaluation of the cause–effect relationship between the input(s) (i.e. rainfall, pollutant concentrations on catchment surface and in sewer system) and the resulting water quality response. The conventional approach to the system (i.e. sewer system, wastewater treatment plant and receiving water body), considering each component separately, does not enable optimisation of the whole system. However, recent gains in understanding and modelling make it possible to represent the system as a whole and optimise its overall performance. Indeed, integrated urban drainage modelling is of growing interest for tools to …
Automatic Quality Assessment of Cardiac MR Images with Motion Artefacts using Multi-task Learning and K-Space Motion Artefact Augmentation
2022
The movement of patients and respiratory motion during MRI acquisition produce image artefacts that reduce the image quality and its diagnostic value. Quality assessment of the images is essential to minimize segmentation errors and avoid wrong clinical decisions in the downstream tasks. In this paper, we propose automatic multi-task learning (MTL) based classification model to detect cardiac MR images with different levels of motion artefact. We also develop an automatic segmentation model that leverages k-space based motion artefact augmentation (MAA) and a novel compound loss that utilizes Dice loss with a polynomial version of cross-entropy loss (PolyLoss) to robustly segment cardiac st…