Christophe Martinsons - Academia.edu (original) (raw)
Papers by Christophe Martinsons
Bookmarks Related papers MentionsView impact
La radiometrie infrarouge photothermique est utilisee pour analyser les proprietes thermiques de ... more La radiometrie infrarouge photothermique est utilisee pour analyser les proprietes thermiques de couches dures ceramiques sur substrat d'acier. La technique consiste a induire un echauffement periodique par une source laser modulee et a detecter le rayonnement infrarouge synchrone avec l'excitation. Pour resoudre le probleme inverse, les donnees experimentales sont d'abord calibrees precisement. Puis, la modelisation est optimisee et la procedure d'estimation de parametres est adaptee aux problemes inverses mal poses apparaissant en thermique. L'introduction de la fonction de transfert photothermique, tenant compte de la non linearite du signal avec la temperature, permet d'aboutir a un modele simple dont l'application numerique est rapide. L'analyse dimensionnelle du probleme direct fournit un ensemble minimal et complet de parametres modeles. La non satisfaction d'un critere statistique, le critere k, signale l'impossibilite d'accomplir leur identification simultanee. L'approche developpee dans ce travail consiste alors a determiner les parametres les mieux resolus par l'inversion des donnees. Ces parametres optimaux, mutuellement independants, sont recherches de maniere iterative sous la forme de combinaisons lineaires des logarithmes des parametres modeles. Apres inversion des donnees, les proprietes thermiques dimensionnelles du revetement, de l'interface et du substrat sont estimees. Les resultats experimentaux conduisent a une estimation assez precise de l'effusivite thermique des revetements et la detection de tres faibles resistances thermiques d'interface (10#-#7w#-#1m#2k). En relation avec la microstructure, l'interpretation des proprietes thermiques d'echantillons d'acier revetus de nitrure de titane tin et de nitrure de titane carbure ti(n,c) montre que la resistance thermique d'interface n'est pas correlee a l'adherence, telle qu'elle est mesuree par le test de rayure ou des essais fonctionnels. En revanche, les resultats du test de rayure sont relies a la dispersion des mesures photothermiques, provoquee par des variations d'epaisseur et de diffusivite thermique du revetement.
Bookmarks Related papers MentionsView impact
Springer eBooks, 2017
Bookmarks Related papers MentionsView impact
International Journal of Environmental Research and Public Health, Jun 13, 2019
Bookmarks Related papers MentionsView impact
Thin Solid Films, Apr 1, 1998
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, Jul 16, 2021
The spectral responsivity of a photometer is usually measured using very narrow optical excitatio... more The spectral responsivity of a photometer is usually measured using very narrow optical excitations, provided by a monochromator or a tuneable laser. This article describes a technique to measure the spectral responsivity using an arbitrary number of optical excitations having any type of spectral distribution. The problem is formulated as an inverse problem which is solved using a probabilistic approach based on Bayes’ theorem. The method requires a prior knowledge of the spectral responsivity, which can be proportional to the standard photopic function, with an uncertainty level related to the spectral match index of the photometer. Using this method, the estimation can be performed from data provided by a simple experimental set-up. The numerical application provides a stable and unique solution to the inverse problem, along with the estimation uncertainties. Using a tuneable LED source, the method was applied to an illuminance measurement head, giving an estimation of its spectral responsivity from 380 to 780 nm with a step of 1 nm. The results were in good agreement with data obtained by a monochromator-based technique. Our measurement had larger uncertainties towards the red and blue limits of the spectrum as the light source provided very little light at these wavelengths.
Bookmarks Related papers MentionsView impact
High Temperatures-high Pressures, 1999
ABSTRACT
Bookmarks Related papers MentionsView impact
Inverse Problems in Science and Engineering, Apr 1, 2005
This article presents a method to solve parameter estimation problems by finding an optimal param... more This article presents a method to solve parameter estimation problems by finding an optimal parameterization of the mathematical model. The pi-theorem of dimensional analysis is used to establish a formulation of the model based on dimensionless products and scaling parameters, together with the rules of a parameterization change. Logarithmic parameters are introduced for the purpose of working in a linear parameter space in which a given base corresponds to a specific parameterization. The optimal parameterization is assumed to yield uncorrelated estimators. A statistical independence criterion based on the Fisher information matrix is derived for maximum-likelihood estimators. The method allows one to solve inverse problems with highly correlated model parameters by identifying well-resolved parameters, leading to a solution expressed in terms of correlation laws between physical quantities.
Bookmarks Related papers MentionsView impact
Buildings
As attention to indoor environmental quality (IEQ) grows, a systematic strategy for assessing IEQ... more As attention to indoor environmental quality (IEQ) grows, a systematic strategy for assessing IEQ in schools needs to be developed. For this purpose, this paper presents a summary of parameters measured in school classrooms to characterize the quality of thermal, acoustic, and visual environments and indoor air quality (IAQ). The summary is based on a review of published literature reporting measurements in schools in Europe and North America in the past ten years. It also summarizes the measurement protocols and measured concentrations. Eighty-eight papers describing measurements in schools were identified and analyzed. No unique standardized measuring method was used in the reviewed studies and different parameters were measured. The most often measured parameters were those describing the thermal environment and IAQ. The former mainly comprised air temperature and relative humidity. The latter mainly comprised concentrations of carbon dioxide, particulate matter, radon, formaldeh...
Bookmarks Related papers MentionsView impact
IEICE Proceeding Series
In a context where energy is valued, the use of Compact Fluorescent Light bulbs with low energy c... more In a context where energy is valued, the use of Compact Fluorescent Light bulbs with low energy consumption (CFL) tends to generalize. However, the radio noise produced by these sources is currently the subject of many discussions, particularly about the issue of human exposure. This paper is dedicated to the characterization of the electric and magnetic fields radiated by various models of lamps. For this purpose, we have carried out tests in the immediate vicinity (near field) of these CFLs in order to identify the frequencies involved, and the EM fields produced at very short distance. These measurements were conducted insitu to study the evolution of the electro-magnetic field over several minutes.
Bookmarks Related papers MentionsView impact
Radiation Protection Dosimetry, 2001
Electromagnetic radiation, which is used by broadcasting and mobile telephone systems to transmit... more Electromagnetic radiation, which is used by broadcasting and mobile telephone systems to transmit information, permeates the city environment. In order to properly evaluate population exposure to electromagnetic fields, knowledge of their intensity and spectral components is necessary. In this study the results of radiofrequency field monitoring carried out in Torino, a large town located in the north-west of Italy are shown: the variation of the electromagnetic field strength is evaluated as a function of the height from the ground, the location in the urban area and the frequency. separating the contributions of the different sources (broadcasting antennas and radio base stations for mobile phones). Furthermore, the contribution of the radio base stations is theoretically evaluated, adding the emissions off all installations situated in Torino and examining the field strength maps calculated, considering the orography, for different heights. The theoretical values are also compared with those measured in the frequency range of mobile telephony emissions.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, Feb 12, 2020
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, 2021
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Archives Des Maladies Professionnelles Et De L Environnement, Sep 1, 2017
Bookmarks Related papers MentionsView impact
Leukos, Jul 21, 2021
ABSTRACT In lighting simulations, a luminaire is usually modeled using a luminous intensity distr... more ABSTRACT In lighting simulations, a luminaire is usually modeled using a luminous intensity distribution emitted by a single-point source. This so-called far-field approach is valid as long as the dimensions of the luminaire are much smaller than the distance to the calculation surface. This assumption is generally not met in standard indoor lighting and may lead to significant errors in the prediction of illuminances and discomfort glare. This work describes a practical near-field approach based on splitting the luminaire into N point sources. The errors in relation to the near field (infinite value of N) are evaluated as a function of N. This approach generates a more accurate assessment of the Unified Glare Rating in the case of luminaires with non-uniform emission.
Bookmarks Related papers MentionsView impact
Analytical Sciences/Supplements Proceedings of 11th International Conference of Photoacoustic and Photothermal Phenomena, 2002
Bookmarks Related papers MentionsView impact
Graefes Archive for Clinical and Experimental Ophthalmology, Jan 3, 2020
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
La radiometrie infrarouge photothermique est utilisee pour analyser les proprietes thermiques de ... more La radiometrie infrarouge photothermique est utilisee pour analyser les proprietes thermiques de couches dures ceramiques sur substrat d'acier. La technique consiste a induire un echauffement periodique par une source laser modulee et a detecter le rayonnement infrarouge synchrone avec l'excitation. Pour resoudre le probleme inverse, les donnees experimentales sont d'abord calibrees precisement. Puis, la modelisation est optimisee et la procedure d'estimation de parametres est adaptee aux problemes inverses mal poses apparaissant en thermique. L'introduction de la fonction de transfert photothermique, tenant compte de la non linearite du signal avec la temperature, permet d'aboutir a un modele simple dont l'application numerique est rapide. L'analyse dimensionnelle du probleme direct fournit un ensemble minimal et complet de parametres modeles. La non satisfaction d'un critere statistique, le critere k, signale l'impossibilite d'accomplir leur identification simultanee. L'approche developpee dans ce travail consiste alors a determiner les parametres les mieux resolus par l'inversion des donnees. Ces parametres optimaux, mutuellement independants, sont recherches de maniere iterative sous la forme de combinaisons lineaires des logarithmes des parametres modeles. Apres inversion des donnees, les proprietes thermiques dimensionnelles du revetement, de l'interface et du substrat sont estimees. Les resultats experimentaux conduisent a une estimation assez precise de l'effusivite thermique des revetements et la detection de tres faibles resistances thermiques d'interface (10#-#7w#-#1m#2k). En relation avec la microstructure, l'interpretation des proprietes thermiques d'echantillons d'acier revetus de nitrure de titane tin et de nitrure de titane carbure ti(n,c) montre que la resistance thermique d'interface n'est pas correlee a l'adherence, telle qu'elle est mesuree par le test de rayure ou des essais fonctionnels. En revanche, les resultats du test de rayure sont relies a la dispersion des mesures photothermiques, provoquee par des variations d'epaisseur et de diffusivite thermique du revetement.
Bookmarks Related papers MentionsView impact
Springer eBooks, 2017
Bookmarks Related papers MentionsView impact
International Journal of Environmental Research and Public Health, Jun 13, 2019
Bookmarks Related papers MentionsView impact
Thin Solid Films, Apr 1, 1998
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, Jul 16, 2021
The spectral responsivity of a photometer is usually measured using very narrow optical excitatio... more The spectral responsivity of a photometer is usually measured using very narrow optical excitations, provided by a monochromator or a tuneable laser. This article describes a technique to measure the spectral responsivity using an arbitrary number of optical excitations having any type of spectral distribution. The problem is formulated as an inverse problem which is solved using a probabilistic approach based on Bayes’ theorem. The method requires a prior knowledge of the spectral responsivity, which can be proportional to the standard photopic function, with an uncertainty level related to the spectral match index of the photometer. Using this method, the estimation can be performed from data provided by a simple experimental set-up. The numerical application provides a stable and unique solution to the inverse problem, along with the estimation uncertainties. Using a tuneable LED source, the method was applied to an illuminance measurement head, giving an estimation of its spectral responsivity from 380 to 780 nm with a step of 1 nm. The results were in good agreement with data obtained by a monochromator-based technique. Our measurement had larger uncertainties towards the red and blue limits of the spectrum as the light source provided very little light at these wavelengths.
Bookmarks Related papers MentionsView impact
High Temperatures-high Pressures, 1999
ABSTRACT
Bookmarks Related papers MentionsView impact
Inverse Problems in Science and Engineering, Apr 1, 2005
This article presents a method to solve parameter estimation problems by finding an optimal param... more This article presents a method to solve parameter estimation problems by finding an optimal parameterization of the mathematical model. The pi-theorem of dimensional analysis is used to establish a formulation of the model based on dimensionless products and scaling parameters, together with the rules of a parameterization change. Logarithmic parameters are introduced for the purpose of working in a linear parameter space in which a given base corresponds to a specific parameterization. The optimal parameterization is assumed to yield uncorrelated estimators. A statistical independence criterion based on the Fisher information matrix is derived for maximum-likelihood estimators. The method allows one to solve inverse problems with highly correlated model parameters by identifying well-resolved parameters, leading to a solution expressed in terms of correlation laws between physical quantities.
Bookmarks Related papers MentionsView impact
Buildings
As attention to indoor environmental quality (IEQ) grows, a systematic strategy for assessing IEQ... more As attention to indoor environmental quality (IEQ) grows, a systematic strategy for assessing IEQ in schools needs to be developed. For this purpose, this paper presents a summary of parameters measured in school classrooms to characterize the quality of thermal, acoustic, and visual environments and indoor air quality (IAQ). The summary is based on a review of published literature reporting measurements in schools in Europe and North America in the past ten years. It also summarizes the measurement protocols and measured concentrations. Eighty-eight papers describing measurements in schools were identified and analyzed. No unique standardized measuring method was used in the reviewed studies and different parameters were measured. The most often measured parameters were those describing the thermal environment and IAQ. The former mainly comprised air temperature and relative humidity. The latter mainly comprised concentrations of carbon dioxide, particulate matter, radon, formaldeh...
Bookmarks Related papers MentionsView impact
IEICE Proceeding Series
In a context where energy is valued, the use of Compact Fluorescent Light bulbs with low energy c... more In a context where energy is valued, the use of Compact Fluorescent Light bulbs with low energy consumption (CFL) tends to generalize. However, the radio noise produced by these sources is currently the subject of many discussions, particularly about the issue of human exposure. This paper is dedicated to the characterization of the electric and magnetic fields radiated by various models of lamps. For this purpose, we have carried out tests in the immediate vicinity (near field) of these CFLs in order to identify the frequencies involved, and the EM fields produced at very short distance. These measurements were conducted insitu to study the evolution of the electro-magnetic field over several minutes.
Bookmarks Related papers MentionsView impact
Radiation Protection Dosimetry, 2001
Electromagnetic radiation, which is used by broadcasting and mobile telephone systems to transmit... more Electromagnetic radiation, which is used by broadcasting and mobile telephone systems to transmit information, permeates the city environment. In order to properly evaluate population exposure to electromagnetic fields, knowledge of their intensity and spectral components is necessary. In this study the results of radiofrequency field monitoring carried out in Torino, a large town located in the north-west of Italy are shown: the variation of the electromagnetic field strength is evaluated as a function of the height from the ground, the location in the urban area and the frequency. separating the contributions of the different sources (broadcasting antennas and radio base stations for mobile phones). Furthermore, the contribution of the radio base stations is theoretically evaluated, adding the emissions off all installations situated in Torino and examining the field strength maps calculated, considering the orography, for different heights. The theoretical values are also compared with those measured in the frequency range of mobile telephony emissions.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, Feb 12, 2020
Bookmarks Related papers MentionsView impact
Lighting Research & Technology, 2021
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Archives Des Maladies Professionnelles Et De L Environnement, Sep 1, 2017
Bookmarks Related papers MentionsView impact
Leukos, Jul 21, 2021
ABSTRACT In lighting simulations, a luminaire is usually modeled using a luminous intensity distr... more ABSTRACT In lighting simulations, a luminaire is usually modeled using a luminous intensity distribution emitted by a single-point source. This so-called far-field approach is valid as long as the dimensions of the luminaire are much smaller than the distance to the calculation surface. This assumption is generally not met in standard indoor lighting and may lead to significant errors in the prediction of illuminances and discomfort glare. This work describes a practical near-field approach based on splitting the luminaire into N point sources. The errors in relation to the near field (infinite value of N) are evaluated as a function of N. This approach generates a more accurate assessment of the Unified Glare Rating in the case of luminaires with non-uniform emission.
Bookmarks Related papers MentionsView impact
Analytical Sciences/Supplements Proceedings of 11th International Conference of Photoacoustic and Photothermal Phenomena, 2002
Bookmarks Related papers MentionsView impact
Graefes Archive for Clinical and Experimental Ophthalmology, Jan 3, 2020
Bookmarks Related papers MentionsView impact