Search results for "Measure"

Frequency Stability Measurement of Cryogenic Sapphire Oscillators with a Multichannel Tracking DDS and the Two-Sample Covariance

2018

This article shows the first measurement of three 100 MHz signals exhibiting fluctuations from 2E-16 to parts in 1E-15 for integration time tau between 1 s and 1 day. Such stable signals are provided by three Cryogenic Sapphire Oscillators (CSOs) operating at about 10 GHz, also delivering the 100 MHz output via a dedicated synthesizer. The measurement is made possible by a 6-channel Tracking DDS (TDDS) and the two-sample covariance tool, used to estimate the Allan variance. The use of two TDDS channels per CSO enables high rejection of the instrument background noise. The covariance outperforms the Three-Cornered Hat (TCH) method in that the background converges to zero "out of the box," wi…

Quantification of land-atmosphere exchanges of water, energy and carbon dioxide in space and time over the heterogeneous Barrax site

2008

International audience; To advance our understanding of land-atmosphere exchanges of water, energy and carbon dioxide (CO2) in space and time over heterogeneous land surfaces, two intensive field campaigns were carried out at the Barrax agricultural test site in Spain during 12-21 July 2004 (SPARC 2004) and 8-14 July 2005 (SEN2FLEX 2005) involving multiple field, satellite and airborne instruments for characterizing the state of the atmosphere, the vegetation and the soil from the visible to the microwave range of the spectrum. Part of the experimental area is a core site of area 25 km2, within which numerous crops are grown, on both irrigated and dry land, alongside fields of bare soil. Th…

Evaluation Metric for Rate of Background Detection

2016

International audience; This paper proposes an evaluation metric which derive the effectiveness of background modeling algorithms. Background modeling is a key process on developing visual surveillance systems. The requirement of adapting to dynamic environments has motivated researchers to modify existing background modeling algorithms and develop new algorithms with better adaptability. Having the algorithms developed, credentials of each of the algorithms have to be assessed to exploit their effectiveness. Various evaluation metrics have been used for evaluating the rate of foreground extraction, foreground detection, and overall accuracy. However, the rate of background detection has no…

Caractérisation physique de matériaux poreux pour l'étude des interactions acoustique/structure

2005

Cette thèse d'habilitation synthétise les dix ans de recherche qui suivirent ma thèse de doctorat dans les domaines des paramètres physiques et de l'acoustique des milieux poreux et des interactions fluide/squelette. Ce mémoire est divisé en trois parties principales A, B et C correspondant aux trois principales périodes de ma carrière scientifique: la période entre 1994 et 1997 passée au Laboratorium voor Akoestiek en Thermische Fysica de la K. U. Leuven en Belgique en collaboration avec le Laboratoire d'Acoustique de l'Université du Maine au Mans, la période entre 1997 et 2003 passée à Bradford (UK) en tant que chercheur (1997-2000) et les trois années passées à Hull (UK) en tant que maît…

Thermomechanical Behavior of Beams Covered with Viscoelastic Patches

2018

International audience; Infrared thermography is a non-destructive test method based on infrared measurement that provides a luminance map of the thermal scene observed, converting to temperature. The thermographic study allows a surface observation of the thermal effects in order to display the result as a film of the temperature distribution [1]. The present study focuses on the detection of volumetric energy sources in beams covered by viscoelastic patches.

Optimal Source Selection for Image Photoplethysmography

2016

International audience; This paper presents an optimal selection on the region of interest (ROI) and color spaces to extract photoplethysmography signals from facial videos. The study is carried out under two sections; ROI selection and color space selection. We compared five different ROI selection for different regions of the face. We also investigated three color spectrums namely additive, perceptual and orthogonal color spaces. The study experimented on the publicly available human-computer interaction (HCI) database. When evaluated on 30 subjects, the results showed that the ROI selection on the forehead and the green spectrum of the additive color space to provides higher accuracy for…

Reliable numerical solution of a class of nonlinear elliptic problems generated by the Poisson-Boltzmann equation

2020

We consider a class of nonlinear elliptic problems associated with models in biophysics, which are described by the Poisson-Boltzmann equation (PBE). We prove mathematical correctness of the problem, study a suitable class of approximations, and deduce guaranteed and fully computable bounds of approximation errors. The latter goal is achieved by means of the approach suggested in [S. Repin, A posteriori error estimation for variational problems with uniformly convex functionals. Math. Comp., 69:481-500, 2000] for convex variational problems. Moreover, we establish the error identity, which defines the error measure natural for the considered class of problems and show that it yields computa…

Accelerometry - Simple, but challenging

2017

The association of childhood commuting modes and physical activity in adult age

2022

Background Physically active lifestyle prevents and contributes to managing non-communicable diseases. Childhood physical activities have shown to associate with physically active lifestyle in adulthood. More research on which childhood physical activity modes associate with physical activity in later life is still needed. Within the present study, we examined how physically active commuting to school in childhood contributed to overall physical activity in adulhood. Methods The participants (N = 3596) were from the population-based, longitudinal Cardiovascular Risks in Young Finns Study. Questionnaires were used in assessing subjects' childhood (1980) and adulthood (2001-2018) physical act…

An intensimetric method to localize secondary sources

2003

Research is presented to find out the amount and direction of the early reflections of a primary sound source in a room. Two rooms, very different in dimensions, were taken into account: the smallest one is about 100 m3 and the largest one 1100 m3. The measurement system consists of a PC equipped with a sound-board connected to the signals coming from the two microphones of an intensity probe at the input and to a loudspeaker at the output. A sweep signal was used for the excitation of the environment. Signal processing software was developed using LabVIEW by National Instruments. The results of the two measurement sessions are presented as amplitude-direction diagrams and amplitude-directi…