The visual sensation of gloss is built on cues deduced from the interaction between light, surfaces sunder evaluation, and surrounding conditions. Gloss is a second-order attribute of the visual appearance, this means that its perception is not directly encoded on biological sensors but constructed from the global scene in the field of view of the observer. It is then a complex quantity to measure. When most studies based on simulated samples stress on the importance of realistic observation conditions, we measure the effect of environment complexity over perception of real samples. We test two different lighting conditions: either diffuse or a combination of diffuse and collimated lighting in order to approach natural complex illumination patterns. Under both lighting conditions, we test two environments: a standard black light booth, designed according to the ASTM D4449, and a realistic office cubicle. Samples consist in a seven-level gloss scale ranging from full matt to high gloss. These are presented to observers through pair comparison protocol, according to a maximum likelihood difference scaling algorithm. Our results confirm that gloss constancy is maintained even if the convergence of illumination varies. We however measure that the constancy is lost for matt samples perception.

Le Laboratoire commun de métrologie LNE-Cnam (LCM) a développé un moyen de référence en calorimétrie permettant des mesures précises d'enthalpie de fusion et de capacité thermique massique sur la plage de température [23 • C, 1 000 • C].La solution métrologique retenue a été d'améliorer un calorimètre de type Calvet, et de mettre au point des procédures d'étalonnage et de mesure permettant d'atteindre des incertitudes de mesure suffisamment faibles pour la certification de matériaux de référence.Cet article décrit un système d'étalonnage fonctionnant à haute température qui a été spécifiquement conçu et intégré dans le calorimètre afin d'effectuer son étalonnage en énergie par substitution électrique.Ce système permet de réaliser successivement des étalonnages par effet Joule et des mesures d'enthalpie de fusion, sans modification des conditions expérimentales.Ce nouveau calorimètre de référence ainsi que la méthode de mesure associée ont été qualifiés en mesurant les enthalpies de fusion de métaux purs (indium, étain et argent).Les résultats obtenus sur ces trois matériaux métalliques sont en très bon accord avec les données obtenues par d'autres laboratoires nationaux de métrologie.

The French National Metrology Laboratory LNE-LCM has developed a high temperature reference facility for accurate measurements of the specific heat capacity and of the enthalpy of fusion of materials over the temperature range [23 °C, 1000 °C]. The metrological approach was to modify a commercial Calvet calorimeter in order to lower the uncertainty of measurement and to insure the metrological traceability of the measurements to the SI units, in particular by designing a new calibration system. The enthalpies of fusion of pure metals (indium, tin and silver) and of a binary alloy Ag-28Cu have been measured. The results obtained on the three pure metallic materials are in very good agreement with data obtained by other National Metrology Institutes (NMIs) using adiabatic calorimetry.

We describe a transportable system based on synthetic wavelength interferometry for absolute distance measurement. The synthetic wavelength is generated using two frequency-doubled Nd:YAG lasers. Main feature is the elimination of polarization cross-talk issue using a setup where spatial separation is preferred to polarization separation. A superheterodyne technique has been implemented to detect the synthetic phase, enabling a fringe interpolation of ~2/5600. A resolution of 700 nm over 60 s of integration time is demonstrated for a synthetic wavelength of 7,5 mm. An accuracy better than 10 μm is demonstrated over 25m, based on an indoor comparison with a classical fringe counting interferometer at VSL (Netherlands).

This paper presents a newly developed system for bridges post-tensioned devices inspection. These devices are generally composed of cables placed inside a duct, the residual space being filled with a particular cement to avoid corrosion. The nondestructive experimental setup uses a capacitive sensor that gives some relevant information about the electrical properties of the materials located inside the duct. Then, using an original modeling of the interactions between the sensor and the post-tensioned device, a signal processing extracts useful information from the sensors data, like the thickness of an eventual air gap between the cement and the duct. Experimental and theoretical derivations and comparisons are presented in the different parts of this paper.

The paper reports a new experiment to determine the value of the Boltzmann constant, , with a relative standard uncertainty of 1.2 parts in 10 6 . k B was deduced from measurements of the velocity of sound in argon, inside a closed quasi-spherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of k B is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: ( k new B / k B_CODATA −1)=−1.96×10 −6 , where the relative uncertainties are and u r ( k B_CODATA )=1.7×10 −6 . The new relative uncertainty approaches the target value of 1×10 −6 set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin.

There is currently great interest in the international metrological community for new accurate determinations of the Boltzmann constant k B , with the prospect of a new definition of the unit of thermodynamic temperature, the kelvin. In fact, k B relates the unit of energy (the joule) to the unit of the thermodynamic temperature (the kelvin). One of the most accurate ways to access the value of the Boltzmann constant is from measurements of the velocity of the sound in a noble gas. In the method described here, the experimental determination has been performed in a closed quasi-spherical cavity. To improve the accuracy, all the parameters in the experiment (purity of the gas, static pressure, temperature, exact shape of the cavity monitored by EM microwaves, etc.) have to be carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic and microwave signals. We report on two sets of isothermal acoustic measurements yielding the value k B = 1.380 647 74(171) × 10 −23 J · K −1 with a relative standard uncertainty of 1.24 parts in 10 6 . This value lies 1.9 parts in 10 6 below the 2006 CODATA value (Mohr et al., Rev. Mod. Phys. 80 , 633 ( 2008 )), but, according to the uncertainties, remains consistent with it.

There is currently great interest in the international metrology community for new accurate determinations of the Boltzmann constant k B , with a view to a new definition of the unit of thermodynamic temperature, the kelvin. Indeed, k is related to the quantum of energy k B T, where T is the thermodynamic temperature. The value of the Boltzmann constant can be obtained from measurements of the velocity of the sound in a noble gas. In the method described here, the experiment has been performed in a closed spherical cavity. To obtain an accurate value for k B , all the parameters of the experiment (gas purity, static pressure, temperature of the device, exact shape of the cavity, etc.) have been carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic signals. We report on two sets of isothermal acoustic measurements yielding to values for k B which differ by 0.3 part in 10 6 , and have an average value of k B =(1.380 647 8 + 0.000 003 1-0.000 001 7) × 10 -23 (+ -lstd).

This paper presents both theoretical and experimental aspects of a measurement problem in the field of non-destructive evaluation. The purpose of our work is to develop a capacitive probe devoted to post-tensioned cable inspection, mainly for bridge monitoring applications. In this paper will successively be presented the industrial problem, the current probe in use, and an original modeling achieved for sensor design and signal processing. In a first step, we will compare the experimental and theoretical data obtained with different 'devices under test' configurations. Then we will discuss about both capabilities of our direct model, on one hand to provide some help in sensor design improvements and on other hand to be inserted in an inverse problem scheme, to get an estimate of some interesting data of our problem from the measured signals.

There is currently great interest in the international metrology community for new accurate determinations of the Boltzmann constant k, with a view to a new definition of the unit of thermodynamic temperature, the kelvin. Indeed, k is related to the quantum of energy U, where T is the thermodynamic temperature.The value of the Boltzmann constant can be obtained from measurements of the velocity of the sound in a noble gas. In the method described here, the experiment is performed in a closed spherical cavity. To obtain an accurate value for k, all the parameters of the experiment (gas purity, static pressure, temperature of the device, exact shape of the cavity, etc.) have to be carefully controlled. As correction terms have to be applied to the acoustic signals, the validity of the theoretical models from which they are derived is crucial.The new determination carried out at the LNE-INM/CNAM is based on the same principles as in the acoustic experiment of Moldover et at. at NIST in 1988, which led to the most accurate determination of the Boltzmann constant up to now. However, several fundamental modifications and improvements have been made in this new experiment to measure and control the parameters that set the measured value of k. To cite this article: L. Pitre et al., C R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

We describe and analyse an original technique for all-optical and high gain (similar to 10(3) - 10(6)) amplification of a periodically modulated (PM) intensity low-power (similar to muW) laser radiation. The amplification is based on the injection locking control in linear laser schemes with homogeneously broadened active medium. The main problem of the injection locking amplifiers is to obtain a linear response to the PM injection. We propose to solve this problem by injecting a second laser beam with a constant power and a slightly different wavelength or orthogonal polarization compared to the injected PM beam.

This paper describes the feasibility analysis of using Holmium-doped single-mode fiber and spread-spectrum techniques to monitor a temperature distribution in the cryogenic range. An optimized holmium-doped fiber was realized and thermally characterized. For probing the sensitive fiber we realized an optical time domain reflectometer using pseudorandom sequences to improve the dynamic range at the operating wavelength and to obtain both rapid response time and high spatial resolution. The system, tested over a fiber length of 240 m, provides temperature dependent fiber attenuation measurements in good agreement with the transmission results. With a 10 MHz pseudorandom binary sequence the system detects changes of 24 °C with a spatial resolution of 30 m.