USING A MONTE-CARLO-BASED APPROACH TO EVALUATE THE UNCERTAINTY ON FRINGE PROJECTION TECHNIQUE

A complete uncertainty analysis on a given fringe projection set-up has been performed using Monte-Carlo approach. In particular the calibration procedure is taken into account. Two applications are given: at a macroscopic scale, phase noise is predominant whilst at microscopic scale, both phase noise and calibration errors are important. Finally, uncertainty found at macroscopic scale is close to some experimental tests (~100 µm). 1

IDENTIFICATION OF MATERIAL PROPERTIES OF HUMAN SKIN IN VIVO

International audienceThe mechanical properties of skin are of interest for many applications, including the design of devices that interact with the skin and simulation of skin deformation for applications such as animation. There is also a need to better understand the mechanical behavior of the skin in order to be able to measure its properties, for example to evaluate the effect of medical treatments or cosmetics. The mechanical properties of the skin are parameters in a constitutive model, and without a suitable constitutive model they cannot be measured properly. For example, many studies have considered the skin to be linearly elastic and measured its Young's modulus but this is of limited value because of its extreme nonlinearity. The aim of this study was to use an extensive set of data obtained from tests on human subjects with multiple tests in different directions to identify anisotropic material properties. The anisotropy of the skin is complicated by the large anisotropic initial strain that it has in vivo, which has the effect of making its in situ behavior anisotropic even if its actual material properties are not. Tensile tests on ex vivo human skin [1] have shown two phases of deformation, similar to other biological membranes [2]. In the initial phase the stiffness is very low, and then when the collagen fibres in the dermis become taught the stiffness increases dramatically. It was found that the major difference between loading directions was the length of the first phase, the stiffness in the second phase was similar in all directions. There is thus close relationship between the initial strain and the anisotropic material behavior; both determine the strain that is needed to reach the stiffer second phase of deformation

Full-field strain measurements for validation of meso-FE analysis of textile composites

Meso-scale (unit cell of an impregnated textile reinforcement) finite element (FE) modelling of textile composites is a powerful tool for homogenisation of mechanical properties, study of stress–strain fields inside the unit cell, determination of damage initiation conditions and sites and simulation of damage development and associated deterioration of the homogenised mechanical properties of the composite. Validation of meso-FE modelling requires registration of details of the deformed state on the scale of individual yarns inside the textile, registered using full-field strain measurements on the surface of the sample. The paper presents examples of such a validation of meso-FE models of woven (carbon/epoxy and glass/polypropylene) and braided (carbon/epoxy) composites. Digital image correlation and digital phase shifting grating shearography are used for full-field strain registration. The resolution of the strain field during elastic deformation is improved and damage onset is identified using time-dependent linear regression of the registered field.status: publishe

The sustainable impact of an educational approach to improve the appropriateness of laboratory test orders in the ICU

International audienceINTRODUCTION: Few studies described strategies to improve the use of diagnostic tests in intensive care units (ICU). No study assessed whether their impact was sustained or not. In this study, we assessed whether a multi-faceted intervention for more appropriate use of laboratory testing can decrease the number of tests, is sustainable, is not associated with additional morbidity and represents a potential cost saving.MATERIAL AND METHODS: An open-label prospective cohort study in two separated units of the same medical intensive care unit (ICU) including respectively 3315 and 2392 consecutive patients. After the observation period (2010), a reduction in ICU A of unnecessary diagnostics tests as part of a program including senior supervisory of juniors' orders, encouragements for orders containment at each everyday round discussions (period 2; 2011). Period 3 (2012) consisted in the prolongation of the protocol as a routine care without supervision; Period 4 (2013) was a new period of observation without intervention. No modification was implemented in ICU B in periods 2-4.RESULTS: After the intervention, a decrease in the overall number of tests per ICU-patient-days (37.3±5.5 (baseline) to 15.2±3.2 (- 59%); p<0.0001) was observed. The total cost of the tests decreased from 239±41 to 104±28 euros per ICU-patient days; p<0.0001. The effect on laboratory test orders was sustainable in period 3 (-49%) and 4 (-30%). No significant secondary effect of the intervention was observed in period 2. In ICU B, there was no significant change in the overall laboratory test orders in between the periods.CONCLUSIONS: Laboratory test containment is effective, likely safe and sustainable provided that an educational program is repeatedly promoted, that it makes sense for the whole team, that senior and junior physicians are both committed in the program, and that encouragements for laboratory orders containment at each everyday round discussions