Stress Sensing by an Optical Fiber Sensor: Method and Process for the Characterization of the Sensor Response Depending on Several Designs

In this paper we propose an analyzing of the response of a stress optical fiber sensor of which we proposed several design. We show that an optical fiber sensor with these designs can covenanting allow the measuring the force/stress applied to a mechanical structure or which it is linked, by optimizing the uses of appropriate materials for constituting the sensor support. The experiment that we introduce to validate our approach based in principles includes design with a support bearing a multimode optical fiber organized in such a way that the transmitted light is attenuated when the fiber-bending angle coming from stitching in holes of the support is modified by the effects of the force/stress applied to the optical fiber sensor realized in this way. The tests realized concern the most relevant parameters that define the performances of the stress sensor that we propose. We present the problems that we to solved for the optimization of the sensor for selecting the more efficient material for the optical fiber sensor support related to a relevant choice of optical fibers.

Cloth simulation-based construction of pitfree canopy height models from airborne LiDAR data

Background:The universal occurrence of randomly distributed dark holes(i.e.,data pits appearing within the tree crown)in LiDAR-derived canopy height models(CHMs)negatively affects the accuracy of extracted forest inventory parameters.Methods:We develop an algorithm based on cloth simulation for constructing a pit-free CHM.Results:The proposed algorithm effectively fills data pits of various sizes whilst preserving canopy details.Our pitfree CHMs derived from point clouds at different proportions of data pits are remarkably better than those constructed using other algorithms,as evidenced by the lowest average root mean square error(0.4981 m)between the reference CHMs and the constructed pit-free CHMs.Moreover,our pit-free CHMs show the best performance overall in terms of maximum tree height estimation(average bias=0.9674 m).Conclusion:The proposed algorithm can be adopted when working with different quality LiDAR data and shows high potential in forestry applications.

Individual and Environmental Risk Factors for COVID-19 Mortality in Elderly in 7 European University Hospitals

Because the elderly account for 80% of deaths from COVID-19 and they may be more vulnerable to air pollution, in this retrospective study we aimed to explore individual and environmental risk factors for COVID-19 mortality in the geriatric departments of seven European University hospitals, between February and May 2020. Long-term exposure to air pollution was estimated through annual pollutant concentrations at the residential address over the last two years. Short-term variations in air pollutants and weather parameters were also examined through a 20-day period before the confirmed PCR diagnostic of COVID-19. We found positive associations for diabetes and COVID-19 mortality (OR 2.2 CI 95%: 1.1, 4.4). Regarding environmental factors, we found no association between COVID-19 mortality and air pollutants and weather parameters;however, our study suffers from strong disparities—such as patient characteristics—between fairly polluted and less polluted cities. In order to overcome those disparities between cities, we aimed to explore the relationship between air pollution and COVID-19 mortality within each city, but even with the high-efficiency modelisation systems, differences in air pollutants were too small to estimate the effect of air pollution at the city level. Thus, this study highlights the need to improve the estimation of individual exposure to air pollution. To address this issue, solutions exist such as the increase of the number of fixed air monitors, or even better, through the use of individual markers of air pollution exposure such as urinary black carbon or passive individual samplers. Furthermore, we underline that outdoor air pollutant concentrations may not be representative of individual exposure, especially in the elderly, thus, we suggest that further studies focus on indoor air pollution. Regarding meteorological conditions, we found no association between UV, temperature, wind speed and COVID-19 mortality. We found a positive association between an increase in relative humidity (RH) and COVID-19 mortality, however, the influence of RH on COVID-19 mortality remains unclear, and additional studies are needed to confirm this potential link.

Ship maneuvering prediction based on virtual captive model test and system dynamics approaches

The maneuvering simulation is carried out through the continuous captive model test and the system dynamics approach.The mathematical maneuvering group(MMG)model is implemented in the virtual captive model tests by using the computational fluid dynamics(CFD)techniques.The oblique towing test(OTT),the circular motion test(CMT),the rudder force test and the open water test are performed to obtain the hydrodynamic derivatives of the hull,the rudder and the propeller,and the results are validated by experimental data.By designing the tests,the number of cases is reduced to a low level,to allow us to evaluate the maneuverability with a low cost and in a short time.Using these obtained coefficients,the system-based maneuvering simulations are conducted to calculate the position and the attitude of the ship,with results in agreement with the free running test results.This procedure can also be used for other hull forms,with reduced workload and with convenience for maneuvering simulation tasks.