Precision and Accuracy of a Simple Consumer-oriented Wristband Activity Tracker During Walking at Different Speeds

Objective: FAIT Tag is a wrist-worn consumer-oriented pedometer composed of a small and lightweight core and silicone wrist band. The aim of this study was to validate the measurement precision and accuracy of the FAIT Tag during walking.Results: To assess intra-subject precision, five subjects wearing a FAIT Tag performed a repeated 200-step walking test in which they walked 200 steps a total of 10 times. To assess inter-subject accuracy, 30 subjects wearing a FAIT Tag and ActiGraph walked for 3 minutes at two different speeds. Step count measured by these devices was compared with the actual step count counted visually and simultaneously by an investigator. The average intra-subject precision was 2.2. For the inter-subject precision of FAIT Tag, the concordance correlation coefficient and the absolute percentage error ranged from 0.35 to 0.39 and 5.4% to 10.0%, respectively. In conclusion, the FAIT Tag is a practical pedometer with low intra-subject error and acceptable measurement accuracy. It may be a useful tool for long-term patient monitoring and digital biomarker acquisition.

BENDING OF AN ELASTIC THREE-LAYER PLATE WITH A HOLE CONNECTED TO THE SOIL FOUNDATION

The relevance of this paper is explained by a demand for the development of mechanical and mathematical models and methods for calculating the stress-strain state of the sandwich structural elements. The statement of the boundary value problem on the deformation of a circular sandwich plate with a central hole, connected to the soil foundation, was given. To describe the kinematics of an asymmetric plate pack, the broken line hypotheses are accepted. In a relatively thick lightweight core, the normal does not change its length, remains rectilinear, but rotates through some additional angle. Tuff, coarse grained soil, granite, and gneiss are accepted as the soil foundation. The bearing reaction is described by the Winkler model. The system of equilibrium equations is obtained by the variational method. Its solution is written in displacements through Kelvin functions. A numerical parametric analysis of displacements and stresses in the plate is carried out, their dependence on the type of soil foundation is shown.

Mathematical models and experimental data for HDF based sandwich panels with dual corrugated lightweight core

Light layer honeycomb panels could replace traditional wood materials, if their stiffness and strength properties could be improved. The aim of this research was to design and determine elastic properties of sandwich panels (SPs) based on a dual corrugated HDF core. Stiffness matrix values of elements were determined by a numerical method. The 3D calculation results were compared with those of the homogeneous model. The calculation results were collated with those of experimental investigations. It was demonstrated that the linear elasticity modulus as well as the modulus of rupture of the SPs were comparable with mechanical properties of a particle board with identical thickness, while the SP has a 1/3 lower density. The panel core exhibited significant orthotropic properties. In the xy plane it could be characterized as an auxetic structure. The homogeneous model leads to results similar to those achieved from the 3D model and observed in experimental tests.

Structural Response of Sandwich Beams with Different Facing Materials Subjected to Bending

Sandwich elements with structural functions are widely used in engineering applications, offering outstanding advantages, such as high strength and stiffness compared to its low specific weight. The sandwich elements consist in two stiff and thin faces, separated by a thick and lightweight core. A numerical analysis is performed in this paper, in order to evaluate the flexural structural response of sandwich beams with foam core and various facing materials. It has been noticed that the deflections decrease when the stiffness of the facings increase. The results are represented in terms of maximum deflections and direct stress distributions.