Search

This paper describes a system for the measurement of the apparent mass (AM) matrix of standing subjects. The system uses two electrodynamic shakers to generate vibrations along two mutually perpendicular axes (vertical and horizontal) and allows the identification of the full AM matrix with two tests, in which the standing subject is exposed to vertical excitation combined in turn with fore-and-aft and lateral vibration. A 3-D force platform measures the forces and the torques transmitted from the vibrating platform to the feet. The force platform, set up with piezoelectric load cells, has been designed in order to obtain a measurement bandwidth of 20 Hz. The supports of different load cells are meant to minimize bending moments on the sensors and to minimize the axes crosstalk. The force platform has been calibrated with a least-squares approach, using reference masses and a dynamometric hammer. The AM uncertainty, evaluated through the experiments’ repeatability and reproducibility, is lower than 3.4% along the three axes (confidence level 68%). The measurement bandwidth is 20 Hz (±2%) and the crosstalk between orthogonal axes is lower than 5%, in accordance with the design requirements. [ABSTRACT FROM AUTHOR]

This paper describes a method for the comparison of the cooling capability of over-the-counter devices for skin tags removal. The comparison is performed by measuring the heat flux produced by the gas identified assessing the temperature difference across an element with a known thermal resistance; the temperature reached at the interface between the device and the heat-flux meter is also analyzed, although it is different from that of the skin during the treatment. The measurement accuracy has been experimentally evaluated and, with a confidence interval of 95%, is better than 6% for heat-flux measurements and lower than 0.3 °C for temperature measurements. The instrument allowed comparing the thermal efficiency of 19 dimethyl ether and propane devices of different types (dispenser, spray, and foam). Results are by far more reliable than those obtained with tests performed on subjects, where the intrinsic skin thermal properties variability prevents from assessing differences smaller than 30%. [ABSTRACT FROM PUBLISHER]

Plantar pressure measurements provide useful information to diagnose a diverse range of foot disorders; unfortunately, the commercially available measurement systems are undesirably sensitive to several disturbances, but this aspect is mostly neglected in the literature. This paper describes the results of an experimental campaign aiming at the identification of pressure measuring system metrological performances, at system modeling, and at the implementation of correction procedures. The sensor model was implemented using the results of static and dynamic tests performed on a pedar-X plantar pressure measurement system. The static calibration was performed by analyzing the effect of temperature, single sensor coverage area, local curvature, tangential forces, long-term stability (creep), and sensor crosstalk on the system performances. The dynamic calibration was performed on an electrodynamic shaker, identifying the single sensor frequency response function and the hysteresis under different average loads. The dynamic sensor model is based on the Kelvin–Voigt model, which is representative of the viscoelastic behavior of the material. The model allowed us to compensate both the creep (i.e., the behavior under static loads) and the nonunitary frequency response function. A deconvolution-based algorithm has been proposed to compensate the sensor crosstalk effects, although its implementation requires additional investigations. Experimental results of bobbing and gait tests showed that, with the adoption of the proposed compensation algorithms, the force and center of pressure errors could be reduced by more than 50\% of their initial values. [ABSTRACT FROM PUBLISHER]

The skin–contact thermal resistance is a parameter that allows evaluating, in steady condition, the heat flow at the interface between the skin and a rigid surface at a known temperature. At the current state of the art, it is evaluated with empirical equations and is known to be dependent on the contact pressure, on the surface characteristics, and on the skin conductivity. The need to measure skin and contact thermal resistance with low uncertainty led to the realization of the device described in this paper. The instrument—based on the principle of the thermoflowmeter—has been designed with the goal of minimizing the measurement uncertainty with contact temperatures ranging between 12 ^\circ\C and 27 ^\circ\C and contact areas from 50 to 314 \mm^2. The device allows varying and controlling the interface pressure and temperature that, according to existing literature studies, are likely to influence the skin thermal properties. The different temperatures needed for the evaluation of the thermal resistance are measured with individually calibrated thermocouples. The metrological characterization of the flowmeter was performed under vacuum, and the effect of convective heat exchanges in normal operation was modeled and compensated. Measurement repeatability and reproducibility were assessed by measuring the thermal resistance of plastic materials in operational conditions. Preliminary tests showed that the skin–contact thermal resistances measured in different conditions are compatible with the theoretically evaluated ones, with improvement in uncertainty due to direct measurement. [ABSTRACT FROM PUBLISHER]

Very often in environmental and industrial acoustics, it is necessary to identify the contribution of single sources to global sound levels. Under this perspective, interests arise from the necessity of controlling noise or verifying whether a single source exceeds legal limits while there are other active sources around. Currently available methods are typically based on coherence or expert system techniques. Both approaches have relevant limitations, but for current purposes, coherence methods are usually more robust, particularly if carried out using vibration sensors in vibroacoustic interactions. Nevertheless, when a measurement system has to be based only on microphone measurements, those methods also have too little reliability and unsatisfying accuracy. In fact, it is quite impossible to eliminate in the input signals the effects of other sources, which usually also have some coherence with the output signal. In this paper, a relevant enhancement to coherence-based methods is described and discussed. The proposed approach leverages on the use of an acoustic intensity measurement approach instead of the sound pressure one. Method advantages and limitations are addressed with a theoretical approach; method performances are experimentally verified. [ABSTRACT FROM AUTHOR]