18 research outputs found
Identification of noise sources using a time domain beamforming on pneumatic, gas and electric nail guns
In the construction industry, many workers are exposed daily to harmful levels of impulsive noise from nail guns. Therefore, a better knowledge of the noise generated by these tools is required in order to propose noise reduction solutions. The objective of this work is to propose an approach for source identification using a microphone array together with a source identification algorithm based on recent development in the generalized cross-correlation technique. In addition to the pneumatic nail gun, for which sources have been partially identified in the literature, the proposed approach is applied to two other types of nail guns, an electric and a gas powered one. First, the standardized acoustic power spectrum of these three nail guns is measured for global comparison purposes and result in a ranking of the three nail guns. Second, the generalized cross-correlation technique applied to nail gun noise source identification is presented. Third, acoustic maps for successive small time segments are presented, providing a fine identification of noise sources for the three nail guns and an explanation of the observed sound power level ranking. © 2019 Institute of Noise Control Engineering
Tonal noise of a controlled-diffusion airfoil at low angle of attack and Reynolds number
Production of high power microwaves for particle acceleration with an FEL bunched electron beam
Comparison of beam bunching in amplifier and SASE modes at the CEA-CESTA free-electron laser
Characterization of a polyurethane-based controlled release system for local delivery of chlorhexidine diacetate
Conventional formulations of chlorhexidine usually provide short-term efficiency, requiring repeated
applications to maintain antibacterial activity. Therefore, appropriate release system of chlorhexidine
controlling local drug delivery would reduce the number of applications and enhance patient compliance.
The aim of this study was to develop a controlled release system based on medical polyurethane for the
local delivery of chlorhexidine diacetate (CDA). CDA-loaded polyurethane films (CDA-Films) and CDAloaded
polyurethane sandwiches (CDA-Sandwiches) were obtained by casting and solvent evaporation.
The physico-chemical aspects of CDA-loaded polyurethane systems were investigated, and the crystalline
state of CDA in the polymeric system was highlighted. CDA-Films exhibited appropriate mechanical
properties for further applications. Drug release was measured in two different media: (i) distilled water
and (ii) physiological saline solution to mimic in vivo conditions. Drug release studies were performed up
to 11 days on CDA-Films and 29 days for CDA-Sandwiches. Release of CDA depended on drug loading and
the structure of the system. In particular, release of CDA from the sandwich system followed zero-order
kinetic. The release rate was significantly lower in physiological solution. Antibacterial studies were carried
out on CDA-Films against Staphylococcus aureus and Staphylococcus epidermidis showing 35 days persisting
antibacterial activity.
In conclusion, the polyurethane-based system developed in this study is potentially useful as a local
delivery system for CDA and could be used not only in surgery but also in dental and clinical applications
A review of acoustic imaging methods using phased microphone arrays
Phased microphone arrays have become a well-established tool for performing aeroacoustic measurements in wind tunnels (both open-jet and closed-section), flying aircraft, and engine test beds. This paper provides a review of the most wellknown and state-of-the-art acoustic imaging methods and recommendations on when to use them. Several exemplary results showing the performance of most methods in aeroacoustic applications are included. This manuscript provides a general introduction to aeroacoustic measurements for non-experienced microphone-array users as well as a broad overview for general aeroacoustic experts