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Your search keyword '"C. Bujoreanu"' showing total 20 results
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20 results on '"C. Bujoreanu"'

2. Experimental investigation of noise characteristics for HVAC silencers

Author

Marcelin Benchea and C. Bujoreanu

Subjects
Engineering, Anechoic chamber, business.industry, Attenuation, Flow (psychology), Mechanical engineering, Silencer, 01 natural sciences, 030205 complementary & alternative medicine, 0104 chemical sciences, 010404 medicinal & biomolecular chemistry, 03 medical and health sciences, Noise, 0302 clinical medicine, lcsh:TA1-2040, HVAC, Insertion loss, business, lcsh:Engineering (General). Civil engineering (General), Acoustic attenuation
Abstract

Heating, ventilating and air-conditioning (HVAC) systems represent a major source of inside buildings noise with a negative effect on the acoustical environment. Therefore, it is necessary to add attenuation to the system. This is provided by sound attenuators or silencers manufactured in different geometrical configurations and with various absorptive lining materials. The paper deals with the insertion loss, as a performance criterion for in-duct noise, of some dissipative silencers types. The measured data are compared in order to establish the efficiency of every tested silencer type. Third-octave band analysis of random noise of an air handling unit (AHU) from a HVAC system is realized without and with silencers (ducts fitted). Insertion loss measurements are made in an anechoic room using a test facility that agrees the requirements of ISO 7235:2009. The results highlight the effects of the silencers geometry, pressure-air flow and loading relations upon the sound attenuation level. The silencers selection could be a difficult task for the designers which have to consider all these parameters.

Published
2017

20. Experimental testing on free vibration behaviour for silicone rubbers proposed within lumbar disc prosthesis.

Author

Rotaru I, Bujoreanu C, Bele A, Cazacu M, and Olaru D

Subjects
Calorimetry, Differential Scanning, Humans, Lumbar Vertebrae physiology, Materials Testing, Microscopy, Electron, Scanning, Models, Biological, Prostheses and Implants, Biocompatible Materials chemistry, Silicone Elastomers chemistry, Total Disc Replacement instrumentation, Vibration
Abstract

This research was focused on the damping capacity study of two types of silicone rubbers proposed as layers within total lumbar disc prostheses of ball-and-socket model. In order to investigate the damping capacity, the two silicone rubber types mainly differing by the molecular mass of polymeric matrix and the filler content, as was emphasized by scanning electron microscopy and differential scanning calorimetry, were subjected to free vibration testing. Using an adapted experimental installation, three kinds of damping testing were realised: tests without samples and tests with three samples of each type of silicone rubber (69 ShA and 99 ShA). The free vibration tests were performed at a frequency of about 6 Hz using a weight of 11.8 kg. The relative damping coefficient was determined by measuring of two successive amplitudes on the vibrogram and calculating of the logarithmic decrement. The test results with silicone rubber samples showed a relative damping coefficient of 0.058 and respectively 0.077, whilst test results without samples showed a relative damping coefficient of 0.042. These silicone rubbers were found to have acceptable damping properties to be used as layers placed inside the prosthetic components., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Published
2014
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