Search results for "ACOUSTIC"
showing 10 items of 1590 documents
Thermolytic reverse electrodialysis heat engine: model development, integration and performance analysis
2019
Abstract Salinity gradient heat engines represent an innovative and promising way to convert low-grade heat into electricity by employing salinity gradient technology in a closed-loop configuration. Among the aqueous solutions which can be used as working fluid, ammonium bicarbonate-water solutions appear very promising due to their capability to decompose at low temperature. In this work, an experimentally validated model for a reverse electrodialysis heat engine fed with ammonium bicarbonate-water solutions was developed. The model consists of two validated sub-models purposely integrated, one for the reverse electrodialysis unit and the other for the stripping/absorption regeneration uni…
Optimizing and Modeling the drying process of the Natural Gas through the Taguchi method
2018
The aim of this study is to highlight the optimization method of the drying process of natural gas, using the Taguchi method. The natural gas undergoes several stages from its extraction until reaching its end consumer. As the natural gas contains several impurities and a certain quantity of water and vapors, the drying process is very important to obtain a product of high quality. Gas dehydration can be obtained through several methods, the method presented here being the absorption method - by use of a drying station with triglycol. This method is considered to be the most convenient one taking into account the obtained results. Nevertheless, cost reducing is the main objective for compan…
The influence of the momentum coefficient and the number of the averaging points of the power spectrum density on the recognition effectiveness of th…
2006
The subject matter of this paper refers to the next stage of the research work connected with the improvement of the acoustic emission method (AE) used for the evaluation of partial discharges (PDs) generated in paper-oil insulation systems of high-voltage power appliances. The subject matter discussed here refers to one of the aspects of the analysis of the signals registered - a correct and effective recognition of the AE signals generated by basic PD forms. The paper presents research results of the application of the unidirectional artificial neuron networks (ANN) used for the recognition of basic PD forms that can occur in paper-oil insulation impaired by aging processes.
Experimental investigation of the relation between H− negative ion density and Lyman-α emission intensity in a microwave discharge
2016
International audience; A new mechanism for producing negative ions in low density and low power hydrogen plasmas was proposed recently. It refers to anion formation due to collisions between hydrogen atoms being in the first excited state. The proposed mechanism was indirectly supported by the quadratic relation observed between the extracted negative ion current and Lyman-α radiation of a filament-driven arc discharge, when borrowed data from the literature were combined. The present work provides experimental data comparing directly the absolute negative ion density and Lyman-α radiation in an ECR-driven hydrogen plasma source. The previously mentioned quadratic relation is not observed …
High energy, high resolution photoelectron spectroscopy of Co2Mn(1-x)Fe(x)Si
2006
This work reports on high resolution photoelectron spectroscopy for the valence band of Co2Mn(1-x)Fe(x)Si (x=0,0.5,1) excited by photons of about 8 keV energy. The measurements show a good agreement to calculations of the electronic structure using the LDA+U scheme. It is shown that the high energy spectra reveal the bulk electronic structure better compared to low energy XPS spectra. The high resolution measurements of the valence band close to the Fermi energy indicate the existence of the gap in the minority states for all three alloys.
Cutting Conditions and Work Material State Identification through Acoustic Emission Methods
1992
Summary This paper examines the problem of in-process monitoring of metal cutting operations carried out on aluminum alloys for aeronautical applications. Turning tests were conducted on annealed and heat treated aluminum alloy bars, using carbide tools. For both work material conditions, different combinations of cutting parameters were used. During cutting tests, acoustic emission (AE) and cutting force sensor data were detected and processed. The comparison between AE responses from the annealed and heat treated aluminum alloys allowed, with the help of force sensor data, to verify the applicability of AE and sensor fusion techniques for in-process and real time identification of work ma…
Narrow Band Solid-Liquid Composite Arrangements: Alternative Solutions for Phononic Crystal-Based Liquid Sensors
2019
Periodic elastic composite structures attract great attention. They offer the ability to design artificial properties to advance the control over the propagation of elastic/acoustic waves. In previous work, we drew attention to composite periodic structures comprising liquids. It was shown that the transmission spectrum of the structure, specifically a well-isolated peak, follows the material properties of liquid constituent in a distinct manner. This idea was realized in several liquid sensor concepts that launched the field of phononic crystal liquid sensors. In this work we introduce a novel concept&mdash
Localized magnetic moments in the Heusler alloy Rh2MnGe
2009
X-ray magnetic circular dichroism (XMCD) of core-level absorption (x-ray absorption spectroscopy, XAS) spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloy Rh2MnGe at the Rh M3,2 and Mn L3,2 edges. The ratio of Rh and Mn spin moments amounts to 0.05 which is smaller than the ratio of 0.1 determined by a local density approximation electronic band structure calculation. We have found that the orbital moments of the Rh 4d and Mn 3d states are very small. The observed Rh 2p XAS spectrum can be understood on the basis of the Rh 3d partial density of unoccupied states as is typical for metals. The observed features of the Mn 2p XAS and XMCD spectra are dominated…
Motorcyclists Safety System to avoid Rear End Collisions based on Acoustic Signatures
2017
International audience; In many Asian countries, motorcyclists have a higher fatality rate as compared to other vehicles. Among many other factors, rear end collisions are also contributing for these fatalities. Collision detection systems can be useful to minimize these accidents. However, the designing of efficient and cost effective collision detection system for motorcyclist is still a major challenge. In this paper, an acoustic information based, cost effective and efficient collision detection system is proposed for motorcycle applications. The proposed technique uses the Short time Fourier Transform (STFT) to extract the features from the audio signal and Principal component analysis…
Modeling by the finite element method of acoustic radiation in waveguides lined with locally or non locally reacting absorbent materials in the prese…
2011
Our concern in this work is the problem of acoustic propagation in guides lined with locally or non locally reacting materials with the presence of mean fluid flow. In several industrial systems such as aircraft jet engines, mufflers exhaust and ventilation systems, noise is mostly channeled outside by guides of more or less complex geometries. A study of waveguides makes it possible to predict and understand the physical phenomena such as refraction, convection, absorption and wave attenuation. In waveguides studies, guides are often considered infinitely long to get rid of some phenomena (reflection for example) at their ends. Solving the problem of acoustic propagation in infinite guides…