Search results for "ACOUSTICS"
showing 10 items of 984 documents
Performance analysis and comparison of symmetrical and asymmetrical configurations of evanescent mode ridge waveguide filters
2009
[1] In this paper, the trade-offs between out-of-band performance, filter length, power-handling capability, and insertion loss of both symmetrical and asymmetrical evanescent mode ridge rectangular waveguide filters are investigated. As a result, clear design methodologies for optimizing such performances are proposed. The developed methodologies are then applied to design several evanescent mode filters, and a complete performance analysis of the symmetrical and asymmetrical structures is performed. From the performance analysis results, the designer can choose the more appropriate filter topology and design strategy to satisfy the prescribed specifications.
An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits
2011
In this paper a new and efficient integral equation formulation is presented for the analysis of arbitrarily shaped capacitive waveguide devices. The technique benefits from the symmetry of the structure in order to reduce the dimensions of the problem from three to two dimensions. For the first time, this technique formulates the waveguide capacitive discontinuity problem as a 2D scattering problem with oblique incidence, combined with an efficient calculation of the parallel plate Green's functions. Results for a capacitive impedance transformer are successfully compared with measurements for validation of the proposed theory.
Disentangling canid howls across multiple species and subspecies: Structure in a complex communication channel
2016
Wolves, coyotes, and other canids are members of a diverse genus of top predators of considerable conservation and management interest. Canid howls are long-range communication signals, used both for territorial defence and group cohesion. Previous studies have shown that howls can encode individual and group identity. However, no comprehensive study has investigated the nature of variation in canid howls across the wide range of species. We analysed a database of over 2000 howls recorded from 13 different canid species and subspecies. We applied a quantitative similarity measure to compare the modulation pattern in howls from different populations, and then applied an unsupervised clusteri…
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…
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.
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…
Terpyridine-based metallopolymer thin films as active layer in ammonia sensor device
2016
International audience; A metal-containing polymer has been prepared by electropolymerization of an homoleptic Ru(II)-terpyridine complex bearing pyrrole heterocycles. The polymer is obtained as a thinfilm at the surface ofelectrodes, and has been characterized by electrochemical measurements, XPS and microscopy. It hasbeen shown that this polymer acts as an active gas sensitive layer since it enables the detection of anammonia gasflow through layer’s resistivity measurements.