Search results for "ACOUSTICS"
showing 10 items of 984 documents
Twenty Years of Airborne Water Vapor and Total Water Measurements of a Diode Laser Based Photoacoustic Instruments
2020
We present relevant issues collected over twenty years of development and operation of an airborne water vapour / total water detector based on photoacoustic spectroscopy. The WaSulHygro instrument possesses high selectivity, short response time, and wide dynamic range, that are key requirements against trace gas measurement systems for applications in atmospheric sciences. Besides the major properties of WaSul-Hygro we discuss our efforts to develop a robust instruments that have proved its long-term reliability over the last fifteen years operating on-board a commercial aircraft within the framework of the CARIBIC project.2
Current transformers effects on the measurement of harmonic active power in LV and MV networks
2011
The harmonic active power is used to determine the location of polluting loads, the direction of harmonic power flow and to estimate how consequential a certain current harmonic source is. The highest uncertainties, when measuring harmonic active power, are introduced by the current and voltage transducers. This paper presents experimental results which show the impact of current transformers (CTs) on the accuracy of the harmonic power measurements. An expression for the evaluation of the power error in distorted conditions was developed which can be easily utilized in the case of linear current transducers. It is shown how CTs cannot be considered linear transducers and how the higher the …
On the Fast and Rigorous Analysis of Compensated Waveguide Junctions Using Off-Centered Partial-Height Metallic Posts
2007
In this paper, we present an efficient and rigorous method, based on the 3-D boundary integral-resonant-mode expansion technique, for the analysis of multiport rectangular waveguide junctions compensated with partial-height cylindrical metallic posts. The electrical performance of a great variety of commonly used wideband microwave circuits has been improved drastically thanks to the introduction of a new design parameter, i.e., the relative position of the metallic post in the structure. To the authors' knowledge, this parameter has not been taken into account in previous studies concerning compensated junctions using partial-height metallic posts. The developed tool has been successfully …
Time of flight for photon in human skin
2016
The time of flight for photons in human skin was measured using picosecond diode laser. Two different wavelength lasers were used - 405 nm and 510 nm. A difference for time of flight in normal skin and in nevus was observed as well as a difference for different wavelength laser irradiation was observed. For 405 nm laser irradiation the difference was 41 ps while comparison of time of flights skin and nevi using 510 nm irradiation showed a result of 32 ps. Results allow to conclude that the time photon travels in skin might depend on the characteristics of the medium and wavelength of the irradiation. This can be related to known data for light penetration depth in human skin for different w…
Comparison of a near-infrared reflectance spectroscopy system and skin conductance measurements for in vivo estimation of skin hydration: a clinical …
2017
Diffuse reflectance spectroscopy system was developed for estimation of skin hydration in the near-infrared spectral range of 900-1700 nm. Experimental setup consisted of a near-infrared spectrometer, Y-type fiber optics probe with 1 detection and 6 illumination fibers, halogen-tungsten light source and a PC. By analyzing diffuse reflectance spectrum, a parameter representing skin hydration by performing baseline correction and calculating the area under the 1450 nm water absorption maximum is proposed. A clinical study was performed acquiring data of skin hydration of 39 patients' forearm skin. Results of the developed system are compared to results obtained by a commercial device based on…
Theoretical Proposals on How Vertical Harmony May Convey Nostalgia and Longing in Music
2015
<p>Music is often associated with the emotions of nostalgia and longing. According to previous survey studies both nostalgia and longing are among the most commonly evoked emotions by music (Juslin, 2011). Despite nostalgia&rsquo;s significance as a musical emotion, research on the specific properties of music that might contribute to this particular emotion has been scarce. A recent empirical experiment by Lahdelma and Eerola (2014) sought to explore whether single chords could be effective at conveying musical emotions to listeners, which spanned complex emotions such as nostalgia. According to the results single chords such as the minor triad, the minor seventh and the major se…
Física por un tubo. Mide la velocidad del sonido en el aire y diviértete con los tubos sonoros
2011
En este trabajo damos las claves para diseñar un conjunto de tubos sonoros de PVC que permiten realizar una ejecución musical en grupo con la participación de un gran número de personas sin cultura musical previa. Proponemos además la utilización de los tubos para el estudio cuantitativo de los fenómenos físicos involucrados en la generación del sonido con instrumentos de viento. Se describe la utilización de los tubos sonoros, en combinación con un ordenador y un programa de análisis de sonido, para el análisis de ondas estacionarias y la determinación de la velocidad de propagación del sonido en el aire mediante distintos procedimientos.
Complex dynamics, hidden attractors and continuous approximation of a fractional-order hyperchaotic PWC system
2018
In this paper, a continuous approximation to studying a class of PWC systems of fractionalorder is presented. Some known results of set-valued analysis and differential inclusions are utilized. The example of a hyperchaotic PWC system of fractional order is analyzed. It is found that without equilibria, the system has hidden attractors.
Numerical methods for acoustics and noise control
2010
Artikkeliväitöskirja. Sisältää yhteenveto-osan ja viisi artikkelia. Article dissertation. Contains an introduction part and five articles. This dissertation considers numerical methods for wave propagation modelling and noise control. The first part of the dissertation discusses an efficient method for solving time-harmonic wave equations in acoustic (the Helmholtz equation) and elastic domains (the Navier equation). The solver is based on preconditioning a Krylov subspace method, such as GMRES, with approximations of damped variants of the corresponding wave equations. An algebraic multigrid method is used in approximating the inverse of damped operators. The method can be used in complex …
Multi-objective actuator placement optimization for local sound control evaluated in a stochastic domain
2011
A method to find optimal locations and properties of anti-noise actuators in local noise control system is considered. The local noise control performance is approximated by a finite element method based approach, that attempts to estimate the average performance of optimal active noise control (ANC) system. The local noise control uses a fixed number of circular actuators that are located on the boundary of a three-dimensional enclosed acoustic space. Actuator signals are used to minimize the known harmonic noise at specified locations. The average noise reduction is maximized at two frequency ranges by adjusting the anti-noise actuator configuration, which is a non-linear multi-objective …