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    Wyświetlanie 1-7 z 7
    Tytuł:
    Effect of Transverse Acoustic Flow on the Input Impedance of Rapidly Flaring Horns
    Autorzy:
    Nederveen, C. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/177015.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    input impedance
    horn
    wind musical instruments
    boundary conditions
    Opis:
    In slowly flaring horns the wave fronts can be considered approximately plane and the input impedance can be calculated with the transmission line method (short cones in series). In a rapidly flaring horn the kinetic energy of transverse flow adds to the local inertance, resulting in an effective increase in length when it is located in a pressure node. For low frequencies corrections are available. These fail at higher frequencies when cross-dimensions become comparable to the wavelength, causing resonances in the cross-direction. To investigate this, the pipe radiating in outer space is modelled with a finite difference method. The outer boundaries must be fully absorbing as the walls of an anechoic chamber. To achieve this, Berenger’s perfectly matched layer technique is applied. Results are presented for conical horns, they are compared with earlier published investigations on flanges. The input impedance changes when the largest cross-dimension (outer diameter of flange or diameter of the horn end) becomes comparable to half a wavelength. This effect shifts the position of higher modes in the pipe, influencing the conditions for mode locking, important for ease of playing, dynamic range and sound quality.
    Źródło:
    Archives of Acoustics; 2011, 36, 3; 533-544
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wpływ zjawiska naskórkowości na impedancję wejściową kabla współosiowego w stanie jałowym i w stanie zwarcia
    The influence of the skin effect on input impedance in a coaxial cable in a no-load state and a short-circuit state
    Autorzy:
    Bugajska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/159024.pdf
    Data publikacji:
    2011
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Elektrotechniki
    Tematy:
    kabel współosiowy
    impedancja wejściowa
    zjawisko naskórkowości
    skin effect
    coaxial cable
    input impedance
    Opis:
    W artykule przedstawiono wpływ zjawiska naskórkowości na impedancję wejściową kabla współosiowego w stanie jałowym i zwarcia, przy uwzględnieniu jakościowego i ilościowego wpływu tego zjawiska na całkowitą impedancję jednostkową kabla współosiowego,czyli na rezystancje, indukcyjności własne żyły i ekranu,a także na indukcyjność wzajemną między nimi. Dla wybranej częstotliwości obliczenia wykonano dla kabla typu YHKXS zmieniając grubość jego izolacji i ekranu.
    The article presents the influence of the skin effect on input impedance of a coaxial cable in a no-load state and a short circuit state, when taking into account qualitative and quantitative influence of this effect on total unit impedance of a coaxial cable, that is resistance, self inductance of the conductor of the cable and the cable screen, and on the mutual inductance between them. The calculations have been performed for the type YHKXS cable assuming: wire radius R1 = 0.01 m, relative thickness of the cable insulation characterized by the parameter [WZÓR], whereas the relative thickness of the screen by the parameter [WZÓR] (R- interior radius of the cable screen, R2 - exterior radius of the cable screen). Assumed frequency value was f = 100 kHz. With a given load impedance, the input impedance of a coaxial cable depends on the skin effect. Figures 2, 3, 5 and 6 show that with the increase of the line's length, the maximum value of the input impedance module in no-load state (Fig. 2, 3) as well as in shortcircuited state (Fig. 5, 6) decrease, moreover, the amplitudes of input impedance module, after taking into consideration the skin effect, are considerably smaller than without accounting for this effect. The wavelength in a coaxial cable without taking into consideration the skin effect equals [WZÓR] and is smaller than the wavelength when taking the mentioned effect into consideration. In that case [WZÓR]. It is the result of the fact, that the phase lag coefficient depends primarily on total inductance of a coaxial cable chich causes its decrease, as well as of total inductance, with the increase of frequency.
    Źródło:
    Prace Instytutu Elektrotechniki; 2011, 252; 5-18
    0032-6216
    Pojawia się w:
    Prace Instytutu Elektrotechniki
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelling and control of an omnidirectional mobile manipulator
    Autorzy:
    Djebrani, S.
    Benali, A.
    Abdessemed, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/330102.pdf
    Data publikacji:
    2012
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    manipulator mobilny
    sterowanie impedancyjne
    logika rozmyta
    holonome mobile manipulators
    input state linearization
    virtual impedance control
    fuzzy logic
    Opis:
    A new approach to control an omnidirectional mobile manipulator is developed. The robot is considered to be an individual agent aimed at performing robotic tasks described in terms of a displacement and a force interaction with the environment. A reactive architecture and impedance control are used to ensure reliable task execution in response to environment stimuli. The mechanical structure of our holonomic mobile manipulator is built of two joint manipulators mounted on a holonomic vehicle. The vehicle is equipped with three driven axles with two spherical orthogonal wheels. Taking into account the dynamical interaction between the base and the manipulator, one can define the dynamics of the mobile manipulator and design a nonlinear controller using the input-state linearization method. The control structure of the robot is built in order to demonstrate the main capabilities regarding navigation and obstacle avoidance. Several simulations were conducted to prove the effectiveness of this approach.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2012, 22, 3; 601-616
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Trombone Transfer Functions: Comparison Between Frequency-Swept Sine Wave and Human Performer Input
    Autorzy:
    Beauchamp, J. W.
    Powiązania:
    https://bibliotekanauki.pl/articles/176612.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    brass acoustics
    trombone
    transfer function
    nonlinear propagation
    input impedance
    Opis:
    Source/filter models have frequently been used to model sound production of the vocal apparatus and musical instruments. Beginning in 1968, in an effort to measure the transfer function (i.e., transmission response or filter characteristic) of a trombone while being played by expert musicians, sound pressure signals from the mouthpiece and the trombone bell output were recorded in an anechoic room and then subjected to harmonic spectrum analysis. Output/input ratios of the signals’ harmonic amplitudes plotted vs. harmonic frequency then became points on the trombone’s transfer function. The first such recordings were made on analog 1/4 inch stereo magnetic tape. In 2000 digital recordings of trombone mouthpiece and anechoic output signals were made that provide a more accurate measurement of the trombone filter characteristic. Results show that the filter is a high-pass type with a cutoff frequency around 1000 Hz. Whereas the characteristic below cutoff is quite stable, above cutoff it is extremely variable, depending on level. In addition, measurements made using a swept-sine-wave system in 1972 verified the high-pass behavior, but they also showed a series of resonances whose minima correspond to the harmonic frequencies which occur under performance conditions. For frequencies below cutoff the two types of measurements corresponded well, but above cutoff there was a considerable difference. The general effect is that output harmonics above cutoff are greater than would be expected from linear filter theory, and this effect becomes stronger as input pressure increases. In the 1990s and early 2000s this nonlinear effect was verified by theory and measurements which showed that nonlinear propagation takes place in the trombone, causing a wave steepening effect at high amplitudes, thus increasing the relative strengths of the upper harmonics.
    Źródło:
    Archives of Acoustics; 2012, 37, 4; 447-454
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Aktywny transformator izolujący do zastosowań w pomiarach dokładnych w paśmie akustycznym
    Amplifier-aided isolation voltage transformer for use in accurate measurements in the audio frequency range
    Autorzy:
    Rybski, R.
    Kaczmarek, J.
    Kozioł, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/154849.pdf
    Data publikacji:
    2013
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    transformator pomiarowy
    transformator izolujący
    impedancja wejściowa
    błąd przekładni napięciowej
    instrument transformer
    isolation voltage transformer
    input impedance
    voltage ratio error
    Opis:
    Scharakteryzowano dwurdzeniowy aktywny napięciowy transformator izolujący. Przedstawiono i porównano wyniki pomiarów impedancji wejściowej transformatorów o takiej samej konstrukcji z rdzeniami nanokrystalicznymi i permalojowymi. Przedstawiono charakterystyki częstotliwościowe błędów modułu fazy przekładni napięciowej transformatora.
    In the paper the characteristic of an isolating instrument transformer is presented. The transformer is intended for use in a measurement system to calibrate low-value alternating-current standard resistors at audio frequencies. In the developed system a resistor RX is directly compared with a standard resistor RN (Fig. 1). The impedance ratio ZX/ZN of the resistors is determined from the measurement of the voltage ratio UX/UN. The measurement of floating voltages by a digitizer with grounded inputs requires isolating transformers (T1, T2). Due to the assumptions concerning the system being developed, transformers should be characterized by a relatively high input impedance and small errors of the transformer voltage ratio over a frequency bandwidth from 40 Hz to 10 kHz. The developed transformer has a two stage dual-core construction and an additional amplifier that increases the input impedance (Fig. 2). All the windings of the transformer have 100 turns each and are wound on a toroidal nanocrystalline core. The primary and secondary windings are placed in the electrostatic screens E1, E2. The frequency characteristics of the input impedance of two transformers of the same design made of nanocrystalline core and permalloy core operating without an amplifier W (Fig. 3) and with an amplifier (Fig. 4) are compared. In Figs. 5 and 6 the frequency characteristics of the module and phase error of the transformer voltage ratio are shown. They are determined by a digital system for measuring the complex voltage ratio, developed by the authors.
    Źródło:
    Pomiary Automatyka Kontrola; 2013, R. 59, nr 4, 4; 323-325
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A hybrid (hydro-numerical) circulatory model: investigations of mechanical aortic valves and a numerical valve model
    Autorzy:
    Kozarski, M.
    Suwalski, P.
    Zieliński, K.
    Górczyńska, K.
    Szafron, B.
    Pałko, K. J.
    Smoczyński, R.
    Darowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/202199.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    biological and mechanical heart valves
    numerical heart valve
    hybrid (hydro-numerical) circulatory model
    voltage-controlled hydraulic pressure (flow) source
    hydraulic input impedance
    varying-elastance left ventricle
    Opis:
    In most cases of diseased heart valves, they can be repaired or replaced with biological or mechanical prostheses. Biological prostheses seem to be safer than mechanical ones and are applied with good clinical outcomes. Their disadvantage, when compared with mechanical valves, is durability. In the development and application of mechanical and biological heart valves, a significant role can be played by a Hybrid (Hydro-Numerical) Circulatory Model. The aim of this paper is to demonstrate the opportunities created by the hybrid model for investigations of mechanical heart valves and their computer models under conditions similar to those of the circulatory system. A diode-resistor numerical valve model and three different design mechanical aortic valves were tested. To perform their investigations, computer applications were developed under RT LabView to be run on a PC. Static and dynamic characteristics of the valves were measured and registered - pressure in the numerical time-varying elastance left ventricle (pLV), in the aorta (pas) and flow (f), proving, among other factors, that 1) time delay of pas with respect to pLV is mainly related to the valve’s opening time, and 2) the valves of substantially different designs tested under identical hydrodynamic conditions reveal nearly the same dynamic performance.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 3; 605-612
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A 5.5 µW 42nV/√ Hz Chopper stabilized Amplifier for Biomedical Application with Input Impedance Enhancement
    Autorzy:
    Adesara, Ankit
    Naik, Amisha
    Powiązania:
    https://bibliotekanauki.pl/articles/1844492.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    biopotential amplifier
    input impedance
    noise
    power
    ECG
    EEG
    Opis:
    The continuous real-time monitoring of diverse physical parameters using biosignals like ECG and EEG requires the biomedical sensors. Such sensor consists of analog front-end unit for which low noise and low power Operational transconductance amplifier (OTA) is essential. In this paper, the novel chopper-stabilized bio-potential amplifier is proposed. The chopper stabilization technique is used to reduce the offset and flicker noise. Further, the OTA is likewise comprised of a method to enhance the input impedance without consuming more power. Also, the ripple reduction technique is used at the output branch of the OTA. The designed amplifier consumes 5.5 µW power with the mid-band gain of 40dB. The pass-band for the designed amplifier is 0.1Hz to 1KHz. The input impedance is likewise boosted with the proposed method. The noise is 42 nV/√ Hz with CMRR of 82 dB. All simulations are carried out in 180nm parameters.
    Źródło:
    International Journal of Electronics and Telecommunications; 2021, 67, 3; 523-530
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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