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    Wyświetlanie 1-5 z 5
    Tytuł:
    Semiconductor contact layer characterization in a context of hall effect measurements
    Autorzy:
    Kowalewski, Andrzej
    Wróbel, Jarosław
    Boguski, Jacek
    Gorczyca, Kinga
    Martyniuk, Piotr
    Powiązania:
    https://bibliotekanauki.pl/articles/220890.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    metal contact
    contact layer
    contact resistance
    Hall effect
    resistivity
    van der Pauw method
    MSM structure
    semiconductors’ characterization
    Opis:
    A revision of the standard approach to characterization of thin-semiconductor-layer Hall samples has been proposed. Our results show that simple checking of I(V) curve linearity at room temperature might be insufficient for correct determination of bias conditions of a sample before measurements of Hall effect. It is caused by the nonlinear behaviour of electrical contact layers, which should be treated together with the tested layer a priori as a metal-semiconductor-metal (MSM) structure. Our approach was examined with a Be-doped p-type InAs epitaxial layer, with four gold contacts. Despite using full high-quality photolithography a significant asymmetry in maximum differential resistance (Rd) values and positions relative to zero voltage (or current) value was observed for different contacts. This suggests that such characterization should be performed before each high-precision magneto-transport measurement in order to optimize the bias conditions.
    Źródło:
    Metrology and Measurement Systems; 2019, 26, 1; 109-114
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural Aspects of Remelting of the AZ91 Magnesium Alloy Surface Layer
    Autorzy:
    Iwaszko, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/381789.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    magnesium alloy
    surface layer
    laser remelting
    laser beam
    structure
    stop magnezu
    warstwa wierzchnia
    przetapianie
    wiązka laserowa
    struktura
    Opis:
    In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam.
    Źródło:
    Archives of Foundry Engineering; 2016, 16, 1; 13-18
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach
    Autorzy:
    De Gennaro, M.
    Küehnelt, H.
    Zanon, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/178116.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    tonal airborne noise
    NACA 0012
    Laminar Boundary Layer-Vortex Shedding noise
    Ladder-like tonal structure of the acoustic spectrum
    multi-tonal structure of the acoustic spectrum
    Opis:
    Tonal airborne noise of aerofoils appears in a limited range of moderate Reynolds numbers and angles of attack. In these specific conditions, the aerofoil is characterised by a large region of laminar flow over the aerodynamic surface, typically resulting in two-dimensional laminar instabilities in the boundary layer, generating one or more acoustic tones. The numerical simulation of such phenomenon requires, beside an accurate prediction of the unsteady flow field, a proper modelling of the laminar to turbulent transition of the boundary layer, which generally imposes the use of highly CPU demanding approaches such as large eddy simulation (LES) or direct numerical simulation (DNS). This paper aims at presenting the results of numerical experiments for evaluating the capability of capturing the tonal airborne noise by using an advanced, yet low computationally demanding, unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence model augmented with a transitional model to account for the laminar to turbulent transition. This approach, coupled with the Ffowcs Williams and Hawkings (FW-H) acoustic analogy, is adopted for predicting the far-field acoustic sound pressure of a NACA 0012 aerofoil with Reynolds number ranging from 0.39 · 106 to 1.09 · 106. The results show a main tone located approximately at 1.6–1.8 kHz for a Reynolds number equal to 0.62 · 106, increasing to 2.4 kHz at Reynolds number equal to 0.85 · 106 and 3.4 kHz at 1.09 · 106, while no main tones are observed at 0.39 · 106. The computed spectra confirm that the acoustic emission of the aerofoil is dominated by tonal structures and that the frequency of the main tone depends on the Reynolds number consistently with the ladder-like tonal structure suggested by Paterson et al. Moreover, in specific conditions, the acoustic spectra exhibit a multi-tonal structure visible in narrowband spectra, in line with the findings of Arbey and Bataille. The presented results demonstrate the capability of the numerical model of predicting the physics of the tonal airborne noise generation.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 653-675
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structure of X5CrNi18-10 and S355NL steels after remelting with the electric arc
    Autorzy:
    Adamiak, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/947417.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    stal konstrukcyjna
    przetapianie
    warstwa powierzchniowa
    plazma
    łuk elektryczny
    badanie strukturalne
    construction steel
    remelting
    surface layer
    plasma
    electric arc
    structure research
    Opis:
    The work presents the results of the research and tests of the surface machining of the S355NL and X5CrNi18-10 steels with the concentraded stream of heat with the usage of the GTAW method. The surface layers of the tested steels were remelted with the electric arc using the current of the electric arc 50, 100, 150 and 200A.The machining was done in the atmosphere of argon with the constant speed of the welding head. A microscope examination was performed of the obtained structure and measurements of depth, width and hardness of the received surface layer were performed. Moreover the relation between the current of the electric arc and geometry of the remelted layers with their microhardeness was examined.
    Źródło:
    Archives of Foundry Engineering; 2012, 12, 2; 139-142
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical investigation of the basilar membrane vibration induced by the unsteady fluid flow in the human inner ear
    Autorzy:
    Wahl, Philipp
    Ziegler, Pascal
    Eberhard, Peter
    Powiązania:
    https://bibliotekanauki.pl/articles/1845019.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    human cochlea
    basilar membrane
    unsteady viscous fluid flow
    fluid-structure interaction
    pressure-displacement-based fluid element
    viscous boundary layer
    tonotopy
    auditory threshold
    ludzki ślimak
    membrana podstawna
    niestabilny przepływ cieczy lepkiej
    interakcja płyn-struktura
    element hydrauliczny oparty na ciśnieniu wyporowym
    lepka warstwa graniczna
    tonotopia
    próg słyszalności
    Opis:
    For a deeper understanding of the inner ear dynamics, a Finite-Element model of the human cochlea is developed. To describe the unsteady, viscous creeping flow of the liquid, a pressure-displacement-based Finite-Element formulation is used. This allows one to efficiently compute the basilar membrane vibrations resulting from the fluid-structure interaction leading to hearing nerve stimulation. The results show the formation of a traveling wave on the basilar membrane propagating with decreasing velocity towards the peaking at a frequency dependent position. This tonotopic behavior allows the brain to distinguish between sounds of different frequencies. Additionally, not only the middle ear, but also the transfer behavior of the cochlea contributes to the frequency dependence of the auditory threshold. Furthermore, the fluid velocity and pressure fields show the effect of viscous damping forces and allow us to deeper understand the formation of the pressure difference, responsible to excite the basilar membrane.
    Źródło:
    Archive of Mechanical Engineering; 2020, LXVII, 4; 381-414
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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