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    Wyświetlanie 1-3 z 3
    Tytuł:
    Photonic band gap in negative ternary refractive indices of two-dimensional photonic crystal
    Autorzy:
    Gharaati, A
    Mohamadebrahimi, L
    Roozitalab, Z
    Powiązania:
    https://bibliotekanauki.pl/articles/174931.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    negative refraction
    two dimensional photonic crystals
    metamaterials
    band gaps
    Opis:
    In this paper, we study propagation of electromagnetic wave in negative ternary refractive indices of two-dimensional photonic crystals. We consider two structures with two concentric cylindrical rod and shell in which one of them has negative refractive indices, in positive dielectric background. It is shown that by increasing the diameter of the rod in both structures, we can obtain more and wider band gaps in comparison with the structures in which there is no negative refractive index materials. This increase is more considerable in the first structure, in which the rod has a negative refractive index, in comparison with the second one, where the rod has a positive refractive index.
    Źródło:
    Optica Applicata; 2014, 44, 4; 637-648
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the Interaction of Resonance And Bragg Scattering Effects for the Locally Resonant Phononic Crystal with Alternating Elastic and Fluid Matrices
    Autorzy:
    Yuan, B.
    Chen, Y.
    Jiang, M.
    Tang, S.
    He, M.
    Tu, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177103.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    locally resonant phononic crystals
    effective speed of sound
    coupling band gaps
    underwater acoustic materials
    Opis:
    Three-dimensional (3D) locally resonant phononic crystals (LRPCs) are studied with the aim of optimising the sub-wavelength band gaps of such composites. By analysing their effective acoustic properties, it has been found that the effective acoustic speed of the composite will drop to zero when local resonance arise, and will increase monotonically when Bragg scattering effects occur. Moreover, if the matrix is a low-shear-speed medium, local resonators can significantly reduce the effective acoustic speed of the composite and, therefore, lower the frequency where Bragg scattering effects occur. Hence, a specific LRPC with alternating elastic and fluid matrices is proposed, whose resonance and Bragg gaps are already close in frequency. The fluid matrix behaves as a wave filter, which prevents the shear waves from propagating in the composite. By using the layer-multiple-scattering theory, the coupling behaviour of local resonance and Bragg scattering band gaps has been investigated. Both gaps are enhanced when they move closer to each other. Finally, a gap-coupled case is obtained that displays a broad sub-wavelength band gap. Such proposal excels at the application of underwater acoustic materials since the arrangement of structure can be handily adjusted for tuning the frequency of coupled gap.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 725-733
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The analysis of surface morphology, band gaps and optical properties of PAN/GO thin films
    Autorzy:
    Matysiak, W.
    Adamczyk, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818502.pdf
    Data publikacji:
    2020
    Wydawca:
    Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
    Tematy:
    nanomaterials
    spin coating
    nanocomposite
    polyacrylonitrile
    graphene oxide
    band gaps
    nanomateriały
    powłoka typu spin
    nanokompozyt
    poliakrylonitryl
    tlenek grafenu
    Opis:
    Purpose: PAN/GO nanocomposites are gaining more and more interest from research and industrial environments. According to theoretical studies and experimental tests, PAN/ GO exhibits excellent properties such as tensile strength, good thermal and electrical conductivity, excellent thermal and tribological properties. Thanks to this property, the composite is considered the ideal successor to the nanocomposites used so far. The PAN/GO nanocomposite has great potential in the filtration, automotive, electrical and photovoltaic industry. Design/methodology/approach: The spin-coating process is used to produce thin layers by centrifuging a liquid substance on flat surfaces. The advantages of the spin- coating process are simplicity and ease with which the process can be carried out. Due to the ability to high spin speeds, high airflow leads to fast drying time, which in turn results in high consistency in both macroscopic and nanometre scales. The spin-coting method is usually the starting point and reference point for most academic and industrial processes that require a thin and uniform coating. The use of spin coating has a wide spectrum. This technique can be used to coat small substrates (from a few square mm) up to the coating of flat displays, e.g. TV sets, which may have a meter or more in diameter. Findings: Among the existing methods for producing thin layers, including physical and chemical methods for gas phase deposition or the self-assembly process, the spin-coating process makes it possible to produce uniform thin nanocomposite layers in an easy and cheap way. Spin coating is usually the starting point and reference point for most academic and industrial processes that require a thin and uniform coating. The advantage of the method is the wide spectrum of use. It is used for coating substrates with everything from photoresists, insulators, organic semiconductors, synthetic metals, nanomaterials, metal precursors and metal oxides, transparent conductive oxides and many other materials. Often, spin coating is used to unravel polymer layers or photoresist on semiconductor substrates. Research limitations/implications: Due to the ongoing research on the potential applications of PAN/GO thin layers, including electronics, automotive and photovoltaics, it is worth trying to optimize the parameters of the spin-coiling process such as rotational speed or duration of the process. It is also worth trying to optimize the concentration of GO in the nanocomposite. Practical implications: Despite mixing the solution with an ultrasonic homogenizer to disperse the nanoparticles, the particles dispersed to form a rough surface. Originality/value: Low-cost, easy to carry out method of producing thin nanocomposite layers, having significant application in laboratory environments.
    Źródło:
    Archives of Materials Science and Engineering; 2020, 101, 2; 49--56
    1897-2764
    Pojawia się w:
    Archives of Materials Science and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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