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    Wyświetlanie 1-14 z 14
    Tytuł:
    Defect modes properties in one-dimensional photonic crystals employing a superconducting nanocomposite material
    Autorzy:
    Aly, A. H.
    Elsayed, H. A.
    Malek, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/173888.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    photonic crystals
    band gap
    defect mode
    nanocomposite
    Opis:
    In the present work, we investigate theoretically the transmission characteristics of one-dimensional photonic crystals that contain a defect layer of a nanocomposite material in infrared radiation. The theoretical treatment is obtained depending on the fundamentals of the characteristic matrix method. Here, the nanocomposite designed from nanoparticles of a superconducting material is arranged into a dielectric medium. The numerical results clarify the acute effect of the volume fraction and the operating temperature on the effective permittivity of the nanocomposite material. Therefore, the volume fraction, the operating temperature and other parameters such as the permittivity of the dielectric material and the threshold frequency could have a significant effect on the characteristics of the defect modes. Thus, our structure may be very promising in many applications such as narrow band filters and among optoelectronic applications.
    Źródło:
    Optica Applicata; 2018, 48, 1; 53-64
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Properties of ZnO Nanoparticles Synthesised from a Polysaccharide and ZnCl₂
    Autorzy:
    Bindu, P.
    Thomas, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032335.pdf
    Data publikacji:
    2017-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    ZnO nanoparticles
    UV-vis
    band gap
    Urbach energy
    Opis:
    In this article we study the optical properties of ZnO nanoparticles. This paper describes cost effective, high yield, and a facile synthetic method for the synthesis of ZnO nanoparticles from precursors viz. linear polysaccharide, chitosan, and ZnCl₂ by a precipitation method. The synthesized ZnO nanoparticles were characterized by surface area, pore size, and UV-visible measurements. The optical band gap and the Urbach energy were also calculated and the optical band gap energy of the synthesized ZnO nanoparticles was found to be 3.26 eV and the nature of the optical transition has been identified as direct allowed.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 6; 1474-1478
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimization of a Bandgap in the Ultrasonic Phononic Coating
    Autorzy:
    Garus, Sebastian
    Sochacki, Wojciech
    Garus, Justyna
    Sandu, Andrei Victor
    Powiązania:
    https://bibliotekanauki.pl/articles/2049725.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    reflectance coating
    mechanical waves
    phononic crystal
    band gap
    optimization
    Opis:
    This work concerns the study of the coatings for the ultrasound frequency range as a quasi one-dimensional phononic crystal structure protecting a sea object against high resolution active sonar in the frequency range most commonly found for this type of equipment. The topology of the examined structure was optimized to obtain a band gap in the 2.2-2.3 MHz frequency band. For this purpose, a genetic algorithm was used, which allows for optimal distribution of individual elements of the ultrasound multilayer composite. By optimal distribution is meant to achieve a structure that will allow minimal reflectance in a given frequency range without height reflectance peaks with a small half width. Analysis of the wave propagation was made using the Transfer Matrix Method (TMM). As part of the research, 15 and 20-layer structures with reflectance at the level of 0.23% and 0.18%, respectively, were obtained. increasing the number of layers in the analyzed structures resulted in finding such a distribution in which a narrow band of low reflectance was obtained, such distributions could also be used as bandpass filters. The use of a genetic algorithm for designing allows to obtain modern coatings, the characteristics of which result from the structure.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 2; 537-542
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation characteristics of longitudinal-torsion coupled waves in phononic crystal rods of chiral materials
    Autorzy:
    Dai, P.
    Wang, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/38697111.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    chiral material
    band gap
    phononic crystal rods
    longitudinal-torsion waves
    Opis:
    The chiral properties of chiral materials have a great influence on the wave propagation. Applying chiral materials to the design of phononic crystal rods not only increases the design space, but also may have other potential advantages. There is a lack of research on designing phononic crystal rods using chiral materials and the propagation characteristics of elastic waves in phononic crystal rods made of chiral materials. In this study, chiral materials are introduced into the design of phonon crystal rods for the first time, Bragg scattering type and local resonance type phononic crystal rods are designed using chiral materials. Dispersion equations for the propagation of longitudinal-torsion coupled waves in the phononic crystal rods are derived, and the effect of the chirality of the materials on their bandgap range is studied. The study shows that: in Bragg scattering type phonon crystal rods, material chirality can greatly affect the bandgap, among them, the chiral direction has the greatest effect, and in order to obtain a low-frequency wide bandgap, the chiral coefficients of the materials should be increased as much as possible with the chiral directions of the two cells being opposite; in the local resonance type phonon crystal rod, only two types of oscillators are added to the material simultaneously to produce a band gap, and the starting frequency obtained is much lower than that of the Bragg scattering type.
    Źródło:
    Archives of Mechanics; 2023, 75, 5; 543-558
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Band gap properties of periodic tapered beam structure using traveling wave method
    Autorzy:
    Li, T.
    Ma, X.
    Zhang, Q.
    Wang, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/279452.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    band gap
    periodic structure
    traveling wave method
    Bloch theorem
    tapered beam
    Opis:
    The wave motion equations of a tapered beam with respect to axial, torsional and flexural deformations are deduced including the transmission and waveguide equations. Combining the force equilibrium and displacement coordination conditions at the junction, we obtain the relation between the wavenumber and frequency, and the band gap properties of periodic tapered beam structures by the Bloch theorem. The modeling accuracy and efficiency of the traveling wave method are verified by the finite element method. The band gap properties of periodic tampered and uniform beam structures are analyzed and compared for the same materials and lengths as well as the same volumes.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2016, 54, 4; 1297-1308
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Critical modeling issues of SiGe semiconductor devices
    Autorzy:
    Palankovski, V.
    Selberherr, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/308035.pdf
    Data publikacji:
    2004
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    SiGe HBT
    numerical simulation
    band gap
    mobility
    small-signal simulation
    S-parameters
    Opis:
    We present the state-of-the-art in simulation of silicon-germanium (SiGe) semiconductor devices. The work includes a detailed comparison of device simulators and current transport models. Among the critical modeling issues addressed in the paper, special attention is focused on the description of the anisotropic majority/minority electron mobility in strained SiGe grown on Si. We use a direct approach to obtain scattering parameters (S-parameters) and other derived figures of merit of SiGe heterojunction bipolar transistors (HBTs) by means of small-signal AC-analysis. Results from two-dimensional hydrodynamic simulations of SiGe HBTs are presented in good agreement with measured data. The examples are chosen to demonstrate technologically important issues which can be addressed and solved by device simulation.
    Źródło:
    Journal of Telecommunications and Information Technology; 2004, 1; 15-25
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Biosynthetic of Titanium Dioxide Nanoparticles Using Zizyphus Spina-Christi Leaves Extract: Properties
    Autorzy:
    Alobaidi, Tuqa B.
    Alwared, Abeer I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2025518.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    green synthesis
    TiO2
    Zizyphus Spina-Christi
    band gap
    XRD
    FE-SEM
    Opis:
    The present project utilizes a straightforward, inexpensive, and environmentally friendly approach to produce Titanium dioxide nanoparticles utilizing Zizyphus Spina-Christi leaves (Z-TiO2). Ultra-Spectrophotometry (UV-Vis) was used to characterize the synthesized nanoparticles, which showed the production of nanoparticles at 320 nm absorbance. To investigate functional groups, Fourier Transform Infrared Spectroscopy (FTIR) has been used. The presence of Titanium Dioxide was verified using Energy Distribution X-ray Spectroscopy (EDS). Surface area is calculated using the Brunauer Emmett Teller (BET) formula. Images from Field Emission Electron Microscopy (FE-SEM) verified the nanoparticles' spherical shape and relatively homogenous size distribution. These findings demonstrated that the production of Z-TiO2 nanoparticles was successful.
    Źródło:
    Journal of Ecological Engineering; 2022, 23, 1; 315-324
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Manufacturing process and characterization of electrospun PVP/ZnO NPs nanofibers
    Autorzy:
    Matysiak, W.
    Tański, T.
    Zaborowska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/201889.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    electrospinning
    PVP
    ZnO
    nanofibers
    band gap
    nanocomposites
    optical properties
    elektrospining
    nanowłókna
    pasmo wzbronione
    nanokompozyty
    właściwości optyczne
    Opis:
    Constantly developing nanotechnology provides the possibility of manufacturing nanostructured composites with a polymer matrix doped with ceramic nanoparticles, including ZnO. A specific feature of polymers, i.e. ceramic composite materials, is an amelioration in physical properties for polymer matrix and reinforcement. The aim of the paper was to produce thin fibrous composite mats, reinforced with ZnO nanoparticles and a polyvinylpyrrolidone (PVP) matrix obtained by means of the electrospinning process and then examining the influence of the strength of the reinforcement on the morphology and optical properties of the composite nanofibers. The morphology and structure of the fibrous mats was examined by a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) and Fourier-transform infrared spectroscopy (FTIR). UV –Vis spectroscopy allowed to examine the impact of zinc oxide on the optical properties of PVP/ZnO nanofibers and to investigate the width of the energy gap.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 2; 193-200
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fluid-fluid phononic crystal with elastic coat working in audible frequencies
    Autorzy:
    Klimek, Aleksandra
    Powiązania:
    https://bibliotekanauki.pl/articles/128012.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    phononic crystals
    band gap
    Finite Element Method
    viscoelasticity
    kryształ fononiczny
    przerwa fotoniczna
    metoda elementów skończonych
    lepkosprężystość
    Opis:
    Phononic Crystals are receiving rising attention in the field of modern acoustic materials. PCs are artificial structures of periodically arranged scatterers. Such a structure enables creating a band gap in which, due to the Bragg diffraction phenomenon, vibrations are restrained or even forbidden. In this paperwork, the fluid-fluid PC is tested and simulated - the scatterers are constructed of water cylinders with an ethylene propylene diene monomer coat (EPDM - a hyperelastic rubber) and are embedded in air. The band gap is calculated to emerge in the audible range of frequency. Every simulation is performed with the use of the finite element method.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-7
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Minimizing the number of layers of the quasi one-dimensional phononic structures
    Autorzy:
    Garus, Sebastian
    Sochacki, Wojciech
    Kubanek, Mariusz
    Nabiałek, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/2173523.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    mechanical waves
    phononic
    transfer matrix
    band gap
    genetic algorithm
    fale mechaniczne
    fononiczny
    macierz przejścia
    pasmo wzbronione
    algorytm genetyczny
    Opis:
    In the work, multi-criteria optimization of phononic structures was performed to minimize the transmission in the frequency range of acoustic waves, eliminate high transmission peaks with a small half-width inside of the band gap, and what was the most important part of the work – to minimize the number of layers in the structure. Two types of the genetic algorithm were compared in the study. The first one was characterized by a constant number of layers (GACL) of the phononic structure of each individual in each population. Then, the algorithm was run for a different number of layers, as a result of which the structures with the best value of the objective function were determined. In the second version of the algorithm, individuals in populations had a variable number of layers (GAVL) which required a different type of target function and crossover procedure. The transmission for quasi-one-dimensional phononic structures was determined with the use of the transfer matrix method algorithm. Based on the research, it can be concluded that the developed GAVL algorithm with an appropriately selected objective function achieved optimal solutions in a much smaller number of iterations than the GACL algorithm, and the value of the k parameter below 1 leads to faster achievement of the optimal structure.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 1; e139394, 1--8
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    High-performance quasi one-dimensional mirrors of mechanical waves built of periodic and aperiodic structures
    Autorzy:
    Garus, S.
    Sochacki, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/122921.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
    Tematy:
    mechanical waves
    phononic
    reflectance
    transfer matrix
    band gap
    fale mechaniczne
    struktura okresowa
    współczynnik odbicia
    macierz transferu
    pasmo wzbronione
    Opis:
    The work studied the reflectance for quasi one-dimensional phononical structures. In composite superlattices, the thickness of the layers, their arrangement and selection of constituent materials with appropriate properties such as the density and velocity of mechanical waves propagation allows for the creation of a phononic band gap (PhBG) phenomenon. PhBG is characterized by high reflectance of the mechanical wave incident on the analyzed structure, which means that the wave does not propagate in the superlattice. The paper proposes periodic and aperiodic structures characterized by a wide range of reflectance for the ultrasonic frequencies of mechanical waves and shows how the change the thickness of the layer affects the properties of the analyzed structures.
    Źródło:
    Journal of Applied Mathematics and Computational Mechanics; 2018, 17, 4; 19-24
    2299-9965
    Pojawia się w:
    Journal of Applied Mathematics and Computational Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Novel, microwave assisted route of synthesis of binary oxide semiconducting phases - PbMoO4 and PbWo4
    Nowa metoda syntezy binarnych faz tlenkowych o charakterze półprzewodnikowym w polu mikrofalowym - PbMoO4 i PbWo4
    Autorzy:
    Kwolek, P.
    Tokarski, T.
    Łokcik, T.
    Szaciłowski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/350836.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    molibdenian ołowiu
    wolframian ołowiu
    półprzewodnik
    pasmo wzbronione
    pole mikrofalowe
    lead molybdate
    lead tungstate
    semiconductor
    band gap
    microwave assisted synthesis
    Opis:
    Highly crystalline powders of lead molybdate and tungstate were synthesized by a microwave assisted hydrothermal process in a microwave heated high pressure autoclave. Application of this novel and environmentally friendly technique in the synthesis of these compounds has never been reported before. The influence of a time of synthesis on a crystal structure, morphology and a value of a band gap for both PbMoO4 and PbWO4 was examined. The value of the band gap was determined using diffuse reflectance spectroscopy. For lead molybdate the medium value of the band gap equals to ca. 3.2 eV whereas for lead tungstate it oscillates around 4 eV and does not depend on the duration time of the synthesis.
    Krystaliczne proszki molibdenianu ołowiu i wolframianu ołowiu otrzymano metodą hydrotermalną w polu mikrofalowym za pomocą wysokociśnieniowego autoklawu mikrofalowego. Metodę ta można uznać za przyjazną dla środowiska, jak dotad nie odnotowano jej zastosowania do syntezy wymienionych związków ołowiu. Zbadano wpływ czasu trwania procesu na strukturę krystaliczną, morfologię i szerokość przerwy energetycznej proszków PbWO4 i PbMoO4. Szerokość pasma wzbronionego wyznaczono za pomocą spektroskopii refleksyjnej. Dla molibdenianu ołowiu otrzymane wartości oscylują wokół 3.2 eV, natomiast dla wolframianu ołowiu przerwa energetyczna jest szersza i wynosi ok. 4 eV. Szerokość pasma wzbronionego w obu przypadkach nie zależy od czasu syntezy.
    Źródło:
    Archives of Metallurgy and Materials; 2013, 58, 1; 217-222
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Voltage reference with programmable temperature coefficient and offset voltage compensation
    Autorzy:
    Gruber, D.
    Hilber, G.
    Ostermann, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/398075.pdf
    Data publikacji:
    2011
    Wydawca:
    Politechnika Łódzka. Wydział Mikroelektroniki i Informatyki
    Tematy:
    napięcie odniesienia
    energetyczne pasmo wzbronione
    współczynnik temperaturowy
    napięcie niezrównoważenia
    kalibracja
    voltage reference
    band gap
    temperature coefficient
    offset voltage
    trimmable
    programmable
    calibration
    Opis:
    This paper demonstrates an integrated circuit for compensation of errors in voltage references, that not only is able to compensate first order changes of the temperature coefficient, but can also correct for the offset error that is unavoidable in production due to variations in process conditions and mismatches. The temperature compensation circuit is programmable via three control bits, the remaining offset error is compensated by setting eight control bits and an external provided reference voltage. The compensation procedure can be controlled by an internal digital block or via external signals. The actual calibration data can then be saved in several possible ways (EPROM, laser fuses, external Memory, ...). Extensive simulations and measurements show that the described circuit reduces the average temperature error by more than 40% and the overall absolute error by more than 90% wth regards to the uncalibrated reference voltage.
    Źródło:
    International Journal of Microelectronics and Computer Science; 2011, 2, 2; 73-80
    2080-8755
    2353-9607
    Pojawia się w:
    International Journal of Microelectronics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of spatial distribution and the type of material on the occurrence of bandgaps in phononic crystals
    Autorzy:
    Garus, Sebastian
    Sochacki, Wojciech
    Kwiatoń, Paweł
    Nabiałek, Marcin
    Petrů, Jana
    Kubanek, Mariusz
    Powiązania:
    https://bibliotekanauki.pl/articles/27311439.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    finite difference time domain
    band gap
    phononic crystal
    mechanical waves
    propagation
    domena czasowa różnic skończonych
    kryształ fononiczny
    fale mechaniczne
    propagacja
    przerwa energetyczna
    Opis:
    The study investigated the effect of the fill factor, lattice constant, and the shape and type of meta-atom material on the reduction of mechanical wave transmission in quasi-two-dimensional phononic structures. A finite difference algorithm in the time domain was used for the analysis, and the obtained time series were converted into the frequency domain using the discrete Fourier transform. The use of materials with large differences in acoustic impedance allowed to determine the influence of the meta-atom material on the propagation of the mechanical wave.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2023, 71, 3; art. no. e144609
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-14 z 14

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