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Wyszukujesz frazę "bandgap" wg kryterium: Temat


Wyświetlanie 1-8 z 8
Tytuł:
The Effect of Layer Thickness on the Reflectance of a Quasi One-Dimensional Composite Built with Zr55Cu30Ni5Al10 Amorphous Alloy and Epoxy Resin
Autorzy:
Garus, Sebastian
Sochacki, Wojciech
Powiązania:
https://bibliotekanauki.pl/articles/2049717.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
amorphous alloy
aperiodic multilayer
mechanical waves
phononic crystal
bandgap
Opis:
The study examined the impact of the angle of incidence of mechanical waves on various types of quasi one-dimensional superlattice. Binary periodic structure, quasi-periodic distribution of Thue-Morse layers and Severin’s aperiodic multilayer were used. Using the concatenation and recursive rules, the distribution of layers was determined for individual structure types for generation numbers equal to 3, 4 and 5. The structures were selected so that the thickness of the composite was the same for each type of distribution for a given generation number value. Transfer Matrix Method algorithm was used to determine reflectance. The band structure of reflectance has been demonstrated for incidence angles up to 90 degrees at mechanical wave frequencies up to 50 kHz. The existence of wide bands of high reflectance above the acoustic frequencies was demonstrated for the analyzed structures. Increasing the layer thickness caused an inhomogeneous shifts of transmission peaks towards lower frequencies.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 2; 503-510
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photonic crystal fibre characterisation with the method of lines
Autorzy:
Goncharenko, I.A.
Marciniak, M.
Powiązania:
https://bibliotekanauki.pl/articles/308198.pdf
Data publikacji:
2004
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
optical crystal fibres
photonic bandgap
method of lines
Opis:
Photonic crystal fibres are longitudinally uniform fibres in which in lateral directions periodic refractive index changes occur. Two basically different light guiding mechanisms occur in crystal fibres: index guiding and bandgap guiding. In the paper different modelling methods have been evaluated when applied to photonic crystal fibres. In particular, the method of lines has been shown to be effective and reliable for both classes of photonic crystal fibres. High accuracy results for optical field distribution and dispersion characteristics in a photonic crystal fibre have been achieved with the method of lines.
Źródło:
Journal of Telecommunications and Information Technology; 2004, 1; 106-111
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Analysis of a Directive Antenna with a 3D-EBG Superstrate
Autorzy:
Pajewski, L.
Frezza, F.
Marciniak, M.
Piuzzi, E.
Rossi, G. V.
Powiązania:
https://bibliotekanauki.pl/articles/307787.pdf
Data publikacji:
2017
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
directivity enhancement
electromagnetic bandgap materials
Fabry-Perot cavities
periodic structures
woodpile
Opis:
A three-dimensional electromagnetic crystal is employed as a directivity-enhancing superstrate for planar antennas. The crystal is a woodpile made of alumina rods. In a shielded anechoic chamber, the performance of a patch antenna covered with the woodpile is measured. The superstrate is positioned at different distances from the antenna and its orientation is varied in the 8–12 GHz frequency range. The return loss, gain and radiation pattern in the E- and H-planes are measured. The electromagnetic behavior of Fabry-Perot cavities with woodpile mirrors, equivalent to the compound radiator, is also studied. The main effect of the crystal on the antenna performance is an enhancement of about 10 dB in maximum gain. A rather complete series of experiments is presented, highlighting the role of the periodic structure in the directivity enhancement and allowing a deeper understanding of the electromagnetic phenomena involved in EBG resonator antennas. Benefits and disadvantages of this kind of antennas are discussed and ideas for future research are given.
Źródło:
Journal of Telecommunications and Information Technology; 2017, 3; 113-124
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Nitridation and Pre-Growth Annealing of the Sapphire Substrate on the Quality of Zinc Oxide Thin Films Grown by RF-Magnetron Sputtering
Autorzy:
Baseer Haider, M.
Powiązania:
https://bibliotekanauki.pl/articles/1032562.pdf
Data publikacji:
2017-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
thin films
wide bandgap semiconductors
ZnO
magnetron sputtering
Opis:
ZnO has attracted much attention due to its wide bandgap (3.2 eV) and high exciton binding energy of 60 meV. These properties make ZnO a highly desirable material for high frequency devices that can work in harsh environment. We have grown ZnO thin films at different temperatures ranging from 100°C to 500°C. We have observed that surface roughness is first decreased with the increase in the growth temperature but then by further increasing the growth temperature beyond 300°C, results in increased surface roughness of the grown samples, whereas grain size of the samples increases with the increase in the growth temperature. Crystalline quality of the films is also improved with the increase in the growth temperature but then degrades by further increase beyond 200°C. We achieved the highest Hall mobility for the ZnO sample grown at 200°C. The optimum growth condition of ZnO thin films on sapphire (0001) in our RF/DC magnetron-sputtering unit were achieved for the films grown at 200°C. Subsequently, we performed pre-growth treatment to the sapphire substrate then grew ZnO films at 200°C. Pre-growth treatment involved heating the substrate at 500°C for about half an hour and then etching the sapphire surface with nitrogen plasma. We have observed that pre-growth heating and nitridation of the sapphire substrate results in bigger grain size whereas no improvement was observed in the crystallinity of the film.
Źródło:
Acta Physica Polonica A; 2017, 132, 4; 1325-1328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Lattice Damage and Recovery of Rare-Earth implanted Wide Bandgap Oxides
Autorzy:
Sarwar, Mahwish
Ratajczak, Renata
Ivanov, Vitalii
Mishra, Sushma
Turek, Marcin
Wierzbicka, Aleksandra
Woźniak, Wojciech
Guziewicz, Elżbieta
Powiązania:
https://bibliotekanauki.pl/articles/2204945.pdf
Data publikacji:
2022
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
wide bandgap oxides
zinc oxide
gallium oxide
rare earth
ion implantation
Rutherford backscattering spectrometry
low temperature photoluminescence
Opis:
Rare earth (RE) elements are important for the optical tuning of wide bandgap oxides (WBO) such as β-Ga2O3 or ZnO, because β-Ga2O3:RE or ZnO:RE show narrow emission lines in the visible, ultra-violet and infra-red region. Ion implantation is an attractive method to introduce dopant into the crystal lattice with an extraordinary control of the dopant ion composition and location, but it creates the lattice damage, which may render the dopant optically inactive. In this research work, we investigate the post-implantation crystal lattice damage of two matrices of wide-bandgap oxides, β-Ga2O3 and ZnO, implanted with rare-earth (RE) to a fluence of 5 x 10^14, 1 x 10^15 and 3 x 10^15 atoms/cm^2, and post-growth annealed in Ar and O2 atmosphere, respectively. The effect of implantation and annealing on both crystal lattices was investigated by channeling Rutherford backscattering spectrometry (RBS/C) technique. The level of crystal lattice damage caused by implantation with the same RE fluences in the case of β-Ga2O3 seems to be higher than in the case of ZnO. Low temperature photoluminescence was used to investigate the optical activation of RE in both matrices after performed annealing.
Źródło:
Advances in Science and Technology. Research Journal; 2022, 16, 5; 147--154
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Broadside coupled stripline with double-side UC-PBG structure
Autorzy:
Meissner, P.
Kitliński, M.
Powiązania:
https://bibliotekanauki.pl/articles/309389.pdf
Data publikacji:
2005
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
UC-PBG
uniplanar photonic bandgap
coupler
3 dB coupler
broadside coupled line coupler
stripline coupler
slow-wave effect
photonic
PBG bandgap
electromagnetic band gap
EBG
Opis:
A stripline waveguide with double-side UC-PBG pattern is considered. To verify usefulness of the stripline structure with UC-PBG a 3 dB coupler has been designed and fabricated. Reduction of the coupler size (due to slow wave effect) has been predicted and observed. Numerical and experimental investigation confirmed enhanced backward coupling phenomena.
Źródło:
Journal of Telecommunications and Information Technology; 2005, 2; 61-64
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bandgap properties in locally resonant phononic crystal double panel structures with periodically attached pillars
Autorzy:
Qian, D.
Shi, Z.
Powiązania:
https://bibliotekanauki.pl/articles/280927.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
bandgap property
phononic crystal double panel
band structure
displacement field
transmission power spectrum
Opis:
The locally resonant (LR) phononic crystal double panel structure made of a two-dimensional periodic array of a two-component cylindrical LR pillar connected between the upper and lower plates is proposed, and the bandgap properties of the structure are investigated theoretically in this paper. The band structures, displacement fields of eigenmodes and transmission power spectrums of the corresponding 8×8 finite structure are calculated by the finite element method. Numerical results and further analysis demonstrate that a band gap with a low starting frequency and a wide band width is opened by the coupling between dominant vibrations of the pillars and plate modes of the upper and lower plates when the vibration source and the receiver are considered on different sides of the structure. By comparing the band structures and displacement fields of the double panel and those of the single plate with the same parameters, many common characteristics are displayed. Then, the influence of geometrical parameters on the band gap are studied and understood with the help of a simple ‘spring-mass’ model.
Źródło:
Journal of Theoretical and Applied Mechanics; 2017, 55, 4; 1167-1179
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Photonic-Crystal Selective Filter
Autorzy:
Pajewski, L.
Schettini, G.
Powiązania:
https://bibliotekanauki.pl/articles/308475.pdf
Data publikacji:
2017
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
filter
Fourier Modal Method
periodic structures
photonic bandgap materials
photonic crystals
Opis:
A highly selective filter is designed, working at 1.55 μm and having a 3-dB bandwidth narrower than 0.4 nm, as is required in Dense Wavelength Division Multiplexed systems. Different solutions are proposed, involving photonic crystals made rectangular- or circular-section dielectric rods, or else of holes drilled in a dielectric bulk. The polarization and frequency selective properties are achieved by introducing a defect in the periodic structure. The device is studied by using in-house codes implementing the full-wave Fourier Modal Method. Practical guidelines about advantages and limits of the investigated solutions are given.
Źródło:
Journal of Telecommunications and Information Technology; 2017, 3; 107-112
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-8 z 8

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