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Wyświetlanie 1-8 z 8
Tytuł:
Material symmetry: a key to specification of interatomic potentials
Autorzy:
Nalepka, K.
Powiązania:
https://bibliotekanauki.pl/articles/201282.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
crystal symmetry
interatomic potentials
elasticity
phase transformations
stacking fault
Opis:
The paper shows that symmetry forms a basis for relations between different properties of material. In this way, the key quantities for specification of an atomistic model are identified. Material symmetry distinguishes representative processes of small strains. It is proved that the errors in the densities of the energies stored in these processes determine the range of inaccuracies with which an atomistic model recreates processes of small deformations. The errors are equal to the inaccuracies in the eigenvalues of the elasticity tensor, that is in the Kelvin moduli. For cubic crystals, the elementary processes indicated by the symmetry initiate the key paths of large deformations: Bain and trigonal ones. Therefore, the substantial errors in the Kelvin moduli lead to incorrect reconstructing the metastable phases: bcc, sc and bct. The elastic constants commonly used in the literature do not provide such information as the Kelvin moduli. Using the eigenvalues of the elasticity tensor as well as other key properties indicated by the symmetry, the EAM model proposed by A.F. Voter for copper is specified. The obtained potential more accurately reproduces small and large deformations and additionally, correctly describes defect formation as well as Cu dimer properties.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2013, 61, 2; 441-450
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Utilization of symmetry of solids in some experiments
Autorzy:
Kontrym-Sznajd, Grażyna
Powiązania:
https://bibliotekanauki.pl/articles/971520.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Brillouin zone (BZ)
Compton scattering experiment
crystal symmetry
electron momentum densities
lattice harmonics
Opis:
It is known that some anisotropic quantities, that describe the properties of solids, can be determined, to a reasonable accuracy, by a limited number of data along the "special directions" (SD). SDs are very useful in various theoretical and experimental investigations. Among other things, they define projections which are the most efficient to reconstruct three-dimensional (3-D) electron momentum densities from Compton scattering spectra. The concept of SDs and their power is illustrated by comparing an isotropic average of the function based on either three high-symmetry directions or even only one, but SD.
Źródło:
Nukleonika; 2013, 58, 1; 207-210
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A polarization filter at 1550 nm based on photonic crystal fiber with symmetry around gold-coated holes
Autorzy:
Zha, F.
Li, J.
Sun, P.
Wang, X.
Powiązania:
https://bibliotekanauki.pl/articles/173897.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
photonic crystal fiber
polarization filter
finite element method
surface plasmon resonance
Opis:
A polarization photonic crystal fiber based on surface plasmon resonance is proposed in this paper. The photonic crystal fiber with gold coated holes is studied through using the finite element method. The impacts of structural parameters on the resonance characteristics are discussed. Numerical simulations show that the resonance wavelength can be modulated by changing the parameters of the air holes and thickness of gold layer. At the resonance wavelength 1550 nm, the loss is 3.8045 dB/m in x-polarization and the loss is 28464 dB/m in y-polarization by adjusting the size of the gold-coated holes and the place of air holes. Results show that the loss of y-polarized mode is much larger than the loss of x-polarized mode. The y-polarized mode is suppressed, and only x-polarized mode can be guided at the resonance wavelength of y-polarized mode. The results indicate that the mode polarized in one direction can be filtered out selectively by adjusting the diameter of air holes, and the filtering effect in a communication band is achieved.
Źródło:
Optica Applicata; 2018, 48, 4; 609-620
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Symmetry of Two-Dimensional Hybrid Metal-Dielectric Photonic Crystal within Maple
Autorzy:
Chuiko, G.
Dvornik, O.
Powiązania:
https://bibliotekanauki.pl/articles/1030064.pdf
Data publikacji:
2017-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.90.+g
61.44.Br
78.66.-w
Opis:
2D-photonic crystal has the close packed hexagonal structure of metallized spheres. The selection rules are first necessary thing for understanding of interactions between differently polarized light and artificial photonic structure. This problem is the object of our paper. Known methods of group theory allow to solve such problems. However, the knowledge about symmetry of structure is the starting point of them. Usually the X-ray diffraction provides such information about natural 3D-crystals. Such assumptions so far have to do after the visual research of photonic structures in practice. Further these assumptions may be confirmed (or vice versa) by experimental research of optical response of photonic structures. We assumed that the symmetry of photonic structure is close to 2D (P6mm) group. Group-theoretical calculations were provided using the system of computer mathematics Maple. Both polarizations, normal to surface and parallel to that plane, were taken into consideration. The obtained selections rules were confirmed later by independent experiments.
Źródło:
Acta Physica Polonica A; 2017, 132, 4; 1227-1229
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Telecommunication filter based on the symmetrical photonic crystal Bg5/Cu1/Bg5
Autorzy:
Baraket, Z.
Zaghdoudi, J.
Kanzari, M.
Powiązania:
https://bibliotekanauki.pl/articles/175028.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
symmetry
telecommunication
photonic crystals
Opis:
Thanks to the transfer matrix method, we perform a theoretical investigation of the optical properties of the symmetrical photonic crystal designed as Bg5/Cu1/Bg5, where Cu1 is the first generation of the copper mean sequence and Bg5 is the fifth generation of the Bragg sequence. We design a developed polychromatic filter which allows the transmission of all the telecommunication wavelengths 0.85, 1.3, and 1.55 µm at oblique incidence for both of TE and TM polarization with a high transmission rate and high quality factor. This photonic crystal can be employed in the fabrication of telecommunication devices.
Źródło:
Optica Applicata; 2018, 48, 3; 361-371
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of circular crested waves in a micropolar porous medium possessing cubic symmetry
Autorzy:
Kumar, R.
Panchal, M.
Powiązania:
https://bibliotekanauki.pl/articles/202328.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
cubic crystal
micropolar
porous
phase velocity
attenuation coefficient
frequency equation
Opis:
The paper is concerned with the propagation of circular crested Lamb waves in a homogeneous micpropolar porous medium possessing cubic symmetry. The frequency equations, connecting the phase velocity with wave number and other material parameters, for symmetric as well as antisymmetric modes of wave propagation are derived. The amplitudes of displacement components, microrotation and volume fraction field are computed numerically. The numerical results obtained have been illustrated graphically to understand the behavior of phase velocity and attenuation coefficient versus wave number of a wave.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2011, 59, 1; 103-110
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Response of thermoelastic micropolar cubic crystal under dynamic load at an interface
Autorzy:
Ailawalia, P.
Sachdeva, S. K.
Pathania, D.
Powiązania:
https://bibliotekanauki.pl/articles/265037.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
thermoelasticity
cubic symmetry
microtemperatures
normal mode
termoelastyczność
ciało stałe
sprężystość
Opis:
The purpose of this paper is to study the two dimensional deformation in a thermoelastic micropolar solid with cubic symmetry. A mechanical force is applied along the interface of a thermoelastic micropolar solid with cubic symmetry (Medium I) and a thermoelastic solid with microtemperatures (Medium II). The normal mode analysis has been applied to obtain the exact expressions for components of normal displacement, temperature distribution, normal force stress and tangential coupled stress for a thermoelastic micropolar solid with cubic symmetry. The effects of anisotropy, micropolarity and thermoelasticity on the above components have been depicted graphically.
Źródło:
International Journal of Applied Mechanics and Engineering; 2017, 22, 1; 5-23
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Symmetry Aspects in EPR Spectra of Mn$\text{}^{2+}$ at Bi$\text{}^{3+}$ Sites in BiVO$\text{}_{4}$ Single Crystal
Autorzy:
Yeom, T. H.
Choh, S. H.
Rudowicz, Cz.
Powiązania:
https://bibliotekanauki.pl/articles/1920948.pdf
Data publikacji:
1992-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
76.30.Da
61.16.Hn
78.20.Hp
Opis:
Zero-field splitting parameters obtained from EPR X-band experiments of Baran et al. (1985) and Yeom et al. (1992) are reanalyzed. Transformation relations are derived to express the two sets of data in the same axis system. Problems arising from using a truncated zero-field splitting Hamiltonian in fitting the experimental data are elucidated. Low-symmetry aspects in EPR spectra of Mn$\text{}^{2+}$ at Bi$\text{}^{3+}$ sites in BiVO$\text{}_{4}$ single crystal are considered. Good agreement for orthorhombic parameters b$\text{}_{2}^{0}$ and b$\text{}_{2}^{2}$ is obtained indicating that the centres observed in the two cases are the same Mn centres. The remaining b$\text{}_{k}^{q}$ parameters accounting for the actual site symmetry around Mn$\text{}^{2+}$ impurity which seems to be lower than orthorhombic in the ferroelastic phase cannot be unambiguously determined from the existing EPR data.
Źródło:
Acta Physica Polonica A; 1992, 82, 3; 503-510
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-8 z 8

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