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Wyświetlanie 1-15 z 267
Tytuł:
First-principle study of structural, elastic anisotropic, and thermodynamic properties of P4̅m2-BC₇
Autorzy:
Zhang, Quan
Wei, Qun
Yan, Haiyan
Zhang, Zixia
Fan, Qingyang
Jia, Xiaofei
Zhang, Junqin
Zhang, Dongyun
Powiązania:
https://bibliotekanauki.pl/articles/1070533.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
65.40.De
62.20.de
Opis:
The structural, elastic anisotropy and thermodynamic properties of the P4̅m2-BC₇ are investigated using first-principles density functional calculations and the quasi-harmonic Debye model. The obtained structural parameters and elastic modulus are in consistency with the available theoretical data. Elastic constants calculations show that P4̅m2-BC₇ is elastic anisotropic. The bulk modulus as well as other thermodynamic quantities of P4̅m2-BC₇ (including the Grüneisen constant, heat capacity and thermal expansion) on temperatures and pressures have also been obtained.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 329-333
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The elastic anisotropic and thermodynamic properties of I4mm-B₃C
Autorzy:
Fan, Qingyang
Wei, Qun
Chai, Changchun
Yang, Yintang
Yu, Xinhai
Liu, Yang
Zheng, Junping
Zhou, Peikun
Zhang, Dongyun
Powiązania:
https://bibliotekanauki.pl/articles/1075538.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
65.40.De
62.20.de
Opis:
The structural, elastic anisotropy and thermodynamic properties of the I4mm-B₃C are investigated using first-principles calculations and the quasi-harmonic Debye model. The calculated elastic anisotropic suggest that I4mm-B₃C is elastically anisotropic with its Poisson ratio, shear modulus, the Young modulus, the universal anisotropic index, shear anisotropic factors, and the percentage of elastic anisotropy for bulk modulus and shear modulus. The quasi-harmonic Debye model, using a set of total energy versus molar volume obtained with the first-principles calculations, is applied to the study of the thermal and vibrational effects. The thermal expansions, heat capacities, the Grüneisen parameters and the Debye temperatures dependence on the temperature and pressure are obtained in the whole pressure range from 0 to 90 GPa and temperature range from 0 to 2000 K.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 103-107
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Study of the Mechanical, Thermal and Optoelectronic Properties of the Cubic CsBaF₃
Autorzy:
Harmel, M.
Khachai, H.
Haddou, A.
Khenata, R.
Murtaza, G.
Abbar, B.
Bin Omran, S.
Khalfa, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402310.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.de
65.40.Ba
65.40.De
Opis:
We have investigated the structural, elastic, electronic, optical and thermal properties of CsBaF₃ perovskite using the full-potential linearized augmented plane wave method within the generalized gradient approximation and the local density approximation. Moreover, the modified Becke-Johnson potential (TB-mBJ) was also applied to improve the electronic band structure calculations. The ground state properties such as lattice parameter, bulk modulus and its pressure derivative were calculated and the results are compared with the available theoretical data. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young's modulus and Poisson's ratio are obtained for the first time. Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron charge density. The contribution of the different bands was analyzed from the total and partial density of states curves. The different interband transitions have been determined from the imaginary part of the dielectric function. The thermal effect on the volume, bulk modulus, heat capacities $C_V$ and the Debye temperature was predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account.
Źródło:
Acta Physica Polonica A; 2015, 128, 1; 34-42
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural and Elastic Properties of Wurtzite Al-Rich In$\text{}_{x}$Al$\text{}_{1 - x}$N Alloys
Autorzy:
Łepkowski, S. P.
Gorczyca, I.
Powiązania:
https://bibliotekanauki.pl/articles/2048088.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.de
Opis:
We present theoretical study of lattice parameters and elastic constants of wurtzite Al-rich In$\text{}_{x}$Al$\text{}_{1 - x}$N (x = 0.125, 0.1875 and 0.25) alloys using self-consistent ab initio calculations with a supercell model. Two different atomic arrangements have been considered for a given x, by either distributing the In atoms as uniformly as possible over the supercell or by clustering the In atoms together in a small part of the supercell. Our calculations reveal that the a and c lattice parameters show almost linear dependence on composition for the alloys with uniform distribution of In atoms, while for the case of alloys with clustered In atoms the c lattice parameter deviates from linearity quite significantly. For the alloys with clustered In atoms, we observe that the values of C$\text{}_{11}$, C$\text{}_{12}$, and C$\text{}_{44}$ elastic constants are significantly smaller than the linear interpolated values between the elastic constants of AlN and InN, and the values of C$\text{}_{33}$ elastic constant are significantly larger than the corresponding interpolated values. For the alloys with uniform distribution of In atoms, only C$\text{}_{11}$ elastic constant deviates significantly from linear dependence on composition.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 666-668
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Enhancement of High Power High Repetition Rate Semiconductor Opening Switches
Autorzy:
Abbasi, A.
Niayesh, K.
Shakeri, J.
Powiązania:
https://bibliotekanauki.pl/articles/1807869.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
85.30.De
Opis:
High power semiconductor opening switches (SOSs) with $P^+PNN^+$ doping profile have been used in different pulsed power applications because of their fast high current interruption capability. In high pulsed power applications with high repetition rate, temperature increase of the semiconductor switch during its operation is no more negligible. In this paper, the cut-off characteristics of SOSs with different doping profiles are compared and then the impact of the temperature increase on the performance of the semiconductor opening switch is investigated using a detailed physical model. The simulation results indicate that due to the temperature increase of the switch, both the current amplitude and the cut-off characteristics of the switch are affected. Semiconductor opening switches with different base materials (Si and SiC) are studied. Due to favorable intrinsic characteristics of SiC (higher thermal conductivity, higher saturation velocity and higher breakdown electric field), the performance of the SOS can be enhanced using SiC as the base material and the design of compact high pulsed power applications can be achieved.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 983-985
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Functionalization and characterization of MWCNT produced by different methods
Autorzy:
Tomova, A.
Gentile, G.
Grozdanov, A.
Errico, M.
Paunović, P.
Avella, M.
Dimitrov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1070616.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.De
Opis:
The subject of this study is chemical functionalization as means of structural modification of multiwalled carbon nanotubes. The main goal of the experiments was to create highest density of carboxyl groups on multiwalled carbon nanotubes surface, necessary for further nanocomposite application. Two different types of multiwalled carbon nanotubes (I: outer diameter d=50÷ 100 nm, purity ≈84%, synthesized by pyrolysis and II: outer diameter d=10÷40 nm, purity ≈94%, synthesized by chemical vapor deposition) were treated by concentrated nitric acid (HNO₃) and by alkaline mixture (NH₄OH+H₂O₂). The alkaline medium as "milder" and less aggressive than nitric acid, was expected to be less destructive and cause minimal structural damage on multiwalled carbon nanotubes surface. Structural changes due to oxidation were observed by the Raman analysis, while the ratio of the intensities of the D and G peak was used to estimate the concentration of defects. Pristine and functionalized multiwalled carbon nanotubes were characterized by thermogravimetric analysis, scanning electron microscopy, ultraviolet-visible spectroscopy and zeta (ζ) spectroscopy. The results showed that functionalization initiates changes in carbon nanotubes structure as well as in their density of states. It also results in carbon nanotubes shortening and exfoliation and decreases their agglomeration tendency. Carbon nanotubes functionalized by both acid and alkaline treatment can successfully replace conventional carbon fibers as fillers in polymer composites for sensing application.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 405-408
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photocatalytic Activity of $TiO_2$ Powders Synthesized by Supercritical Gas Antisolvent Method
Autorzy:
Tuncer, M.
Ozdemir, B.
Powiązania:
https://bibliotekanauki.pl/articles/1293650.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.33.De
Opis:
Synthesis of nanocrystalline, spherical, and anatase type $TiO_2$ photocatalyst were performed by supercritical gas antisolvent process in the range of 50-150C and 100-150 bar. As-prepared samples were calcined at 500C and characterized by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller method, differential thermal analysis/thermal gravimetry. In X-ray diffraction analysis, the anatase crystalline phase of titanium dioxide has been detected. The mean crystalline size of powders is about 13 nm. The photoactivity test of the powders was evaluated by the photodegradation of aqueous RR 180 (reactive red 180) solution under UV light. While the photocatalytic performance of $TiO_2$ powders (Brunauer-Emmett-Teller surface area of 69.2 $m^2$/g) produced at 150 bar and 150C was found to be 98%, only 25% degradation was observed with powder produced at 150 bar and 100°C. Results showed that the powder properties and photocatalytic activity can be tuned by controlling the supercritical conditions such as temperature and pressure.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 608-610
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Numerical Investigation of the Effect of Cubic Crystals Orientation on the Indentation Modulus
Autorzy:
Materna, A.
Haušild, P.
Nohava, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402128.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.de
Opis:
The elastic finite element computations of the indentation process with the Berkovich indenter are performed to examine the effect of cubic crystal and indenter orientation on indentation moduli of anisotropic material. Three metals with a cubic crystal lattice and various degree of elastic anisotropy from 1 to 9 are studied: tungsten, AISI 304 steel and β -brass. Differences in anisotropy ratios expressed by the Young moduli on the one side and by the indentation moduli on the other side are quantified.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 693-696
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Numerical Synthesis of a Radar Signal Based on Iterative Method
Autorzy:
Lesnik, C.
Kawalec, A.
Szugajew, M.
Powiązania:
https://bibliotekanauki.pl/articles/1493250.pdf
Data publikacji:
2011-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.50.De
Opis:
This paper presents the impact of numerical methods used to solve the problem of synthesis of signals modulated in frequency with an autocorrelation function that implements an optimal approximation to a given autocorrelation function. After theoretical introduction an algorithm of frequency modulated signal synthesis is presented. Simulation results made in Matlab are presented in the last section.
Źródło:
Acta Physica Polonica A; 2011, 120, 4; 693-697
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Studies on Structural, Elastic, Thermodynamic and Electronic Properties of FeCrAs under Pressures
Autorzy:
He, De-Chun
Peng, Yong
He, Yong-Wei
Powiązania:
https://bibliotekanauki.pl/articles/1400506.pdf
Data publikacji:
2015-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.de
65.40.Ba
65.40.De
72.15.-v
Opis:
The structural, elastic, thermodynamic and electronic properties of nonmetallic metal FeCrAs are studied within density function perturbation theory. The thermodynamic properties of FeCrAs were deduced based on phonon frequencies within the framework of the quasiharmonic approximation. The calculated elastic modulus under various pressures indicates that FeCrAs is mechanically stable under pressure. The pressure-dependence of bulk and shear modulus, transverse and longitudinal sound velocities V (i.e. $V_{S}$ and $V_{L}$), elastic Debye temperature $\Theta_{E}$ of FeCrAs have also been investigated. The calculated values of B/G indicate that FeCrAs presents high ductility under pressure. However, it is interesting that the value of B/G reaches a maximum under 40 GPa and almost remains unchanged when the pressure is above 70 GPa. The calculations show that the heat capacity $C_{V}$ of this material is close to the Dulong-Petit limit 3R (about 224.61 J $mol^{-1} K^{-1}$) at high temperature regime. The analysis of electronic properties find that as the pressure increases, the absolute value of charge for As and Fe atom increases while Cr remains nearly a constant, indicating that the mechanic properties of FeCrAs under pressure should be mostly attributed to the interaction between Fe and As atoms.
Źródło:
Acta Physica Polonica A; 2015, 127, 6; 1637-1644
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fermi-Edge Singularity in Excitonic Spectra of Modulation Doped AlGaAs/GaAs Quantum Wells
Autorzy:
Bugajski, M.
Regiński, K.
Godlewski, M.
Wesołowski, M.
Holtz, P. O.
Buyanov, A. V.
Monemar, B.
Powiązania:
https://bibliotekanauki.pl/articles/1950741.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.+z
85.30.De
Opis:
The dynamic response of an electron Fermi sea to the presence of optically generated holes gives rise to an enhanced interaction of correlated electron-hole pairs near the Fermi level, resulting in an enhanced oscillator strength for optical transitions, referred to as the Fermi-edge singularity. We studied this effect in modulation-doped quantum wells which provide confined dense Fermi sea, spatially separated from dopant atoms, easily accessible for investigations under low excitation conditions. The Fermi-edge singularity was observed in both photoluminescence and photoluminescence excitation experiments, although in the case of photoluminescence the samples had to be either co-doped with acceptors in the wells to provide necessary localization of holes or designed to allow for nearly resonant scattering between the electronic states near the Fermi energy and the next unoccupied subband of the 2D electron gas.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 751-754
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Electrodynamical Self-Interaction
Autorzy:
Kijowski, Jerzy
Powiązania:
https://bibliotekanauki.pl/articles/1931284.pdf
Data publikacji:
1994-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.50.De
04.20.Me
Opis:
It is shown that the classical Maxwell theory admits a simple and natural renormalization of the self-interaction energy. This leads to a consistent, local and causal, relativistic theory of the Maxwell field interacting with classical, charged, point-like particles. The theory may be regarded as a simple and necessary completion of special relativity. The renormalization method proposed here is a realization of Einstein's idea of "deriving equations of motion from field equations". It is shown that Dirac's "3-dots" equation does not describe a fundamental law of physics, but only a specific family of solutions of our theory, corresponding to a specific choice of the field initial data.
Źródło:
Acta Physica Polonica A; 1994, 85, 4; 771-787
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
NMR on Surfaces: Present Achievements and Future Prospects
Autorzy:
Fick, D.
Powiązania:
https://bibliotekanauki.pl/articles/2028916.pdf
Data publikacji:
2001-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.-p
68.47.De
Opis:
β-NMR experiments with hyperpolarized $\text{}^{8}$Li adsorbed on semiconductor and metal surfaces are described (adsorption on Si(111)-(7×7), Si(111)-H, Si(111)-(1×1):H, Ru(001)). They yield detailed information on the electronic properties of these adsorbate-surface systems. Briefly a scenario using hyperpolarized Xe isotopes is sketched, which will extend the potential of the use of hyperpolarized species in NMR experiments on surfaces.
Źródło:
Acta Physica Polonica A; 2001, 100, 5; 615-627
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum-Interference Semiconductor Devices Revisited
Autorzy:
Figielski, T.
Powiązania:
https://bibliotekanauki.pl/articles/2027427.pdf
Data publikacji:
2001-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.23.-b
85.30.De
Opis:
First, a simple semiclassical approach has been applied to the problem of a quantum phase acquired by an electron carrying both the charge and spin, which travels in an electromagnetic field. Basic hypothetical devices whose operation relies on the quantum interference, including spin-related interference, are discussed in the following. Finally, experimental results demonstrating two-beam interference in a planar quantum dot are presented.
Źródło:
Acta Physica Polonica A; 2001, 99, 6; 699-708
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Retardation in Special Relativity and the Design of a Relativistic Motor
Autorzy:
Yahalom, A.
Powiązania:
https://bibliotekanauki.pl/articles/1032908.pdf
Data publikacji:
2017-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.30.+p
03.50.De
Opis:
The Newton third law states that any action is countered by a reaction of equal magnitude but opposite direction. The total force in a system not affected by external forces is thus zero. However, according to the principles of relativity, a signal cannot propagate at speeds exceeding the speed of light. Thus the total force cannot be null at a given time. The above conclusion leads to the possibility of a relativistic engine in particular one that is based on a permanent magnet. The analysis is based on a previous paper in which we studied the relativistic effects in a system of two current conducting loops.
Źródło:
Acta Physica Polonica A; 2017, 131, 5; 1285-1288
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 267

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