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Wyszukujesz frazę "Singh, S.R." wg kryterium: Autor

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    Wyświetlanie 1-7 z 7
    Tytuł:
    Effect of Temperature on Non-Destructive Wave Propagation in Uranium Monopnictides
    Autorzy:
    Singh, R.
    Singh, M.
    Chaurasia, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1808103.pdf
    Data publikacji:
    2009-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.35.Cg
    62.20.de
    62.20.D-
    Opis:
    Acoustic attenuation due to phonon-phonon interaction, thermoelastic mechanism and dislocation damping were evaluated in uranium monopnictides (viz. UN, UAs and USb) in the temperature range 50-500 K, along the three crystallographic directions of propagation, viz. [100], [110] and [111] for longitudinal and shear modes of propagation. Due to antiferromagnetic property of these compounds ultrasonic attenuation due to magnon-phonon interaction was also obtained. The second- and third-order elastic moduli of B1-type uranium monopnictides were obtained using electrostatic and the Born repulsive potentials. Gruneisen numbers and acoustic coupling constants were evaluated for longitudinal and shear waves along different directions of propagation and polarization. Results were discussed and compared with available data. It was found that the temperature dependence of attenuation due to phonon-phonon interaction and thermoelastic loss mechanisms follow the third and fourth order polynomial fit laws, respectively, and acoustic attenuation is mainly governed by phonon-phonon interaction in this temperature range.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 3; 664-670
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dielectric and Ac Conductivity Studies of Mn-Doped $Na_{1.86}Li_{0.10}K_{0.04}Ti_3O_7$ Ceramics
    Autorzy:
    Singh, R.
    Shripal, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1206481.pdf
    Data publikacji:
    2014-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.Bg
    72.20.Ee
    72.60.+g
    77.22.-d
    77.22.Gm
    77.22.Jp
    Opis:
    Dielectric-spectroscopic and ac conductivity studies on 0.01 and 1.0 molar percentage manganese doped layered $Na_{1.86}Li_{0.10}K_{0.04}Ti_3O_7$ ceramics have been reported. The dependence of loss tangent (tan δ) and relative permittivity ($ε_{r}$) on temperature in the range 350-775 K and on frequency in the range 10 kHz-1 MHz have been undertaken. The losses are the characteristics of dipole mechanism, electrical conduction and space charge polarization. The obtained conductivity plots between log($σ_{ac}T$) versus 1000/T have been divided into four regions namely region I, II, III, and IV. The mechanism of conduction in region I is acknowledged to electronic hopping conduction. The less frequency and more temperature dependent region II is ascribed as a mixed mechanism "associated interlayer ionic conduction, electron hopping, and alkali ion hopping conduction". The unassociated interlayer ionic conduction along with alkali ion hopping conduction mechanisms are contributing to the transport process in the mid temperature region III. The mechanism of conduction in the highest temperature region IV may be recognized as the modified interlayer ionic conduction. The conductivity versus frequency curves lead to conclude that the electronic hopping conduction diminishes with the rise of temperature.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 1; 67-72
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ultrasonic Attenuation in Alloys
    Autorzy:
    Kor, S. K.
    Singh, R. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1929339.pdf
    Data publikacji:
    1993-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.20.Dc
    62.65.+k
    Opis:
    Ultrasonic attenuation was evaluated in metallic alloys, Ni$\text{}_{x}$Cu$\text{}_{1-x}$ (x = 1.00, 0.70, 0.60, 0.45 and 0) due to phonon-phonon (p-p) interaction and thermoelastic loss in a wide temperature region along ⟨110⟩ crystallographic direction for longitudinal and shear waves. Ultrasonic Grüneisen parameters, nonlinearity constants and ultrasonic attenuation due to p-p interaction and thermoelastic loss were determined from 50 K to 500 K using the Born-Mayer and electrostatic potentials. The results were compared with available experimental results.
    Źródło:
    Acta Physica Polonica A; 1993, 83, 6; 751-758
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride
    Autorzy:
    Singh, S.
    Chauhan, R.
    Gour, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492770.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    64.70.K-
    62.20.de
    62.50.-p
    Opis:
    We have carried out high pressure theoretical structural studies of yttrium nitride to examine the phase transition phenomena from the NaCl structure to CsCl structure by using a three-body potential model. The phase transition pressure (140 GPa) predicted by this approach is close to the phase transition pressure, predicted by others (138 GPa). Yttrium nitride is a novel and less explored material. Under high pressure yttrium nitride goes through a sudden collapse in volume showing the first order phase transition. To understand the effect of pressure we studied bulk properties, elastic constants and their combination. The pressure volume equation of state provides meaningful signatures of physical and chemical phenomena under high pressure. Moreover we have successfully checked the stability criterion for this compound.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6; 1021-1025
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ultrasonic Attenuation in Dielectric Crystals
    Autorzy:
    Kor, S. K.
    Singh, R. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1891964.pdf
    Data publikacji:
    1991-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.20.Dc
    62.65.+K
    Opis:
    Ultrasonic attenuation and non-linearity parameters have been evaluated for dielectric crystals RbCl, RbBr and RbI in a wide temperature range. Basic physical parameters, nearest neighbour distance and hardness parameters of the substance and Coulomb and Born-Mayer potentials have been used to obtain ultrasonic attenuation due to phonon-viscosity mechanism along (100) direction of propagation for longitudinal and shear waves. Results are as expected and it has been concluded that ultrasonic attenuation is a fundamental property of the substance.
    Źródło:
    Acta Physica Polonica A; 1991, 80, 6; 805-810
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of van Hove Singularity on T$\text{}_{c}$ in Rb doped C$\text{}_{60}$
    Autorzy:
    Agrawal, B. K.
    Agrawal, S.
    Yadav, P. S.
    Srivastava, P.
    Srivastava, R.
    Singh, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2035748.pdf
    Data publikacji:
    2003-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.25.Jb
    74.62.Fj
    74.70.Wz
    Opis:
    In the present study we investigate the role of van Hove singularity on the optimization of T$\text{}_{c}$ in Rb doped fullerenes C$\text{}_{60}$ Rb$\text{}_{3}$. A first principles self-consistent full potential linear muffin-tin orbital method using density functional theory in local density approximation was employed. The doped Rb atoms are of two types occupying the tetrahedral and interstitial positions in the fcc lattice. The added Rb atoms fill the t$\text{}_{1u}$ band of the undoped fullerenes C$\text{}_{60}$ up to half which makes C$\text{}_{60}$Rb$\text{}_{3}$ conducting. Saddle points leading to van Hove singularities are observed in the neighbourhood of the symmetry point L. The shifting of the van Hove singularity with the volume of the lattice is investigated. We observe a saddle point just at the Fermi level for a lattice constant of 14.435Å. The highest value of T$\text{}_{c}$ should thus be observed at the above lattice constant. This result is in excellent agreement with the observed high value of T$\text{}_{c}$ measured in C$\text{}_{60}$Rb$\text{}_{3}$ for a lattice constant of 14.435Å.
    Źródło:
    Acta Physica Polonica A; 2003, 103, 5; 477-482
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Leaching of Al-Based Polygrain Quasicrystalline and Related Crystalline Surfaces
    Autorzy:
    Yadav, T.
    Mishra, S.
    Pandey, S.
    Singh, D.
    Lowe, M.
    Tamura, R.
    Mukhopadhyay, N.
    Srivastava, O.
    McGrath, R.
    Sharma, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1373698.pdf
    Data publikacji:
    2014-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.44.Br
    81.16.Hc
    61.66.Dk
    68.37.Hk
    Opis:
    In the present investigation, we have studied leaching on polygrain Al-based quasicrystalline $(i-Al_{63}Cu_{25}Fe_{12})$ as well as crystalline (B2 phase; $Al_{55}Cu_{30}Fe_{15})$ alloy surfaces using a 10 mole NaOH solution. The surface was leached at varying times from 30 min to 8 h and subsequently characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis. Leaching of the samples for 30 min generated a homogeneous layer. However further leaching for 1-8 h yielded nano-size particles on the surface. Spherical microstructure has been observed on the Al-Cu-Fe crystalline surface whereas on the quasicrystalline surface a petal-like microstructure appeared. The implications of the evolution of different microstructures in the context of structure, stability and activity are discussed. The results are compared with the microstructure of leached polygrained samples containing a mixture of different surface orientations.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 2; 629-632
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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