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    Wyświetlanie 1-14 z 14
    Tytuł:
    Calculation of Optical Parameters of Liquid Crystals
    Autorzy:
    Kumar, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1814025.pdf
    Data publikacji:
    2007-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.20.-e
    78.20.Ci
    78.20.Fm
    77.84.Nh
    Opis:
    Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 6; 1213-1221
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrical Transport and Electronic Structure Calculation of Al-Ga Binary Alloys
    Autorzy:
    Kumar, A.
    Ojha, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505365.pdf
    Data publikacji:
    2011-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.15.Cz
    76.60.Cq
    71.20.-b
    71.22.+i
    Opis:
    The Harrison first principle pseudopotential technique based on the concept of orthogonalized plane waves has been used to study the liquid electrical resistivity and other physical properties viz., Knight shift, Fermi energy and electronic density of states of liquid binary alloys of simple metals. We have also performed a first-principles calculation of the electronic band structure of Al-Ga binary alloy at equiatomic composition employing the full-potential linearized augmented plane wave method. Total energy minimization enables us to estimate the equilibrium volume, bulk modulus and its pressure derivative. We have also described the total density of states and the partial density of states around the Fermi energy.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 3; 408-415
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    First Principle Investigations on Electronic, Magnetic, Thermodynamic, and Transport Properties of TlGdX₂ (X = S, Se, Te)
    Autorzy:
    Gautam, R.
    Kumar, A.
    Singh, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032602.pdf
    Data publikacji:
    2017-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    semiconductors
    electronic structure
    magnetic properties and thermodynamic properties
    Opis:
    In the present research paper, we investigated spin polarized electronic, magnetic, thermodynamic, and transport properties of thallium gadolinium dichalcogenides TlGdX₂ (X = S, Se, Te) using density functional theory. Electronic structure reveals that all the three compounds are wide band gap semiconductors which are beneficial for good thermoelectric performance. Calculated magnetic moment of TlGdX₂ is found to be in good agreement with available experimental values and mainly dominant by Gd³⁺ ions. Semiclassical Boltzmann transport theory has been used to calculate the Seebeck coefficient and electrical conductivity for the proposed dichalcogenides. Calculated values of the Seebeck coefficient and electrical conductivity are found to be consistent with available experimental values in literature. Thermodynamic properties of TlGdX₂ have also been estimated for the first time and explained on the basic facts.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 4; 1371-1378
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Quantitative Approach for the Determination of Light Induced Defects in $a-Se_{90}Sb_{10-x}Ag_x$ Thin Films by Using Thermally Stimulated Current Technique
    Autorzy:
    Kumar, Anjani
    Tripathi, S.
    Kumar, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398969.pdf
    Data publikacji:
    2016-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.55.Jv
    72.80.Ng
    Opis:
    Thin films of $Se_{90}Sb_{10-x}Ag_x$ (x=0, 2, 4, 6, 8) glasses have been prepared by vacuum evaporation technique. Present study reports the quantitative estimation of light induced defects in aforesaid thin films by using thermally stimulated current technique. Measurements have been made in a vacuum ≈10¯³ Torr before and after exposing amorphous films to white light for different exposure times (0 to 6 h). Results indicate that light induced defects are created due to prolonged exposure of light and this is explained by a microscopic model proposed by Shimakawa and co-workers. It is also found that fractional increase in light induced defect density decreases as Ag concentration increases. A discontinuity has, however, been observed at 4 at.% of Ag which is explained in terms of average coordination number.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 6; 1178-1183
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Collision cascade and spike effects of X-ray irradiation on optoelectronic devices
    Autorzy:
    Salleh, S.
    Abdul Amir, H.
    Kumar Tiwari, A.
    Pien Chee, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/1065735.pdf
    Data publikacji:
    2016-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    24.10.-i
    25.45.De
    25.45.Hi
    32.80.-t
    32.80.Fb
    Opis:
    Bombardment with high energy particles and photons can cause potential hazards to the electronic systems. These effects range from degradation of performance to functional failure, which can affect the operation of a system. Such failures become increasingly likely as electronic components are getting more sophisticated, while decreasing in size and tending to a larger integration. In this paper, the effects of X-ray irradiation on a plastic encapsulated infrared light emitting diode, coupled to a plastic encapsulated silicon infrared phototransistor, with both of them being electrically isolated at ON and OFF modes, are investigated. All the devices are exposed to a total dose of up to 1000 mAs. The electrical parameters of the optoelectronic devices during the radiation exposure and at post-irradiation are compared to the pre-irradiation readings. The findings show that the highest degradation occurs at low dose of exposure; beyond 100 mAs the relative decrease in collector current of the phototransistor is gradually reduced. The most remarkable feature found, is the operational dependence of the bias collector current, indicating a higher degradation for low bias forward current of the light emitting diode. The degradation induced at the forward current of the light emitting diode by X-rays irradiation is almost negligible whereas a decrease of the rate of change in current transfer ratio is significant during the X-ray irradiation. The results show that there is no significant difference between current transfer ratio of ON mode and OFF mode radiation. It is observed that the operating mode of the optoelectronic devices after exposure to 1000 mAs of X-ray irradiation contributes no major variation in the degree of damage.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 1; 93-97
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Point Spread Function of Asymmetrically Apodized Optical Systems with Complex Pupil Filters: The One-Dimensional Case with Slit Aperture
    Autorzy:
    Keshavulu Goud, M.
    Komala, R.
    Naresh Kumar Reddy, A.
    Goud, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1419735.pdf
    Data publikacji:
    2012-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.25.Fx
    42.30.Kq
    42.79.Ci
    Opis:
    Aimed at high resolution, an asymmetric point spread function has been obtained with good and bad sides by introducing three level asymmetric pupil functions. The good side has decreased side lobes while the bad side has increased side lobes. The asymmetry has been found to increase with the width of the edge strips within the slit aperture. On the other hand, there does not appear dependence of the asymmetry of the point spread function on the degree of amplitude apodization. But the magnitude of reduction of optical side-lobes is found to increase to a great extent by the amplitude apodization.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 1; 90-95
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamics of Shallow Water Waves with Various Boussinesq Equations
    Autorzy:
    Kumar, H.
    Malik, A.
    Singh Gautam, M.
    Chand, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033427.pdf
    Data publikacji:
    2017-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    Solitons
    exact solutions
    Boussinesq equation
    Opis:
    Attempt has been made to construct the solitary waves and shock wave solutions or domain walls (in higher dimension) for various Boussinesq equations. The method of undetermined coefficients have been used to explore the exact analytical solitary waves and shock wave solutions in terms of bell-shaped sech^p function and kink-shaped tanh^p function for the considered equations. The Boussinesq equation in the (1+1)-dimensional, the (2+1)-dimensional and the (3+1)-dimensional equations are studied and the parametric constraint conditions and uniqueness in view of both solitary waves and shock wave solutions are determined. Such solutions can be valuable and desirable for explaining some nonlinear physical phenomena in nonlinear science described by the Boussinesq equations. The effect of the varying parameters on the development of solitary waves and shock wave solutions have been demonstrated by direct numerical simulation technique.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 2; 275-282
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Core-Shell Mechanocomposites of Drugs with Inorganic Oxides and Hydroxides
    Autorzy:
    Shakhtshneider, T.
    Myz, S.
    Boldyreva, E.
    Nizovskii, A.
    Kumar, Rakesh
    Powiązania:
    https://bibliotekanauki.pl/articles/1375599.pdf
    Data publikacji:
    2014-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.25.-g
    Opis:
    The composites of piroxicam and meloxicam with gamma-alumina, aluminium hydroxides (gibbsite and boehmite), alpha and gamma polymorphs of iron(III) oxide having different surface area and morphology were prepared by planetary ball-milling. It has been shown that the initial state of the excipient (specific surface area, particle size and morphology) had a pronounced effect on the formation of the core-shell composites with the drugs and their properties. The X-ray diffraction patterns and IR spectra measured for co-milled samples as well as X-ray photoelectron spectroscopy studies gave evidence that the components of the mixtures interacted with each other and became amorphous, as composites were formed. The drug release from the composites was different as compared with pure drugs, meloxicam and piroxicam behaving differently that can be explained by formation of strong or weak bonds with the active sites of the carriers. In the case of mechanocomposites, the drugs dissolved quickly due to high surface of organic phase in the core-shell composites. The high-porous carriers can serve as the sorbents for the drugs in solution.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 4; 1019-1024
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Synthesis of $Fe_4[Fe(CN)_6]_3$·$14H_2O$ Nanopowder by Co-Precipitation Technique and Effect of Heat Treatment
    Autorzy:
    Rohilla, S.
    Lal, B.
    Sunder, S.
    Aghamkar, P.
    Kumar, S.
    Aggarwal, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535871.pdf
    Data publikacji:
    2010-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.07.-b
    64.70.Nd
    61.82.Rx
    Opis:
    Nanopowder of iron cyanide hydrate (member of Prussian blue family) was obtained using ferric chloride and potassium cyanide in their dilute solution through co-precipitation method. The effect of thermal annealing on iron cyanide hydrate nanocrystallites have been studied in detail. The formation of $Fe_4[Fe(CN)_6]_3$·$14H_2O$ and iron oxides was revealed by the Fourier transform infrared spectroscopy. The crystal structure, morphology and size of nanocrystallites were investigated by X-ray diffraction and transmission electron microscope. Results suggest that using co-precipitation technique, nanopowder of iron cyanide hydrate, in typically spherical shape, can be obtained and their thermal treatment also yield iron oxide nanocrystallites of spherical with good homogeneity. The size of the prepared nanocrystallites was found in the range 20-36 nm. It was observed that thermal treatment, typically at 800°C (4 h), iron cyanide hydrate ($Fe_4[Fe(CN)_6]_3$·$14H_2O$) nanocrystallites transformed into iron oxide ($α-Fe_2O_{3,}$ hematite) nanocrystallites.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 4; 696-700
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Vibrational Spectroscopy of H_2O by Lie Algebraic Methods
    Autorzy:
    Karumuri, S.
    Srinivas, G.
    Sunil Babu, K.
    Sundara Siva Kumar, V.
    Hanumaiah, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399490.pdf
    Data publikacji:
    2013-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    03.65.Fd
    02.20.Sv
    33.20.Ea
    Opis:
    An algebraic model of coupled anharmonic oscillators is introduced, capable of describing the stretching vibrations of medium-size molecules. This model is applied to the calculation of O-H vibrational modes of water molecules. In this paper, we have reported the stretching and bending vibrational energy levels of water molecule using the algebraic and density functional theory method. The results obtained by theoretical models show good agreement with the experimental values.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 1; 3-5
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mechanochemical Preparation of Organic-Inorganic Hybrid Materials of Drugs with Inorganic Oxides
    Autorzy:
    Shakhtshneider, T.
    Myz, S.
    Dyakonova, M.
    Boldyrev, V.
    Boldyreva, E.
    Nizovskii, A.
    Kalinkin, A.
    Kumar, Rakesh
    Powiązania:
    https://bibliotekanauki.pl/articles/1503409.pdf
    Data publikacji:
    2011-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.25.-g
    Opis:
    The nanocomposites of piroxicam and meloxicam with alumina were obtained by ball-milling as a result of distribution of the drugs at the surface of oxide with formation of the stable composites. The observed changes in the IR spectra of the ball-milled mixtures suggested the interaction of the drugs with the alumina active surface sites. The functional groups in molecules of piroxicam and meloxicam involved into formation of bonds between the drugs and the surface of the oxide were determined, they are amide, sulfate, enol groups, and pyridyl / thiazolyl nitrogen atoms. It appears that the formation of the new bonds at the contacts of particles in the composite leads to the stabilization of the drugs in metastable state inhibiting their transformation into initial crystalline form.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 2; 272-278
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Embedded Solitons and Conservation Law with $χ^{(2)}$ and $χ^{(3)}$ Nonlinear Susceptibilities
    Autorzy:
    Savescu, M.
    Kara, A.
    Kumar, S.
    Krishnan, E.
    Zaka Ullah, M.
    Moshokoa, S.
    Zhou, Qin
    Biswas, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398312.pdf
    Data publikacji:
    2017-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    solitons
    χ^{(2)}
    conservation laws
    Opis:
    This paper studies embedded solitons that are confined to continuous spectrum, with $χ^{(2)}$ and $χ^{(3)}$ nonlinear susceptibilities. Bright and singular soliton solutions are obtained by the method of undetermined coefficients. Subsequently, the Lie symmetry analysis and mapping method retrieves additional solutions to the model such as shock waves, singular solitons, cnoidal waves, and several others. Finally, a conservation law for this model is secured through the Lie symmetry analysis.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 2; 297-303
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural and Optical Behaviour οf~Ni Doped CdS Nanoparticles Synthesized by Chemical Co-Precipitation Method
    Autorzy:
    Siva Kumar, K.
    Divya, A.
    Sreedhara Reddy, P.
    Uthanna, S.
    Martins, R.
    Elangovan, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492639.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.05.Cp
    61.72.-y
    78.55.Et
    78.67.Bf
    Opis:
    Pure and Ni (2 at.%) doped cadmium sulfide (CdS) nanoparticles have been synthesized by chemical co-precipitation method at room temperature. Effect of Ni doping on CdS compound semiconductors has been analyzed using X-ray diffractometer, transmission electron microscope, energy dispersive spectroscopy, Raman and optical absorption studies. X-ray diffraction study confirmed the structure of the obtained nanoparticles to be single-phase zinc blende with the diffractions from (111), (220) and (311) planes. Energy dispersive spectroscopy study confirmed the presence of Ni in the CdS lattice. The average particle size obtained from the transmission electron microscopy studies are in agreement with the crystallite size calculated from X-ray diffraction data. The optical studies exhibited a clear red shift of absorption edge as a function of Ni doping.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6A; A-052-A-054
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Investigation of the Cu Ions Diffusion into Bulk Lithium Niobate
    Autorzy:
    Sugak, D.
    Syvorotka, I.
    Yakhnevych, U.
    Buryy, O.
    Martynyuk, N.
    Ubizskii, S.
    Zhydachevskyy, Ya.
    Suchocki, A.
    Kumar, H.
    Janyani, V.
    Singh, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030967.pdf
    Data publikacji:
    2018-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    66.30.-h
    78.20.-e
    Opis:
    Spatial changes of optical properties of bulk LiNbO₃ crystal were investigated after annealing in CuO powder. The incorporation of copper ions into the crystal was confirmed by registration of additional absorption spectra that revealed formation of the absorption bands of both Cu⁺ (400 nm) and Cu²⁺ (1000 nm) ions. The changes of optical absorption caused by thermal treatment were registered along the direction of diffusion by the probe beam perpendicular to this direction. The anisotropy of diffusion was revealed. The maxima were observed on the depth dependences of additional absorption both for the wavelengths of 400 and 1000 nm for all main crystallographic directions. The concentrations of copper ions were calculated in accordance with the Smakula-Dexter formula. The X-ray diffraction study revealed reflexes which probably belong to CuNb₂O₆, CuNbO₃ and CuO. The halo was observed on these diffraction patterns that confirms the formation of the scattering centers (about 1 nm in diameter) in the near-surface region.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 4; 965-972
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-14 z 14

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