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1
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Differential Reflection Spectroscopy: A Novel Method for Explosive Detection

100%
Yuksel S., Dubroca T., Hummel R., Gader P.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
263-264
EN
In the aftermath of the recent terrorist attacks, there has been an increasing need for automated, high-speed detection technologies that can detect trace amounts of explosives without human intervention. Our group at the University of Florida has developed differential reflection spectroscopy which can detect explosive residue on surfaces such as parcel, cargo and luggage. In this differential reflection device, explosives show spectral finger-prints at specific wavelengths, for example, the spectrum of 2,4,6, trinitrotoluene shows an absorption edge at 420 nm. Additionally, we have developed a support vector machine based computer software to classify the explosives and non-explosive materials. In this study we will (i) describe this system and give an insight into the operation of our prototype, (ii) demonstrate our software for the detection of the spectral finger-prints, and (iii) discuss the normalization of the data which significantly increases classification rates and decreases the number of parameters.
2
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Evolution from the BCS to the Bose-Einstein Limit in a d-Wave Superconductor at T=0

80%
Borkowski L., Sá de Melo C.
Acta Physica Polonica A
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2001
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vol. 99
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issue 6
691-698
EN
We study the evolution from BCS to Bose limit in a two-dimensional d-wave superconductor at zero temperature and low density of charge carriers within the mean-field theory. We examine single quasiparticle properties when particle density and attraction strength are varied. For sufficiently high interaction strength there is a critical density below which the system has a gap. The spectral and thermodynamic properties of the system do not evolve smoothly from the BCS-like to the Bose-like regime.
3
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Substrate Temperature Influenced Structural and Electrical Behaviour of~RF Magnetron Sputtered Ag_2Cu_2O_3 Films

80%
Sreedhar A., Hari Prasad Reddy M., Uthanna S., Martins R., Elangovan E., Pierson J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-37-A-39
EN
Ag_2Cu_2O_3 films were deposited on glass and silicon substrates by RF magnetron sputtering of metallic equimolar (Ag_{50}Cu_{50}) alloy target in Ar-O_{2} mixture at different substrate temperature (T_{s}) ranging between 303 and 523 K. The effect of T_{s} on the core level binding energies, structural and electrical properties of the films was systematically studied. The films deposited at room temperature were amorphous. The films deposited at 373 K were polycrystalline and the crystallinity was increased when the T_{s} was increased to 423 K. The films deposited at 423 K and subsequently annealed at 498 K exhibits single phase Ag_2Cu_2O_3. In the case of films deposited at higher T_{s} of 523 K, Ag_2O was decomposed into Ag. The electrical resistivity of the films deposited at 303 K was 1.2 × 10^{-5} Ω cm, whereas the films formed at 423 K and subsequently annealed at 498 K showed electrical resistivity of 2.2 × 10^{-3} Ω cm due to improvement in the crystallinity of single phase Ag_2Cu_2O_3.
4
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Raman Scattering Study of (Sr,Ca)_{10}Cu_{17}O_{29} Single Crystals

80%
Strzeszewski J., Szymczak H., Leonyuk L., Szymczak R.
Acta Physica Polonica A
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2000
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vol. 98
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issue 4
429-439
EN
Polarized Raman spectra of high temperature superconducting single crystals of A_{10}Cu_{17}O_{29} (A_{10}=Ca_{4.7}Sr_{4.1}Bi_{0.3}) were studied in various scattering configurations in the range of 40-700cm^{-1}. In very distinctive spectra there were found over 20 peaks. It was observed that the flat continuum of electronic excitations in the normal state was redistributed below the critical temperature. The frequency dependent redistribution is consistent with the value of energy gap estimated using tunnelling spectroscopy techniques.
5
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Interpretation of Switching Properties of InGaSe_2 Single Crystal

80%
Al Orainy R.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
666-672
EN
The goal of this paper is to present experimental results of the switching effect and analyze qualitatively the influence of various factors, such as temperature, light illumination and sample thickness on switching behavior of the high quality ternary chalcogenide semiconductor InGaSe_2. Current-controlled negative resistance of InGaSe_2 single crystals has been observed for the first time. It has been found that indium gallium diselenide single crystals exhibit bistable or memory switching. The switching process takes place with both polarities on the crystal and has symmetric shapes. Current-voltage characteristics of Ag-InGaSe_2-Ag structures exhibit two distinct regions, high resistance OFF state and low-resistance ON state having negative differential resistance. InGaSe_2 is a ternary semiconductor exhibiting S-type I-V characteristics. The specimen under test showed threshold switching with critical field of the switching being 10^3 V/cm at room temperature.
6
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Optical and Optoelectronic Properties of ZnS Nanostructured Thin Film

80%
Borah J., Sarma K.
Acta Physica Polonica A
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2008
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vol. 114
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issue 4
713-719
EN
ZnS nanocrystalline thin films were grown into the polyvinyl alcohol matrix and were synthesized by chemical route. Films were prepared on glass substrate by varying the deposition parameters and pH of the solution. Nanocrystalline thin film prepared under optimum growth conditions shows band gap value 3.88 eV as observed from optical absorption data. The band gap is found to be higher (3.88 eV) indicating blue shift. The particle size, calculated from the shift of direct band gap, due to quantum confinement effect is 5.8 nm. Photoluminescence spectrum shows the blue luminescence peaks (centered at 425 nm), which can be attributed to the recombination of the defect states. ZnS nanocrystalline thin films are also found to be photosensitive in nature. However, the photosensitivity decreases due to ageing and exposure to oxygen. In case of nanostructured film, the I-V characteristics are observed in dark and under illumination showing photosensitive nature of these films, too. The dark current, however, is found to be greater when observed in vacuum compared to air. Both dark current and photocurrent are found to be ohmic in nature up to a certain applied bias. The observed data shows that nanostructured films are found to be suitable for device application. The surface morphology of the film is also characterized by scanning electron microscope.
7
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Optical Responses in Asymmetric Inverse Parabolic Quantum Wells: Effects of Laser Fields and Hydrostatic Pressure

80%
Mora-Ramos M., Morales A., Duque C.
Acta Physica Polonica A
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2014
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vol. 125
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issue 2
202-204
EN
We report the theoretical calculation of the electronic states in a Al_{x}Ga_{1-x}As-based quantum well with inverse parabolic confinement under the combined effects of the intense laser field and hydrostatic pressure. Calculations are in the effective mass and parabolic band approximations and using a variational procedure and the so-called Floquet method in order to obtain the energies and wave functions for the conduction band states. We use the obtained information to investigate the intersubband-related nonlinear optical absorption and optical rectification coefficients.
8
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Quantization of Electromagnetic Modes in a Hyperbolic Negative-Index Layered Superconductor Slab

80%
Cortés-López S., Pérez-Rodríguez F.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
641-644
EN
We theoretically study the infrared reflectivity and transmissivity of a high-temperature layered superconductor slab. Both infrared spectra exhibit very narrow Fabry-Perot resonances associated with the quantization of the wave vector of the TM electromagnetic modes. The resonances are observed in a pass band where the refractive index of the layered superconductor is negative. The pass band of negative dispersion is above the Josephson plasma frequency which appears in the expression for the effective permittivity component, corresponding to the direction perpendicular to the layers. It was found that the Fabry-Perot resonances undergo a blue shift as the slab thickness or the angle of incidence are increased. Moreover, the quantized electromagnetic modes turn out to be quasi-longitudinal because of the strong anisotropy of the infrared dielectric response of the layered superconductor.
9
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Luminescence Properties of Manganese Doped CdS Nanoparticles under Various Synthesis Conditions

80%
Salimian S., Farjami Shayesteh S.
Acta Physica Polonica A
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2010
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vol. 118
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issue 4
633-636
EN
An aqueous solution method has been developed for synthesizing size-controlled Mn^{2+} doped CdS nanocrystals with a relatively narrow size distribution. The nanocrystal samples were characterized by UV-Vis absorption spectra and photoluminescence spectra. We prepared narrow size distribution particles under different synthesis conditions. The effect of manganese concentration on the photoluminescence properties was investigated. Luminescence intensity in different excitation wavelength correlates with different size of CdS:Mn nanocrystals on luminescence spectra. We found that by narrowing the size distribution and doping concentration, CdS samples can be prepared with high luminescence intensity.
10
Content available remote

Electron Behaviour of (Nd_{0.33}Eu_{0.2}Gd_{0.47})Ba_2Cu_3O_{y} Studied by Infrared Measurements

80%
Rameš M., Železný V., Phuoc V., Gervais F., Wolf T., Jirsa M.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
938-939
EN
Optical properties of a are (Nd_{0.33}Eu_{0.2}Gd_{0.47})Ba_2 Cu_3O_y (NEG-123) single crystal interpreted in terms of the extended Drude model.
11
Content available remote

Electro-Optical Properties of II-VI Superlattices

70%
Schillak P., Czajkowski G.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
301-304
EN
We show how to compute electro-optical spectra of semiconductor superlattices in the region of interband electronic transitions. The method uses the microscopic calculation of eigenvalues and eigenfunctions and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities. The electron-hole screened Coulomb potential is adapted and the valence band structure is taken into account in the cylindrical approximation, thus separating light- and heavy-hole motions. We calculate the electro-optical functions, including the optical Stokes parameters and ellipsometric functions for the case of oblique incidence. Results are given for Zn_{1-x}Cd_xSe/ZnSe superlattices and a good agreement with experiments is obtained.
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