455 research outputs found
Degenerate Series Representations of the -Deformed Algebra
The q-deformed algebra is a real form of the q-deformed
algebra , , which differs from the quantum
algebra of Drinfeld and Jimbo. We study
representations of the most degenerate series of the algebra . The formulas of action of operators of these representations upon
the basis corresponding to restriction of representations onto the subalgebra
are given. Most of these representations
are irreducible. Reducible representations appear under some conditions for the
parameters determining the representations. All irreducible constituents which
appear in reducible representations of the degenerate series are found. All
-representations of are separated in the set of
irreducible representations obtained in the paper.Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and
Applications) at http://www.emis.de/journals/SIGMA
Direct comparison of the performance of CZT detectors contacted with various metals
Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good
energy resolution over the broad energy range from several keV into the MeV
energy range. In this paper we present the results of a systematic study of the
performance of CZT detectors manufacturered by Orbotech (before IMARAD)
depending on surface preparation, contact materials and contact deposition. The
standard Orbotech detectors have the dimension of 2.0 x 2.0 x 0.5 cm. They have
a pixellated In anode with 8 x 8 pixels and a monolithic In cathode. Using the
same CZT substrates several times, we have made a direct comparison of the
performance of different contact materials by replacing the cathode and/or the
anode contacts with several high-workfunction metals. We present the
performance of the detectors and conclude with an overview over our ongoing
detector optimization.Comment: 8 pages, 5 figures, to appear in the proceedings of the conference
5922, "Hard X-Ray and Gamma-Ray Detector Physics VII" on the "Optics &
Photonics 2005" SPIE Symposium, July 31- August 4, 2005, San Diego, C
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A short survey of discourse representation models
With the advancement of technology and the wide adoption of ontologies as knowledge representation formats, in the last decade, a handful of models were proposed for the externalization of the rhetoric and argumentation captured within scientific publications. Conceptually, most of these models share a similar representation form of the scientific publication, i.e. as a series of interconnected elementary knowledge items. The main differences are given by the terminology used, the types of rhetorical and/or argumentation relations connecting the knowledge items and the foundational theories supporting these relations. This paper analyzes the state of the art and provides a concise comparative overview of the five most prominent discourse representation models, with the goal of sketching an unified model for discourse representation
Above-light-line Nonlinear Surface Polaritons near a Conductive Interface: Threshold Case
We investigate the TM-polarized nonlinear surface polaritons (NLSP) propagating along aguided structure consisting of a magnetic optically linear medium and a non-magnetic opticallynonlinear medium with saturable permittivity separated by a flat conductive layer of zerothickness. We consider those values of hosting media bulk material parameters for which theNLSP existence (for zero sheet conductance) has threshold character with respect to the wavesintensity. Based on the exact solution of Maxwell's equations we show that the energy andpropagation properties of the NLSP near the above-light-line condition (1 > n > 0) dependconsiderably on the surface conductivity of the layer, even the threshold character of the NLSPcan be lost; for certain sheet conductance values these waves can exist in a linear limit. TheNLSP propagation constant is defined by both the surface conductivity and field intensity andcan be varied in a wide diapason, which gives an opportunity to obtain and control the importantfor quantum information processing 0 n condition. For a chosen value of the NLSPpropagation constant the NLSP field intensity and energy flux decries when the surfaceconductivity grows; saturation of the nonlinear permittivity leads to an increase of the NLSPenergy flux compared with Kerr-like nonlinearity
Characterization of the Oxides Present in a Polydimethylsiloxane Layer Obtained by Polymerisation of Its Liquid Precursor in Corona Discharge
By combining the reflection-absorption infrared spectral studies with the peak fitting analysis we determined the type of the silicon oxides present in polydimethylsiloxane layers obtained on germanium and aluminium substrates in corona discharges. We have also evidenced that the dependence of silicon oxides density on the corona discharge current intensity is related to the existence of a concurrent anodizing process occurring at the polymer/Al substrate interface. The morphology of the Al substrate surface investigated by scanning electron microscopy proved that the anodizing process occurs
Thick CZT Detectors for Space-Borne X-ray Astronomy
Cadmium Zinc Telluride (CZT) detectors are having a major impact on the field
of hard X-ray astronomy. Without the need for cryogenic cooling they achieve
good spatial and energy resolutions over the broad energy range from 10 keV to
600 keV. In this paper, we briefly review the historical development of
detectors used in X-ray astronomy. Subsequently, we present an evaluation of
CZT detectors from the company Imarad. The standard 2x2x0.5 cm detectors,
contacted with 8x8 In pixels and an In cathode, exhibit FWHM energy resolutions
of 7 keV at 59 keV, and 10 keV at 662 keV. A direct measurement of the 662 keV
photopeak efficiency gives 67%. We have started a detailed study of the
performance of Imarad detectors depending on surface preparation, contact
materials, contact deposition, post-deposition detector annealing, and detector
passivation techniques. We present first results from contacting detectors with
Cr, Ag, Au, and Pt.Comment: Invited Contribution to the 49th International Symposium on Optical
Science and Technology (SPIE), August 2004, Denver, CO, SPIE, 49, 5540,
13.01. (2004
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FeCr₂S₄ in magnetic fields: possible evidence for a multiferroic ground state.
We report on neutron diffraction, thermal expansion, magnetostriction, dielectric, and specific heat measurements on polycrystalline FeCr2S4 in external magnetic fields. The ferrimagnetic ordering temperatures TC ≈ 170 K and the transition at TOO ≈ 10 K, which has been associated with orbital ordering, are only weakly shifted in magnetic fields up to 9 T. The cubic lattice parameter is found to decrease when entering the state below TOO. The magnetic moments of the Cr- and Fe-ions are reduced from the spin-only values throughout the magnetically ordered regime, but approach the spin-only values for fields >5.5 T. Thermal expansion in magnetic fields and magnetostriction experiments indicate a contraction of the sample below about 60 K. Below TOO this contraction is followed by a moderate expansion of the sample for fields larger than ~4.5 T. The transition at TOO is accompanied by an anomaly in the dielectric constant. The dielectric constant depends on both the strength and orientation of the external magnetic field with respect to the applied electric field for T < TOO. A linear correlation of the magnetic-field-induced change of the dielectric constant and the magnetic-field dependent magnetization is observed. This behaviour is consistent with the existence of a ferroelectric polarization and a multiferroic ground state below 10 K
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