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ICTON Mediterranean Winter Conference

作者： Ewa Gondek Jacek Niziol Andrzej Danel Jerzy Sanetra Institute of Physics Cracow University of Technology Krakow Poland Faculty of Physics and Applied Computer Science AGH University of Science and Technology Krakow Poland Department of Chemistry Agricultural University Krakow Poland

The challenge of this work was to test two new electron donating dyes in photovoltaic cells of standard layered architecture. The active layer was a blend containing electron donating polymer poly(3-octyl)thiophene (P3OT) and a pyrazole derivative dye serving as electron acceptor. Optimized photovoltaic efficiency was observed for sample with 50% wt. load of the dye.

关键词： Photovoltaic effects Electrons Photovoltaic systems Solar power generation Organic materials Electrodes physics Chemical technology Polymers Copper

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Analyzing interactive QA dialogues using logistic regression models

Analyzing interactive QA dialogues using logistic regression...

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11th International Conference of the Italian Association for Artificial Intelligence: Emergent Perspectives in Artificial Intelligence, AI IA 2009

作者： Kirschner, Manuel Bernardi, Raffaella Baroni, Marco Dinh, Le Thanh KRDB Faculty of Computer Science Free University of Bozen-Bolzano Italy Center for Mind/Brain Sciences University of Trento Italy Institute of Formal and Applied Linguistics Faculty of Mathematics and Physics Charles University in Prague Czech Republic

ISBN: (纸本)3642102905

With traditional Question Answering (QA) systems having reached nearly satisfactory performance, an emerging challenge is the development of successful Interactive Question Answering (IQA) systems. Important IQA subtasks are the identification of a dialogue-dependent typology of Follow Up Questions (FU Qs), automatic detection of the identified types, and the development of different context fusion strategies for each type. In this paper, we show how a system relying on shallow cues to similarity between utterances in a narrow dialogue context and other simple information sources, embedded in a machine learning framework, can improve FU Q answering performance by implicitly detecting different FU Q types and learning different context fusion strategies to help re-ranking their candidate answers. © Springer-Verlag 2009.

关键词： Learning systems

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Magnetism of ultra-thin iron films seen by the nuclear resonant scattering of synchrotron radiation

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Journal of physics: Conference Series 2010年第1期217卷

作者： T Ślȩzak K Freindl A Kozioł-Rachwał K Matlak M Rennhofer R Rüffer B Sepioł N Spiridis S Stankov M Ślȩzak D Wilgocka-Ślȩzak M Zaja̧c J Korecki Faculty of Physics and Applied Computer Science AGH University of Science and Technology Al. Mickiewicza 30 30-059 Kraków Poland Institute of Catalysis and Surface Chemistry Polish Academy of Sciences ul. Niezapominajek 8 30-239 Kraków Poland Fakultät für Physik Universität Wien Strudlhofgasse 4 A-1090 Wien Austria European Synchrotron Radiation Facility BP220 F-38043 Grenoble France

Conversion electron Mössbauer spectroscopy proved in the past to be very useful in studying surface and ultrathin film magnetism with monolayer resolution. Twenty years later, its time-domain analogue, the nuclear resonant scattering (NRS) of synchrotron radiation, showed up to be by orders of magnitude faster and more efficient. The evolution of the spin structure in epitaxial 57Fe films on a tungsten W(110) was studied via the accumulation of the NRS time spectra directly during Fe film deposition. In the 0.5 – 4 monolayers Fe thickness range, the complex non-collinear magnetic structure was derived from the NRS data, resulting from the deviation from the layer by layer growth mode. For thicker Fe films, the in-plane thickness induced spin reorientation transition could be clearly identified. Based on the NRS analysis it is shown that SRT process originates at the Fe/W(110) interface and proceeds through a transient fan-like magnetization structure.

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Structural, magnetic, and Mössbauer spectral study of the icosahedral quasicrystal Zn77Fe7Sc16

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Physical Review B 2009年第22期79卷 224202-224202页

作者： K. Al-Qadi P. Wang Z. M. Stadnik J. Przewoźnik Department of Physics University of Ottawa Ottawa Ontario Canada K1N 6N5 Department of Solid State Physics Faculty of Physics and Applied Computer Science AGH University of Science and Technology 30-059 Kraków Poland

The structural, magnetic, and Mössbauer spectral properties of the icosahedral quasicrystal Zn77Fe7Sc16 are reported. The thermodynamically stable quasicrystal Zn77Fe7Sc16 has a primitive six-dimensional Bravais lattice at room temperature with a six-dimensional hypercubic lattice constant of 7.087(1) Å. Based on dc magnetization measurements, no evidence is found for a transition to a ground state with long-range magnetic order in the temperature range between 2 and 300 K. The dc zero-field-cooled and field-cooled susceptibility data indicate that the studied quasicrystal is a spin glass with freezing temperature Tf=7.75(2) K. This is further confirmed by observing aging effects through the dc zero-field-cooled magnetization and the thermoremanent magnetization time decays and by the analysis of the frequency dependence of Tf using the Vogel-Fulcher law and the dynamic scaling behavior near Tf. However, the observed increase in the thermoremanent magnetization with the magnetic field in the low-field regime is incompatible with the ultrametrically organized phase space of a canonical spin glass. The nature of the spin-glass state of the icosahedral quasicrystal Zn77Fe7Sc16 is therefore fundamentally different from that of a canonical spin glass. The bimodal distribution of the electric quadrupole splitting and of the hyperfine magnetic field derived from Mössbauer spectra indicates the existence of two classes of Fe sites.

关键词： freezing ground states iron alloys lattice constants long-range order magnetic susceptibility magnetic transition temperature Mossbauer effect quasicrystals remanence scandium alloys spin glasses zinc alloys

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Nonclassical properties of electronic states of aperiodic chains in a homogeneous electric field

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Physical Review B 2009年第3期80卷 035127-035127页

作者： B. J. Spisak M. Wołoszyn School of Physics and Astronomy University of Leeds Leeds LS2 9JT United Kingdom Faculty of Physics and Applied Computer Science AGH University of Science and Technology Aleja Mickiewicza 30 30-059 Kraków Poland

The electronic energy levels of one-dimensional aperiodic systems driven by a homogeneous electric field are studied by means of a phase-space description based on the Wigner distribution function. The formulation provides physical insight into the quantum nature of the electronic states for the aperiodic systems generated by the Fibonacci and Thue-Morse sequences. The nonclassical parameter for electronic states is studied as a function of the magnitude of homogeneous electric field to achieve the main result of this work, which is to prove that the nonclassical properties of the electronic states in the aperiodic systems determine the transition probability between electronic states in the region of anticrossings. The localization properties of electronic states and the uncertainty product of momentum and position variables are also calculated as functions of the electric field.

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Oscillatory Magnetic Anisotropy Originating from Quantum Well States in Fe Films

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Physical Review Letters 2009年第20期102卷 207206-207206页

作者： J. Li M. Przybylski F. Yildiz X. D. Ma Y. Z. Wu Max-Planck-Institut für Mikrostrukturphysik Weinberg 2 D-06120 Halle Germany Department of Physics Applied Surface Physics State Key Laboratory and Advanced Materials Laboratory Fudan University Shanghai 200433 China Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Kraków Poland

The magnetic anisotropy of Fe film grown on vicinal Ag(1,1,10) surfaces was studied with the in situ magneto-optic Kerr effect. Below 200 K, strong oscillations of the uniaxial magnetic anisotropy as a function of Fe thickness with a period of 5.7 monolayers are found, which can even cause the easy magnetization axis to oscillate between perpendicular and parallel to the steps. Such novel oscillation of the anisotropy is attributed to the quantum well states of d-band electrons at the Fermi level in the Fe film. This is unlike the previously observed oscillatory behaviors of ferromagnetic films caused by the quantum well states in nonmagnetic interfacing layers.

关键词： Magnetic anisotropy

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A simple approach to magnetoelectric correlations in ferroelectric ferromagnets: the case of BiMnO3

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AIP Conference Proceedings 2009年第1期1198卷 55-63页

作者： O. Howczak J. Spałek aMarian Smoluchowski Institute of Physics Jagiellonian University Reymonta 4 30‐059 Kraków Poland bFaculty of Physics and Applied Computer Science AGH University of Science and Technology 30‐059 Kraków Poland

We discuss a simple version of Landau theory with two single‐component order parameters, P and M, corresponding to the ferroelectric and ferromagnetic phases coupled to each other via a −|λ|P2M2 term. In the case of ferroelectricity appearing at a temperature Tf much higher than that of a ferromagnetic transition, the latter is strongly renormalized ( TM→TRM>> TM ). The thermodynamics of the model in spatially homogeneous phases is elaborated first. Our simple formulation is applied next to BiMnO3 and provides a good semiquantitative description of the magnetic and dielectric properties except for the specific heat, which is not entirely explained in the regime T≈TRM even when the Gaussian fluctuations of the order parameters are included. Possible improvements to our approach are briefly discussed.

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Selective suppression of Dresselhaus or Rashba spin-orbit coupling effects by the Zeeman interaction in quantum dots

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Physical Review B 2009年第23期79卷 235303-235303页

作者： B. Szafran M. P. Nowak S. Bednarek T. Chwiej F. M. Peeters Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Kraków Poland Departement Fysica Universiteit Antwerpen Groenenborgerlaan 171 B-2020 Antwerpen Belgium

We study single- and two-electron parabolic quantum dots in the presence of linear Dresselhaus and Rashba spin-orbit interactions. Contributions of both types of spin-orbit coupling are investigated in the context of the spin polarization of the system at high magnetic fields. We demonstrate that for negative Landé factors the effect of the Dresselhaus coupling is suppressed at high magnetic field, which for structures without inversion asymmetry leads to a completely spin-polarized system and a strict antisymmetry of the wave functions with respect to the interchange of spatial-electron coordinates. For negative Landé factor the Rashba coupling is preserved at high field and consequently the spin polarization of the systems as well as the spatial antisymmetry of the two-electron wave function remain approximate.

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Strong perpendicular anisotropy in Fe1−xCox alloy films epitaxially grown on mismatching Pd(001), Ir(001), and Rh(001) substrates

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Physical Review B 2009年第6期80卷 064415-064415页

作者： F. Yildiz M. Przybylski X.-D. Ma J. Kirschner Max-Planck-Institut für Mikrostrukturphysik Weinberg 2 06120 Halle Germany Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Kraków Poland

In tetragonally distorted Fe1−xCox alloy films grown epitaxially on Pd(001), Ir(001), and Rh(001) substrates, a strong uniaxial anisotropy and an easy-magnetization axis perpendicular to the film plane are observed. The strongest perpendicular anisotropy is achieved when the Fe0.5Co0.5 films are grown on Rh(001) (c/a=1.24) and it systematically decreases for Ir(001) (c/a=1.18) and Pd(001) (c/a=1.13) substrates in agreement with the theoretical predictions. For the Fe1−xCox films grown on Rh(001) the easy-magnetization axis remains perpendicular up to 15 ML in a broad composition range even at room temperature, which is different from the Fe1−xCox films grown on Pd(001) showing a perpendicular easy-magnetization axis only for x=0.5 and only at low temperature. By growing a pseudomorphic buffer layer of Pd on Rh(001) it is shown that the substrate lattice constant and the resulting film distortion are the factors which are decisive for the uniaxial magnetic anisotropy of the Fe1−xCox films of the same composition.

关键词： buffer layers cobalt alloys iron alloys lattice constants magnetic anisotropy magnetic thin films magnetisation

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Superconductivity in an almost localized Fermi liquid of quasiparticles with spin-dependent masses and effective-field induced by electron correlations

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Physical Review B 2009年第21期79卷 214519-214519页

作者： Jan Kaczmarczyk Jozef Spałek Marian Smoluchowski Institute of Physics Jagiellonian University ul. Reymonta 4 30-059 Kraków Poland Faculty of Physics and Applied Computer Science AGH University of Science and Technology ul. Reymonta 19 30-059 Kraków Poland

Paired state of nonstandard quasiparticles is analyzed in detail in two model situations. Namely, we consider the Cooper-pair bound state and the condensed phase of an almost localized Fermi liquid composed of quasiparticles in a narrow band with the spin-dependent masses and an effective field, both introduced earlier and induced by strong electronic correlations. Each of these novel characteristics is calculated in a self-consistent manner. We analyze the bound states as a function of Cooper-pair momentum |Q| in applied magnetic field in the strongly Pauli limiting case (i.e., when the orbital effects of applied magnetic field are disregarded). The spin-direction dependence of the effective mass makes the quasiparticles comprising Cooper-pair spin distinguishable in the quantum-mechanical sense, whereas the condensed gas of pairs may still be regarded as composed of identical entities. The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) condensed phase of moving pairs is by far more robust in the applied field for the case with spin-dependent masses than in the situation with equal masses of quasiparticles. Relative stability of the Bardeen-Cooper-Schrieffer vs FFLO phase is analyzed in detail on temperature-applied field plane. Although our calculations are carried out for a model situation, we can conclude that the spin-dependent masses should play an important role in stabilizing high-field low-temperature unconventional superconducting phases (FFLO, for instance) in systems such as CeCoIn5, organic metals, and possibly others.

关键词： cerium compounds cobalt compounds Cooper pairs effective mass electron correlations Fermi liquid heavy fermion superconductors

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