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71.
We propose two novel approaches to study the temperature dependence of the magnetization and the spin polarization at the Fermi level in magnetic compounds, and apply them to half-metallic ferromagnets. We reveal a new mechanism, where the hybridization of states forming the half-metallic gap depends on thermal spin fluctuations and the polarization can drop abruptly at temperatures much lower than the Curie point. We verify this for NiMnSb by ab initio calculations. The thermal properties are studied by mapping ab initio results to an extended Heisenberg model which includes longitudinal fluctuations and is solved by a Monte Carlo method. 相似文献
72.
Czechoslovak Mathematical Journal - The goal of this paper is to present a different approach to the homogenization of the Dirichlet boundary value problem in porous medium. Unlike the standard... 相似文献
73.
Durković M Habigt T Rothbucher M Diepold K 《The Journal of the Acoustical Society of America》2011,130(6):EL392-EL398
Sound source localization algorithms determine the physical position of a sound source in respect to a listener. For practical applications, a localization algorithm design has to take into account real world conditions like multiple active sources, reverberation, and noise. The application can impose additional constraints on the algorithm, e.g., a requirement for low latency. This work defines the most important constraints for practical applications, introduces an algorithm, which tries to fulfill all requirements as good as possible, and compares it to state-of-the-art sound source localization approaches. 相似文献
74.
B. Grabež Ž. Todorović R. Antanasijević 《Zeitschrift für Physik A Hadrons and Nuclei》1976,279(4):433-436
A silver target was exposed to 14, 18 and 23 GeV protons. The values of the cross-sections for production of events with two and three fragments have been determined by the use of a polycarbonate detector. The results obtained show that these events are due to fission as well as to fragmentation and spallation. 相似文献
75.
Sigmund EE Calder ES Thomas GW Mitrović VF Bachman HN Halperin WP Kuhns PL Reyes AP 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,148(2):309-313
We have studied the temporal instability of a high field resistive Bitter magnet through nuclear magnetic resonance (NMR). This instability leads to transverse spin decoherence in repeated and accumulated NMR experiments as is normally performed during signal averaging. We demonstrate this effect via Hahn echo and Carr--Purcell--Meiboom--Gill (CPMG) transverse relaxation experiments in a 23-T resistive magnet. Quantitative analysis was found to be consistent with separate measurements of the magnetic field frequency fluctuation spectrum, as well as with independent NMR experiments performed in a magnetic field with a controlled instability. Finally, the CPMG sequence with short pulse delays is shown to be successful in recovering the intrinsic spin--spin relaxation even in the presence of magnetic field temporal instability. 相似文献
76.
The spatial inhomogeneity of pulsed atmospheric pressure discharge in argon is investigated using the electron number density Ne diagnostics procedure applied to asymmetrically broadened Ar I lines. A dedicated fitting procedure is used for describing Ar I 703.0 nm line shape recorded from argon gas discharge and H I (at 486.13 and 656.28 nm) lines recorded from Ar-H2 gas mixture discharge. The results revealed the change in Ne in both axial and radial directions. The additional Ar I lines at 614.5, 710.7, 731.2, and 731.6 nm, recorded from integral spatial radiation, are analysed as well to confirm the results from the plasma column region. The possibility of using AlO (B2∑+–X2∑+) and CN (B2∑+–X2∑+) molecular bands for gas temperature Tg measurements in this type of gas discharge source is demonstrated and Tg used as an input parameter for the Ne diagnostics procedure. For the proper identification of molecular band spectral lines, the Fortrat parabolas are constructed. The results obtained from Ar I 703.0 nm line indicate three different Ne values, with Ne1 ≈ 0.6 × 1016 cm−3, Ne2 ≈ 3.6 × 1016 cm−3, and Ne3 ≈ 19 × 1016 cm−3 measured from the plasma column. These Ne values increase in the cathode and anode region. 相似文献
77.
M. Pavičić 《International Journal of Theoretical Physics》1993,32(9):1481-1505
It is shown that an orthomodular lattice is an ortholattice in which aunique operation of bi-implication corresponds to the equality relation and that the ordering relation in the binary formulation of quantum logic as well as the operation of implication (conditional) in quantum logic are completely irrelevant for their axiomatization. The soundness and completeness theorems for the corresponding algebraic unified quantum logic are proved. A proper semantics, i.e., a representation of quantum logic, is given by means of a new YES-NO relation which might enable a proof of the finite model property and the decidability of quantum logic. A statistical YES-NO physical interpretation of the quantum logical propositions is provided. 相似文献
78.
An analysis is given of the behavior of an interface above a stepped substrate in the presence of an external pinning potential for the lattice solid-on-solid (SOS) interface model in 2D. Step-free energy including step-step interaction free energy is calculated, for large step separation. It is found it vanishes at temperatures lower thanT
w
(wetting transition temperature), which is different from the case having only one step on a substrate where, as it is well known, step-free energy vanishes at the wetting transition. 相似文献
79.
80.
Equilibrium heat relaxation experiments provide evidence that the ground state of the commensurate spin-density-wave compound (TMTTF)2Br after the application of a sufficient magnetic field is different from the conventional ground state. The experiments are interpreted on the basis of the local model of strong pinning as the deconfinement of soliton-antisoliton pairs triggered by the Zeeman coupling to spin degrees of freedom, resulting in a magnetic-field-induced density-wave glass for the spin carrying the phase configuration. 相似文献