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991.
L. S. Lima A. S.T. Pires 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):335-342
In this paper we study the dynamics of the two-dimensional XY model with single-ion anisotropy, and spin S = 1, in the large
D phase, and low temperatures, using the bond operator formalism. The in-plane structure factor is a delta function. The out
of plane shows a three peak structure, which merges in a single peak at the Brillouin zone boundary. We analyze also spin
currents generated by a magnetic field gradient. The spin conductivity is calculated, at finite temperature, using the Kubo
formula. The model shows unconventional ballistic spin transport at finite temperature. The computed spin conductivity exhibits
a nonzero Drude weight at finite temperature. For ω< 2m, where m is the energy gap, the spin conductivity is described solely
by the Drude weight. There is a regular contribution to the spin conductivity for ω> 2m, which persist in the zero temperature
limit. The conductivity at the critical point, and for small frequencies, is (gμB)2/ħ times a universal scaling function of ħω/kB T. 相似文献
992.
应用平面电磁波理论和菲涅耳公式分析了电磁波穿透不同介质的衰减特性,对不同的极化方式、入射角、介电常数、电导率、损耗角正切和频率下,电磁波在介质间的透射性能及介质中的传输衰减特性进行了分析,对常见的普通混凝土墙、37砖墙、24砖墙、石膏空心板、水泥泡沫板、木板和玻璃与频率的衰减特性进行了数值仿真,比较了新砌混凝土墙、实心粘土砖墙和多孔粘土砖墙的损耗特点,将仿真结果与实际测量及参考文献测量结果进行了比较,结果表明仿真的墙体频率衰减趋势与实际测量结果一致,衰减数值接近并略低于实测结果。 相似文献
993.
994.
995.
C. Kunz B.C.C. Cowie W. Drube T.-L. Lee S. Thiess C. Wild J. Zegenhagen 《Journal of Electron Spectroscopy and Related Phenomena》2009
We used hard X-ray photoelectron spectroscopy (HAXPES) with 8 keV X-rays to investigate the 1s emission of carbon. We recorded spectra extending from the peak of the C 1s electrons (“elastic” line) to electrons with up to 110 eV energy-loss. Using two samples side by side, we could compare the inelastic mean free paths (IMFPs) of the electrons of almost 8 keV in diamond and graphite and find them to be practically identical despite about 50% difference in densities. Published extrapolations of their IMFP calculations at lower energies are in good agreement with this result. We show that information from the almost structureless region of overlapping multiple extrinsic energy-losses can be used to quantify the fraction of photoelectrons experiencing intrinsic energy-losses (those due to the sudden creation of the hole). We find that this fraction is 58% of the primary excited C 1s electrons for diamond and is practically the same for graphite. This is at first sight an unexpected result since hole-screening should differ in a semimetal from that in an insulator. The observation can be accounted for by dynamic screening in contrast to static screening. 相似文献
996.
In this paper, complex phasor (CP) method is employed in digital holographic interferometry. Unlike commonly used digital phase subtraction (DPS), the proposed technique processes a CP instead of phase. It is shown that the results obtained by directly filtering the phase produce large errors. It is demonstrated that the phase is not a signal but rather a property of a signal. In addition, the results obtained by the CP method are also compared with those obtained by conventional sine/cosine transformation method. 相似文献
997.
We present a novel reference compensation method for eliminating environmental noise in interferometric wavelength shift demodulation for dynamic fiber Bragg grating (FBG) sensors. By employing a shielded wavelength-division-multiplexed reference FBG in the system, the environmental noise is measured from the reference channel, and then subtracted from the demodulation result of each sensor channel. An approximate 40 dB reduction of the environmental noise has been experimentally achieved over a frequency range from 20 Hz to 2 kHz. This method is also suitable for the elimination of broadband environmental noise. The corresponding FBG sensor array system proposed in this paper has shown a wavelength resolution of . 相似文献
998.
Dynamical theory of electron scattering is used to describe the electron transport in the surface regions of crystals. The angle resolved attenuation length of electrons is derived from the transmitted LEED electron current decay. Electron attenuation length energy dependence and anisotropy in polar angle are found for crystalline Cu(1 1 1) for two high symmetry azimuths. Pronounced anisotropy in polar angle distributions of attenuation lengths is found to be in qualitative agreement with the results obtained from the photoelectron diffraction. Comparison with the attenuation lengths obtained from semiclassical simulations for amorphous copper is given. This comparison demonstrates that simple transfers of the smoothly behaving surface sensitivity from amorphous materials oversimplifies the electron attenuation process and can lead to incorrect results in quantitative analyses of crystalline surfaces. 相似文献
999.
1000.