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91.
We report a systematic study of the spin polarization of epitaxial CrO2 films at and across an interface using planar junctions with a superconducting counterelectrode. By chemical modification of the CrO2 surface before the deposition of the superconductor, junctions with a wide range of barrier strength were obtained. Analysis of the conductance data on these junctions, especially under Zeeman splitting of the superconducting density of states, yields consistent, close to full spin polarization for CrO2 regardless of the barrier strength. 相似文献
92.
93.
Jigang Yin Yin Hang Lianhan Zhang Jing Xiong Pengchao Hu 《Journal of luminescence》2010,130(8):1338-1342
The electronic structures of LiYF4 (YLF) crystals containing F color center (YLF-F) and Yb doped YLF crystals (Yb3+:YLF, Yb2+:YLF) are systematically studied within the framework of the density functional theory. The calculated results indicate that the 330 nm absorption band originates from the F center in YLF crystals. Thus the doping of Yb3+ can weaken the 330 nm absorption band by competing with F vacancies in capturing free electrons arising after γ-irradiation and change to Yb2. By analyzing the lattice relaxation and the electronic structure of YLF containing Yb2+, we can reasonably believe that once Yb2+ is formed in YLF crystal, its compensating hole will turn out to be shared by two F− nearest to Yb2+ forming a diatomic fluoride molecular ion () perturbed by Yb2+, or to say VF color center. According to the molecular-orbital linear combination of atomic orbital (MO-LCAOs) theory, compared to the alkali halides, e.g. LiF, the in VF center in LiYF4 peaks at about 340 nm, which is in agreement with the experimental results. 相似文献
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95.
简述了聚氧化乙烯介质中的铽、铕、铥、钆、钇、镓、锰掺杂的硫化锌纳米晶的制备方法以及紫外吸收光谱、激发光谱和光激发发射光谱.制成的硫化锌纳米晶直径为3.0~3.5nm. 相似文献
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以硬焊料传导制冷,30%填充因子半导体激光器阵列为例,建立了三维有限元模型,对阵列内部各发光单元之间的热串扰行为进行了分析研究。结果表明,当其连续波工作时间大于1.2 ms后,阵列内发光单元之间出现热串扰现象;当次热沉由CuW合金改为铜金刚石复合材料时,阵列内发光单元自热阻和相邻发光单元的串扰热阻降低,有效地降低了各发光单元之间的热串扰行为。保持阵列宽度、发光单元数目及发光单元周期不变,发现随阵列填充因子的增加,器件热阻以指数衰减趋势逐渐降低,而发光单元间的热串扰特性对此变化并不敏感;保持阵列单个发光单元输出功率,发光单元尺寸及阵列宽度不变,增加发光单元个数后,阵列内各发光单元之间热串扰加剧,填充因子越高阵列升温速率越快;但在最初约70 s内,包含不同数目发光单元的阵列最高温度差异仅约0.5 ℃,有利于多发光单元高填充因子器件高功率输出。 相似文献
98.
Lei Wang Jun Shen Xiao Yin Yujun Du Yilong Xiong Hengzhi Fu 《Applied Physics A: Materials Science & Processing》2013,112(2):363-370
The effects of melt flow driven by a travelling magnetic field (TMF) on solidification structures of Sn–1.8 wt.% Cd peritectic alloy have been investigated numerically and experimentally. Numerical results indicate that the flow velocity at the solid–liquid interface under a downward TMF is smaller than that under an upward TMF. The experimental results show that the growth directions of dendrites are chaotic, and several crotches among the dendrites are observed at the solid–liquid interface in the case of no field. It is concluded from TMF results that the ordered growth of dendrites at two different directions occurs, and only one crotch among the dendrites appears at the solid–liquid interface. The location of the crotch gradually approaches the interface center with increasing magnetic field intensity (B≤10.3 mT). Moreover, the growth of high-order branches occurs at the crotch under a downward TMF. A simple model is established for explanation and it well corresponds to the experimental results. 相似文献
99.
100.
We propose subject matter expert refined topic (SMERT) allocation, a generative probabilistic model applicable to clustering freestyle text. SMERT models are three‐level hierarchical Bayesian models in which each item is modeled as a finite mixture over a set of topics. In addition to discrete data inputs, we introduce binomial inputs. These ‘high‐level’ data inputs permit the ‘boosting’ or affirming of terms in the topic definitions and the ‘zapping’ of other terms. We also present a collapsed Gibbs sampler for efficient estimation. The methods are illustrated using real world data from a call center. Also, we compare SMERT with three alternative approaches and two criteria. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献