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71.
Zhijun Yi Tingyu LiuQiren Zhang Yuanyuan Sun 《Journal of Electron Spectroscopy and Related Phenomena》2006
The electronic structures of PbWO4 crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F+ centers in PbWO4 crystals. 相似文献
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73.
光谱相似性测度是高光谱遥感影像定量化分析和精细地物直接识别的基础,光谱特征的选择和刻画方式是光谱相似性测度的关键.研究表明,利用光谱的单一特征无法全面反应地物光谱间的相似性,光谱识别时需要综合考虑光谱的多种特征.本文在几何距离、相关系数和相对熵的基础上提出了一种结合多种光谱特征的新型光谱相似性测度,即光谱泛相似测度(s... 相似文献
74.
75.
针对基于经典动力学理论传统模型中忽略扩散效应的问题,通过对基于玻尔兹曼理论的场效应管传输线模型的理论分析,建立了包含扩散效应的太赫兹互补金属氧化物半导体(CMOS)场效应管探测器理论模型,研究扩散效应对场效应管电导及响应度的影响.同时,将此模型与忽略了扩散效应的传统模型进行了对比仿真模拟,给出了两种模型下的电流响应度随温度及频率变化的差别.依据仿真结果,并结合3σ原则明确了场效应管传输线模型中扩散部分省略的依据和条件.研究结果表明:扩散部分引起的响应度差异大小主要由场效应管的工作温度及工作频率决定.其中工作频率起主要作用,温度变化对差异大小影响较为微弱;而对于工作频率而言,当场效应管工作频率小于1 THz时,模型中的扩散部分可以忽略不计;而当工作频率大于1 THz时,扩散部分不可省略,此时场效应管模型需同时包含漂移、散射及扩散三个物理过程.本文的研究结果为太赫兹CMOS场效应管理论模型的精确建立及模拟提供了理论支持. 相似文献
76.
W. G. Kong Alian Wang John J. Freeman Pablo Sobron 《Journal of Raman spectroscopy : JRS》2011,42(5):1120-1129
The identification of iron sulfates on Mars by the Mars Exploration Rovers (MERs) and the Mars Reconnaissance Orbiter emphasized the importance of studying iron sulfates in laboratory simulation experiments. The copiapite group of minerals was suggested as one of the potential iron sulfates occurring on the surface and subsurface on Mars, so it is meaningful to study their spectroscopic features, especially the spectral changes caused by cation substitutions. Four copiapite samples with cation substitutions (Fe3+, Al3+, Fe2+, Mg2+) were synthesized in our laboratory. Their identities were confirmed by powder X‐ray diffraction (XRD). Spectroscopic characterizations by Raman, mid‐IR, vis‐NIR and laser‐induced‐breakdown spectroscopy (LIBS) were conducted on those synthetic copiapite samples, as these technologies are being (and will be) used in current (and future) missions to Mars. We have found a systematic ν1peak shift in the Raman spectra of the copiapite samples with cation substitutions, a consistent atomic ratio detection by LIBS, a set of systematic XRD line shifts representing structural change caused by the cation substitutions and a weakening of selection rules in mid‐IR spectra caused by the low site symmetry of (SO4)2− in the copiapite structures. The near‐infrared (NIR) spectra of the trivalent copiapite species show two strong diagnostic water features near 1.4 and 1.9 µm, with two additional bands near 2.0 µm. In the vis‐NIR spectra, the position of an electronic band shifts from 0.85 µm for ferricopiapite to 0.866 µm for copiapite, and this shift suggests the appearance of a Fe2+ electronic transition band near 0.9 µm. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
77.
We use the transfer matrix method and the Green function technique to theoretically study the quantum tunnelling through a DNA-type molecule. Ferromagnetic electrodes are used to produce the spin-polarized transmission probability and therefore the spin current. The distance-dependent crossover comes from the topological variation from the one-dimensional to the two-dimensional model transform as we switch on the interstrand coupling; a new base pair will present N-1 extrachannels for the charge and spin as N being the total base pairs. This will restrain the decay of the transmission and improve the stability of the quantum transport. The spin and charge transfer through the DNA-type molecule is consistent with the quantum tunneling barrier. 相似文献
78.
本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi2Te3-xSex体系中各原子自旋轨道耦合(SOI)的p1/2修正对体系性质的影响,并对Bi2Te3-xSex(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi2S
关键词:
2Te3-xSex(x≤3)同晶化合物')" href="#">Bi2Te3-xSex(x≤3)同晶化合物
第一性原理
电子结构
自旋轨道耦合 相似文献
79.
Speech recognition in noise improves with combined acoustic and electric stimulation compared to electric stimulation alone [Kong et al., J. Acoust. Soc. Am. 117, 1351-1361 (2005)]. Here the contribution of fundamental frequency (F0) and low-frequency phonetic cues to speech recognition in combined hearing was investigated. Normal-hearing listeners heard vocoded speech in one ear and low-pass (LP) filtered speech in the other. Three listening conditions (vocode-alone, LP-alone, combined) were investigated. Target speech (average F0=120 Hz) was mixed with a time-reversed masker (average F0=172 Hz) at three signal-to-noise ratios (SNRs). LP speech aided performance at all SNRs. Low-frequency phonetic cues were then removed by replacing the LP speech with a LP equal-amplitude harmonic complex, frequency and amplitude modulated by the F0 and temporal envelope of voiced segments of the target. The combined hearing advantage disappeared at 10 and 15 dB SNR, but persisted at 5 dB SNR. A similar finding occurred when, additionally, F0 contour cues were removed. These results are consistent with a role for low-frequency phonetic cues, but not with a combination of F0 information between the two ears. The enhanced performance at 5 dB SNR with F0 contour cues absent suggests that voicing or glimpsing cues may be responsible for the combined hearing benefit. 相似文献
80.
Seong Yong Yoon Hoo San LeeSok Hyun Kong Hoon Sang Oh 《Journal of magnetism and magnetic materials》2007
We studied the magnetic and noise properties with various soft underlayer (SUL) types. For an as-deposited SUL, the results of spectrum, oscilloscope waveform and MFM indicated that the SUL types with IrMn pinning layer have more noise level than that of SUL types without IrMn pinning layer. And, after magnetic filed annealing along radial direction of disk, the exchange bias field increased and the noise level of type B (exchange bias type) decreased. These results reveal that incomplete or partial coupling may be generated at the interface between IrMn and ferromagnetic layer in as-deposited SUL. This incomplete coupling may result in complex or multidomain patterns in ferromagnetic layer. 相似文献