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81.
At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves(KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90° pitch angle is observed throughout the flux rope, where intense KAWs are identified. The KAWs can effectively trap electrons by the wave parallel electric field and the magnetic mirror force, allowing electrons to undergo Landau resonance and be transported into more field-aligned directions. The pitch angle range for the trapped electrons is estimated from the wave analysis, which is in good agreement with direct pitch angle measurements of the electron distributions. The newly formed beam-like electron distribution is unstable and excites whistler waves,as revealed in the observations. We suggest that KAWs could be responsible for the plasma depletion inside a flux rope by this transport process, and thus be responsible for the formation of a typical flux rope. 相似文献
82.
海杂波的多普勒谱建模对采用多普勒处理技术的雷达进行有效的海杂波抑制和目标检测具有重要的意义.本文分别考虑Bragg,白冠和破碎波三种散射机制对应的多普勒谱分量的特征,对三种谱分量的频移和展宽进行分离,并引入附加速度频移量,提出了基于不同散射机制特征的雷达海杂波时变多普勒谱模型.该模型假设谱强度为受观测时间区间影响的随机变量,能够同时适用于平均多普勒谱与短时多普勒谱建模.通过分别对黄海海域实测的岸基P,S波段海杂波平均多普勒谱与短时多普勒谱建模测试,结果表明该模型相对传统模型的建模精度更高,尤其体现在短时谱的观测时间较长和平均谱形式较为复杂的情况下,建模误差显著减小. 相似文献
83.
In this paper, five factors, namely the HF (hydrofluoric acid)
concentration, field strength, illumination intensity as well as the
oxidizing-power and conductivity of electrolytes were found to
strongly affect the fast pore etching. The oxidizing power of
aqueous HF electrolyte of different concentrations was especially
measured and analysed. A positive correlation between optimal bias
and HF concentration was generally observed and the relationship was
semi-quantitatively interpreted. Pore density notably increased with
enhanced HF-concentration or bias even on patterned substrates where
2D (two-dimensional) nuclei were densely pre-textured. The etch rate
can reach 400μm/h and the aspect ratio of pores can be
readily driven up to 250. 相似文献
84.
Enhancing redshift phenomenon in time-resolved photoluminescence spectra of AlGaN epilayer
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AlGaN epitaxial layer has been studied by means of temperature-dependent time-integrated photoluminescence(PL)and time-resolved photoluminescence(TRPL). An enhancing redshift phenomenon in TRPL spectra with increasing temperature was observed, and the localized excitons behaved like quasi two-dimensional excitons between 6 K and 90 K. We demonstrated that these behaviors are caused by a change in the carrier dynamics with increasing temperature due to the competition of carriers' localization and delocalization in the AlGaN alloy. 相似文献
85.
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87.
高效液相色谱法分析高吸水性树脂中的丙烯酸单体 总被引:1,自引:0,他引:1
建立了一种快速测定高吸水性树脂中丙烯酸单体残留的高效液相色谱法,采用常见的Agilent XDB-C18柱(250mm×4.6mm,5μm),流动相为甲醇-0.1%H_3PO_4水溶液,检测波长为210nm,外标法定量。试样的加标浓度为0.50、5.0、20.0μg/mL时,加标回收率在76.0%—97.5%之间,RSD≤3.27%;方法的检出限为60.0ng/mL,线性范围是0.50—25.0μg/mL,相关系数可达0.9995,此方法成功应用于个人护理领域高吸收性树脂中丙烯酸单体残留的分析。 相似文献
88.
本文就单纯形优化法中的两种主要方法,基本单纯形法和改进单纯形法作了简要介绍,提出了适用于上述两种单纯形的计算机程序,最后均用实例作了说明。 相似文献
89.
90.
By optimizing the molecule beam epitaxy growth condition, the quality of quantum cascade (QC) material has greatly been improved. The spectrum of double x-ray diffraction indicates that the interface between the constituent layers is very smooth, the lattice mismatch between the epilayer and the substrate is less than 0.1%,and the periodicity fluctuation of the active region is not more than 4.2%. The QC laser with the emission wavelength of about 5.1μm is operated at the threshold of 0.73 kA/cm^2 at liquid nitrogen temperature with the repetition rate of lOkHz and at a duty cycle of 1%. Meanwhile, the performance of the laser can be improved with suitable post process techniques such as the metallic ohmic contact technology. 相似文献