The dynamical properties of Rydberg hydrogen atom near a metal surface

The dynamical properties of Rydberg hydrogen atom near a metal surface are presented by using the methods of phase space analysis and closed orbit theory. Transforming the coordinates of the Hamiltonian, we find that the phase space of the system is divided into vibrational and rotational region. Both the Poincaré surface of section and the closed orbit theory verify the same conclusion clearly. In this paper we choose the atomic principal quantum number asn=20. The dynamical character of the exited hydrogen atom depends sensitively on the atom-surface distanced. Whend is sufficiently large, the atom-surface potential can be expressed by the traditional van der Waals force and the system is integrable. Whend becomes smaller, there exists a critical valued _c. Ford>d _c, the system is near-integrable and the motion is regular. While chaotic motion appears ford<d _c, and the system tends to be non-integrable. The trajectories become unstable and the electron might be captured onto the metal surface.     

Periodic solution and chaotic strange attractor for shunting inhibitory cellular neural networks with impulses

By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence, uniqueness, and global exponential stability of periodic solution for shunting inhibitory cellular neural networks with impulses, dx(ij)dt=-a(ij)x(ij)- summation operator(C(kl)inN(r)(i,j))C(ij) (kl)f(ij)[x(kl)(t)]x(ij)+L(ij)(t), t>0,t not equal t(k); Deltax(ij)(t(k))=x(ij)(t(k) (+))-x(ij)(t(k) (-))=I(k)[x(ij)(t(k))], k=1,2,...] . Furthermore, the numerical simulation shows that our system can occur in many forms of complexities, including periodic oscillation and chaotic strange attractor. To the best of our knowledge, these results have been obtained for the first time. Some researchers have introduced impulses into their models, but analogous results have never been found.     

基于光谱特征的北京城区植被滞尘分布反演

植被叶片的滞尘量可以表征空气污染的程度, 分析城市植被滞尘的空间特征对于制定更为有效的空气污染控制政策具有重要的现实意义。基于北京市主城区采集的大叶黄杨、国槐、毛白杨和山桃等四种典型绿化植被叶片的滞尘量、光谱反射率和叶面积等数据,比较四种植被叶片滞尘前后的光谱曲线,进行窄波段与卫星波段滞尘前后叶片光谱反射率比值与滞尘量的相关分析。然后,分别建立相关性最大的卫星波段反射率和NDVI与滞尘量之间的回归模型, 选取拟合较好的模型反演北京城区植被的滞尘量分布,进而插值得到整个北京城区的尘埃分布。最后,根据高滞尘区域周围的土地覆盖和土地利用以及滞尘期间PM₁₀浓度的空间分布对反演的的合理性进行检验。结果表明：在780~1 300 nm波段,大叶黄杨、国槐、毛白杨和山桃四种植被的滞尘叶片反射率均明显低于干净叶片;窄波段反射率与滞尘量在520~650 nm波段和1 390~1 600 nm波段具有较高的相关性,相关系数的绝对值最高达到0.626;利用Landsat8的green波段和NDVI构建的滞尘反演模型,决定系数(R2)分别为0.446和0.465。NDVI模型反演的北京城区植被的滞尘量分布结果表明,北京城区滞尘含量呈现出北高南低,东高西低,中心城区高于郊区的空间分布格局。该研究通过高光谱和遥感影像数据反演滞尘量,可以为快速全面监测城市地区尘埃分布提供参考。     

高纯锗探测器的广泛应用和自主研制进展

以目前国际上极为活跃开展的暗物质探测、无中微子双 衰变研究为例,评述了高纯锗探测器的重要性及其广泛的应用前景。介绍了己开展的高纯锗单晶、探测器制备的关键技术研究进展:合作单位已研制出了用于高纯锗单晶材料制备的区熔炉、单晶炉;并制备出直径为20  50 cm、纯度为12N(< 41011  atoms/cm3)、位错< 5000 atoms/cm2 的锗单晶;掌握了高纯锗探测器(平面型、同轴型)制备的关键技术,用进口高纯锗单晶材料制备出的同轴型高纯锗探测器对射线的能量分辨率及探测效率均达到进口产品指标,使用自制的12N 高纯锗单晶材料己制备出平面型高纯锗探测器。呼吁加速高纯锗研制的自主创新步伐,尽早实现其国产化目标。The article reviews importance and wide applications of HPGe detector, especially the application on the dark matter search experiment and double beta decay experiment. The research progress on the Highpurity germanium single crystal and HPGe detector in China has been introduced. The cooperation partner developed new type zone-refining furnace and single crystal furnace. The ultra-purity germanium single crystal with 20~50 cm, purity up to 12N(net impurity concentration is less than 41011 atoms/cm3), and dislocation less than 5 000 /cm3 was prepared. The key technologies for preparing planar and coaxial HPGe detector were mastered. The coaxial detector, which has been made of imported ultra-purity germanium single crystal has excellent energy resolution and efficiency as the imported commercial detector. The planar detector using selfmade germanium single crystal was also successfully manufactured. The research group appeals for speeding up the pace of independent innovation on the high-purity germanium, and achieving the high-purity germanium localization as soon as possible.     

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利用Matlab语言将EFIT程序反演计算过程进行优化整合,简化了程序操作步骤,并增加了对计算结果的分析与存储功能。利用整合后的 EFIT 程序,计算分析了 J-TXET 装置放电过程中等离子体磁场位形和其它参数的演变,绘制了等离子体压强剖面图、等离子体电流密度和安全因子分布等磁面信息的重建结果。此外,还将反演结果与软X射线测算数据进行比对。结果表明,改善后的EFIT程序能够初步满足对实验放电的反演计算分析要求,为J-TXET装置的放电控制和运行提供重要的参考数据。     

具有特大磁电阻效应钙钛矿材料的制备及性能分析

通过固相烧结法制备了具有特大磁电阻效应的钙钛矿材料Pr0.64Ag0.044MnAl0.2O3.利用结构和成分分析,发现此材料只有在1 100℃高温烧结下才能生成完整的钙钛矿结构,且属于立方晶系,晶格常量a≈0.386 nm.在0.4 T的外磁场下,磁电阻值在122 K处达到最大,约为19.2%,为巨磁电阻实验提供了较好的样品.     

利用偏振度研究混合目标的混合比

提出一种利用偏振度研究混合目标混合比的新方法。通过建立混合目标模型将混合目标散射光的偏振度与混合目标的混合比建立直接的关系,在理论上得到了混合目标混合比分别与混合目标偏振度和归一化偏振度之间的数值关系,并且进一步给出了混合目标混合比由归一化偏振度的反演结果,为研究混合目标提供了新的思路与方法,对偏振度探测混合目标的实验以及工程应用都有重要的理论意义。     

Intelligibility enhancement for noisy whispered speech using asymmetric cost function

We proposed two whispered speech enhancement methods based on asymmetric cost functions in this paper to deal with the amplification and attenuation distortions of whispered speech distinctively.The modified Itakura-Saito（MIS）distance function provides more penalties to speech amplification distortion,whereas the Kullback-Leibler（KL）divergence function gives more penalties to speech attenuation distortion.The experimental results show that the MIS function based method achieves significant improvement of intelligibility in contrast to the conventional speech enhancement algorithms when the signal-to-noise ratio（SNR）falls below-6 dB,whereas the KL function based one achieves the similar result as the minimum mean square error（MMSE）speech enhancement method.The results show that the effects of the amplification and attenuation distortions on the intelligibility of the enhanced whisper are different,where larger attenuation distortion may result in better intelligibility of speech with low SNR.However,the attenuation distortion has small effects on intelligibility of speech with high SNR.     

球形充气液泡所带电量及系统能量变化的分析

本文分析了球形充气液泡所带的电量,推导出一个较为普遍的计算公式,并分析了整个系统的能量变化关系.     

改进的TESLA式高阶模衰减器的实验研究

讨论了TESLA型高阶模耦合器的改进, 对所设计的改进型TESLA式高阶模耦合器进行实验, 对理论计算与实验结果进行详细分析, 结果表明改进的高阶模耦合器理论计算和实验结果符合得较好.