无网格方法中粒子分布与自适应研究

给出了一种区域粒子的Voronoi面积均匀的划分方法,先利用边界点得到边界粒子,再得到内部粒子,利用这种方法可以得到一般区域上粒子的均匀分布.同时,给出了计算过程中按流场的物理量对粒子进行自适应分布的方法.并给出了几个算例.     

全球变暖背景下温室效应的光谱能量分布分析

利用一维辐射传递方程及LBLRTM逐线积分模式建立计算模型,对工业革命前与目前大气构成情况下温室效应的能量分布及其光谱吸收机理进行分析,在保持温室气体浓度为当前水平的基础上,研究温室效应能量分布与地表温度之间的相互耦合机理.结果表明:工业革命前地球的温暖环境主要来自于大气温室气体的(100~370)cm^-1、(640~710)cm^-1以及(1370~2000)cm^-1三个强吸收带对于地球长波辐射的吸收,而地球当前的变暖则源自于大气的(370~640)cm^-1和(710~1370)cm^-1两个弱吸收带的作用,其对工业革命以来所额外增加的温室效应贡献分别达到了25%和55%;地表温度升高,温室效应在全波段范围内也会随之增强,但不同谱带处的温室效应贡献以地球平均温度所对应的辐射峰值波数为界线,峰值波数右侧的温室效应贡献将会增加,在其左侧的贡献比例则会减小.     

奇相干光源的测量设备无关量子密钥分配研究

刻画了奇相干光源的光子数分布特征,研究了奇相干光源下诱骗态测量设备无关量子密钥分配系统的密钥生成率与安全传输距离的关系,推导了奇相干光源下的计数率下界和误码率上界.仿真结果表明,奇相干光源光子数分布中多光子脉冲的比例低于弱相干光,可以有效提高诱骗态测量设备无关密钥分配系统的最大安全通信距离,为实用的量子密钥分配实验提供了重要的理论参数.     

The influence of air content in water on ultrasonic cavitation field

Cavitation is a complex physical phenomenon affected by many factors, one of which is the gas dissolved in the medium. Researchers have given some efforts to the influence of gas content on sonoluminescence or some specific chemical reactions in and around the bubble, but limited work has been reported about the influence on the ultrasonic cavitation field distribution. In this work, the intensity distribution of the ultrasound field in a cleaning tank has been measured with the hydrophone. After analysed and visualised by MATLAB software, it was found that the cavitation intensity distribution in degassed water was much better than that in tap water. And further study proved that degassing process can improve the cavitation effect dramatically both in intensity and scope. Finally, the cavitation fields in mediums with different gas content were measured and the specific influence of air content on cavitation field was discussed.     

Defects inspection of the solder bumps using self reference technology in active thermography

With the decrease of solder bumps in dimension and pitch, defects inspection of the solder bumps become more difficult. A nondestructive detection system based on the active thermography has been developed for solder bumps inspection. However, heating non-uniformities and emissivity differences may impede the defects recognition. In this paper, we propose a method using a self reference technology based on a source distribution image (SDI) to eliminate the influence of unevenness in emissivity values and heating power distribution. Three thermograms captured right after the heat pulse are averaged to create the SDI. Then the SDI is subtracted from the original thermograms, and we get the thermal contrast images, in which eight points on the edge of each hot spot are selected as the feature points for the corresponding bump. Thermal difference between the feature points and the central point are adopted to quantify the thermal behaviors of the solder bumps, by which the missing bump is distinguished from the reference bumps. The results show that it is effective using the method to eliminate the impacts of emissivity unevenness and heating non-uniformities on defects identification in the active infrared test.     

大功率高温超导滤波器的设计与功率测试

本文在双面YBCO高温超导薄膜上设计并制备了两节大功率超导滤波器,根据滤波器功率承载能力与最大电流密度之间的关系,减小电流密度和分散电流密度的分布是提高功率承载能力的关键.本文采用增加超导谐振器尺寸、优化几何结构及改进馈线耦合方式的方法,设计了两节2 GHz频段梭型谐振器结构的滤波器.设计及测量结果显示了馈线结构及谐振器几何尺寸优化程度对超导滤波器功率承载能力有不同程度的影响,说明了在大功率超导滤波器设计中应选用无结点间隙耦合式馈线以抑制电流密度的聚集.采用优化后的谐振器结构制备的梭型两节超导滤波器经测试功率承载能力为2 W.超导滤波器的尺寸为25×12 mm LaAlO3基片,中心频率2.022 GHz,相对带宽为2.4%.同时给出了超导滤波器功率测试的结构和方法.     

基于广义极值的混沌电场峰值分布研究

通过分析峰值分布及广义极值分布理论关于混沌电场峰值分布的特点,获得一种混沌电场峰值分布的计算方法,结合Bootstrap重采样技术,提出了混沌电场峰值分布参数估计方法,该方法吸取了重采样技术估计的优点,对分布参数置信区间的估计更为准确、实用。以蒙特卡罗仿真和某机械搅拌混响室内电场数据为实例,结果表明,与传统的正态近似法、百分位法、BC-t等方法相比,其计算结果与实际结果更为吻合,证明了该方法具有更高的准确度。     

Waiting times of entangled electrons in normal–superconducting junctions

We consider a normal–superconducting junction in order to investigate the effect of new physical ingredients on waiting times. First, we study the interplay between Andreev and specular scattering at the interface on the distribution of waiting times of electrons or holes separately. In that case the distribution is not altered dramatically compared to the case of a single quantum channel with a quantum point contact since the interface acts as an Andreev mirror for holes. We then consider a fully entangled state originating from splitting of Cooper pairs at the interface and demonstrate a significant enhancement of the probability to detect two consecutive electrons in a short time interval. Finally, we discuss the electronic waiting time distribution in the more realistic situation of partial entanglement.     

GdBCO超导体的顺磁性及低温下磁通分布的动态观测

本文研究了100～300K之间Gd1．8Ba2.4Cu3．4O7-δ（简写为GdBCO）超导体的顺磁性，对GdBCO的磁化强度随磁场和温度的变化分别在100K和0．1T进行了测试，GdBCO的顺磁性遵从朗之万顺磁性理论．在磁光显微镜下，低温12K场冷下，我们观察了从0mT～29mT磁通线进入GdBCO的超导体的过程，以及磁通线在GdBCO超导体中的分布。