Nuclear Spin Alignment of 12,13B Produced in Heavy Ion Collisions

The nuclear spin alignments of the β-emitting fragments ¹²B(I ^π=1⁺, T _1/2=20.2 ms) and ¹³B(I ^π=3/2⁻, T _1/2=17.4 ms) produced in the 100A-MeV ¹³C, ¹⁵N + ⁹Be collisions respectively have been observed for the first time detecting asymmetric β-ray emission from these nuclei. By means of the spin manipulation technique based on the hyperfine interaction of B isotopes in TiO₂, both the polarization P and the alignment A were determined reliably. The obtained P and A were significantly smaller than the expectation from the kinematical model. From the fact that the quenching factors for P and A are almost the same, there may be some depolarization mechanism in the collision process itself. This revised version was published online in September 2006 with corrections to the Cover Date.     

Microstructures of grain boundaries in (001)-oriented strontium bismuth tantalate thin films grown by pulsed laser deposition

(001)-oriented strontium bismuth tantalate thin films have been grown on Pt/TiO₂/SiO₂/Si (100) substrates by pulsed laser deposition. The room-temperature current–electric field dependence of the films has been investigated, which revealed a space-charge-limited conduction mechanism. The microstructures of grain boundaries and structural defects in these films were also examined by transmission electron microscopy and high-resolution transmission electron microscopy, respectively. The grains of the films deposited at 550 °C exhibited polyhedral morphologies, and the average grain size was about 50 nm in length and 35 nm in width. At a small misorientation angle (8.2°) tilt boundary, a regular array of edge dislocations with about 3-nm periodic distance was observed, and localized strain contrast near the dislocation cores was also observed. The Burgers vector b of the edge dislocation was determined to be [110]. At a high misorientation angle (39.0°) tilt grain boundary lattice strain contrast associated with the distortion of lattice planes was observed, and the mismatching lattice images occurred at about 2 nm along the boundary. The relationship between microstructural defects at grain boundaries and leakage currents of these films is also discussed. Received: 8 September 2000 / Accepted: 18 December 2000 / Published online: 28 February 2001     

HLS注入段束流位置探头定标电场的拟合和误差计算

 描述了束流位置探测器(BPM)探头定标、定标电场的拟合和误差计算。该定标系统采用了具有调节精度为10μm垂直放置真空管道的天线模拟定标装置和分辨率高达1μm外差式、窄带频域信号处理电子学线路。并推导出针对合肥光源（HLS）定标系统条件下的电场拟合函数及相关的BPM-Mapping图和误差计算结果,较精确地计算出该高精度定标系统误差。     

应用BP神经网络识别内层表面细小缺陷的研究

内层表面细小凹坑的识别是超声无损评估的一个难点。本文利用人工神经网络对于信号的分类功能,建构和训练了一个BP神经网络,并用它对尺寸为1mm的圆锥形和半球形两种凹坑成功地进行了识别。研究表明,应用凹坑回波的DCT谱作为缺陷特片输入,可使BP神经网络的训练和缺陷识别既快捷又有效。     

SiO2气凝胶中ZnS∶Mn纳米微晶的发光性质

利用溶胶 凝胶法在SiO2 气凝胶中制得了ZnS∶Mn纳米微晶 ,并对微晶的X射线衍射谱、激发 发射光谱、发光效率、时间分辨光谱进行了研究 ,讨论了发光性质变化的原因。实验表明 ,Mn2 + 在纳米微晶中的发光效率相对于体材料有明显的提高 ,弛豫时间也比在体材料中缩短了约一个数量级     

用于摄像机定位的单目视觉方法研究

利用单目视觉算法确定摄像机相对于被测点的聚焦位置的方法 ,提出了一种新的能量谱 熵函数图像聚集锋利性测度评价函数以及新的单目视觉测量方法 ,即将单目视觉方法中的离焦法和聚焦法结合起来 ,进行聚焦位置的测量。并给出了用于摄像机定位的单目视觉离集法和聚焦法的计算模型。实验验证结果证明了算法的稳定性和可靠性     

反应堆核泵浦~3He-Ar-Xe气体激光腔内能量沉积数值模拟研究

在 TRIM软件计算结果的基础上利用蒙卡方法编制了能量沉积效率与损失率的 EDL计算软件 ,模拟计算了泵浦腔尺寸、混合气体中 3 He分压等参数与能量沉积密度之间的关系 ,研究了反应堆核泵浦激光腔内的能量沉积问题 ,推导出了能量沉积密度的函数关系式。     

MICRO-MOTION EFFECT OF A TRAPPED ULTRA-COLD ION IN A STANDING-WAVE LASER

In the absence of the requirements of the Lamb-Dicke limit and rotating wave approximation, we semi-classically investigate the dynamics of a trapped ultra-cold ion in the standing-wave laser, with the consideration of the time-dependent potential and pseudo-potential of the Paul trap. The specific calculations show that the larger the Lamb-Dicke parameter η and the Rabi frequency Ω, the greater the difference between the dynamics in the time-dependent potential and the pseudo-potential.     

锰/磷、钛/磷二元团簇的激光溅射产生与光解

利用激光溅射法直接产生了锰／磷、钛／磷二元团簇正、负离子MxPy^±(M=Mn、Ti） ,并用串级飞行时间质谱仪研究了团簇离子的组成与激光光解规律。实验表明钛与磷间成簇的能力强于锰与磷间成簇的能力,且MPy^+(M=Ti、Mn)团簇离子系列表现出峰强度了胡所含磷原子数目的奇偶性变化,这可能与P4结构的特殊稳定性有关。激光光解实验表明,失去中性P2、P4的通道为主要光解通道。随着团簇离子的生长,锰／磷团簇正离子逐渐由富磷簇向富金属簇过渡,钛／磷则趋向于形成钛原子数目与磷原子数目接近相等的团簇正离子,而二者与磷形成的团簇负离子MxPy^-(M=Mn、Ti) 逐渐趋向于x ≈ y,随样品中磷含量增加,锰／磷易形成富磷簇,钛／磷的组成趋向不改变。     

改进的Herriott型光学长程池

用凹面反射镜和平面反射镜组成结构简单、光路易调的光多次反射装置,计算了这种光学系统的稳定性条件。考察实际入射光束的直径和发射角,给出了最大反射次数的求法。制成适用于钛宝石激光光声光谱仪的光56次通过的长程池。理论计算的反射光斑分布与实验观测一致。这个技术有利于提高光声光谱和吸收光谱的探测灵敏度。