Comparison of cadmium manganese telluride crystals grown by traveling heater method and vertical Bridgman method

In this paper, the CdMnTe crystals were grown by the Travelling Heater Method (THM) and the Vertical Bridgman (VB) method, respectively. The crystal properties, including the Mn axial distribution, impurity concentrations, resistivity, Hall effects and energy response spectra, were characterized and compared. The results shown that the CdMnTe crystal grown by the THM had more uniform Mn distribution and lower impurity concentrations compared to the crystal grown by VB method. The resistivity of CdMnTe grown by THM was (1.5 ∼ 8) × 10¹⁰ Ω.cm, while the resistivity of CdMnTe grown by VB was 10⁷∼10⁸ Ω.cm. The In dopant distributed uniformly throughout the crystal ingot grown by THM with the doping concentration of 0.6–0.7 ppm, while the In dopant concentration throughout the crystal grown by VB method is in the range of 1.31–2.4 ppm. Hall measurements revealed that the conductivity of the THM grown crystal was weak n‐type conductivity and the VB grown crystal was p‐type conductivity. A planar CdMnTe detector from the THM grown crystal showed a resolution of 8% of the ²⁴¹Am radiation at 59.5 keV peak, however, no energy response was revealed with the CdMnTe detector by the VB method. The results demonstrate that CdMnTe crystal grown by THM have better crystal quality and detector properties compared to that by VB method.     

有限分析法在潮流计算中的应用及问题探讨

应用有限分析法对二维潮流问题进行了研究,并用此法对长江口流场做了数值模拟计算,计算实例表明,有限分析法具有自动迎风性质,而且求解时,较易于获得稳定的收敛解,精度较高,结果表明,有限分析法可以用于计算流场,潮位的计算值与实际值吻合.     

Lamb波频域逆散射全聚焦成像方法研究

Lamb波因其传播距离远、衰减小常被用于板状结构的无损检测中,在基于Lamb波损伤检测的诸多成像技术中,全聚焦方法(Total Focus Method,TFM)方法因其成像分辨率高、信噪比高而受青睐.然而Lamb波的频散效应导致时域延时量不能被准确计算,进而影响传统TFM方法对损伤定位及成像的精度;此外,既有的TFM...     

中国古代的漏箭制度

漏箭是中国古代最主要的计时、守时的仪器漏刻中的显示时间推移的部件,在一年内,一般用多支漏箭来显示不同时日的时刻推移,人们先后取用不同的准则,制定了各异的漏箭制度.如有“一气一易”的48或25支漏箭制度,有“每差一刻为一箭”的41或21支漏箭制度.每支漏箭又各有不同的刻度方法,以符合实际时刻的推移.     

一种考虑界面相物性影响的界面单元法

界面是由复杂的界面相简化而成的,界面破坏实际是界面相材料的破坏。数值计算为了方便,如经典模型和内聚力模型等,都把很薄的界面相作无厚度化处理。导致只能考虑界面的面力,而无法考虑界面相内的应力(平行于界面方向的应力)。使界面失效准则先天性地排除了界面相内部应力的影响,从界面相材料失效机理的角度来看这是不够严谨的。本文将界面相材料等效为一种弹性连续体,由界面本构关系推导得到了一种新的界面单元。该单元具有界面参数易确定、对界面相物性可以进行等效描述等优点。通过商用有限元软件ABAQUS和用户子程序UEL实现了数值分析,并与直接物理模型的数值模拟结果进行对比,证明了本方法的简便及准确性。通过对不同界面相厚度结构的进一步分析,探讨了本文方法的可行范围。     

Dislocation Analysis for Large-sized Sapphire Single Crystal Grown by SAPMAC Method

In this paper,large-sized sapphire (230×210 mm,27.5 kg) was grown by SAPMAC method (sapphire growth technique with micro-pulling and shoulder-expanding at the cooled center). Dislocation peculiarity in large sapphire boule (0001) basal plane was investigated by chemical etching,scanning electron microscopy and X-ray topography method. The triangular dislocation etch pit measured is 7.6×101～8.0×102 cm-2,in which relative high-density dislocations were generated at both initial and final stages of crystal growth. The analysis of single-crystal X-ray topography shows that there are no apparent sub-grain boundaries; the dislocation lines are isolated and straight. Finally,the origins of low-density dislocation in sapphire crystal are discussed by numerical analysis method.     

高分子材料专业涂料课程教学初探

根据涂料行业发展对人才的需求，提出了高校讲授涂料课程的意义，介绍了涂料课程的特点，提出了高分子材料专业讲授涂料课程的内容，以及应采用的教学方法和学时安排。     

国产滤纸室温燐光背景的考察和降低背景方法的研究

固体基质室温燐光法(SS-RTP)的检出限依赖于固体基质的RTP背景的高低。本文考察了七种国产滤纸在重原子存在时和不存在时的RTP背景。研究了各种降低滤纸背景的处理方法。研究结果表明,采用NaOH、β-环糊精、EDTA、乙醇和丙酮浸泡或煮沸滤纸,都能不同程度的降低滤纸背景,最大降低率为88％。KI、NaAc、Pb(Ac)_2、TlNO_3和Cscl等重原子可使滤纸背景有较大幅度的增强,而经处理的滤纸,RTP背景较未处理滤纸背景降低一倍以上,最大可降低94.5％。用NaOH溶液处理滤纸,不仅能有效地降低背景,而且能提高分析物的RTP信号。研究表明纤维素伴生物质——木素,可能是产生燐光背景的杂质之一。     

对固体圆二色光谱测试方法的再认识——兼谈“浓度效应”

对近期发展的固体圆二色(CD)光谱测试方法进行了概述、评价和比较, 着重探讨了“浓度效应”的存在使固体CD光谱失真的原因. 通过对本课题组和其他作者已报道的四种化合物的固体CD谱再测试的反思, 强调了依手性化合物的手性光谱学性质不同, 根据浓度梯度实验选择其合适测试浓度的必要性. 对固有手性的阻转异构化合物(S)-1,1'-联二萘酚(S-BINOL)进行了成膜法固体CD谱浓度梯度测试, 发现所得固体薄膜CD谱中也存在着“浓度效应”     

对固体圆二色光谱测试方法的再认识——兼谈“浓度效应”

对近期发展的固体圆二色(CD)光谱测试方法进行了概述、评价和比较, 着重探讨了“浓度效应”的存在使固体CD光谱失真的原因. 通过对本课题组和其他作者已报道的四种化合物的固体CD谱再测试的反思, 强调了依手性化合物的手性光谱学性质不同, 根据浓度梯度实验选择其合适测试浓度的必要性. 对固有手性的阻转异构化合物(S)-1,1'-联二萘酚(S-BINOL)进行了成膜法固体CD谱浓度梯度测试, 发现所得固体薄膜CD谱中也存在着“浓度效应”