Study of low momentum track reconstruction for the BESⅢ main drift chamber

In order to overcome the difficulty brought by the circling charged tracks with transverse momentum less than 120 MeV in the BESⅢ Main Drift Chamber （MDC）, a specialized method called TCurlFinder was developed. This tracking method focuses on the charged track reconstruction under 120 MeV and possesses a special mechanism to reject background noise hits. The performance of the package has been carefully checked and tuned by both Monte Carlo data and real data. The study shows that this tracking method could obviously enhance the reconstruction efficiency in the low transverse momentum region, providing physics analysis with more and reliable data.     

20-kHz watt-level green laser with LGS crystal electro-optic Q-switch

A diode-end-pumped electro-optic （EO） Q-switched green laser operating at the repetition rate of 20 kHz is reported. A block of La3Ga5SiO14 （LGS） single crystal is used as a Q-switch and the type I phase- matching LiB305 （LBO） is used as the nonlinear crystal in the second harmonic generation. The 2.3-W average power of 532-nm green laser is obtained at the repetition rate of 20 kHz with the pulse width as short as 10 us. When the output power is about 1.5 W, the measured power fluctuation is less than 1.4% （root-mean-square. RMS） with the beam quality factor of M^2 〈 2 in both orthogonal directions.     

偏光全息研究历程与展望

全息是目前一项极具前景的科学技术,即通过信号光和参考光的干涉,在小小的全息图上记录丰富的信息。相比于传统全息仅记录光波的相位、振幅信息,偏光全息可以将额外的偏振信息记录于偏振态敏感材料中。本文从偏光全息材料入手,详细介绍了偏光全息生产过程;同时介绍基于琼斯理论和张量理论的偏光全息原理和研究进展;最后描述了偏光全息在全息存储和纳米光学领域的发展前景。     

An Implantation and Detection System for Spectroscopy of 22,24Si

A new decay detection system with high detection efficiency and low detection threshold has been developed for charged-particle decay studies, including -delayed proton, decay or direct proton emission from proton-rich nuclei. The detection system was tested by using the -delayed proton emitter 24Si and was commissioned in the decay study of 22Si produced by projectile fragmentation at the First Radioactive Ion Beam Line in Lanzhou. Under a continuous-beam mode, the isotopes of interest were implanted into two double-sided silicon strip detectors, where the subsequent decays were measured and correlated to the preceding implantations by using position and time information. The system allows to measure protons with energies down to about 200 keV without obvious background in the proton spectrum. Further application of the detection system can be extended to the measurements of -delayed proton decay and the direct proton emission of other exotic proton-rich nuclei.     

琼脂糖性质对凝胶电泳法分离金属性和半导体性单壁碳纳米管的影响

利用琼脂糖凝胶电泳分离单壁碳纳米管(SWCNTs)技术, 考察了MB, Agarose, Agarose B和LRU 4种琼脂糖对SWCNTs分离效率的影响. 紫外-可见-近红外(UV-Vis-NIR)吸收光谱研究结果表明, 不同的琼脂糖对SWCNTs中s-SWCNTs的分离效率影响较小, 而对m-SWCNTs的分离效率影响较大. 分析4种琼脂糖凝胶的凝胶强度和凝胶网孔尺寸等发现, 影响SWCNTs中m-SWCNTs分离效率的主要因素是琼脂糖的凝胶强度和琼脂糖凝胶形成的网孔尺寸, 小的凝胶网孔尺寸有利于m-SWCNTs富集, 高凝胶强度则不利于其富集.     

设置悬念的时机

教育心理学认为：悬念是一种学习心理机制,学习过程中的心智活动是促进认识、强化理解、提高效果的重要因素．笔者在教学中适时设置悬念,激发兴趣,调动思维积极性,有效地提高了学生的学习兴趣和数学成绩．１设置悬念,引入新概念设置悬念引入新概念,可以激发学生的学...     

镧镍体系(LaNi5-xMx)吸氢化合物的研究(Ⅰ)——LaNi5的化学合成及吸氢性能

过渡金属氢化物因与氢能源的利用紧密有关,近年来在国际上引起极大注意。本文提出了吸氢化合物LaNi₅的一种新的合成方法--共沉淀还原法,并详细研究了反应过程。     

由含时边界条件的两种有限深量子势阱构造的哈密顿算符和它们的复BERRY相位

在量子基础理论的框架下分别从一维含时边界条件的半壁无限高量子势阱和三维含时边界条件的有限深球方势阱构造了两种描述带电粒子在电磁场作用下的新哈密顿算符.在绝热近似下，计算了这两种新量子体系的复Berry相位.     

磁性多层膜层间交换耦合的自由电子模型研究

基于自由电子模型,考虑到不同膜厚和不同磁化排列的费密能的不同,自洽地给出费密能。利用这种方法,计算了材料铁磁层和非磁层电子密度对层间耦合振荡周期的影响,并比较了我们所得结果与他人按巨势法得到的结果的异同,发现振荡周期随着电子密度的变化而改变,并且当铁磁层和非磁层的电子密度不同时,将出现不等周期的振荡。这一新的理论结果与最近的实验相符。此外,还计算了极化强度和由于能带不匹配造成的接触势对耦合强度及振荡相位的影响:前者是决定耦合强度的主要因素,后者则会影响振荡相位,甚至周期。 关键词：