吸收光谱光路的设计与误差

固体、液体和气体物质的吸收光谱是大学普物、光学专业的一个基本实验．如何在普通的设备和实验条件下，较为准确地测量吸收系数？本文从朗伯定律出发，介绍一种“对数测量法”光路．并对实验中出现的“负吸收系数”等误差作了分析．文中还介绍了消除材料样品对探测光的反射误差的固体、液体样品架．     

Quantum logic gates with two-level trapped ions beyond Lamb--Dicke limit

In the system with two two-level ions confined in a linear trap, this paper presents a simple scheme to realize the quantum phase gate (QPG) and the swap gate beyond the Lamb--Dicke (LD) limit. These two-qubit quantum logic gates only involve the internal states of two trapped ions. The scheme does not use the vibrational mode as the data bus and only requires a single resonant interaction of the ions with the lasers. Neither the LD approximation nor the auxiliary atomic level is needed in the proposed scheme. Thus the scheme is simple and the interaction time is very short, which is important in view of decoherence. The experimental feasibility for achieving this scheme is also discussed.     

增量式轴角编码器的电子细分及零位处理

使用单片机对增量式光电轴角编码器产生的叠栅条纹信号进行计数和电子细分,便可将轴的机械转动模拟量转换成数字量;加上固定参考零位后,可使编码器具有"记忆"功能,因此对如何解决零位技术问题做了详细分析说明,并给出了实际解决方案.     

华罗庚轶事——纪念华罗庚先生逝世二十周年

华罗庚(1910-1985)中国现代数学家,中国科学院院士,是新中国数学研究事业的创始人,也是中国在世界上最有影响的数学家之一、1924年金坛中学初中毕业,后刻苦自学.1930年后在清华大学任教.1936年赴英国剑     

双晶单色器弧矢聚焦晶体面形有限元分析

简要介绍了弧矢聚焦双晶单色器的基本原理、聚焦晶体的压弯以及鞍形形变的抑制,提出了柔性铰链弧矢聚焦晶体压弯机构,对弧矢聚焦晶体衍射面的子午形变和弧矢弯曲面形进行了有限元分析;用光学追踪程序SHADOW得出了弧矢聚焦晶体衍射面面形对单色器的光通量和分辨率的影响。     

各向异性超常介质中的反常线性现象

从麦克斯韦方程组出发,结合超常介质的特殊性质,分析了电磁波在一种具有线性色散关系的各向异性超常介质中的传播特性。在线性色散关系的情况下,得到了超常介质的介电张量和磁导率张量各元素之间的条件表达式。根据能量守恒定律和电磁场的边界连续性条件,在横电波(TE)和横磁波(TM)入射时,分析了折射波矢和能流与入射波矢和能流方向之间的关系。发现无论是TE波还是TM波,在这种介质中传输时,都产生了光准直的现象,且TE波和TM波的传输方式是相反的。     

人-机-环境系统安全性的模糊熵评价方法

根据人-机-环境系统安全评价的评价指标体系和权重,基于三角形隶属度函数和模糊熵耦合提出了人-机-环境系统安全性的模糊熵评价方法,应用结果表明,影响某企业人-机-环境系统安全性的模糊熵评价度的主要原因是由于人-机-环境系统安全没有协调发展.该模糊熵评价方法可为人-机-环境系统安全评价提供有力的支持.     

长方体的妙用

长方体是一个很基本的多面体,所含的线线,线面,面面的位置关系的内容十分丰富,数学中的有些问题,如果用常规法去求,将难以求出或十分繁琐,甚感“山穷水复疑无路”,但如果能构造长方体去求,将会把问题化难为易,化繁为简,从而“柳暗花明又一村”了。     

Baseline drift effect on the performance of neutron and γ ray discrimination using frequency gradient analysis

Frequency gradient analysis (FGA) effectively discriminates neutrons and γ rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift similar to other pulse shape discrimination methods. The baseline drift effect is attributed to factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and γ rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSample/s 8-bit oscilloscope. The theoretical and experimental results both show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.     

GaN垒层厚度渐变的双蓝光波长发光二极管

针对单蓝光波长芯片与Y3Al5O12∶Ce3+黄光荧光粉封装白光发光二极管存在显色性不足的问题,提出了采用双蓝光波长芯片激发Y3Al5O12∶Ce3+黄光荧光粉实现高显色性白光发射法,并分析了其可行性.利用金属有机化学气相沉积系统在(0001)蓝宝石衬底上顺序生长两个In0.18Ga0.82N/GaN量子阱和两个In0.12Ga0.88N/GaN量子阱的双蓝光波长发光二极管,并对不同GaN垒层厚度的双蓝光波长发光二极管的光电性能进行分析,结果表明沿n-GaN到p-GaN方向减小GaN垒层厚度能实现双蓝光发射,并有较好的发光效率.交流阻抗谱结果显示相关双蓝光波长发光二极管可以用一个电阻Rp与电容Cp并联后与一个Rs串联电路来模拟,GaN垒层变化能调节并联电阻和电容,对串联电阻没有影响.此外,基于垒层减小的双蓝光波长芯片激发Y3Al5O12∶Ce3+荧光粉实现了高显色指数的白光发射.