Investigation on the intensity noise characteristics of the semiconductor ring laser

Based on the frequency-domain multimode theoretical model, detailed investigations on the noise characteristic of the semiconductor ring laser （SRL） are first performed in this paper. The comprehensive nonlinear terms related to the third order nonlinear susceptibility Z3 are included in this model; the Langevin noise sources for electric field and carrier density fluctuations are also taken into account. As the injection current increases, the SRL may present several operation regimes. Remarkable and unusual low frequency noise enhancement in the form of a broad low frequency tail extending all the way to the relaxation oscillation peak is observed in any of the operation regimes of SRLs. The influences of the backscattering coefficient on the relative intensity noise （RIN） spectrum in typical operation regimes are investigated in detail.     

饱和一元醇远红外光谱的测试及仿真研究

用衰减全反射傅里叶光谱仪(FTIR-ATR)在室温条件下测试了甲醇、乙醇、丙醇、异丙醇、丁醇及异丁醇六种饱和一元醇在30～300 cm-1波段的远红外透射光谱。通过分析这六种具有类似化学结构的一元醇的远红外透射光谱,发现它们在30～150 cm-1波段均有明显的吸收峰,但在150～300 cm-1波段吸收峰不明显; 羟基在一元醇中的质量百分比越高,相关一元醇的远红外光谱的平均透过率越低; 直链一元醇的光谱平均透过率高于支链状的同分异构体。采用密度泛函理论B3LYP/6-311G(d,p)基组对甲醇单体和多聚体进行结构优化和频率计算。计算显示,在30～150 cm-1波段甲醇单体分子没有出现吸收峰,但是甲醇的多聚体则出现明显的吸收峰,计算得到的多聚体吸收峰位置与实际测量的结果相符合。结果表明,甲醇在太赫兹波段吸收的来自于不同形式聚合体的集体振动,甲醇溶液以甲醇三聚体为主要的存在形式。本成果不仅为研究有机分子在太赫兹波段的频率响应提供了新的实验方法,而且对进一步利用FTIR-ATR研究其他有机分子具有借鉴意义。     

一种新型阳离子三硅氧烷表面活性剂的合成及其表面性能

以1,2-环氧-9癸烯(ED)和1,1,1,3,5,5,5-七甲基三硅氧烷(MDHM)为原料,在氯铂酸催化下,经硅氢加成反应先制得烷基环氧基三硅氧烷(AETS),再将AETS与二乙醇胺(DEA)进行开环反应合成了一种新型阳离子三硅氧烷表面活性剂(CTSS)。 通过IR和1H NMR对CTSS的结构进行了表征,测定了CTSS的表面张力、润湿性和对pH值的稳定性。 同时对AETS及CTSS的合成条件进行了优化,优化后的工艺条件为:合成AETS的最佳条件为n(ED)∶n(MDHM)(n为物质的量)为1.1∶1,催化剂用量为n(MDHM)的0.075%,反应时间为5 h,反应温度为80 ℃;合成CTSS的最佳条件为n(AETS)∶n(DEA)=1∶1.05,反应时间3 h,反应温度80 ℃。 性能测试结果表明,CTSS在临界胶束浓度(CMC)为1.3×10-3 mol/L时,可以将水的表面张力降低至20.0 mN/m,同时具有良好的润湿性,另外,CTSS在pH值为6.5~8.0时稳定存在。     

牛蒡多糖组分的高效阴离子交换-脉冲安培分析

应用高效阴离子交换色谱 脉冲安培检测器联用技术,研究了牛蒡多糖组分的检测方法和条件.以牛蒡为原料,采用水提醇沉法提取牛蒡粗多糖,并对其工艺进行探讨.牛蒡粗多糖经超声波酸水解处理后进行离子色谱分析,其最佳色谱条件为：以12 mmol·L-1 NaOH溶液为淋洗液,流动相流速为1.0 mL·min-1,Carbo PaC PA10（250 mm×4 mm i. d.）为分析柱,进样量25 μL.结果表明,牛蒡多糖中主要含有阿拉伯糖、果糖、葡萄糖和半乳糖,在优化的色谱条件下,各种单糖组分在一定浓度范围内线性关系良好,能很好地分离和准确测定.该方法操作简便、灵敏度高、重现性好.     

Surface enhancement of molecular ion H_2~+ yield in a 2.45-GHz electron–cyclotron resonance ion source

High current hydrogen molecular ion beam is obtained with a specially designed stainless steel liner permanent magnet2.45-GHz electron–cyclotron resonance(ECR) ion source(PMECR II) at Peking University(PKU). To further understand the physics of the hydrogen generation process inside a plasma chamber, theoretical and experimental investigations on the liner material of the plasma chamber in different running conditions are carried out. Several kinds of materials, stainless steel(SS), tantalum(Ta), quartz, and aluminum(Al) are selected in our study. Experimental results show that stainless steel and tantalum are much better than others in H~+_2 generation. During the experiment, an increasing trend in H~+_2 fraction is observed with stainless steel liner after O_2 discharge inside the ion source. Surface analyses show that the roughness change on the surface after O_2 discharge may be responsible for this phenomenon. After these studies, the pure current of H~+_2 ions can reach 42.3 mA with a fraction of 52.9%. More details are presented in this paper.     

CDIO模式下的大学物理实验教学改革探索与实践

在大学物理实验教学中,通过实践CDIO模式教学法培养学生的实验技能和创新能力。探索应用性、开放性的学生科技创新性物理实验教学体系。     

Ni离子辐照国产ZIRLO合金的辐照性能研究

国产ZIRLO合金是CAP1400重要的燃料包壳管候选材料之一,因此需要在使用前对该材料进行辐照性能考验。研究了国产ZIRLO合金的辐照性能随辐照温度和损伤剂量的变化。辐照实验在中国原子能科学研究院HI-13串列加速器上,采用80 MeV的Ni离子进行,辐照产生的损伤采用透射电子显微镜、能量色散谱和纳米压痕法等方法表征。国产ZIRLO合金在300℃经10 dpa损伤剂量辐照后观察到均匀分布的析出颗粒,同样剂量在700℃辐照析出颗粒数目减少,析出相的主要成分为Nb。辐照后出现硬化现象,辐照损伤剂量越大,硬化程度越高;随着辐照温度升高,辐照硬化呈减小趋势。The domestic ZIRLO is a promising candidate of cladding materials for CAP1400. It is necessary to test its radiation properties before its use. In this paper, the radiation properties of the domestic ZIRLO have been studied as functions of irradiation temperature and dose respectively. The experiment was performed at the HI-13 tandem accelerator of China Institute of Atomic Energy by using 80 MeV Ni ions at different temperature and different dose. The transmission electron microscopy, electron dispersive spectroscopy and nano-indentation were used to characterize the radiation damage. The experimental results show that the precipitates are uniformly distributed at 10 dpa and 300℃, while at 700℃ the number of precipitates is reduced. Among all the precipitates, Nbisthe dominant element. Hardening phenomenon was also observed after irradiation, the higher the radiation dose, the higher the degree of hardening, and it illustrates a decreasing tendency with the increasing of the irradiation temperature.     

飞机模型高速撞击钢筋混凝土载荷特性实验研究

为得到大型商用飞机撞击的冲击载荷特性及其计算方法,基于火箭橇加载试验平台,搭建了飞机模型撞击钢筋混凝土运动靶体测试系统,开展了两种不同尺寸飞机模型的撞击试验,利用高速摄影技术获得了飞机模型撞靶前的姿态、着速及飞机模型撞靶的破坏过程。采用加速度测试系统和激光干涉测速系统,分别得到撞击过程中运动靶体的加速度和速度历史,据此得到靶体受到的冲击载荷-时间曲线,二者吻合,验证了测试系统的可靠性。通过飞机模型上安装的机载存储过载测试系统,获得了撞击过程中飞机模型的负加速度-时间曲线,由此确定了修正的Riera理论模型中的静载荷项,并进一步计算得到靶体受到的冲击载荷-时间曲线,与通过测试靶体的加速度或速度得到的结果一致,验证了使用修正的Riera理论模型计算飞机模型冲击载荷的合理性及计算方法的正确性,同时确定了适合于本试验中飞机模型的修正系数α。     

基于紫外光谱分析的水质监测技术研究进展

基于紫外光谱分析的水质监测技术具有实时在线、无试剂、无需样品预处理、无二次污染、体积小、成本低等特点,在对饮用水、地表水、工业废水等水体的在线监测中具有显著优势,已成为现代水质监测技术的一个重要发展方向。本文介绍了基于紫外光谱分析的现代水质监测技术的原理、特点、现状及发展的新趋势,并提出亟待解决的关键技术问题。