Short-term frequency characteristics of 2 µm single frequency Solid-state lasers

The Short term frequency stability characteristics of 2 μm single frequency Solid-state lasers was investigated. The two laser systems of 2 μm single longitudinal mode oscillation Tm, Ho:YLF microchip laser and Ho:YAG NPRO laser were designed and constructed. The Short term frequency stability of these two laser were measured with the fiber delay self-beating heterodyne method. The 3dB width of the relative frequency fluctuation of Tm, Ho:YLF microchip laser and Ho:YAG NPRO laser were measured to be 895 and 736 Hz with 500 m fiber optical (2.5 μs delay). The proportional relation between the lasing fluctuation and the delay time were 358 and 263 Hz/μs, respectively. The vibration experiment was presented and it indicated that the NPRO Ho:YAG was more terrible to the influence of vibration, which is important in the practical application of wind measurement lidar.     

利用Keating模型计算Si(1-χ)Geχ及非晶硅的拉曼频移

利用Keating模型计算了Si(1-χ)Geχ合金中Si-Si,Ge-Ge和Si-Ge三种振动模态的拉曼频移,计算分别获得Ge浓度为0.1,0.5和0.9时,Si-Ge的振动拉曼频移分别为402.75,413.39和388.15 cm-1,这些结果与文献的实验结果符合,证明了Keating模型建立的关于原子振动模型是有效的,并可以利用拉伸压缩和相邻原子键之间弹性系数变化获得处于应变状态的拉曼光谱频率.利用Keating模型首次计算得到了非晶硅材料的单声子散射峰为477.029 cm-1,与文献实验结果480.0 cm-1相近,说明了非晶硅中原子的总体效果与晶体硅相比处于拉伸状态.     

Robustness estimation of software-synchronized all-optical sampling for fiber communication systems

The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.     

乙酸乙酯皂化实验装置的改进

在乙酸乙酯皂化反应实验数据的处理过程中,通常要假设反应物NaOH和CH3COOC2H5的起始浓度已知并且相等,因此,实验中要特别注意反应物起始浓度的准确性[1,2]。双管反应器是目前该实验的常用装置(图1)。实验时,先将具有相同浓度的等量反应物NaOH和CH3COOC2H5分别置于反应器的A、B管中,恒温后,用洗耳球将B管中的溶液压入A管进行混合。这一过程的缺点是,学生手动挤压洗耳球时,往往难以控制,不能很好地将A、B管的溶液混合均匀[1,2];另外,溶液混合之后,分别在A、B管中反应。这些都很难保证A、B两管中反应物的起始浓度准确一致,从而可能…     

9-(2-羟乙基)-吖啶酮柱前衍生胆汁酸高效液相色谱分析

采用一种新型紫外、荧光衍生试剂 9 ( 2 羟乙基 ) 吖啶酮 (HEA) ,在缩合剂 1 乙基 3 ( 3 二甲氨丙基 ) 碳酰二亚胺 (EDC·HCl)及碱性催化剂 4 二甲氨基吡啶 (DMAP)的存在下 ,对 1 0种胆汁酸进行柱前衍生 ,并通过荧光检测的方法进行高效液相色谱 (HPLC)分析。在HypersilBDSC18柱上 ,采用梯度洗脱 ,1 0种胆汁酸衍生物获得了基线分离 ,衍生物的激发和发射波长为λex/λem=40 4/44 0nm。衍生产物稳定性好 ,检测灵敏度高 ,按信噪比S/N =3∶1 ,平均检出限可达 8.3fmol。     

基于折反射原理的层去反求技术研究

为了克服传统层去反求测量中图像衬比度较低的缺陷,提出一种新的基于棱镜反射原理的层去反求图像摄取方法。该方法利用棱镜的全发射和折射作用提高图像衬比度,根据物体反射率的高低可分别采用垂直照明和倾斜照明,分别可获得高衬比度的亮目标暗背景和暗目标亮背景图像,为了校正由于折反射引入的几何变形,推出了相应的数学变换模型。该研究已成功投入实际产品校正的应用中,研究表明这种新的层去法比起传统的层去法不仅在于图像衬比度高,而且物体截面图像的轮廓更清晰可靠、无需填充反差材料,有望在零件及模型的反求测量中发挥较大的作用。     

Poly­[[bis(1H‐benz­imidazole‐κN3)cadmium(II)]‐μ‐aqua‐μ‐succinato‐κ2O1:O4]

The title compound, [Cd(C₄H₄O₄)(C₇H₆N₂)₂(H₂O)]_n, is a three‐dimensional polymeric complex. The Cd^II atom is located on an inversion centre and assumes an elongated octahedral coordination geometry, with a long Cd—O distance of 2.5381 (5) Å to the coordinated bridging water molecule. The succinate dianion, located on another inversion centre, bridges adjacent Cd atoms to form succinate‐bridged polymeric chains. The coordinated water mol­ecule is located on a twofold axis and links adjacent succinate‐bridged chains to form a water‐bridged polymeric chain.     

Extraction of Co-Products from Biomass: Example of Thermal Degradation of Silymarin Compounds in Subcritical Water

In an effort to increase revenues from a given feedstock, valuable co-products could be extracted prior to biochemical or thermochemical conversion with subcritical water. Although subcritical water shows significant promise in replacing organic solvents as an extraction solvent, compound degradation has been observed at elevated extraction temperatures. First order thermal degradation kinetics from a model system, silymarin extracted from Silybum marianum, in water at pH 5.1 and 100, 120, 140, and 160 °C were investigated. Water pressure was maintained slightly above its vapor pressure. Silymarin is a mixture of taxifolin, silichristin, silidianin, silibinin, and isosilibinin. The degradation rate constants ranged from 0.0104 min⁻¹ at 100 °C for silichristin to a maximum of 0.0840 min⁻¹ at 160 °C for silybin B. Half-lives, calculated from the rate constants, ranged from a low of 6.2 min at 160 °C to a high of 58.3 min at 100 °C, both for silichristin. The respective activation energies for the compounds ranged from 37.2 kJ/gmole for silidianin to 45.2 kJ/gmole for silichristin. In extracting the silymarin with pure ethanol at 140 °C, no degradation was observed. However, when extracting with ethanol/water mixtures at and 140 °C, degradation increased exponentially as the concentration of water increased. An erratum to this article can be found at     

Thermokinetic studies of the groups on TiO2 surface

The properties of groups on TiO₂ surface were evaluated by infrared (IR) spectra and thermal analysis. It could be found that water and ethanol are removed mainly between 343 and 363 K and the process is accompanied by an endothermic change. The results also show that ethanol could be removed completely below 673 K and the physically bonded or hydrogen‐bonded water could be removed almost completely above 873 K. The exothermic peaks ranging from 573 to 773 K are caused by the changes that chemisorbed water (Ti‐O‐H) on the surface condenses and evolves into water. There appears broad and unstable endothermic process in all temperature ranges due to the adhesions or transformations among the crystal particles. Thermogravimetry (TG) results show that with heat treatment at increasing temperatures, the groups on TiO₂ surface decreases gradually. The half peak breadth of X‐ray diffractometer (XRD) results suggest that TiO₂ crystallize better with higher temperature calcination. The photo‐catalytic efficiency was evaluated by UV‐Vis spectrophotometer. TiO₂ with heat treatment at higher temperature shows more effective photo‐catalytic property. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel naphthalimide derivatives with near-infrared emission: synthesis via photochemical cycloaromatization, fluorescence in solvents and living cell

In this Letter, a pair of novel naphthalimide derivatives with long-wavelength emission (>600 nm) and larger Stokes shift (>140 nm) have been developed through the photochemical cycloaromatization, in which intramolecular radical-induced 1,3-aromatic hydrogen transfer might be occurred. Cell uptake experiments showed that dye 2 could be used as a potential NIR fluorescence imaging agent.