High stability breakdown of noble gases with femtosecond laser pulses

In the past, laser-induced breakdown spectroscopy (LIBS) signals have been reported to have a stability independent of the pulse length in solids. In this Letter, we perform the first stability study of femtosecond LIBS in gases (to our best knowledge) and show a significant improvement in signal stability over those achieved with longer pulses. Our study shows that ultrashort-pulse LIBS has an intrinsically higher stability in gas compared to nanosecond-pulse LIBS because of a deterministic ionization process at work in the femtosecond pulse. Relative standard deviations below 1% are demonstrated and are likely only limited by our laser output fluctuations. This enhanced emission stability may open up possibilities for a range of applications, from monitoring rapid gas dynamics to high-quality broadband light sources.     

A Demonstration of Automatically Switched Optical Network

We build an automatically switched optical network (ASON) testbed with four optical cross-connect nodes. Many fundamental ASON features are demonstrated, which is implemented by control protocols based on generalized multi-protocol label switching (GMPLS) framework.     

精确控制大数值孔径微透镜列阵面形的显影阈值方法

提出了一种可对大矢高、非球面微透镜阵列面形进行精确控制的新方法。针对不同面形的微透镜阵列，该方法首先对光致抗蚀剂表面的曝光分布进行设计，然后，利用光致抗蚀剂显影过程中的阈值特性，对微透镜的面形实行控制。当抗蚀剂显影速率接近0时，即可获得设计的微透镜面形。该方法不仅大大提高了微透镜阵列矢高的加工范围，而且还减小了光刻材料显影特性对微透镜面形的影响，提高了微透镜阵列的面形控制精度，在实验中获得了矢高达114μm的微透镜阵列。最终实现了大浮雕深度、大数值孔径、非球面微列阵光学元件的面形控制。     

Liquid crystalline behavior and fluorescent property of calix[4]arene containing azobenzene photochromic group

The reaction of 4′-hydroxy-4-methyl azobenzene (1) and 1,6-dibromohexane afforded 6-bromo-1-((4-((4-met hylphenyl)azo)phenyl)oxy)hexane (2), which further reacted with p-tert-butylcalix[4]arene to give the calix[4]arene derivative (3) whose lower rim had been modified by the azobenzene photochromic group. The structure of 3 was characterized by ¹H-nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS). The fluorescence intensity of compound 3 was two to four times higher than that of compounds 1 and 2 as the azobenzene group concentration in the range of 1.6 × 10⁻⁵ to 8.0 × 10⁻⁴ mol/L, indicating that the fluorescence quantum yield of the azobenzene group had been improved through being attached to the calix[4]arene skeleton. The liquid crystalline behavior of compound 3 was studied by polarized microscopy (POM) and differential scan calorimeter (DSC). Compound 3 exhibited the enchased texture of a smectic liquid crystal from 209.4°C to 219.5°C on heating, while 2 exhibited a liquid crystalline phase from 87.4 to 83.2°C on cooling. It was found that the calix[4]arene skeleton was a good platform for conformation immobilization of azobenzene photochromic group and the formation of liquid crystalline. Translated from Chinese Journal of Applied Chemistry, 2006, 23(9): 1023–1026 [译自: 应用化学]     

补强片自动贴片系统高精度手眼标定方法

针对补强片自动贴片系统的手眼标定问题,为了消除相机安装的垂直度偏差带来的误差,提出了一种新的手眼标定方法。使用标定板得到相机的外参数,将外参数与常规的二维标定模型相结合,从而间接计算出相机坐标系与机器人基础坐标系的齐次坐标转换矩阵,使手眼标定模型扩展为三维。三维模型的标定计算误差小于0.1 m,相比二维模型降低了1个数量级,有效提高了标定计算精度。利用厚度较小的菲林修正齐次坐标变换矩阵的Z方向分量,系统具有较高的定位精度,手眼标定的误差绝对值小于0.015 mm,有效减小了误差均值,设备性能得到大幅提高。该方法在系统可控自由度有限的情况下,能够得到手眼标定问题的唯一解,提出的三维模型中包括了相机的完整姿态信息,相比常规的标定方法没有相机安装等额外的限制条件,能有效提高系统的手眼标定精度。     

Multiplicity of positive solutions for a class of concave-convex elliptic equations with critical growth

In this article, the following concave and convex nonlinearities elliptic equations involving critical growth is considered,{-△u=g(x)|u|2*-2u+λf(x)|u|q-2u,x∈Ω,u=0,x∈■Ω where Ω■R~N(N≥3) is an open bounded domain with smooth boundary, 1 q 2, λ 0.2*=2 N/(N-2)is the critical Sobolev exponent,f∈L2~*/(2~*-q)(Ω)is nonzero and nonnegative,and g ∈ C(■) is a positive function with k local maximum points. By the Nehari method and variational method,k+1 positive solutions are obtained. Our results complement and optimize the previous work by Lin [MR2870946, Nonlinear Anal. 75(2012) 2660-2671].     

Photodegradation of rhodamine B dye using a microwave electrodeless UV lamp (MWUVL)

The photodegradation of organic dye rhodamine B (RhB) in an aqueous solution was studied using a microwave electrodeless UV lamp (MWUVL). The 185 nm vacuum UV (VUV) intensity of the MWUVL amounted to 12% of the total UV output, about 1.7 times as high as that of the con ventional low-pressure mercury lamp. An acidic condition was preferred for the degradation of RhB. Precipitate was generated during RhB degradation when the initial concentration of RhB solution was above 60 mg · L⁻¹. For 100 mg · L⁻¹ RhB at pH 4.0, the mass of precipitate produced was nearly half of the initial amount of RhB in the solution after irradi ation for 75 min. The corresponding degradation ratio of RhB reached up to 99.4% and COD reduced 77.4%. The photo degradation of RhB is mainly achieved by direct photolysis of RhB by 185 nm and OH radical oxidation. __________ Translated from Journal of Fudan University (Natural Science), 2006, 45(6): 726–731 [译自: 复旦学报 (自然科学版)]     

AN EXISTENCE THEOREM OF SOLUTIONS FOR SEMILINEAR ELLIPTIC EQUATIONS ON R~N

1991MRSubjectClassification35C15,58E50ConsiderthesernilinearellipticdifferentialequationInthestudyofllollliliearSchrodingerequations,nonlinearequationsofKleili~Gordolltypeall(1reaction-diffusiollequatiolls,sollltionsof(1)correspolldtostalldingwavesolutions.stroll(lill~(ortraveling)wavesolutionsandsteadystatesofthesystem.Manypapersdealtwiththeautonomouscasewhere5andfareindependentofatorwiththeradiallysynlluetriccasewherebandfdependonfi](see[1-4]andtheirreferences).Recentlytheperiodiccaseand…