Laser-induced breakdown spectroscopy in analysis of Al3+ liquid droplets: on-line preconcentration by use of flow-injection manifold

Laser-induced breakdown spectroscopy (LIBS), combined with a flow-injection system, is demonstrated to analyze liquid droplets of aluminum salt, as generated with an electrospray ionization device. The spray needle also serves as the anode, through which the analyte solution is spread toward the other metal base as the cathode. Along the passage of the FI manifold, the Al-sample loading speed is controlled at 0.15 mL min⁻¹, restricted to the small diameter of the spray needle, and the loading volume amounts to 0.1 mL. The metal ion is retained in a cation-exchange resin microcolumn immobilized with Chromotrope 2B chelating agent, followed by elution with a 0.5 M HCl solution into LIBS. Upon laser irradiation at the preconcentrated liquid droplets, the time-resolved laser-induced breakdown (LIB) emission and plasma-induced current signals are acquired concurrently on a single-shot basis. The area under the LIB/current distribution increases in linear proportion as the concentration of the sample solution increases. The detection limit thus obtained can reach 1.5 mg L⁻¹, about an order of magnitude lower than those achieved previously using single-laser ablation without involvement of preconcentration. The linear dynamic range is more than two orders of magnitude.     

Development in the application of laser-induced breakdown spectroscopy in recent years: A review

Laser-induced breakdown spectroscopy (LIBS) has been widely studied due to its unique advantages such as remote sensing, real-time multi-elemental detection and none-to-little damage. With the efforts of researchers around the world, LIBS has been developed by leaps and bounds. Moreover, in recent years, more and more Chinese LIBS researchers have put tremendous energy in promoting LIBS applications. It is worth mentioning that the application of LIBS in a specific field has its special application background and technical difficulties, therefore it may develop in different stages. A review summarizing the current development status of LIBS in various fields would be helpful for the development of LIBS technology as well as its applications especially for Chinese LIBS community since most of the researchers in this field work in application. In the present work, we summarized the research status and latest progress of main research groups in coal, metallurgy, and water, etc. Based on the current research status, the challenges and opportunities of LIBS were evaluated, and suggestions were made to further promote LIBS applications.     

安装及管理Novell Netware网络过程中的故障处理

本文对NovellNetware进行了简单的介绍,并以实例说明其联网的安装步骤及安装应用软件过程中常见的故障,进行简单分析,指出了解决办法。同时,也对在使用管理网络过程中出现的故障进行了分析,并作技术处理,进行修复。     

考虑启动压力梯度的直井压裂渗流模型与实验

采用直井压裂技术开发低渗透稠油油藏在工程上表现出较理想的经济效益。基于渗流理论和水电模拟实验,建立了低渗透稠油油藏直井压裂后形成垂直裂缝的渗流模型。由于稠油在低渗地层中表现出非牛顿性,该公式进一步考虑了启动压力梯度、有效运动边界和有效边界压力,建立针对径向流向椭圆流转变的渐变流模型,通过半缝长与供油半径比值判断渐变流模型中的径向流、椭圆流的临界边界。设计一种存在击穿电压的溶液用于电模拟实验,适用于模拟稠油的启动压力梯度,并对启动压力梯度对产能的影响做了分析。     

Control of vortex breakdown in a closed cylinder with a small rotating rod

Effective control of vortex breakdown in a cylinder with a rotating lid was achieved with small rotating rods positioned on the stationary lid. After validation with accurate measurements using a novel stereoscopic particle image velocimetry (SPIV) technique, analysis of numerical simulations using a high-order spectral element method has been undertaken. The effect of a finite length rod creates additional source terms of vorticity as the rod rotates. These additional source terms and their spatial locations influence the occurrence of the vortex breakdown.     

Large Eddy Simulations of Swirling Non-premixed Flames With Flamelet Models: A Comparison of Numerical Methods

This work investigates the application of large eddy simulation (LES) to selected cases of the turbulent non-premixed Sydney swirl flames. Two research groups (Loughborough University, LU and Imperial College, IC) have simulated these cases for different parameter sets, using two different and independent LES methods. The simulations of the non-reactive turbulent flow predicted the experimental results with good agreement and both simulations captured the recirculation structures and the vortex breakdown without major difficulties. For the reactive cases, the LES predictions were less satisfactory, and using two independent simulations has helped to understand the shortcomings of each. Furthermore one of the flames (SMH2) was found to be exceptionally hard to predict, which was supported by the lower amount of turbulent kinetic energy that was resolved in this case. However, the LES has identified modes of flame instability that were similar to those observed in some of the experiments.     

两亲性聚肽三嵌段共聚物的自组装行为

通过开环反应,合成了聚（L-谷氨酸-γ-苯甲酯）-b-聚乙二醇-b-聚（L-谷氨酸-γ-苯甲酯）（PBLG-b-PEG-b-PBLG）三嵌段聚肽共聚物。运用核磁共振氢谱和凝胶渗透色谱表征了聚合物的结构。凝胶渗透色谱测试表明合成的聚合物分子量分布窄。以选择性溶剂透析的方法制备了自组装聚集体,通过透射电子显微镜、扫描电子显...     

HL-2A装置气体击穿延迟时间

气体击穿延迟时间实验数据表明,HL-2A装置的气体击穿过程可以用修改了的有电极放电汤森德电离公式,并考虑电子的几何损失来进行描述。     

激光诱导氩气等离子体时间分辨特性研究

激光诱导击穿光谱(L IB S)以激光诱导微等离子体的原子发射为技术特征,在科研与工业领域正得到重视与蓬勃发展.作为环境气体的氩气对等离子体演化过程中粒子的碰撞过程有重要影响,决定着L IBS技术分析性能的发挥.利用光谱诊断技术深入研究LIBS技术条件下氩气的光谱特征,对于提升LIBS技术及其应用水平具有重要的意义.利...     

基于共振与非共振双线的自吸收免疫LIBS技术研究

激光诱导击穿光谱(LIBS)定量分析中的自吸收效应不仅会降低谱线强度和增加线宽,而且使定标结果饱和,从而影响最终的分析精度。为了消除该效应的影响,提出了一种基于共振双线与非共振双线选择的自吸收免疫激光诱导击穿光谱(SAF-LIBS)技术,通过比较所测谱线强度比值和理论强度比值来确定等离子体的光学薄时刻,并使用共振线与非共振线来拓展元素含量的可测量范围。该技术可以分为定标和定量两个分析过程,其定标过程为:计算待测元素的共振双线及非共振双线的理论强度比,通过对比不同待测元素含量样品的共振双线及非共振双线在不同延时下的强度比和理论比,确定等离子体的光学薄时刻;使用一系列标准样品建立LIBS非共振线的单变量定标曲线;利用准光学薄谱线建立共振线和非共振线的SAF-LIBS单变量分段定标曲线。其定量分析过程为:先用非共振线和LIBS定标曲线确定未知样品所属的含量分段,再用准光学薄谱线以及与所属分段的共振或非共振SAF-LIBS定标曲线完成定量分析。对Cu元素的单变量定标结果表明,对于共振线,最佳延时随着样品含Cu量的增加而增加,且只有当含Cu量低于0.05%时,才可能获得准光学薄的共振线,而随着Cu含量的增加,自吸收变得非常严重,以至于无法获得光学薄的共振线;对于非共振线,当含Cu量在0.01%~30%范围内,均可获得准光学薄的非共振谱线,而当Cu含量大于50.7%时,将无法在等离子体寿命期内捕获到光学薄谱线。对Cu元素的定量分析结果表明,基于共振双线与非共振双线的自吸收免疫LIBS技术可以有效地避免自吸收效应的影响,各分段定标曲线的线性度均大于0.99,对两个未知样品中Cu元素含量的绝对测量误差分别为0.01%和0.1%,探测限达到了1.35×10-4%,最大可测量范围拓展至50.7%。