Detection of lead in water using laser-induced breakdown spectroscopy and laser-induced fluorescence

Laser-induced breakdown spectroscopy (LIBS) is a well-known technique for fast, stand-off, and nondestructive analysis of the elemental composition of a sample. We have been investigating micro-LIBS for the past few years and demonstrating its application to microanalysis of surfaces. Recently, we have integrated micro-LIBS with laser-induced fluorescence (LIF), and this combination, laser ablation laser-induced fluorescence (LA-LIF), allows one to achieve much higher sensitivity than traditional LIBS. In this study, we use a 170 microJ laser pulse to ablate a liquid sample in order to measure the lead content. The plasma created was re-excited by a 10 microJ laser pulse tuned to one of the lead resonant lines. Upon optimization, the 3sigma limit of detection was found to be 35 +/- 7 ppb, which is close to the EPA standard for the level of lead allowed in drinking water.     

Imaging stacking order in few-layer graphene

Few-layer graphene (FLG) has been predicted to exist in various crystallographic stacking sequences, which can strongly influence the material's electronic properties. We demonstrate an accurate and efficient method to characterize stacking order in FLG using the distinctive features of the Raman 2D-mode. Raman imaging allows us to visualize directly the spatial distribution of Bernal (ABA) and rhombohedral (ABC) stacking in tri- and tetralayer graphene. We find that 15% of exfoliated graphene tri- and tetralayers is composed of micrometer-sized domains of rhombohedral stacking, rather than of usual Bernal stacking. These domains are stable and remain unchanged for temperatures exceeding 800 °C.     

厂用变压器备自投电动机再启动控制系统改进

黑龙江建龙钢铁有限公司热电厂低压配电系统采用的是由直流控制交流,厂用变压器采用的是一台明备用变压器（0#厂用变压器）、两台工作变压器（1#和2#厂用变压器）。三台变压器的容量是备用变压器为1000kVA,而其它两台工作变压器为800kVA。当运行的两台工作变压器其中一台或两台因故障跳闸时,备用变压器自动投入运行使低压配电系统的电动机及设备再启动,从而保证了生产的安全运行。     

Use of low dose e-beam irradiation to reduce E. coli O157:H7, non-O157 (VTEC) E. coli and Salmonella viability on meat surfaces

This study determined the extent that irradiation of fresh beef surfaces with an absorbed dose of 1 kGy electron (e-) beam irradiation might reduce the viability of mixtures of O157 and non-O157 verotoxigenic Escherichia coli (VTEC) and Salmonella. These were grouped together based on similar resistances to irradiation and inoculated on beef surfaces (outside flat and inside round, top and bottom muscle cuts), and then e-beam irradiated. Salmonella serovars were most resistant to 1 kGy treatment, showing a reduction of ≤ 1.9 log CFU/g. This treatment reduced the viability of two groups of non-O157 E. coli mixtures by ≤ 4.5 and ≤ 3.9 log CFU/g. Log reductions of ≤ 4.0 log CFU/g were observed for E. coli O157:H7 cocktails. Since under normal processing conditions the levels of these pathogens on beef carcasses would be lower than the lethality caused by the treatment used, irradiation at 1 kGy would be expected to eliminate the hazard represented by VTEC E. coli.     

现代实木家具涂装工艺探讨

本文分别从涂装工具设备、涂装环境、木材材质的选择、涂装前的表面处理、木器涂料的选择、涂装施工和抛光上蜡等工艺环节论述了现代家木家具涂装工艺流程和技术要求。     

Fiber-laser-based wavelength-division multiplexed fiber Bragggrating sensor system

A wavelength-division-multiplexing technique for interrogating 10-cascaded fiber Bragg grating sensing elements based on a ring-compounded-cavity fiber laser is reported. A feedback control technique was introduced to a tunable Fabry-Perot filter that tracks the wavelength-shift of the sensor. The sensors were demodulated using an unbalanced scanning Michelson interferometer and a sensitivity of 1.682°/με has been demonstrated     

高炉喷煤站贮煤系统改造设计构想

通过对高炉喷吹煤粉贮喷工艺的缺点分析,提出改进设想。     

高阻隔性EVOH树脂

介绍了高阻隔性树脂－－乙烯－乙烯醇共聚物（ＥＶＯＨ）的性能及其用途。     

无机高分子絮凝剂PASS的研究

以硅酸钠、硫酸和硫酸铝为原料制备聚合硅酸硫酸铝絮凝剂,其最佳制备条件为pH值为6～7,铝、硅摩尔比为1:1。考察了聚合硅酸硫酸铝加剂量和熟化时间对其絮凝性能的影响,试验结果表明:聚合硅酸硫酸铝的加剂量为3.0mg/L(以SiO2计算),熟化时间为1h时絮凝效果较好。研究对比了聚合硅酸硫酸铝和聚合氯化铝的絮凝性能,在铝含量相同情况下,聚合硅酸硫酸铝的絮凝性能优越于聚合氯化铝。该聚合硅酸硫酸铝絮凝剂与传统的絮凝剂相比,具有较强的去浊能力,对污水处理具有优异的絮凝性能。     

上海电网负荷低电压释放问题的研究

对影响上海电网低电压释放的诸因素作了全面细致的分析,提出了相应的对策.对低电压不释放对系统的影响也作了定性讨论.研究的结论对城市密集型电网具有普遍指导意义.