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1.
The use of a high-speed aerosol flow is proposed for sampling RDX from the surface followed by chromatographic analysis. The aerosol is generated from different solvents by means of a coaxial nebulizer. The effect of the aerosol flow parameters (solvent flowrate, an angle of the nebulizer inclination with respect to the surface) and various solvents (water, acetone, and hexane) on the efficiency of the RDX desorption was investigated. The optimal angle of the nebulizer was found to be 30°, under these conditions, the desorption of RDX from the surfaces of different structure (metal, glass, leather, cotton fabric, and paper) has also been studied. It is shown that under the action of an aerosol created using water and acetone, desorption from a smooth surface occurs most efficiently (1.5 times higher than with hexane). In this case, the sample removes almost completely (about 80%) by the aerosol flow in a few seconds. A relationship between the desorption efficiency and the amount of the solvent sprayed (that is the amount of aerosol particles in desorbing flow) has a characteristic maximum which location depends on the properties of the solvent spray. This effect is associated with a rate of solvent evaporation. Under optimal conditions for desorption of RDX from a smooth surface using an aqueous aerosol, an LOD of ~10?ng can be achieved. For porous and rough surfaces, the efficiency of the analyte desorption decreases (three times for leather and cotton fabric). The results of the experiments conducted allow one to conclude that the RDX solubility in the solvent used does not affect considerably the efficiency of the RDX desorption. It is assumed that small aerosol drops are very active and can capture the particles of the target analyte. This promotes the desorption of RDX molecules from the surface.© 2018 American Association for Aerosol Research 相似文献
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AbstractChinese cooking produces large numbers of particles that can cause both indoor and outdoor air quality problems. To reduce the extraction of particles to the outdoor air, this investigation studied capture efficiency of a rotating disk in an exhaust hood. The studies were performed experimentally in a wind tunnel and numerically by computational fluid dynamics (CFD) models with the Lagrangian method for tracking particle trajectories. The experimental data were used to identify the best turbulence model among the three tested in the CFD simulations. The results show that the capture efficiency increased with disk rotation speed and particle size but decreased with exhaust airflow rate. The CFD simulations provided detailed information about the mechanisms by which particles of different sizes were captured by the rotating disk. CFD was then used to explore two methods for improving the capture efficiency: adding more wires to the middle and outer zones of the disk, and using two layers of disks. Both methods can increase the capture efficiency of the rotating disk at an acceptable pressure loss.Copyright © 2020 American Association for Aerosol Research 相似文献
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《洛阳伽蓝记》详尽记载了北魏时期洛阳佛寺.该文据此对我国佛寺园林发展的历史背景和北魏洛阳城市佛寺园林的形制特征、文化特质以及对后世寺庙园林的历史影响进行了分析概括. 相似文献
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多光谱成像仪具有同目标多谱段信息获取的特点,因此在空间遥感领域占据很重要的位置。由于成像仪光学系统不可避免的存在几何畸变问题,会对获取地面目标信息的精度造成很大的影响,因此对于多光谱成像仪进行几何特征标定对于提升成像仪成像质量的有很大的作用。本文中应用标准网格板、自准直仪和高精度二维转台组合的几何特征标定方法,此方法具有测量原理简单、实验直观、标定结果可靠性高等特点。多次标定结果表明:主点标定精度优于5.2 μm,主距标定精度优于0.02 mm。满足实验要求。 相似文献
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刘凤霞 《成都电子机械高等专科学校学报》2016,(1):65-67
王阳明的《瘗旅文》表达了他对逝者的真切同情,显示出一个儒者独特的诗性审美境界;文中言辞及埋葬死者躯体、祭奠亡灵的义举则是一种达人达己的仁者精神;他在文末所秉承“止于悲伤”之达观态度,表现出通变制宜的智者心境。 相似文献
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阎利华 《北方工业大学学报》2014,26(2):62-66
《万叶集》里的咏梅和歌集中出现在天平时期(729~749年),大多出自大伴旅人、大伴加持等贵族官人之手。本文通过具体分析《万叶集》咏梅和歌中梅与雪、梅与柳、梅与莺以及梅花"插发"等几种主要模式,指出其在构思、选材以及用词上模仿借鉴了魏晋南北朝至初唐的咏梅汉诗赋。但由于中日两国传统审美情趣的不同,汉诗赋与和歌的根本差异,《万叶集》咏梅和歌与魏晋南北朝至初唐的咏梅汉诗赋在意境和文化蕴涵上又存在着本质区别。 相似文献
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Qian Zhang Jenny P. S. Wong Aika Y. Davis Marilyn S. Black 《Aerosol science and technology》2017,51(11):1275-1286
Particle emissions from multiple fused deposition modeling consumer 3D printers were systematically quantified utilizing an established emission testing protocol (Blue Angel) to allow quantitative exposure assessments for printers operating in different environments. The data are consistent with particle generation from volatilization of the polymer filament as it is heated by the extruder. Typically, as printing begins, a burst of new particle formation leads to the smallest sizes and maximum number concentrations produced throughout the print job. For acrylonitrile butadiene styrene (ABS) filaments, instantaneous concentrations were up to 106 #/cm3 with mean particle sizes of 20 to 40 nm when measured in a well mixed 1 m3 chamber with 1 air change per hour. Particles are continuously formed during printing and the size distribution evolves consistent with vapor condensation and particle coagulation. Particles emitted per mass of filament consumed (particle yield) varied widely due to factors including printer brand, and type and brand of filament. Higher extruder temperatures result in larger emissions. For filament materials tested, average particle number yields ranged from 7.3 × 108 to 5.2 × 1010 g?1 (approximately 0.65 to 24 ppm), with trace additives apparently driving the large variations. Nanoparticles (diameters less than 100 nm) dominate number distributions, whereas diameters in the range of 200 to 500 nm contribute most to estimated mass. Because 3D printers are often used in public spaces and personal residences, the general public and particularly susceptible populations, such as children, can be exposed to high concentrations of non-engineered nanoparticles of potential toxicity.Copyright © 2017 American Association for Aerosol Research 相似文献
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秦岭岩白菜多糖的提取纯化工艺研究 总被引:1,自引:0,他引:1
以秦岭岩白菜多糖的含量和得率为指标,采用正交实验对秦岭岩白菜多糖的提取纯化工艺进行了优化。确定秦岭岩白菜多糖的最佳提取工艺为:用20 BV水在90℃提取3次,每次0.5 h;最佳纯化工艺为:用4 BV 70%(体积分数)乙醇醇沉24 h。该优化提取纯化工艺简便、合理、可行。 相似文献