Detection of RDX traces at the surface with sonic aerosol flow desorption

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     

Particle capture by a rotating disk in a kitchen exhaust hood

Abstract

Chinese 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     

Distribution of contact pressure over the surface of ceramic floor tiles during the polishing process

Assisted with computational simulation this work quantitatively determined the distribution of contact pressure over the surface of porcelain stoneware tiles during the industrial polishing process. In modern polishing lines there are basically three movements responsible for the scratching velocity and the position of the abrasives. Combining the kinematic equations obtained by these movements with a pre-existing model the contact pressure between abrasive tool and tile surface could be determined as function of time. The spatial distribution of average, standard deviation and maximum values of contact pressure were then obtained and mapped over the entire surface. The simulation results showed that the contact pressure tends to be 50% higher near to the center, in regions worked by the innermost abrasives. Additionally, periodical variations of up to 10% were found to occur due to the partial retreat of the abrasive tool.     

对出口哥伦比亚陶瓷砖标签技术法规的解析

本文主要研究了哥伦比亚对进口陶瓷砖标签要求的技术法规以及涉及的产品标准,并对该法规中的标签要求做了详细的解析。同时,对哥伦比亚在监督、执行和处罚等方面进行了详细阐述。     

DNA Nanoarchitectures: Steps towards Biological Applications

DNA's remarkable molecular recognition properties, flexibility, and structural features make it one of the most promising scaffolds to design a variety of nanostructures. During recent decades, two major methods have been developed for the construction of DNA nanomaterials in a programmable way; both generate nanostructures in one, two, and three dimensions. The tile‐based assembly process is a useful tool to construct large and simple structures; the DNA origami method is suitable for the production of smaller, more sophisticated and well‐defined structures. Proteins, nanoparticles and other functional elements have been specifically positioned into designed patterns on these structures. They can also act as templates to study chemical reactions, help in the structural determination of proteins, and be used as platform for genomic and drug delivery applications. In this review we examine recent progresses towards the potential use of DNA nanostructures in molecular and cellular biology.     

辽宁王营子钼矿地质特征及找矿标志

辽宁省朝阳市王营子钨钼矿位于努鲁儿虎山脉大青山东部,属辽西凌源—北票金成矿带高杖子—大庙—东五家子金成矿区中部,蝴蝶沟—王营子金钼多金属矿化带。研究区内地层、岩浆岩发育较好,构造未见明显特征。主要岩体以斑状花岗岩、似斑状花岗岩为主,矿体严格受似斑状花岗岩控制,富集于钾化似斑花岗岩中,矿脉与围岩无明显界线。基于野外实际勘查、成矿地质条件等的研究,认为王营子钼矿为细脉浸染型斑岩型钼矿,并总结了找矿标志。     

利用炼铜废渣生产彩色地砖

利用炼铜废渣 (诺砂 )研制开发了彩色地砖产品。概述了诺砂的组成及特性 ,介绍了彩色地砖的生产工艺过程。     

陶瓷墙地砖胶粘剂行业标准的编制及实施意义

陶瓷墙地砖胶粘剂行业标准即将颁发，为配合该标准实施，介绍了标准的编制和实施意义。     

陶土板幕墙系统特性及应用

本文主要介绍了一种新的建筑外立面装饰材料系统--陶土板幕墙.文中描述了陶土板幕墙在外观、性能上的特点,介绍了陶土板幕墙的类型及其安装系统.     

明代琉璃瓦、兽件分析

明代建筑不但大木、斗栱的做工考究，琉璃构件也大都做出榫卯，使构件之间衔接牢固，与大木构造的风格相一致，这充分表明到明代时，琉璃工艺已具有相当高超的技术水平。本文通过几座明代建筑考察中发现的琉璃瓦、小兽残件的特点作初步的探讨和分析。