Identification and quantification of polycarboxylates in detergent products using off-line size exclusion chromatography-nuclear magnetic resonance

The performance of many contemporary detergent products critically depends on polymers. Water-soluble polycarboxylates represent an important class of detergent polymers, and their quantitative assessment in detergent matrices stands as a considerable challenge. The presence of high levels of surfactants is a major complication, due to the strong tendency of surfactants to form micelles and to interact with the polymers. First, we addressed critical steps in the subsequent combined use of liquid extraction and off-line size exclusion chromatography-nuclear magnetic resonance (SEC-NMR) for identification and quantification of polycarboxylates in detergent products. Next, the different steps in the off-line SEC-NMR procedure were optimized with respect to precision and accuracy. This resulted in recoveries of more than 80% for maleic acid/acrylic acid copolymers; in detergent products a proportional bias of 30% is achieved. The method showed good precision with a relative standard deviation of within-laboratory reproducibility between 5% and 14%.     

Measurements of the size distribution of unattached radon progeny by using the imaging plate

The size distribution of unattached radon progeny is an important parameter for an accurate estimation of the internal dose of radon exposure. In this study, a new measuring system was developed to evaluate the size distribution of unattached radon progeny in air. In the system, airborne radon progeny were collected with a newly designed graded screen array (GSA), the activity concentrations were measured by using the imaging plate technique, and the size distribution of unattached fraction was retrieved by using an iterative nonlinear algorithm. The simulation results indicated that the collection characteristics of the new GSA system were well agreed with other systems. Test experiments showed that the activity-weighted median diameters (AMD) for unattached ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi were 0.89 ± 0.11 nm, 0.96 ± 0.13 nm and 1.01 ± 0.25 nm in a particle-free radon chamber, and the distribution changed with different concentrations of particles. As multiple measurements can be simultaneously carried out with a single IP, the new technique is considered as an optional and useful way to measure the size distribution measurement of unattached radon progeny.     

Size effect of lattice material and minimum weight design

The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method（EMsFEM） in the paper. With the same volume of base material and configuration, the structural displacement and maximum axial stress of micro-rod of lattice structures with different sizes of microstructure are analyzed and compared.It is pointed out that different from the traditional mathematical homogenization method, EMsFEM is suitable for analyzing the structures which is constituted with lattice materials and composed of quantities of finite-sized micro-rods.The minimum weight design of structures composed of lattice material is studied with downscaling calculation of EMsFEM under stress constraints of micro-rods. The optimal design results show that the weight of the structure increases with the decrease of the size of basic sub-unit cells. The paper presents a new approach for analysis and optimization of lattice materials in complex engineering constructions.     

Effect of system parameters on the size distributions of hollow nickel microspheres produced by an ultrasound-aided electrical discharge machining process

Ultrasound-aided electric discharge machining（EDM） is an emerging technology for producing hollow nickel microspheres.This technology combines traditional EDM with the cavitation and vibration effects of ultrasound to produce hollow microspheres.In this paper,ultrasound-aided EDM was carried out in a kerosene medium（the working solution）.The effects of various parameters on the sizes of microspheres were investigated using scanning electronic microscopy（SEM）.Smileview software was used to measure the sizes of the microspheres.Originpro software was used for statistical analysis to determine the size distributions of the microspheres.To study the effects of the system parameters on the sizes of the microspheres,we first investigated the necessity of using an ultrasonic wave with EDM.After comparing the experimental results with and without the ultrasonic field,we found that ultrasound-induced cavitation and vibration effects reduced the diameters of the microspheres.We then studied the effects of several electrical parameters,including the arc current,pulse width,and gap voltage,on the sizes of the microspheres at an ultrasound frequency of 40 kHz.Smaller microspheres could be obtained by lowering the arc current,pulse width,and gap voltage.     

Investigation of calcium carbonate precipitated in the presence of alkanols

The influence of myristyl alcohol (CH₃(CH₂)₁₃OH), cetyl alcohol (CH₃(CH₂)₁₅OH) and behenyl alcohol (CH₃(CH₂)₂₁OH) on the structure, morphology, size and surface properties of calcium carbonate (CaCO₃) has been investigated. Changes in the nature of the washing solvent, in the C_nOH/Ca²⁺ and CO₃²⁻/Ca²⁺ molar ratios and in temperature have been also evaluated. The sole polymorph produced was rhombohedral calcite. At room temperature, while microspheres composed of submicrocubes were produced at a high molar ratio CO₃²⁻/Ca²⁺ and low CH₃(CH₂)₁₅OH concentration, a stoichiometric molar ratio CO₃²⁻/Ca²⁺ and high CH₃(CH₂)₁₅OH concentration induced the formation of microcubes and microboxes. In the presence of this alkanol (12 % molar) a significant enhancement of the water contact angle (ca. 40 °) resulted in a sample obtained with a stoichiometric CO₃²⁻/Ca²⁺ ratio. These results emphasize the key role played by the three non‐ionic surfactants in the formation of materials with variable crystal shape and wettability and thus technological interest for a range of applications.     

基于粒子谱分布的无线紫外光通信散射传输特性研究

在非直视无线紫外光通信中,利用大气中的粒子对紫外光进行散射作用来传递信息,非直视紫外光通信在近距离隐蔽通信中有广阔的应用前景。雾霾粒子属于气溶胶范畴,由空气中的灰尘、硫化物、有机碳氢化合物等粒子组成。雾霾粒子的尺度、浓度、形状等因素均会对无线紫外光散射通信的传输特性产生较大的影响。首先,基于蒙特卡罗方法建立了非直视紫外光多次散射模型,将霾粒子的半径和浓度这两个物理量引入该模型中,通过模拟大量光子在雾霾条件下经多次散射到达接收端的概率,进而仿真分析了系统路径损耗与粒子半径和浓度之间的关系。结果表明,(1) 在无线紫外光近距离通信条件下,雾霾浓度越大,路径损耗越小,系统通信性能越好;(2) 通信距离大于500 m时,增加雾霾粒子浓度,系统路径损耗总体先减小再增大;(3) 在粒子浓度一定情况下,增大粒子半径,路径损耗先减小后增大,且随着通信距离的增大,路径损耗极小值的位置不断向粒子半径小的一侧移动。其次,在模型中引入粒子尺度谱分布的概念,对粒子尺度谱分布进行分割,分别求出不同粒径及其所对应浓度。假定粒子尺度谱分布中不同粒径的粒子依次对光子产生散射作用,对相应光子到达接收端的概率求和,得到光子到达接收端的总概率,进而求得多种粒径的粒子共同存在情况下系统的路径损耗,使仿真模型更加逼近实际大气信道中多种半径雾霾粒子共同存在的事实。最后,搭建实验平台,分别在良好、严重雾霾、极严重雾霾三种不同天气条件下,实验测量了系统路径损耗和通信距离、收发仰角之间的关系,并与考虑粒子尺度谱分布模型中计算得到的路径损耗进行对比,实验数据与仿真结果趋势一致,雾霾天气下的通信质量优于良好天气,收发仰角越大对应的路径损耗也越大。     

基于热图像的种蛋气室变化监测算法

种蛋气室的大小是监测种蛋孵化过程的重要指标之一。根据种蛋的热力学结构,种蛋在孵化过程中,包裹气室部分蛋壳会与其他部分蛋壳产生温差,从而可通过热红外图像进行观察。针对在种蛋孵化过程中,人工照蛋检测气室效率低的问题,探索设计了一种基于热图像的种蛋气室变化俯视监测算法。监测种蛋气室热图像的算法主要包括种蛋目标检测,种蛋图像分割和种蛋气室面积计算3个部分,其中种蛋的目标检测采用Faster-RCNN算法实现;种蛋图像分割采用BP神经网络算法实现;种蛋气室面积是在种蛋图像分割的基础上进行计算。使用孵化5天及以上的种蛋作为研究对象,并拍取种蛋的热图像进行试验。试验结果表明：种蛋热图像的目标检测的平均精度（mAP）为99.85%,拥有较好的检测效果。使用BP网络对种蛋进行图像分割。BP神经网络经过调参后,其网络最佳的结构为三层隐藏层,每个隐藏层拥有1 000个神经元,最优初始学习率为0.000 1,最优最大迭代次数为500。以F1-measure作为分割效果的评价指标,BP神经网络的图像分割总体结果为87.02%,Otsu算法的总体结果为65.25%。其中只有一个蛋的情况下,BP神经网络的分割结果为87.17%,Otsu算法的结果为68.86%。存在其他种蛋的干扰条件下,BP神经网络的分割结果为86.94%,Otsu算法的结果为61.64%,BP神经网络的分割效果优于Otsu分割算法,BP神经网络拥有更强的抗干扰能力。最后提取了孵化5～19 d种蛋的气室变化,通过观察种蛋气室大小曲线来监测种蛋的孵化情况,可看出随着天数的增加,气室有着明显变大的趋势。人工测量法与热红外测量法比较结果说明两者相关性为0.934 3,拥有较好的相关性。基于热图像的种蛋气室变化监测算法可在实际生产中实现种蛋的识别与气室大小的快速监测,为实现监测种蛋孵化的自动化提供了技术参考。     

A fractal interpretation of size effects on the strength of metallic glasses

Yielding strength of metallic glasses in the uniaxial tensile and compressive tests is scale-dependent, which is attributed to the self-similar distribution of atomic cluster and free volume in the work. In contrast with the Weibull statistical theory previously employed in scaling phenomena of metallic glasses, fractal scaling laws are for the first time applied to describe the size effect inherent to the material disorder. Especially, the Multifractal Scaling Law (MFSL) originally proposed for quasi-brittle materials is used to interpret some experimental data in the literature. The best-fitted parameters (_fy$f_{\mathrm{y}}$ and l_ch) from the MFSL are in good consistency with the bulk yielding strength and the shear band size of metallic glasses observed in the alternative approaches or experiments. The fractal size effect laws provide insight into not only the scaling phenomena, but also further engineering strength predictions and designs.     

Analysis of sodium polycarboxylates in detergents by size exclusion chromatography

Summary This paper describes the quantitative analysis and preparative isolation of sodium polycarboxylates in detergents by means of gel permeation chromatography. An analytical monitoring method separates the polymers from other low molecular detergent ingredients within 10 minutes. There is no separation of the various molecular weight polycarboxylate macromolecules themselves. They elute from the column as a single narrow peak at the exclusion volume. A second preparative gel filtration method allows isolation of polycarboxylates in amounts necessary for further characterization. Appropriate sample pretreatments and possible interferences are discussed.