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Analysis of the Influence of Electrostatic Probe on Surface Charge Measurements
No full textThe electrostatic probe is among the most popular methods to measure the surface charge. However, the probe influences the surface charge distribution on the sample, which increases measurement error. In this paper, the electrostatic probe system is modeled to study its effect on surface charges on a circular conductor plate using electrostatic field calculation. The influence of the probe on the sample surface charges is found to increase with a decrease in the measurement distance, whereas it has a similar effect on surface charge density at different radial positions. A calibration process is proposed to measure the potential from the induced potential of the probe head. Using the measured potential, we calculate the surface charge density via the method of moments. The measurement error is analyzed when the measurement distance and number of rings are changed. The authors find that the number of rings should be appropriately reduced when the measurement distance increases to ensure the accuracy of the calculations. This research provides theoretical guidance for using the electrostatic probe and establishing a surface charge measurements system
It Seemed Like a Good Idea at the Time (Covid-19 Edition)
No full textConference presentations usually focus on successful innovations: new ideas that yield significant improvements to current practice. Yet we often learn more from failure than from success. In this panel, we present five case studies of good ideas for improving CS education (most related to the COVID-19 pandemic) that didn\u27t go as planned. Each contributor will describe their good idea , the situation that resulted, and wider lessons for the CS community
Improved Conditions for Analysis of the Group Composition of Asphaltenes and Asphaltenes-Containing Materials by Tlc as a Pilot Separation Technique and Tlc-Fid as a Quantitative Analysis Method with Stepwise Development of the Chromatogram
No full textAsphaltenes are the nonvolatile organic components of crude oil insoluble in alkanes. They represent a significant fraction of crude oil distillation residue and residual products, road or industrial asphalts, as well as natural asphalts. To characterize these products and raw materials, a SARA (Saturates, Aromatics, Resins, Asphaltenes) analysis method is used. This work aimed at establishing optimum conditions for the SARA analysis using conventional adsorption thin layer chromatography on silica gel impregnated with berberine salt as a pilot technique for selecting separation conditions with stepwise development of TLC chromatogram at different distances in successive separation steps and thin-layer chromatography with flame ionization detection (TLC-FID) as a method of quantitative analysis. The parameters to be optimized included elution strength (mobile phase polarity) and migration distance of the mobile phase in successive steps of the development of a TLC/TLC-FID chromatogram. The studies revealed that in the first step of stepwise development of a TLC/TLC-FID chromatogram, the mobile phase should dissolve all components of the investigated mixture, including asphaltenes. The preferred conditions for the stepwise development of a TLC or TLC-FID chromatogram for SARA analysis are as follows: in the first step, a mixture of dichloromethane – methanol 95:5 (v/v) as the mobile phase with the development of the chromatogram to a height of 30% of the adsorbent layer; in the second step, toluene as the mobile phase with the development of the chromatogram to a height of 60% of the adsorbent layer; in the third step, n -hexane as the mobile phase with the development of the chromatogram to a height of 100% of the adsorbent layer. The sample mass should not exceed 5 μg for asphalts and similar materials and 2 μg for asphaltenes and asphaltene fractions. Modification of the standard method IP 469 in terms of the sequence of stepwise development of the TLC-FID chromatogram as well as the reduction of sample mass applied to the TLC-FID rod is recommended