RESUMEN
Developing pure organic room-temperature phosphorescent (RTP) hydrogels is important for expanding the practical applications of phosphorescent materials. However, most of the reported RTP hydrogels containing aromatic phosphors suffer from short phosphorescent lifetimes, unstable underwater RTP emissions, and complex preparation processes. Herein, novel nonaromatic RTP hydrogels are prepared by using two types of non-traditional luminescent polymers, sodium alginate and a polymeric carboxylate, which are not RTP emissive or very weakly emissive in aqueous environments. The prepared hydrogels exhibit the following features: I) color-tunable RTP emissions with ultra-long lifetimes up to 451.1 ms, II) excellent anti-swelling properties and stable persistent RTP emission even after being immersed in deionized water for months, III) efficient and large-scale preparation of hydrogel fibers by wet spinning technique. Experiment results and theoretical calculations show that the stable and long-lifetime RTP emissions of the hydrogels originate from the introduction of more nonconventional chromophores which are strongly crosslinked with ionic bonding between carboxylate groups and calcium ions and enhanced through-space interactions between them. This work provides a reliable strategy for designing nonaromatic hydrogels with stable and persistent RTP.
RESUMEN
In actual production tests, there are large fluctuations in the ventilation rate and smoking resistance of cigarettes. In this paper, fluctuations in ventilation rate and smoking resistance are attributed to variations in the number of ventilation holes in the joint paper and the porosity of each component. The effects of small changes in porosity of each component were analyzed by using computational fluid dynamics methods. The results showed that the difference in the effective number of ventilation holes caused by the gluing process had little effect on the ventilation rate and smoking resistance of cigarettes in the practical production process. The smoking resistance is mainly affected by the structural parameters of filter tow and cut tobacco section in the length direction of cigarettes, the porosity of cigarette paper and packaging paper is positively related to the cigarette ventilation rate, the porosity of cut tobacco and the porosity of filter tow are negatively related to the cigarette ventilation rate, and the influence of shaped paper is the smallest. The results can provide technical and theoretical basis for the optimization of cigarette process parameters and the stabilization of ventilation rate.
RESUMEN
Weed control is a substantial challenge in field management. A better weed control method at an earlier growth stage is important for increasing yields. As a promising weed control technique, intelligent weeding based on machine vision can avoid the harm of chemical weeding. For machine vision, it is critical to extract and segment crops from their background. However, there is still no optimal solution for object tracking with occlusion under a similar color background. In this study, it was found that the gray distribution of a maize canopy follows the gradient law. Therefore, the recognition method based on the HLS-SVM (HLS color space and Support Vector Machine) and on the grayscale gradient was developed. First, the HLS color space was used to detect the maize canopy. Second, the SVM method was used to segment the central region of the maize canopy. Finally, the maize canopy center was identified according to the gradient law. The results showed that the average segmentation time was 0.49 s, the average segmentation quality was 87.25%, and the standard deviation of the segmentation was 3.57%. The average recognition rate of the center position was 93.33%. This study provided a machine vision method for intelligent weeding agricultural equipment as well as a theoretical reference for further agricultural machine vision research.