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1,142 results on '"Chen, JiPing"'

10. Assessment of Se, As, Cd, Cr, Hg, and Pb content status in Ankang tea plantations of China

Author

Ji Huawei, Lin Pingxuan, Wang Hui, Chen Jiping, Ren Rui, and Li Aorui

Subjects
selenium, potentially toxic elements, tea leaves, tea plantations, potential ecological risk, Chemistry, QD1-999
Abstract

Selenium (Se) is an essential trace element for humans. The Ankang tea plantation area in China is the best place for producing high-quality and Se-enriched organic tea. However, accumulation of potentially toxic elements (PTEs) in soil and tea leaves has attracted a lot of attention. Therefore, in this research, the content status of Se and five PTEs (As, Cd, Cr, Hg, and Pb) in soil and tea leaf samples collected from 88 Ankang tea plantations was studied. Results showed that the average Se content was 0.17 mg kg−1 and the Se-enrichment rate was 25% for the 88 tea leaf samples, and As, Cd, Cr, Hg, and Pb contents in all tea leaf samples met the Chinese standard for pollution-free tea except for 11.2% excess Cr in only one sample. Cd concentrations in 56.82% soil samples exceeded the Chinese risk screening value for soil contamination of the agricultural land, and therefore the pollution degree of Cd is high in these soil samples. Moreover, the Hakanson potential ecological risk assessment of soil As, Cd, Cr, Hg, and Pb indicated that the Ankang tea plantation area was at a medium potential ecological risk level. These results will provide theoretical support for ecological risk management and safe production of Se-enriched tea in Ankang Se-enriched tea plantations.

Published
2024
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47. Simulation and on-line monitoring using optical fiber Bragg grating sensors of temperature history during laser-assisted automated fiber placement.

Author

Zhao, Dacheng, Liu, Weiping, Chen, Jiping, Zhu, Songhao, Yang, Yang, and Yue, Guangquan

Subjects
FIBER Bragg gratings, ONLINE monitoring systems, POLYMER degradation, OPTICAL fibers, TEMPERATURE effect, OPTICAL fiber detectors
Abstract

Automated fiber placement (AFP) in situ consolidation (ISC) of thermoplastic composite possess the potential to reduce manufacturing costs and improve manufacturing efficiency. The properties of composite manufactured by the ISC are affected by several mechanisms including polymer degradation, crystallization, intimate contact, polymer healing and void dynamics. All these mechanisms are directly affected by the temperature history. Consequently, the control and accurate measurement of temperature history during ISC are particularly important for improving the properties of composite. In this study, a simplified three-dimensional transient heat transfer model was established. The effect of tool temperature and placement speed on the temperature history and peak temperature were predicted. Simultaneously, an online temperature monitoring system was built and the optical Fiber Bragg Grating sensors (FBGS) was used to measure the temperature history. The results indicated that the predicted results of the model were consistent with the measured results, the error was below 8%. In addition, the temperature history of layers was significantly affected by the tool temperature and placement speed. The temperature of the layers decreased to near the tool temperature after cooling, and a higher tool temperature increasing its peak temperature because of the reduce of the cooling rate. On the contrary, an increase in placement speed will reduce the peak temperature of the layers. [ABSTRACT FROM AUTHOR]

Published
2024
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50. Effect of stitching parameters on mechanical properties of foam-core sandwich structure composites

Author

XU Xuehong, ZHENG Yizhu, CHEN Jiping, NING Bo, and LIU Xiaochen

Subjects
stitching, composites, foam-core sandwich, mechanical property, climbing drum peel, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

The stitched foam-core sandwich composites with different stitching methods and stitch density were manufactured using vacuum assisted resin infusion (VARI) molding process. The effect of stitching parameters on their flatwise tensile, three-point flexural, core shear and climbing drum peel properties was investigated. The results show that although stitching makes flatwise tensile strength and core shear strength of foam-core sandwich composites to decrease obviously, it can improve flexural properties as well as substantially enhance climbing drum peel properties. Modified lock stitch method is better than tufting stitch method. Properly increasing stitch space has certain positive effect for mechanical properties, but it is not conducive to the enhancement of climbing drum peel properties. For modified lock stitched foam-core sandwich composites with the stitch density of 30 mm×10 mm, flatwise tensile strength and core shear strength are reduced by 14.75% and 24.79%, respectively, whereas flexural strength and average peel strength are respectively increased by 7.96% and 80.78% compared to those of unstitched foam-core sandwich composites.

Published
2022
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