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The effect of polymer type on electric breakdown strength on a nanosecond time scale

Chinese Physics B 2012年第3期21卷 158-163页

作者：赵亮苏建仓潘亚峰张喜波 Key laboratory of Physical Electronics and Devices of Ministry of Education Xi'an Jiaotong University Science and Technology on High Power Microwave Laboratory Northwest Institute of Nuclear Technology

Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength （EBD） on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE （polyethylene）, PTFE （polytetrafluoroethelene）, PMMA （organic glass） and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD （PTFE）〉 EBD （PMMA）〉 EBD （Nylon）〉 EBD （PE）. This result is consistent with the theoretical prediction.

关键词： electric breakdown strength polymer type nanosecond time scale fast polarization phenomenon

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Microplastics and heavy metals in freshwater fish species in the southwestern region of Bangladesh:An emerging concern for public health

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Emerging Contaminants 2024年第3期10卷 145-157页

作者： Mst Shamima Akter Tapos Kumar Chakraborty Gopal Chandra Ghosh Md Simoon Nice Samina Zaman Abu Shamim Khan Department of Environmental Science and Technology Jashore University of Science and TechnologyJashore 7408Bangladesh Environmental Laboratory Asia Arsenic NetworkJashore 7400Bangladesh

Microplastics(MPs)pollution and its associated toxicity raising concerns among scientists as a result of their toxicological impacts on human health and the *** study aims to investigate the microplastics and heavy metals(HMs)contamination in seventeen freshwater fish species collected from the Southwestern region of *** extracted from these species using the hydrogen peroxide digestion method and characterized by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy(ATR-FTIR).Atomic Absorption Spectrometry(AAS)was used to determine the concentration of HMs in different species for evaluating human health risks.A total of 142 microplastic particles were extracted with an average concentration of 1.13±0.84 items per individual of fish,where the highest microplastics were found in ***(3.43±3.15 items)and lowest in ***(0.14±0.38 items).Identified microplastics were dominated bypolymers.A positive correlation was found between microplastic numbers and fish weight and *** to moderate human health risks were associated with *** concentration(mg/kg)of heavy metals in studied fish samples was Cr(0.47 e2.89;0.79±0.56)>Cu(0.01e1.14;0.50±0.44)>Pb(0.04e0.58;0.22±0.12)>Cd(0.00e0.11;0.03±0.03),*** metals-based human health risk assessment results show that there are no major non-carcinogenic health risks(THI<1),while higher carcinogenic risks are present for consumers.

关键词： Microplastics Edible fish polymer type Heavy metals Human health risk Bangladesh

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