Plasma photonic crystals(PPCs) have been a hot research topic in the band gap(BG) material field in recent years due to their unique advantages, such as the feasibility of changing the parameters and hence the propert...Plasma photonic crystals(PPCs) have been a hot research topic in the band gap(BG) material field in recent years due to their unique advantages, such as the feasibility of changing the parameters and hence the properties of the materials with respect to traditional photonic crystals(PCs). In this paper,we focus mainly on the effects of some types of defects introduced in PPCs on the changes in BG characteristics of microwave(MW) transmittance. The research is carried out using numerical simulation with a one-dimensional finite-difference time-domain(FDTD) method, and six types of defects, including a lattice-constant defect, radii-ratio defect, additional-column defect, column-width defect, plasma-frequency defect, and electron-collision-frequency defect, are concerned. It transpires that introducing a defect in a PPC in different manners may realize the symmetric change, alternative change, shifting, generating, transforming, disappearing, and attenuating of BGs in transmittance spectra, which has great potential for the manufacture of spatiotemporal-controllable MW materials and devices with more feasible modulating functions.展开更多
Eighteen polycyclic aromatic hydrocarbons(PAHs)were detected in benthos collected onboard the‘Snow Dragon’in the Northern Bering Sea Shelf and Chukchi Sea Shelf during the 6 th Chinese National Arctic Research Exped...Eighteen polycyclic aromatic hydrocarbons(PAHs)were detected in benthos collected onboard the‘Snow Dragon’in the Northern Bering Sea Shelf and Chukchi Sea Shelf during the 6 th Chinese National Arctic Research Expedition(CHINARE 2014).18 PAHs for all biota samples ranged from 34.2 to 128.1 ng/g dry weight(dw),with the highest concentration observed in fish muscle(Boreogadus saida)samples close to St.Lawrence Island.The PAH composition pattern was dominated by the presence of lighter 3 ring(57%)and 2 ring(28%)PAHs,indicating oil-related or petrogenic sources as important origins of PAH contamination.Concentrations of alkyl-PAHs(1-methylnaphthalene and 2-methylnaphthalene)were lower than their parent PAH(naphthalene)in all biological tissue,and their percentage also decreased significantly(p<0.05)compared with those in the corresponding sediment.There were no significant relationships between PAH concentrations and trophic levels,which is possibly due to the combined results of the complex benthic foodweb in the subarctic/Arctic shelf region,as well as a low assimilation/effective metabolism for PAHs.According to toxic potency evaluation results from TCDD toxic equivalents(TEQs)and Ba P-equivalent(Ba PE)values,whelk(Neptunea heros)and starfish(Ctenodiscus crispatus)are two macroinvertebrate species showing relatively higher dioxin-like toxicity and carcinogenic risk.展开更多
Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated d...Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.展开更多
Electrostatic discharge(ESD)event usually destroys the electrical properties of dielectric films,resulting in product failure.In this work,the breakdown characteristic of machine mode(MM)ESD on three different nano si...Electrostatic discharge(ESD)event usually destroys the electrical properties of dielectric films,resulting in product failure.In this work,the breakdown characteristic of machine mode(MM)ESD on three different nano size films of head gimble assemble are obtained experimentally.The breakdown voltage and thickness parameters show a positive proportional relationship,but they are generally very low and have large discrete characteristics(~30%).The maximum and minimum breakdown voltages of the tested samples are 1.08 V and 0.46 V,which are far lower than the requirement of the current standard(25 V).In addition,the judgment criterion of product damage is given,and the relationship between discharge voltage polarity,initial resistance and breakdown voltage is studied.Finally,the theoretical analysis of the breakdown characteristic law has been given.展开更多
Capturing and studying the process of cavitation bubble collapse can help elucidate the mechanism of cavitation erosion.In this paper,a high-spatiotemporal-resolution double-exposure photographic method is used to inv...Capturing and studying the process of cavitation bubble collapse can help elucidate the mechanism of cavitation erosion.In this paper,a high-spatiotemporal-resolution double-exposure photographic method is used to investigate the collapse of laser-induced cavitation bubbles at two values of the dimensionless distance from the bubble to the wall,γ=d/R_(max)=0.9 and 1.25(where d is the vertical distance between the bubble center and the wall and R_(max)is the maximum radius of the bubble).Complete high-resolution evolution sequences of bubbles near a rigid wall are captured from optical breakdown to second collapse.The generation and development of microjets and shock waves during cavitation bubble collapse are described in detail.The oscillations of the bubble near the rigid wall and the microjets and shock waves generated by the collapse are analyzed.It is shown that the presence of the rigid wall affects the development of the bubble and microjets.The microjet velocity can reach up to 64 m/s.Multiple shock waves are found to be generated by bubble collapse.展开更多
基金This work was partly supported by National Natural Science Foundation of China(No.11475019)。
文摘Plasma photonic crystals(PPCs) have been a hot research topic in the band gap(BG) material field in recent years due to their unique advantages, such as the feasibility of changing the parameters and hence the properties of the materials with respect to traditional photonic crystals(PCs). In this paper,we focus mainly on the effects of some types of defects introduced in PPCs on the changes in BG characteristics of microwave(MW) transmittance. The research is carried out using numerical simulation with a one-dimensional finite-difference time-domain(FDTD) method, and six types of defects, including a lattice-constant defect, radii-ratio defect, additional-column defect, column-width defect, plasma-frequency defect, and electron-collision-frequency defect, are concerned. It transpires that introducing a defect in a PPC in different manners may realize the symmetric change, alternative change, shifting, generating, transforming, disappearing, and attenuating of BGs in transmittance spectra, which has great potential for the manufacture of spatiotemporal-controllable MW materials and devices with more feasible modulating functions.
基金supported by the National Natural Science Foundation of China(Nos.41506215,41976211)Shanghai Pujiang Talent Program(No.19PJ1404200)。
文摘Eighteen polycyclic aromatic hydrocarbons(PAHs)were detected in benthos collected onboard the‘Snow Dragon’in the Northern Bering Sea Shelf and Chukchi Sea Shelf during the 6 th Chinese National Arctic Research Expedition(CHINARE 2014).18 PAHs for all biota samples ranged from 34.2 to 128.1 ng/g dry weight(dw),with the highest concentration observed in fish muscle(Boreogadus saida)samples close to St.Lawrence Island.The PAH composition pattern was dominated by the presence of lighter 3 ring(57%)and 2 ring(28%)PAHs,indicating oil-related or petrogenic sources as important origins of PAH contamination.Concentrations of alkyl-PAHs(1-methylnaphthalene and 2-methylnaphthalene)were lower than their parent PAH(naphthalene)in all biological tissue,and their percentage also decreased significantly(p<0.05)compared with those in the corresponding sediment.There were no significant relationships between PAH concentrations and trophic levels,which is possibly due to the combined results of the complex benthic foodweb in the subarctic/Arctic shelf region,as well as a low assimilation/effective metabolism for PAHs.According to toxic potency evaluation results from TCDD toxic equivalents(TEQs)and Ba P-equivalent(Ba PE)values,whelk(Neptunea heros)and starfish(Ctenodiscus crispatus)are two macroinvertebrate species showing relatively higher dioxin-like toxicity and carcinogenic risk.
基金supported by National Natural Science Foundation of China(No.52177130)the Key Projects for Industrial Prospects and Core Technology Research in Suzhou City(No.SYC2022029)。
文摘Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.
文摘Electrostatic discharge(ESD)event usually destroys the electrical properties of dielectric films,resulting in product failure.In this work,the breakdown characteristic of machine mode(MM)ESD on three different nano size films of head gimble assemble are obtained experimentally.The breakdown voltage and thickness parameters show a positive proportional relationship,but they are generally very low and have large discrete characteristics(~30%).The maximum and minimum breakdown voltages of the tested samples are 1.08 V and 0.46 V,which are far lower than the requirement of the current standard(25 V).In addition,the judgment criterion of product damage is given,and the relationship between discharge voltage polarity,initial resistance and breakdown voltage is studied.Finally,the theoretical analysis of the breakdown characteristic law has been given.
基金support given by the National Natural Science Foundation of China(Grant Nos.52179092 and 52222904).
文摘Capturing and studying the process of cavitation bubble collapse can help elucidate the mechanism of cavitation erosion.In this paper,a high-spatiotemporal-resolution double-exposure photographic method is used to investigate the collapse of laser-induced cavitation bubbles at two values of the dimensionless distance from the bubble to the wall,γ=d/R_(max)=0.9 and 1.25(where d is the vertical distance between the bubble center and the wall and R_(max)is the maximum radius of the bubble).Complete high-resolution evolution sequences of bubbles near a rigid wall are captured from optical breakdown to second collapse.The generation and development of microjets and shock waves during cavitation bubble collapse are described in detail.The oscillations of the bubble near the rigid wall and the microjets and shock waves generated by the collapse are analyzed.It is shown that the presence of the rigid wall affects the development of the bubble and microjets.The microjet velocity can reach up to 64 m/s.Multiple shock waves are found to be generated by bubble collapse.
