Atmospheric pressure pulsed modulated arc discharge plasma

Direct-current(DC)arc plasma has great application values in the field of the chemical industry,but it has the problem of low energy efficiency.Facing the requirement for improving the energy efficiency of the arc,this paper proposes a unique method of pulsed modulated arc(PMA).This method uses high-frequency pulses and reduces the arc current to improve the control of electron temperature.The electrical characteristics,optical characteristics and products are tested.The test results show that during the PMA process,all of the experimental results which include voltage,current and light will significantly increase.These results are analyzed from the perspective of functionality,repeatability and energy conversion.The analysis results show that although the PMA method does not show good parameter consistency,it has potential application prospects because it increases the energy conversion rate by 4.5%and 8%from the perspective of light and products,respectively.

Hysteresis characteristics of the initiating and extinguishing boundaries in a nanosecond pulsed DBD

The dielectric barrier discharge(DBD)is presently used in many fields,in eluding plasma medicine,surface modification,and ozone synthesis;the influe nee of airflow on the DBD is a widely investigated topic.In this work,a hysteresis characteristic on the initiating and extinguishing boundaries is observed in a nanosecond pulsed DBD,which is sensitive to the variation in the airflow velocities and pulse repetition frequencies(PRFs).It is found that,at a certain airflow velocity,the initiating PRF is higher than the extinguishing PRF.This differenee between the initiating PRF and the extinguishing PRF leads to a hysteresis phenomenon on the initiating and extinguishing boun daries.When the airflow velocity is in creased,both the initiating and extinguishing PRFs are increased and the differenee between the initiating PRF and the extinguishing PRF also increased.The hysteresis width between the initiating and extinguishing boundaries is enhanced.To explain these results,the physical processes involved with the seed particles and the mechanisms of forming discharge channels are discussed.

Numerical simulation of the start-up process of a miniature ion thruster

A particle-in-cell Monte Carlo collision model of a discharge chamber is established to investigate the start-up process of a miniature ion thruster.We present the discharge characteristics at different stages(the initial stage,development stage,and stable stage)according to the trend of the discharge current with time.The discharge current is the sum of the sidewall current and the backplate current.During the start-up process,the sidewall current lags behind the backplate current.The variation and distribution characteristics of the discharge current over time are determined by the electron density distribution and electric potential distribution.

Nonlinearity of initiating and extinguishing boundaries of DBDs with airflows

Various applications of volume dielectric barrier discharges(DBDs)with airflows have attracted significant attention such as in the fields of plasma medicine,surface modification,ozone synthesis,etc.In this work,the nonlinearity characteristics of DBDs in initiating and extinguishing boundaries with airflows are experimentally investigated.It is found that the difference between initiating pulse repetition frequencies(PRFs)and extinguishing PRFs is affected by the addition of airflows.A hysteresis region is produced between these two PRFs.A topological rule of Thom's classification theorem is proposed to investigate the hysteresis phenomenon of discharges with airflows.It is concluded that the discharge state is dependent on the operation route.The discharge state would transit from initiating to extinguishing,or in the opposite direction,while passing along a specific operation route.Based on the topological method,two nonlinear laws of discharge structure transition under the typical operation routes are predicted and verified in the discharge experiments.

Special issue on selected papers from HVDP 2020

High-voltage and discharge plasma technology is playing an increasingly important role in the construction of national economy and social development,and has attracted extensive attention from both academia and industry.As a novel molecular activation method,discharge plasma can enable thermodynamically difficult reactions to occur under relatively mild conditions,and its effectiveness has successfully been demonstrated in gas cleaning and material surface treatment.

Experimental investigation on upstream and downstream discharges in airflows

Dielectric barrier discharge has widely used in airflow control, ignition and combustion, and other applications; the influence of airflow on dielectric barrier discharge is of extensive concern. Previous studies demonstrate that the discharge becomes more uniform and the discharge intensity decreases with increasing of airflow velocity. In this study, we adopt a discharge cell construction with upstream and downstream structure and study the discharge states and intensities. The experimental results demonstrate that within a specific range of airflow speed, the upstream discharge intensity is decreased, and the downstream discharge intensity is enhanced. The physical basis for this phenomenon is proposed as follows： Within a pulse interval time, some particles, such as charged and metastable particles produced by the upstream discharge, could be transported to the downstream region. The concentration of particles in the downstream region is increased, and these particles play a pre-ionization role in the downstream discharge, the intensity of the downstream discharge is enhanced. Further, factors such as the pulse frequency and the distance between electrodes are discussed in detail, along with the conditions for enhancing downstream discharge intensity.

Energy regulation of impulse current generator modulated DC arc discharge

This paper proposes a method of impulse current generator modulated DC arc by combining the advantages of pulse and the RF to solve the low electron energy problem of direct current arc.Through experimental analyzing the electrical,spectral,and optical characteristics of the arc,the effect of impulse current generator(ICG)on improving electron energy is discussed.The results show that the ICG consumes more energy to enhance the strength of arc discharge,and therefore electron energy is increased in a microsecond scale.In addition,it is found that the electron energy of the arc discharge can be adjusted by varying inductance,capacitance,and discharge tube:increasing the inductance or capacitance can increase the electron energy firstly and then decrease it.In adjusting the three adjustable components,adjusting the inductor is the most effective method,followed by adjusting the capacitor,and adjusting the repetition frequency has the least effect.The reason is discussed,and it is believed that the results are related to leakage inductance and distributed capacitance.

Integration of advanced biotechnology for green carbon

Carbon neutralization has been introduced as a long-term policy to control global warming and climate change.As plant photosynthesis produces the most abundant lignocellulosic biomass on Earth,its conversion to biofuels and bioproducts is considered a promising solution for reducing the net carbon release.However,natural lignocellulose recalcitrance crucially results in a costly biomass process along with secondary waste liberation.By updating recent advances in plant biotechnology,biomass engineering,and carbon nanotechnology,this study proposes a novel strategy that integrates the genetic engineering of bioenergy crops with green-like biomass processing for cost-effective biofuel conversion and high-value bioproduction.By selecting key genes and appropriate genetic manipulation approaches for precise lignocellulose modification,this study highlights the desirable genetic site mutants and transgenic lines that are raised in amorphous regions and inner broken chains account for high-density/length-reduced cellulose nanofiber assembly in situ.Since the amorphous regions and inner-broken chains of lignocellulose substrates are defined as the initial breakpoints for enhancing biochemical,chemical,and thermochemical conversions,desirable cellulose nanofibers can be employed to achieve nearcomplete biomass enzymatic saccharification for maximizing biofuels or high-quality biomaterials,even under cost-effective and green-like biomass processes in vitro.This study emphasizes the optimal thermal conversion for generating high-performance nanocarbons by combining appropriate nanomaterials generated from diverse lignocellulose resources.Therefore,this study provides a perspective on the potential of green carbon productivity as a part of the fourth industrial revolution.

B-lymphoid tyrosine kinase-mediated FAM83A phosphorylation elevates pancreatic tumorigenesis through interacting with β-catenin

Abnormal activation of Wnt/β-catenin-mediated transcription is closely associated with the malignancy of pancreatic cancer.Family with sequence similarity 83 member A(FAM83A)was shown recently to have oncogenic effects in a variety of cancer types,but the biological roles and molecular mechanisms of FAM83A in pancreatic cancer need further investigation.Here,we newly discovered that FAM83A binds directly toβ-catenin and inhibits the assembly of the cytoplasmic destruction complex thus inhibiting the subsequent phosphorylation and degradation.FAM83A is mainly phosphorylated by the SRC non-receptor kinase family member BLK(B-lymphoid tyrosine kinase)at tyrosine 138 residue within the DUF1669 domain that mediates the FAM83A-β-catenin interaction.Moreover,FAM83A tyrosine 138 phosphorylation enhances oncogenic Wnt/β-catenin-mediated transcription through promotingβ-catenin-TCF4 interaction and showed an elevated nucleus translocation,which inhibits the recruitment of histone deacetylases by TCF4.We also showed that FAM83A is a direct downstream target of Wnt/β-catenin signaling and correlates with the levels of Wnt target genes in human clinical pancreatic cancer tissues.Notably,the inhibitory peptides that target the FAM83A-β-catenin interaction significantly suppressed pancreatic cancer growth and metastasis in vitro and in vivo.Our results revealed that blocking the FAM83A cascade signaling defines a therapeutic target in human pancreatic cancer.

Theoretical Investigation of Operation Modes of MHD Generators for Energy-bypass Engines

A MHD generator with different arrangements of electromagnetic fields will lead the generator working in three modes.A quasi-one-dimensional approximation is used for the model of the MHD generator to analyze the inner mechanism of operation modes.For the MHD generator with a uniform constant magnetic field,a specific critical electric field E_(cr) is required to decelerate a supersonic entrance flow into a subsonic exit flow.Otherwise,the generator works in a steady mode with a larger electric field than E_(cr) in which a steady supersonic flow is provided at the exit,or the generator works in a choked mode with a smaller electric field than E_(cr) in which the supersonic entrance flow is choked in the channel.The detailed flow field characteristics in different operation modes are discussed,demonstrating the relationship of operation modes with electromagnetic fields.