Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence o...Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.展开更多
The effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti-34Nb and Ti-34Nb-0.2O alloys was investigated.The addition of O suppresses the martensitic transformation.The phase co...The effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti-34Nb and Ti-34Nb-0.2O alloys was investigated.The addition of O suppresses the martensitic transformation.The phase composition changes from singleα''phase toα''+βphases with oxygen addition.The addition of oxygen increases strength significantly at as-received,cold-rolled,and annealed alloys through solid solution strengthening.The accumulation of abundance of defects and grain refinement introduced by cold rolling have a significant strengthening effect but also damage plasticity.The addition of oxygen increasesα/βtransformation temperature and promotes the precipitation ofαphase during annealing in Ti-34Nb-0.2O alloy.αprecipitates can inhibit grain growth during annealing.The strength decreases with annealing time increased due to the increase in grain size in Ti-34Nb alloy,while the strength increases in Ti-34Nb-0.2O alloy mainly due to the precipitation ofαphase.The cold rolling followed by annealing and addition of oxygen can improve the properties of alloys.展开更多
Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the r...Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the reactivity of DBDs,in this work,the O_(2) is added into Ar nanosecond(ns)pulsed and AC DBDs.The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O_(2) contents are investigated with optical and electrical diagnosis methods.The DBD uniformity is quantitatively analyzed by gray value standard deviation method.The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n_(e).The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T_(e) with the ratio of two emission lines.It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time.With the addition of O_(2),the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O_(2)^(-),which promotes the filamentary formation.While,in AC DBD,the added O_(2) can reduce the intensity of filaments,which enhances the discharge uniformity.The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD.The ratio of Ar emission intensities indicates that the T_(e) drops quickly with the addition of O_(2) both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T_(e) and n_(e) than AC DBD.The results are helpful for the realization of the reactive and uniform low temperature plasma sources.展开更多
<span style="font-family:Verdana;">The objective of this study was to evaluate the effect of blends of different oxygenated additives on gasoline in SI engine Otto cycle. The formulations analyzed were...<span style="font-family:Verdana;">The objective of this study was to evaluate the effect of blends of different oxygenated additives on gasoline in SI engine Otto cycle. The formulations analyzed were: pure gasoline (type A), common gasoline (type C), gasoline type A + 15% (v/v) oxygenated additives (ethanol, ethyl octanoate, ethyl oleate). The experiments were performed using engine Branco 4-stroke and 2-cylinder, electric dynamometer, exhaust system, control unit composed of Multi-K unit, variable selector and load cell, stroboscope tachometer, fuel supply system and stopwatch. The rotation was conserved at 4400 rpm and wheel power varied from 3 kW to 12 kW, with intervals of 3 kW to obtain hourly consumption curves and brake specific fuel consumption. Even esters and ethanol having lower heat of combustion, hourly consumption was similar to pure gasoline (type A). In relation to the brake specific fuel consumption, increasing the wheel power had a better conversion of the mass of fuel burned into energy. Thus, this study showed that the mixture of gasoline and esters (ethyl octanoate and ethyl oleate) presented good efficiency in terms of consumption. This research contributes to the needs and to the current studi</span><span style="font-family:Verdana;">es in which industries started to add renewable products to petroleum-</span><span style="font-family:Verdana;">derived fuels;in order to obtain more sustainable fuels at lower costs.</span>展开更多
Acetalization represents an appealing approach for the valorization of biobased platform molecules into valuable chemicals and fuels.Typically,it serves as both a synthesis tool for renewable cyclic acetals and a prot...Acetalization represents an appealing approach for the valorization of biobased platform molecules into valuable chemicals and fuels.Typically,it serves as both a synthesis tool for renewable cyclic acetals and a protection strategy to improve selectivity in biomass conversion.This contribution provides an overview on the application of the acetalization strategy in biomass valorization including synthesis of cyclic acetal fuel additives from the acetalization of biobased furanic compounds with biogenic ethylene glycol/glycerol and acetalization as a protection approach to improve product selectivity in biomass valorization.The latest progresses in the development of catalytic systems for the acetalization of biobased furanic compounds and biogenic ethylene glycol/glycerol are systematically summarized and discussed,with an emphasis on the reaction pathway,relationship between catalyst structures and their performance,and relevant catalytic mechanism.Moreover,the application of the acetalization strategy for protecting carbonyl groups/diol structure functionalities to improve the target products'selectivity in lignin depolymerization,5-hydroxymethylfurfural oxidation,sorbitol dehydration,and xylose hydrogenation is also highlighted.Eventually,the prospects and challenges in the synthesis of cyclic acetal fuel additives as well as applying acetalization as a protection strategy in biomass valorization are outlined.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51977057 and 11875121)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2020201025 and A2019201100)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University(Grant Nos.DXK202011 and DXK201908)Post-graduate’s Innovation Fund Project of Hebei Province,China(Grant Nos.CXZZBS2019023 and CXZZBS2019029)Postgraduate’s Innovation Fund Project of Hebei University(Grant Nos.HBU2021ss063 and HBU2021bs011)。
文摘Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.
基金supported by the National Natural Science Foundation of China (No.51671012)the China Postdoctoral Science Foundation (2019TQ0015).
文摘The effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti-34Nb and Ti-34Nb-0.2O alloys was investigated.The addition of O suppresses the martensitic transformation.The phase composition changes from singleα''phase toα''+βphases with oxygen addition.The addition of oxygen increases strength significantly at as-received,cold-rolled,and annealed alloys through solid solution strengthening.The accumulation of abundance of defects and grain refinement introduced by cold rolling have a significant strengthening effect but also damage plasticity.The addition of oxygen increasesα/βtransformation temperature and promotes the precipitation ofαphase during annealing in Ti-34Nb-0.2O alloy.αprecipitates can inhibit grain growth during annealing.The strength decreases with annealing time increased due to the increase in grain size in Ti-34Nb alloy,while the strength increases in Ti-34Nb-0.2O alloy mainly due to the precipitation ofαphase.The cold rolling followed by annealing and addition of oxygen can improve the properties of alloys.
基金supported by National Natural Science Foundation of China(Nos.52037004 and 51777091)。
文摘Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the reactivity of DBDs,in this work,the O_(2) is added into Ar nanosecond(ns)pulsed and AC DBDs.The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O_(2) contents are investigated with optical and electrical diagnosis methods.The DBD uniformity is quantitatively analyzed by gray value standard deviation method.The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n_(e).The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T_(e) with the ratio of two emission lines.It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time.With the addition of O_(2),the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O_(2)^(-),which promotes the filamentary formation.While,in AC DBD,the added O_(2) can reduce the intensity of filaments,which enhances the discharge uniformity.The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD.The ratio of Ar emission intensities indicates that the T_(e) drops quickly with the addition of O_(2) both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T_(e) and n_(e) than AC DBD.The results are helpful for the realization of the reactive and uniform low temperature plasma sources.
文摘<span style="font-family:Verdana;">The objective of this study was to evaluate the effect of blends of different oxygenated additives on gasoline in SI engine Otto cycle. The formulations analyzed were: pure gasoline (type A), common gasoline (type C), gasoline type A + 15% (v/v) oxygenated additives (ethanol, ethyl octanoate, ethyl oleate). The experiments were performed using engine Branco 4-stroke and 2-cylinder, electric dynamometer, exhaust system, control unit composed of Multi-K unit, variable selector and load cell, stroboscope tachometer, fuel supply system and stopwatch. The rotation was conserved at 4400 rpm and wheel power varied from 3 kW to 12 kW, with intervals of 3 kW to obtain hourly consumption curves and brake specific fuel consumption. Even esters and ethanol having lower heat of combustion, hourly consumption was similar to pure gasoline (type A). In relation to the brake specific fuel consumption, increasing the wheel power had a better conversion of the mass of fuel burned into energy. Thus, this study showed that the mixture of gasoline and esters (ethyl octanoate and ethyl oleate) presented good efficiency in terms of consumption. This research contributes to the needs and to the current studi</span><span style="font-family:Verdana;">es in which industries started to add renewable products to petroleum-</span><span style="font-family:Verdana;">derived fuels;in order to obtain more sustainable fuels at lower costs.</span>
基金The authors gratefully acknowledge financial support from National Key R&D Program of China(2019YFC1905300)National Natural Science Foundation of China(No.22268019)Hunan Provincial Natural Science Foundation of China(No.2021JJ40436)。
文摘Acetalization represents an appealing approach for the valorization of biobased platform molecules into valuable chemicals and fuels.Typically,it serves as both a synthesis tool for renewable cyclic acetals and a protection strategy to improve selectivity in biomass conversion.This contribution provides an overview on the application of the acetalization strategy in biomass valorization including synthesis of cyclic acetal fuel additives from the acetalization of biobased furanic compounds with biogenic ethylene glycol/glycerol and acetalization as a protection approach to improve product selectivity in biomass valorization.The latest progresses in the development of catalytic systems for the acetalization of biobased furanic compounds and biogenic ethylene glycol/glycerol are systematically summarized and discussed,with an emphasis on the reaction pathway,relationship between catalyst structures and their performance,and relevant catalytic mechanism.Moreover,the application of the acetalization strategy for protecting carbonyl groups/diol structure functionalities to improve the target products'selectivity in lignin depolymerization,5-hydroxymethylfurfural oxidation,sorbitol dehydration,and xylose hydrogenation is also highlighted.Eventually,the prospects and challenges in the synthesis of cyclic acetal fuel additives as well as applying acetalization as a protection strategy in biomass valorization are outlined.
