A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The d...A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The decomposition rate of epoxy resin raised rapidly as the reaction time and reaction temperature increased. The decomposition reaction products were characterized by infra-red spectra and gas chromatography-mass spectrometry. The phenol, isopropylphenol, 4, 4'-(1-methylethylidene) bis-phenol were found as the main compounds in liquid products, which were common monomers from epoxy resin. When reaction was carried out at the temperature of 260℃ -300 ℃, the decomposition mechanism of epoxy resin was envisaged as the ether and ester bonds cracking.展开更多
An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are i...An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are investigated numerically. It is found that the positron yield is mainly affected by the number of electrons of energies up to several hundreds of MeV. Using near-critical density targets for electron acceleration, the number of high energy electrons can be increased dramatically. Through start-to-end simulations, it is shown that up to 6.78×10106.78×1010 positrons can be generated with state-of-the-art Joule-class femtosecond laser systems.展开更多
The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particula...The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.展开更多
Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication techniqu...Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.展开更多
A Glaser coupling reaction of terminal alkynes in the presence of cupric chloride without organic solvents and bases under near-critical water has been developed.
In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations t...In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations that relativistic toroidal solitons,composed of intense light self-consistently trapped in toroidal plasma cavities,can be produced by azimuthallypolarized relativistic laser pulses in a near-critical underdense plasma.展开更多
The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In...The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.展开更多
基金Funded by the National Natural Science Foundation of China(No.50973023)the Program for New Century Excellent Talents in University(No.NCET-09-0060)
文摘A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The decomposition rate of epoxy resin raised rapidly as the reaction time and reaction temperature increased. The decomposition reaction products were characterized by infra-red spectra and gas chromatography-mass spectrometry. The phenol, isopropylphenol, 4, 4'-(1-methylethylidene) bis-phenol were found as the main compounds in liquid products, which were common monomers from epoxy resin. When reaction was carried out at the temperature of 260℃ -300 ℃, the decomposition mechanism of epoxy resin was envisaged as the ether and ester bonds cracking.
基金Supported by the National Basic Research Program of China under Grant No 2013CBA01502the National Natural Science Foundation of China under Grant Nos 11575011 and 11535001+1 种基金the National Grand Instrument Project under Grant No2012YQ030142the UK EPSRC under Grant Nos EP/G054950/1,EP/G056803/1,EP/G055165/1 and EP/M022463/1
文摘An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are investigated numerically. It is found that the positron yield is mainly affected by the number of electrons of energies up to several hundreds of MeV. Using near-critical density targets for electron acceleration, the number of high energy electrons can be increased dramatically. Through start-to-end simulations, it is shown that up to 6.78×10106.78×1010 positrons can be generated with state-of-the-art Joule-class femtosecond laser systems.
基金supported by the National Natural Science Foundation of China(No.52076172)。
文摘The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.
基金National Grand Instrument Project(No.2019YFF01014402)NSFC innovation group project(No.11921006)National Natural Science Foundation of China(Nos.11775010,11535001,and 61631001).
文摘Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.
基金Project supported by the National Natural Science Foundation of China (Nos. 2037202420172018)+1 种基金 the Excellent Scientist Foundation of Anhui Province (No. 2001040) the Natural Science Foundation of the Education Department of Anhui Province (No. 2002kj25
文摘A Glaser coupling reaction of terminal alkynes in the presence of cupric chloride without organic solvents and bases under near-critical water has been developed.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA17040502)。
文摘In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations that relativistic toroidal solitons,composed of intense light self-consistently trapped in toroidal plasma cavities,can be produced by azimuthallypolarized relativistic laser pulses in a near-critical underdense plasma.
基金supported by the National Natural Science Foundation of China(Grant No.51506001)Beijing Municipal Education Commission(KM201710005029)National Key R&D Program of China(Grant No.2016YFE0124900)
文摘The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.