In a tokamak fusion reactor operated at steady state,the equilibrium magnetic field is likely to have reversed shear in the core region,as the noninductive bootstrap current profile generally peaks off-axis.The revers...In a tokamak fusion reactor operated at steady state,the equilibrium magnetic field is likely to have reversed shear in the core region,as the noninductive bootstrap current profile generally peaks off-axis.The reversed shear Alfvén eigenmode(RSAE)as a unique branch of the shear Alfvén wave in this equilibrium,can exist with a broad spectrum in wavenumber and frequency,and be resonantly driven unstable by energetic particles(EP).After briefly discussing the RSAE linear properties in burning plasma condition,we review several key topics of the nonlinear dynamics for the RSAE through both wave-EP resonance and wave-wave coupling channels,and illustrate their potentially important role in reactor-scale fusion plasmas.By means of simplified hybrid MHD-kinetic simulations,the RSAEs are shown to have typically broad phase space resonance structure with both circulating and trapped EP,as results of weak/vanishing magnetic shear and relatively low frequency.Through the route of wave-EP nonlinearity,the dominant saturation mechanism is mainly due to the transported resonant EP radially decoupling with the localized RSAE mode structure,and the resultant EP transport generally has a convective feature.The saturated RSAEs also undergo various nonlinear couplings with other collective oscillations.Two typical routes as parametric decay and modulational instability are studied using nonlinear gyrokinetic theory,and applied to the scenario of spontaneous excitation by a finite amplitude pump RSAE.Multiple RSAEs could naturally couple and induce the spectral energy cascade into a low frequency Alfvénic mode,which may effectively transfer the EP energy to fuel ions via collisionless Landau damping.Moreover,zero frequency zonal field structure could be spontaneously excited by modulation of the pump RSAE envelope,and may also lead to saturation of the pump RSAE by both scattering into stable domain and local distortion of the continuum structure.展开更多
Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture c...Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture content（x3）, wind velocity（x4）, aspect（xs）, slope（x6）, forest height（x7）, propagation velocity（x8）, fire line intensity（xg） and prescribed burning width of fire isolated belt（y）. The results showed that the multivari- ate linear model was y=-12.371 ＋4.182x1 ＋0.435x2 ＋0.013x3＋0.083x4＋0.017x5＋0.916x6＋ 0.540x7, and the influences of the factors on the prescribed burning width of fire isolated belt were in the order of x6, x7, x1, x4, x3, x2, x5. This model make it easier to establish fire isolated belt by using fuel characteristics, topographic factors, meteorological factors, and forest stand factors, providing basis for the development of prescribed burning and forest management fire.展开更多
基金supported by National Natural Science Foundation of China (Nos. 12205251, 12275236 and 12261131622)Italian Ministry for Foreign Affairs and International Cooperation Project (No. CN23GR02)+2 种基金the National Key Research and Development Program of China (Nos. 2019YFE03020003 and 2017YFE0301900)Users of Excellence program of Hefei Science Center CAS (No. 2021HSC-UE016)funded by the European Union via the Euratom Research and Training Programme (No. 101052200–EUROfusion)
文摘In a tokamak fusion reactor operated at steady state,the equilibrium magnetic field is likely to have reversed shear in the core region,as the noninductive bootstrap current profile generally peaks off-axis.The reversed shear Alfvén eigenmode(RSAE)as a unique branch of the shear Alfvén wave in this equilibrium,can exist with a broad spectrum in wavenumber and frequency,and be resonantly driven unstable by energetic particles(EP).After briefly discussing the RSAE linear properties in burning plasma condition,we review several key topics of the nonlinear dynamics for the RSAE through both wave-EP resonance and wave-wave coupling channels,and illustrate their potentially important role in reactor-scale fusion plasmas.By means of simplified hybrid MHD-kinetic simulations,the RSAEs are shown to have typically broad phase space resonance structure with both circulating and trapped EP,as results of weak/vanishing magnetic shear and relatively low frequency.Through the route of wave-EP nonlinearity,the dominant saturation mechanism is mainly due to the transported resonant EP radially decoupling with the localized RSAE mode structure,and the resultant EP transport generally has a convective feature.The saturated RSAEs also undergo various nonlinear couplings with other collective oscillations.Two typical routes as parametric decay and modulational instability are studied using nonlinear gyrokinetic theory,and applied to the scenario of spontaneous excitation by a finite amplitude pump RSAE.Multiple RSAEs could naturally couple and induce the spectral energy cascade into a low frequency Alfvénic mode,which may effectively transfer the EP energy to fuel ions via collisionless Landau damping.Moreover,zero frequency zonal field structure could be spontaneously excited by modulation of the pump RSAE envelope,and may also lead to saturation of the pump RSAE by both scattering into stable domain and local distortion of the continuum structure.
基金Supported by the Scientific Research Fund of the Education Bureau of Yunnan Province,China (2011C113)the Science and Technology Innovation Program for Undergraduates,Southwest Forestry University,China (1031)the "Forest Protection"Key Discipline of Yunnan Province,China (XKZ200905)~~
文摘Based on field survey and measurement, and the simulated field burning test by indoor burning bed, a multiple linear regression model was established with factors of fuel load（x1）, temperature（x2）, fuel moisture content（x3）, wind velocity（x4）, aspect（xs）, slope（x6）, forest height（x7）, propagation velocity（x8）, fire line intensity（xg） and prescribed burning width of fire isolated belt（y）. The results showed that the multivari- ate linear model was y=-12.371 ＋4.182x1 ＋0.435x2 ＋0.013x3＋0.083x4＋0.017x5＋0.916x6＋ 0.540x7, and the influences of the factors on the prescribed burning width of fire isolated belt were in the order of x6, x7, x1, x4, x3, x2, x5. This model make it easier to establish fire isolated belt by using fuel characteristics, topographic factors, meteorological factors, and forest stand factors, providing basis for the development of prescribed burning and forest management fire.
