A tokamak fusion-fission hybrid reatcor is proposed as one of candidates for disposal ofthe long-lived actinides and fission product wastes and supply of future energy.To assess thefeasibility of transmutation of long...A tokamak fusion-fission hybrid reatcor is proposed as one of candidates for disposal ofthe long-lived actinides and fission product wastes and supply of future energy.To assess thefeasibility of transmutation of long-lived radiowastes using fusion-fission hybrid reactors,afusion core design is presented and several possible conceptual blankets are studied,for,re-spectively,actinides transmutation and fission product transmutation.The results show thatactinides and fission products may be effectively transmuted using the presented hybrid reac-tors.展开更多
The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</su...The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</sup>O+<sup>238</sup>U at near-and sub-barrier energies were measured.The measured fragment anisotropies obviously deviate from the predictions ofscission-point transition-state model.We also compared the excitation energy of tiltingmode with the statistical assumption.It was found that thermal equilibrium is not estab-lished at scission for the reactions studied.展开更多
A fusion-fission hybrid conceptual reactor is established. It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium. The tritium production rate （TPR） distribution in the con...A fusion-fission hybrid conceptual reactor is established. It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium. The tritium production rate （TPR） distribution in the conceptual reactor was measured by DT neutrons using two sets of lithium glass detectors with different thicknesses in the hole in the vertical direction with respect to the D＋ beam of the Cockcroft-Walton neutron generator in direct current mode. The measured TPR distribution is compared with the calculated results obtained by the three- dimensional Monte Carlo code MCNP5 and the ENDF/B-VI data file. The discrepancy between the measured and calculated values can be attributed to the neutron data library of the hydrogen lithium lack S（α, β） thermal scattering model, so we show that a special database of low-energy and thermal neutrons should be established in the physics design of fusion-fission hybrid reactors.展开更多
With a projective equation and a linear variable separation method, this paper derives new families of variable separation solutions （including solitory wave solutions, periodic wave solutions, and rational function ...With a projective equation and a linear variable separation method, this paper derives new families of variable separation solutions （including solitory wave solutions, periodic wave solutions, and rational function solutions） with arbitrary functions for （2＋1）-dimensional generalized Breor-Kaup （GBK） system. Based on the derived solitary wave excitation, it obtains fusion and fission solitons.展开更多
By means of a special Painlevé-Backlund transformation and a multilinear variable separation approach,an exact solution with arbitrary functions of the (2+1)-dimensional Boiti-Leon-Pempinelli system (BLP) is deri...By means of a special Painlevé-Backlund transformation and a multilinear variable separation approach,an exact solution with arbitrary functions of the (2+1)-dimensional Boiti-Leon-Pempinelli system (BLP) is derived.Based on the derived variable separation solution, we obtain some special soliton fission and fusion solutions for the higher dimensional BLP system.展开更多
With the help of the symbolic computation system, Maple and Riccati equation （ξ＇ = ao ＋ a1ξ＋ a2ξ2）, expansion method, and a linear variable separation approach, a new family of exact solutions with q = lx ＋ ...With the help of the symbolic computation system, Maple and Riccati equation （ξ＇ = ao ＋ a1ξ＋ a2ξ2）, expansion method, and a linear variable separation approach, a new family of exact solutions with q = lx ＋ my ＋ nt ＋ Г（x,y, t） for the （2＋1）-dimensional generalized Calogero-Bogoyavlenskii-Schiff system （GCBS） are derived. Based on the derived solitary wave solution, some novel localized excitations such as fusion, fission, and annihilation of complex waves are investigated.展开更多
The reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted ...The reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted the fusion hindrance factor from the evaporation residue cross sections for the reactions of ^82Se＋^138 Ba and ^96Zr＋^124Sn and compared with the results calculated using a two-parameter Smoluchowski equation. The theoretical predictions are basically in agreement with the experimental data. It is found that the probability of forming a compact ^220Th is less than 10% for the reactions considered. For the systems more massive than ^220Th, fusion should be much more strongly suppressed due to the competition of quasifission with complete fusion. Understanding of this inhibition is essential to forming new superheavy nuclei.展开更多
Patterns of variation in the size of vulture foraging groups,and their ecological causes and consequences,remain litle explored despite strong links with the carrion recycling service that this key functional group pr...Patterns of variation in the size of vulture foraging groups,and their ecological causes and consequences,remain litle explored despite strong links with the carrion recycling service that this key functional group provides.We documented the group size-frequency pattern of Andean con-dors Vultur gryphus gathered to feed on 42 equine carcasses experimentally placed in Bolivia,between 2012 and 2019,along an elevation range of 1,300-4,500 m asl.Based on the location(altitude and latitude)of the foraging groups,we examined the relationship between their size and species'population parameters(size and trend),habitat conditions,and livestock carcass availability and predictability.Condors utilized a high frequency(93%)of carcasses forming groups that ranged from 1 to 80 individuals(mean=25,median=18)and shaped a"lazy-J curve"typical pattern of size-frequency distribution whereby few groups(5,12%)were large(>55 individuals)and most(21,50%)were relatively small(<19 individuals).Group size related to altitude in that most larger groups formed at lower sites(below c.3,000 m asl),likely following an altitudinal gradient whereby larger groups are more likely to form around larger carcasses(i.e.,cattle),which are more likely to occur at lower elevations.Regardless of population size,group size could be an adaptive response of condors via local enhancement for improving individual scavenging efficiency.Many information gaps on this topic still exist,thus we provide a set of questions to address them,especially amidst the unrestricted impacts of human activities that condition vulture survival globally.展开更多
The dissipative dynamics of nuclear fission is a well confirmed phenomenon that can be either described by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation.Although dynamica...The dissipative dynamics of nuclear fission is a well confirmed phenomenon that can be either described by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation.Although dynamical models as well as statistical models incorporating fission delays have been found to explain the measured fission observables in several studies,they present conflicting results for shell closed nuclei in the mass region of 200.Notably,an analysis of the recent data on neutron shell closed nuclei in the excitation energy range of 40-80 MeV failed to provide a satisfactory description of the data,which was attributed to a mismatch with shell effects and/or entrance channel effects,without reaching a definite conclusion.In the present study,we demonstrate that a well established stochastic dynamical code can simultaneously reproduce the available data for pre-scission neutron multiplicities and fission and evaporation residue excitation functions for the following neutron shell closed nuclei^(210)Po and^(212)Rn and their isotopes^(206)Po and^(214,216)Rn without the need for including any extra shell or entrance channel effects.The relevant calculations are performed by using a phenomenological universal friction form factor with no ad-hoc adjustment of the model parameters.However,we note a significant deviation,beyond experimental errors,for some Frisotopes.展开更多
The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are d...The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32S+90,96Zr in an energy range from above to below the Coulomb barrier are measured and analyzed within a semi-classical model. The obvious effect of positive Q-value multi-neutron transfers on the sub-barrier fusion enhancement is observed in the 32S+96Zr system. In addition, the excitation functions of quasi-elastic scattering at a backward angle have been measured with high precision for the systems of 16O+208Pb, 196Pt, 184W, and 154,152Sm at energies well below the Coulomb barrier. Considering the deformed coupling effects, the extracted diffuseness parameters are close to the values extracted from the systematic analysis of elastic and inelastic scattering data. The elastic scattering angular distribution of 17F+12C at 60 MeV is measured and calculated by using the continuum-discretized coupled-channels (CDCC) approach. It is found that the diffuseness parameter of the real part of core-target potential has to be increased by 20% to reproduce the experimental result, which corresponds to an increment of potential depth at the surface re gion. The breakup cross section and the coupling between breakup and elastic scattering are small.展开更多
基金the High Technology Research and Development Programme of china.
文摘A tokamak fusion-fission hybrid reatcor is proposed as one of candidates for disposal ofthe long-lived actinides and fission product wastes and supply of future energy.To assess thefeasibility of transmutation of long-lived radiowastes using fusion-fission hybrid reactors,afusion core design is presented and several possible conceptual blankets are studied,for,re-spectively,actinides transmutation and fission product transmutation.The results show thatactinides and fission products may be effectively transmuted using the presented hybrid reac-tors.
基金The project supported by the National Natural Science Foundation of China under the contract No.19275067.
文摘The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</sup>O+<sup>238</sup>U at near-and sub-barrier energies were measured.The measured fragment anisotropies obviously deviate from the predictions ofscission-point transition-state model.We also compared the excitation energy of tiltingmode with the statistical assumption.It was found that thermal equilibrium is not estab-lished at scission for the reactions studied.
基金Supported by Chinese Special Project for ITER (2010GB111002)
文摘A fusion-fission hybrid conceptual reactor is established. It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium. The tritium production rate （TPR） distribution in the conceptual reactor was measured by DT neutrons using two sets of lithium glass detectors with different thicknesses in the hole in the vertical direction with respect to the D＋ beam of the Cockcroft-Walton neutron generator in direct current mode. The measured TPR distribution is compared with the calculated results obtained by the three- dimensional Monte Carlo code MCNP5 and the ENDF/B-VI data file. The discrepancy between the measured and calculated values can be attributed to the neutron data library of the hydrogen lithium lack S（α, β） thermal scattering model, so we show that a special database of low-energy and thermal neutrons should be established in the physics design of fusion-fission hybrid reactors.
基金supported by the Natural Science Foundation of Zhejiang Province of China (Grant Nos.Y604106 and Y606252)the Natural Science Foundation of Zhejiang Lishui University of China (Grant No.KZ09005)
文摘With a projective equation and a linear variable separation method, this paper derives new families of variable separation solutions （including solitory wave solutions, periodic wave solutions, and rational function solutions） with arbitrary functions for （2＋1）-dimensional generalized Breor-Kaup （GBK） system. Based on the derived solitary wave excitation, it obtains fusion and fission solitons.
基金国家自然科学基金，the Scientific Research Fund of Educational Department of Zhejiang Province of China under，浙江省自然科学基金
文摘By means of a special Painlevé-Backlund transformation and a multilinear variable separation approach,an exact solution with arbitrary functions of the (2+1)-dimensional Boiti-Leon-Pempinelli system (BLP) is derived.Based on the derived variable separation solution, we obtain some special soliton fission and fusion solutions for the higher dimensional BLP system.
基金supported by the National Natural Science Foundation of China(Grant No.11375079)the Scientific Research Fund of Zhejiang Provincial Education Department of China(Grant No.Y 201120994)the Natural Science Foundation of Zhejiang Province,China(Grant Nos.Y6100257,LY14A010005,and Y6110140)
文摘With the help of the symbolic computation system, Maple and Riccati equation （ξ＇ = ao ＋ a1ξ＋ a2ξ2）, expansion method, and a linear variable separation approach, a new family of exact solutions with q = lx ＋ my ＋ nt ＋ Г（x,y, t） for the （2＋1）-dimensional generalized Calogero-Bogoyavlenskii-Schiff system （GCBS） are derived. Based on the derived solitary wave solution, some novel localized excitations such as fusion, fission, and annihilation of complex waves are investigated.
基金The project supported by the Natural Science Foundation of Zhejiang Province of China under Grant No. Y604106, the Foundation of ＂New Century 151 Talent Engineering＂ of Zhejiang Province, and the Key Academic Discipline Foundation of Zhejiang Province .The authors would like to thank Profs. J.F. Zhang, L.Q. Chen, and J.P. Fang for their fruitful discussions.
基金Supported by the National Natural Science Foundation of China under Grants Nos 10235020 and 10235030.
文摘The reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted the fusion hindrance factor from the evaporation residue cross sections for the reactions of ^82Se＋^138 Ba and ^96Zr＋^124Sn and compared with the results calculated using a two-parameter Smoluchowski equation. The theoretical predictions are basically in agreement with the experimental data. It is found that the probability of forming a compact ^220Th is less than 10% for the reactions considered. For the systems more massive than ^220Th, fusion should be much more strongly suppressed due to the competition of quasifission with complete fusion. Understanding of this inhibition is essential to forming new superheavy nuclei.
基金funded by The Peregrine Fund's Neotropical Science and Student Education Program,a British Ornithologists'Union Small Ornithological Research Grant,a Neotropical Birding and Conservation(formerly known as Neotropical Bird Club)Conservation Award granted to D.Méndez in 2014,and two 2018 grants to D.Méndez,one from the Rufford Small Grants Foundation(24763-1)another from the International Foundation for Science(I-1-D-6156-1).
文摘Patterns of variation in the size of vulture foraging groups,and their ecological causes and consequences,remain litle explored despite strong links with the carrion recycling service that this key functional group provides.We documented the group size-frequency pattern of Andean con-dors Vultur gryphus gathered to feed on 42 equine carcasses experimentally placed in Bolivia,between 2012 and 2019,along an elevation range of 1,300-4,500 m asl.Based on the location(altitude and latitude)of the foraging groups,we examined the relationship between their size and species'population parameters(size and trend),habitat conditions,and livestock carcass availability and predictability.Condors utilized a high frequency(93%)of carcasses forming groups that ranged from 1 to 80 individuals(mean=25,median=18)and shaped a"lazy-J curve"typical pattern of size-frequency distribution whereby few groups(5,12%)were large(>55 individuals)and most(21,50%)were relatively small(<19 individuals).Group size related to altitude in that most larger groups formed at lower sites(below c.3,000 m asl),likely following an altitudinal gradient whereby larger groups are more likely to form around larger carcasses(i.e.,cattle),which are more likely to occur at lower elevations.Regardless of population size,group size could be an adaptive response of condors via local enhancement for improving individual scavenging efficiency.Many information gaps on this topic still exist,thus we provide a set of questions to address them,especially amidst the unrestricted impacts of human activities that condition vulture survival globally.
基金D.A.acknowledges the financial support from the University Grants Commission(UGC),Government of India,received in the form of a research fellowship(Ref.No.19/06/2016/(i)EU-V,Sr.No.2061651303)。
文摘The dissipative dynamics of nuclear fission is a well confirmed phenomenon that can be either described by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation.Although dynamical models as well as statistical models incorporating fission delays have been found to explain the measured fission observables in several studies,they present conflicting results for shell closed nuclei in the mass region of 200.Notably,an analysis of the recent data on neutron shell closed nuclei in the excitation energy range of 40-80 MeV failed to provide a satisfactory description of the data,which was attributed to a mismatch with shell effects and/or entrance channel effects,without reaching a definite conclusion.In the present study,we demonstrate that a well established stochastic dynamical code can simultaneously reproduce the available data for pre-scission neutron multiplicities and fission and evaporation residue excitation functions for the following neutron shell closed nuclei^(210)Po and^(212)Rn and their isotopes^(206)Po and^(214,216)Rn without the need for including any extra shell or entrance channel effects.The relevant calculations are performed by using a phenomenological universal friction form factor with no ad-hoc adjustment of the model parameters.However,we note a significant deviation,beyond experimental errors,for some Frisotopes.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10575134, 10675169 and 10735100)the Major State Basic Research Developing Program (Grant No. 2007CB815003)
文摘The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32S+90,96Zr in an energy range from above to below the Coulomb barrier are measured and analyzed within a semi-classical model. The obvious effect of positive Q-value multi-neutron transfers on the sub-barrier fusion enhancement is observed in the 32S+96Zr system. In addition, the excitation functions of quasi-elastic scattering at a backward angle have been measured with high precision for the systems of 16O+208Pb, 196Pt, 184W, and 154,152Sm at energies well below the Coulomb barrier. Considering the deformed coupling effects, the extracted diffuseness parameters are close to the values extracted from the systematic analysis of elastic and inelastic scattering data. The elastic scattering angular distribution of 17F+12C at 60 MeV is measured and calculated by using the continuum-discretized coupled-channels (CDCC) approach. It is found that the diffuseness parameter of the real part of core-target potential has to be increased by 20% to reproduce the experimental result, which corresponds to an increment of potential depth at the surface re gion. The breakup cross section and the coupling between breakup and elastic scattering are small.
