The 12C+12C fusion reaction plays a crucial role in stellar evolution and explosions.Its main open reaction channels includeα,p,n,and 8Be.Despite more than a half century of efforts,large differences remain among the...The 12C+12C fusion reaction plays a crucial role in stellar evolution and explosions.Its main open reaction channels includeα,p,n,and 8Be.Despite more than a half century of efforts,large differences remain among the experimental data of this reaction measured using various techniques.In this work,we analyze the existing data using a statistical model.Our calculation shows the following:1)the relative systematic uncertainties of the predicted branching ratios decrease as the predicted ratios increase;2)the total modified astrophysical S-factors(S^* factors)of the p andαchannels can be obtained by summing the S^* factors of their corresponding ground-state transitions and the characteristicγrays,while taking into account the contributions of the missing channels to the latter.After applying corrections based on branching ratios predicted by the statistical model,an agreement is achieved among the different data sets at Ecm>4 MeV,while some discrepancies remain at lower energies,suggesting the need for better measurements in the near future.We find that the S^* factor recently obtained from an indirect measurement is inconsistent with the direct measurement value at energies below 2.6 MeV.We recommend upper and lower limits for the 12C+12C S^* factor based on the existing models.A new 12C+12C reaction rate is also recommended.展开更多
We summarize the recent effective field theory （EFT） studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S（0） factor for the t...We summarize the recent effective field theory （EFT） studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S（0） factor for the thermal proton radiative capture by deuteron is calculated with pionless EFT. The astrophysical S（0） factor is accurately determined to be S（0）=0.243 eV·b up to the leading order （LO）. At zero energies, magnetic transition M1 gives the dominant contribution. The M1 amplitude is calculated up to the LO. A good, quantitative agreement between theoretical and experimental results is found for all observables. The demonstrations of cutoff independent calculation have also been presented.展开更多
The astrophysical S-factor of the 4He＋12C radiative capture is calculated in the potential model at the energy range 0.1-2.0 MeV. Radiative capture 12C（α,γ） 16O is extremely relevant for the fate of massive stars...The astrophysical S-factor of the 4He＋12C radiative capture is calculated in the potential model at the energy range 0.1-2.0 MeV. Radiative capture 12C（α,γ） 16O is extremely relevant for the fate of massive stars and determines if the remnant of a supernova explosion becomes a black hole or a neutron star. Because this reaction occurs at low energies, the experimental measurements are very difficult and perhaps impossible. In this paper, radiative capture of the 12C（α,γ） 16O reaction at very low energies is taken as a case study. In comparison with other theoretical methods and available experimental data, good agreement is achieved for the astrophysical S-factor of this process.展开更多
The thick-target yield of the ^(9)Be(d,α0)7Li and ^(9)Be(d,α1)7Li*reactions has been first directly measured over deuteron energies from 66 to 94 keV.The obtained S(Ei)ofα0 andα1 have similar trends calculated by ...The thick-target yield of the ^(9)Be(d,α0)7Li and ^(9)Be(d,α1)7Li*reactions has been first directly measured over deuteron energies from 66 to 94 keV.The obtained S(Ei)ofα0 andα1 have similar trends calculated by the thin-target yield,consistent with Yan’s report within the errors.Furthermore,the parametric expression of S(E)was obtained to calculate the theoretical thick target yield,and it roughly agrees with the experimental thick target yield.展开更多
目的探索幻想性视错觉是否存在于特发性快速眼动睡眠期行为障碍(idiopathic rapid eye movement sleep behavior disorder,iRBD)患者中并分析相关风险因素以及与前驱期帕金森病(Parkinson′s disease,PD)风险的关系。方法本研究采用横...目的探索幻想性视错觉是否存在于特发性快速眼动睡眠期行为障碍(idiopathic rapid eye movement sleep behavior disorder,iRBD)患者中并分析相关风险因素以及与前驱期帕金森病(Parkinson′s disease,PD)风险的关系。方法本研究采用横断面研究设计,于2023年3月至2024年12月在广州社区招募53名健康对照者(对照组)以及在广州医科大学附属脑科医院纳入78名iRBD患者(iRBD组)和30例帕金森病患者(PD组)。所有受试者均完成幻想性视错觉测试,并采用统一帕金森病评定量表第三部分、蒙特利尔认知评估量表与连线测试、帕金森病自主神经症状量表、嗅棒测试及9项患者健康问卷和7项广泛性焦虑量表等评估运动、认知、自主神经、嗅觉功能和抑郁或焦虑症状等。3组人口统计学和一般资料比较采用方差分析或Kruskal-Wallis检验。采用广义线性模型分析3组间临床特征以及帕金森病前驱期相关风险得分的差异,在iRBD患者中根据是否存在幻想性视错觉进行亚组比较分析。采用接收者操作特征曲线分析幻想性视错觉等指标对iRBD的鉴别效能。结果iRBD组和PD组幻想性视错觉症状均显著多于对照组[(0.9±0.2)、(1.2±0.3)、(0.2±0.2)个,Waldχ^(2)=9.24,P=0.010],但iRBD组与PD组之间差异无统计学意义。相比无幻想性视错觉的iRBD患者,有幻想性视错觉的iRBD患者年龄更大[(62.4±1.1)岁与(67.2±1.4)岁,Waldχ^(2)=7.26,P=0.007]、连线测试-B时间更长[(72.1±6.3)s与(99.0±8.4)s,Waldχ^(2)=6.33,P=0.012]和嗅棒测试阈值得分更低[(5.1±0.4)分与(3.6±0.6)分,Waldχ^(2)=4.30,P=0.038],而前驱期帕金森病风险得分组间差异无统计学意义。幻想性视错觉对iRBD诊断效能有限,曲线下面积(area under the curve,AUC)=0.64,在整合蒙特利尔认知评估量表的前部脑区得分、连线测试-B和嗅棒测试得分后,其诊断效能显著提高(AUC=0.83)。结论iRBD患者已表现出幻想性视错觉增多,但其与前驱期帕金森病风险得分无显著关联,其对疾病进展的预测价值需前瞻性研究进一步证实。展开更多
构网型储能设备(grid-forming energy storage system,GFM-ESS)因具备主动构网和提供惯量支持等能力,已成为解决大规模新能源接入引发宽频振荡问题的重要手段。然而,GFM-ESS的容量配置直接影响系统投资成本,在保障系统稳定性的前提下如...构网型储能设备(grid-forming energy storage system,GFM-ESS)因具备主动构网和提供惯量支持等能力,已成为解决大规模新能源接入引发宽频振荡问题的重要手段。然而,GFM-ESS的容量配置直接影响系统投资成本,在保障系统稳定性的前提下如何实现其经济性配置,成为当前研究热点。现有研究多侧重于提升系统稳定裕度,较少考虑GFM-ESS容量与选址的协同优化,且缺乏统一的量化指标指导配置方案的制定。为此,本工作基于s域模态分析理论,构建了一条集模态识别、关键节点筛选与容量协同优化于一体的完整技术链条,并提出一种考虑经济性约束的GFM-ESS容量与选址协同优化方法。首先,通过归一化模态参与因子对各母线的振荡模态贡献进行定量评估,识别影响不稳定模态的关键节点;针对系统多模态振荡特性,引入粒子群优化(particle swarm optimization,PSO)算法,在预选节点上对储能容量进行协同优化,以满足预设的稳定裕度指标。仿真结果表明,所提技术链能够有效识别关键控制节点,并以较小的GFM-ESS投入容量将原本不稳定的系统恢复至稳定状态,且具备明确的稳定裕度,为新型电力系统中GFM-ESS的合理配置提供了理论支撑。展开更多
基金Supported by the National Key Research and Development Program of China(2016YFA0400501)National Natural Science Foundation of China(11805291,11575292,11475228,11490564,11875329)+5 种基金the U.S.Department of Energy(DE-AC07-05ID14517)Fundamental Research Funds for the Central Universities(18lgpy84)Continuous Basic Scientific Research Project(WDJC-2019-13)CNNC R&D program(FA18000201)the support of the Strategic Priority Research Program of Chinese Academy of Sciences(XDB34000000)the“Hundred Talents Program”of the Chinese Academy of Sciences。
文摘The 12C+12C fusion reaction plays a crucial role in stellar evolution and explosions.Its main open reaction channels includeα,p,n,and 8Be.Despite more than a half century of efforts,large differences remain among the experimental data of this reaction measured using various techniques.In this work,we analyze the existing data using a statistical model.Our calculation shows the following:1)the relative systematic uncertainties of the predicted branching ratios decrease as the predicted ratios increase;2)the total modified astrophysical S-factors(S^* factors)of the p andαchannels can be obtained by summing the S^* factors of their corresponding ground-state transitions and the characteristicγrays,while taking into account the contributions of the missing channels to the latter.After applying corrections based on branching ratios predicted by the statistical model,an agreement is achieved among the different data sets at Ecm>4 MeV,while some discrepancies remain at lower energies,suggesting the need for better measurements in the near future.We find that the S^* factor recently obtained from an indirect measurement is inconsistent with the direct measurement value at energies below 2.6 MeV.We recommend upper and lower limits for the 12C+12C S^* factor based on the existing models.A new 12C+12C reaction rate is also recommended.
文摘We summarize the recent effective field theory （EFT） studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S（0） factor for the thermal proton radiative capture by deuteron is calculated with pionless EFT. The astrophysical S（0） factor is accurately determined to be S（0）=0.243 eV·b up to the leading order （LO）. At zero energies, magnetic transition M1 gives the dominant contribution. The M1 amplitude is calculated up to the LO. A good, quantitative agreement between theoretical and experimental results is found for all observables. The demonstrations of cutoff independent calculation have also been presented.
文摘The astrophysical S-factor of the 4He＋12C radiative capture is calculated in the potential model at the energy range 0.1-2.0 MeV. Radiative capture 12C（α,γ） 16O is extremely relevant for the fate of massive stars and determines if the remnant of a supernova explosion becomes a black hole or a neutron star. Because this reaction occurs at low energies, the experimental measurements are very difficult and perhaps impossible. In this paper, radiative capture of the 12C（α,γ） 16O reaction at very low energies is taken as a case study. In comparison with other theoretical methods and available experimental data, good agreement is achieved for the astrophysical S-factor of this process.
基金Partly supported by National Natural Science Foundation of China(11305080)The Fundamental Research Funds for the Central Universities(lzujbky-2019-53)。
文摘The thick-target yield of the ^(9)Be(d,α0)7Li and ^(9)Be(d,α1)7Li*reactions has been first directly measured over deuteron energies from 66 to 94 keV.The obtained S(Ei)ofα0 andα1 have similar trends calculated by the thin-target yield,consistent with Yan’s report within the errors.Furthermore,the parametric expression of S(E)was obtained to calculate the theoretical thick target yield,and it roughly agrees with the experimental thick target yield.
文摘目的探索幻想性视错觉是否存在于特发性快速眼动睡眠期行为障碍(idiopathic rapid eye movement sleep behavior disorder,iRBD)患者中并分析相关风险因素以及与前驱期帕金森病(Parkinson′s disease,PD)风险的关系。方法本研究采用横断面研究设计,于2023年3月至2024年12月在广州社区招募53名健康对照者(对照组)以及在广州医科大学附属脑科医院纳入78名iRBD患者(iRBD组)和30例帕金森病患者(PD组)。所有受试者均完成幻想性视错觉测试,并采用统一帕金森病评定量表第三部分、蒙特利尔认知评估量表与连线测试、帕金森病自主神经症状量表、嗅棒测试及9项患者健康问卷和7项广泛性焦虑量表等评估运动、认知、自主神经、嗅觉功能和抑郁或焦虑症状等。3组人口统计学和一般资料比较采用方差分析或Kruskal-Wallis检验。采用广义线性模型分析3组间临床特征以及帕金森病前驱期相关风险得分的差异,在iRBD患者中根据是否存在幻想性视错觉进行亚组比较分析。采用接收者操作特征曲线分析幻想性视错觉等指标对iRBD的鉴别效能。结果iRBD组和PD组幻想性视错觉症状均显著多于对照组[(0.9±0.2)、(1.2±0.3)、(0.2±0.2)个,Waldχ^(2)=9.24,P=0.010],但iRBD组与PD组之间差异无统计学意义。相比无幻想性视错觉的iRBD患者,有幻想性视错觉的iRBD患者年龄更大[(62.4±1.1)岁与(67.2±1.4)岁,Waldχ^(2)=7.26,P=0.007]、连线测试-B时间更长[(72.1±6.3)s与(99.0±8.4)s,Waldχ^(2)=6.33,P=0.012]和嗅棒测试阈值得分更低[(5.1±0.4)分与(3.6±0.6)分,Waldχ^(2)=4.30,P=0.038],而前驱期帕金森病风险得分组间差异无统计学意义。幻想性视错觉对iRBD诊断效能有限,曲线下面积(area under the curve,AUC)=0.64,在整合蒙特利尔认知评估量表的前部脑区得分、连线测试-B和嗅棒测试得分后,其诊断效能显著提高(AUC=0.83)。结论iRBD患者已表现出幻想性视错觉增多,但其与前驱期帕金森病风险得分无显著关联,其对疾病进展的预测价值需前瞻性研究进一步证实。
