Based on the transverse-longitudinal mapping of Bessel beams,we propose a simple method to construct a self-similar Bessel-like beam whose transverse profile maintains a stretched form during propagation.Specifically,...Based on the transverse-longitudinal mapping of Bessel beams,we propose a simple method to construct a self-similar Bessel-like beam whose transverse profile maintains a stretched form during propagation.Specifically,the propagatingvariant width of this beam can be flexibly predesigned.We experimentally demonstrate three types of self-similar Bessellike beams whose width variations are linear,piecewise,and period functions of propagation distance,respectively.The experimental results match well with the theoretical predictions.We also demonstrate that our approach enables the generation of self-similar higher-order vortex Bessel-like beams.展开更多
设计和制备具有优异稳定性和高活性的催化剂对于提高锂-氧气电池的性能至关重要.由于其可调节的结构及促进氧还原反应和析氧反应动力学的有效性,异质结构催化剂引起了广泛的研究兴趣.在这项工作中,CuCo_(2)S_(4)/CoS_(1.097)多元金属硫...设计和制备具有优异稳定性和高活性的催化剂对于提高锂-氧气电池的性能至关重要.由于其可调节的结构及促进氧还原反应和析氧反应动力学的有效性,异质结构催化剂引起了广泛的研究兴趣.在这项工作中,CuCo_(2)S_(4)/CoS_(1.097)多元金属硫化物被证明是锂-氧气电池氧电极反应的有效电催化剂.密度泛函理论计算表明,CuCo_(2)S_(4)/CoS_(1.097)的电子结构在异相界面处受到调控,有利于优化氧电极反应过程中间体的吸附,最终加速氧电极反应动力学.实验结果表明,基于CuCo_(2)S_(4)/CoS_(1.097)的锂-氧气电池在100 m A g^(-1)下具有26,727.8 m A h g^(-1)的高比容量和超过267次循环的出色耐久性.该工作为锂-氧气电池高性能正极材料的设计和构造提供了新视角.展开更多
We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus(DOF).The ultra-long focal field can be controlled by appropriately regulating the order of...We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus(DOF).The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the polarization.An optical needle and an optical dark channel with nearly 100λDOF are generated.The optical needle has a DOF of~104.9λand a super-diffraction-limited focal spot with the size of 0.19λ^(2).The dark channel has a full-width at halfmaximum of~0.346λand a DOF of~103.8λ.Furthermore,the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel beam.Our results are expected to contribute to potential applications in optical tweezers,atom guidance and capture,and laser processing.展开更多
High-order harmonics q(ψ_(s))=1 energetic particle modes(EPMs)have been observed in toroidal plasmas experiments with neutral beam injection.To investigate these phenomena,linear properties and nonlinear dynamics of ...High-order harmonics q(ψ_(s))=1 energetic particle modes(EPMs)have been observed in toroidal plasmas experiments with neutral beam injection.To investigate these phenomena,linear properties and nonlinear dynamics of these EPMs driven by passing energetic particles(EPs)are studied via the global hybrid kinetic-magnetohydrodynamic code M3D-K.Simulation results demonstrate that passing EPs'effects on high mode-number harmonics(q(ψ_(s))=m/n=2/2,3/3,4/4)instability are more obvious than the q(ψ_(s))=1/1 mode,especially when q-profile is sufficiently flat in the core region.Furthermore,the effects of the pitch angleΛ_0 and beam ion pressure P_(hot)/P_(total)on the features of high n components are also analyzed specifically.It is found that there exists only one resonant condition for these EPMs.In the nonlinear phase,these high mode-number harmonics can induce significant energetic ions redistribution and chirping up phenomena,which differs from the classical fishbone excited by passing EPs.These discoveries are conducive to better apprehend the underlying physical mechanisms of the highorder harmonics driven by passing EPs.展开更多
农业在黄河三角洲地区占有重要地位,及时、准确地掌握该地区农作物分布信息对政府有关部门制定农业政策、指导农业生产具有十分重要的意义。时序植被指数能够反映农作物物候特征,帮助识别农作物类型,在农作物种植信息提取方面具有明显...农业在黄河三角洲地区占有重要地位,及时、准确地掌握该地区农作物分布信息对政府有关部门制定农业政策、指导农业生产具有十分重要的意义。时序植被指数能够反映农作物物候特征,帮助识别农作物类型,在农作物种植信息提取方面具有明显优势。论文选取2014年MOD09Q1时序遥感数据集,以黄河三角洲主要农作物为研究对象,利用Harmonic Analysis of NDVI Time-Series(Hants)滤波重构NDVI时序曲线,通过对比待分像元NDVI时序曲线与参考时序曲线的相似性,实现农作物种植信息提取。对分类结果进行面积统计和空间分布精度检验:冬小麦、棉花、玉米的面积提取精度分别达到96.8%、95.5%、85.1%,空间匹配总体精度达86.9%。结果表明该方法有效可行,能够为该地区农业监测提供技术基础。展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFA1404800)the National Natural Science Foundation of China(Nos.12074312,12174309,12074313,and 62175200)the Fundamental Research Funds for the Central Universities(No.3102019JC008)。
文摘Based on the transverse-longitudinal mapping of Bessel beams,we propose a simple method to construct a self-similar Bessel-like beam whose transverse profile maintains a stretched form during propagation.Specifically,the propagatingvariant width of this beam can be flexibly predesigned.We experimentally demonstrate three types of self-similar Bessellike beams whose width variations are linear,piecewise,and period functions of propagation distance,respectively.The experimental results match well with the theoretical predictions.We also demonstrate that our approach enables the generation of self-similar higher-order vortex Bessel-like beams.
文摘目的探讨高敏肌钙蛋白T(high-sensitivity cardiac troponin T,hs-cTnT)动态变化与晚时间窗内接受机械取栓治疗的前循环大血管闭塞型急性缺血性脑卒中患者不良预后的相关性。方法共纳入161例患者,分别于入院时和24 h测量血清hs-cTnT。hs-cTnT升高定义为大于14 ng/L;hs-cTnT动态变化定义为两次测量值上升或下降超过20%且至少有一次大于14 ng/L。评价hs-cTnT动态变化与3个月时不良预后的相关性;比较入院时hs-cTnT升高与hs-cTnT动态变化预测3个月时不良预后的接收者操作特征(receiver-operating characteristic,ROC)曲线下面积(areas under the ROC curve,AUC)。结果67(41.6%)例患者发生hs-cTnT动态变化。多因素分析显示,hs-cTnT升高(P=0.014,P=0.038)和hs-cTnT动态变化(P<0.001,P<0.001)分别是不良预后和死亡的独立预测因素。AUC比较显示hs-cTnT动态变化对不良预后(AUC 0.765 vs 0.689,P=0.043)和死亡(AUC 0.818 vs 0.687,P=0.008)的预测价值要显著优于入院时hs-cTnT升高。结论hs-cTnT动态变化是晚时间窗进行血管内治疗的急性颅内大血管闭塞性脑卒中患者3个月时不良预后和死亡的独立预测因素。hs-cTnT动态变化对不良预后的预测价值要显著优于入院时hs-cTnT升高。
基金supported by the National Natural Science Foundation of China(21935006,22075151,and 22279064)the Fundamental Research Funds for the Central Universities of China.
基金supported by the National Natural Science Foundation of China(21905033 and 52271201)the Science and Technology Department of Sichuan Province(2022YFG0100)the State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization(2020P4FZG02A)。
文摘设计和制备具有优异稳定性和高活性的催化剂对于提高锂-氧气电池的性能至关重要.由于其可调节的结构及促进氧还原反应和析氧反应动力学的有效性,异质结构催化剂引起了广泛的研究兴趣.在这项工作中,CuCo_(2)S_(4)/CoS_(1.097)多元金属硫化物被证明是锂-氧气电池氧电极反应的有效电催化剂.密度泛函理论计算表明,CuCo_(2)S_(4)/CoS_(1.097)的电子结构在异相界面处受到调控,有利于优化氧电极反应过程中间体的吸附,最终加速氧电极反应动力学.实验结果表明,基于CuCo_(2)S_(4)/CoS_(1.097)的锂-氧气电池在100 m A g^(-1)下具有26,727.8 m A h g^(-1)的高比容量和超过267次循环的出色耐久性.该工作为锂-氧气电池高性能正极材料的设计和构造提供了新视角.
基金supported by the National Key Research and Development Program of China(No.2022YFA1404800)National Natural Science Foundation of China(NSFC)(Nos.12074312,11634010,12074313,and 12174309)+1 种基金Fundamental Research Funds for the Central Universities(No.3102019JC008)Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2021115)。
文摘We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus(DOF).The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the polarization.An optical needle and an optical dark channel with nearly 100λDOF are generated.The optical needle has a DOF of~104.9λand a super-diffraction-limited focal spot with the size of 0.19λ^(2).The dark channel has a full-width at halfmaximum of~0.346λand a DOF of~103.8λ.Furthermore,the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel beam.Our results are expected to contribute to potential applications in optical tweezers,atom guidance and capture,and laser processing.
基金supported by National Key R&D Program of China(Nos.2019YFE03050002,2018YFE0310400,and 2022YFE03040002)National Natural Science Foundation of China(Nos.12005003 and 11975270)Science Foundation of Institute of Plasma Physics,Chinese Academy of Sciences(No.DSJJ-2022-04)。
文摘High-order harmonics q(ψ_(s))=1 energetic particle modes(EPMs)have been observed in toroidal plasmas experiments with neutral beam injection.To investigate these phenomena,linear properties and nonlinear dynamics of these EPMs driven by passing energetic particles(EPs)are studied via the global hybrid kinetic-magnetohydrodynamic code M3D-K.Simulation results demonstrate that passing EPs'effects on high mode-number harmonics(q(ψ_(s))=m/n=2/2,3/3,4/4)instability are more obvious than the q(ψ_(s))=1/1 mode,especially when q-profile is sufficiently flat in the core region.Furthermore,the effects of the pitch angleΛ_0 and beam ion pressure P_(hot)/P_(total)on the features of high n components are also analyzed specifically.It is found that there exists only one resonant condition for these EPMs.In the nonlinear phase,these high mode-number harmonics can induce significant energetic ions redistribution and chirping up phenomena,which differs from the classical fishbone excited by passing EPs.These discoveries are conducive to better apprehend the underlying physical mechanisms of the highorder harmonics driven by passing EPs.
文摘农业在黄河三角洲地区占有重要地位,及时、准确地掌握该地区农作物分布信息对政府有关部门制定农业政策、指导农业生产具有十分重要的意义。时序植被指数能够反映农作物物候特征,帮助识别农作物类型,在农作物种植信息提取方面具有明显优势。论文选取2014年MOD09Q1时序遥感数据集,以黄河三角洲主要农作物为研究对象,利用Harmonic Analysis of NDVI Time-Series(Hants)滤波重构NDVI时序曲线,通过对比待分像元NDVI时序曲线与参考时序曲线的相似性,实现农作物种植信息提取。对分类结果进行面积统计和空间分布精度检验:冬小麦、棉花、玉米的面积提取精度分别达到96.8%、95.5%、85.1%,空间匹配总体精度达86.9%。结果表明该方法有效可行,能够为该地区农业监测提供技术基础。
