This study investigates the effect of the initial tropical cyclone(TC)vortex structure on the intensity change during the eyewall replacement cycle(ERC)of TCs based on two idealized simulations using the Weather Resea...This study investigates the effect of the initial tropical cyclone(TC)vortex structure on the intensity change during the eyewall replacement cycle(ERC)of TCs based on two idealized simulations using the Weather Research and Forecasting(WRF)model.Results show that an initially smaller TC with weaker outer winds experienced a much more drastic intensity change during the ERC than an initially larger TC with stronger outer winds.It is found that an initially larger TC vortex with stronger outer winds favored the development of more active spiral rainbands outside the outer eyewall,which slowed down the contraction and intensification of the outer eyewall and thus prolonged the duration of the concentric eyewall and slow intensity evolution.In contrast,the initially smaller TC with weaker outer winds corresponded to higher inertial stability in the inner core and weaker inertial stability but stronger filamentation outside the outer eyewall.These led to stronger boundary layer inflow,stronger updraft and convection in the outer eyewall,and suppressed convective activity outside the outer eyewall.These resulted in the rapid weakening during the formation of the outer eyewall,followed by a rapid re-intensification of the TC during the ERC.Our study demonstrates that accurate initialization of the TC structure in numerical models is crucial for predicting changes in TC intensity during the ERC.Additionally,monitoring the activity of spiral rainbands outside the outer eyewall can help to improve short-term intensity forecasts for TCs experiencing ERCs.展开更多
目的总结经胃窦后胆肠吻合术的临床优势。方法回顾性分析2007年1月至2017年12月间第二军医大学东方肝胆外科医院胆道外科行胆肠吻合术患者392例临床资料,其中70例行胃窦后胆肠吻合手术(改良组),其余322例行传统的结肠后胆肠吻合术(对照...目的总结经胃窦后胆肠吻合术的临床优势。方法回顾性分析2007年1月至2017年12月间第二军医大学东方肝胆外科医院胆道外科行胆肠吻合术患者392例临床资料,其中70例行胃窦后胆肠吻合手术(改良组),其余322例行传统的结肠后胆肠吻合术(对照组)。对比分析两组患者的临床病理特点和术后恢复情况。结果与传统结肠后胆肠吻合术相比,两组在住院时间、术中出血量、术后胆漏发生率和并发症发生率方面无统计学差异(P> 0.05)。经胃窦后胆肠吻合手术组胃排空障碍的发生率明显下降[2(2.9%) vs 32(9.9%),P=0.003],术后进食流质时间间隔明显缩短[(64.7±16.3)h vs (76.1±24.6)h,P=0.041]。结论经胃窦后胆肠吻合术有助于早期胃肠功能恢复,特别适合于肥胖和肠系膜较短的患者。展开更多
针对采煤机在实际工作过程中的振动问题,运用多体动力学理论,综合考虑采煤机导向滑靴与销排的接触特性、平滑靴与刮板输送机的中部槽之间的摩擦及采煤机滚筒、摇臂、机身各部分之间的连接特性和机身的振动摆角,建立了采煤机侧向的6个自...针对采煤机在实际工作过程中的振动问题,运用多体动力学理论,综合考虑采煤机导向滑靴与销排的接触特性、平滑靴与刮板输送机的中部槽之间的摩擦及采煤机滚筒、摇臂、机身各部分之间的连接特性和机身的振动摆角,建立了采煤机侧向的6个自由度的动力学模型。并将采煤机滚筒轴向栽荷作为外部激励,采用数值分析方法,求解了不同煤岩硬度对采煤机侧向振动特性的影响。结果表明:当煤岩的截割阻抗均值在200〜400 kN/m之间变化时,对采煤机前后截割部的振动位移影响较大,前后滚筒的变化范围分别为3.241~7.062 m m和3.077~6.703 m m,前后摇臂的变化范围分别为1.298~2.829 mm,1.133~2.468 m m,最后通过试验对模型结果进行了验证。展开更多
The effects of constant excitation on the recently proposed smooth-and-discontinuous(SD)oscillator are investigated,which may lead to the variation of equilibrium and the property of phase portrait.By solving a quarti...The effects of constant excitation on the recently proposed smooth-and-discontinuous(SD)oscillator are investigated,which may lead to the variation of equilibrium and the property of phase portrait.By solving a quartic algebraic equation,the transition set and bifurcation for SD oscillator under constant excitation(CSD)are presented,while the number of equilibria depends on the values of the smoothness parameter and the constant excitation.Complicated structures of Kolmogorov–Arnold–Moser(KAM)structures on the Poincarésection are depicted for the driven system without dissipation.Chaotic behaviour is also demonstrated numerically for the system perturbed by both viscous-damping and external excitation.The results show that CSD is an unsymmetrical system that displays different dynamical behaviours from an SD oscillator and will enrich the range of the SD oscillator in research and application.展开更多
Nonlinear dynamical systems with an irrational restoring force often occur in both science and engineering, and always lead to a barrier for conventional nonlinear techniques. In this paper, we have investigated the g...Nonlinear dynamical systems with an irrational restoring force often occur in both science and engineering, and always lead to a barrier for conventional nonlinear techniques. In this paper, we have investigated the global bifurcations and the chaos directly for a nonlinear system with irrational nonlinearity avoiding the conventional Taylor＇s expansion to retain the natural characteristics of the system. A series of transformations are proposed to convert the homoclinic orbits of the unperturbed system to the heteroclinic orbits in the new coordinate, which can be transformed back to the analytical expressions of the homoclinic orbits. Melnikov＇s method is employed to obtain the criteria for chaotic motion, which implies that the existence of homoclinic orbits to chaos arose from the breaking of homoclinic orbits under the perturbation of damping and external forcing. The efficiency of the criteria for chaotic motion obtained in this paper is verified via bifurcation diagrams, Lyapunov exponents, and numerical simulations. It is worthwhile noting that our study is an attempt to make a step toward the solution of the problem proposed by Cao Q J et al. （Cao Q J, Wiercigroch M, Pavlovskaia E E, Thompson J M T and Grebogi C 2008 Phil. Trans. R. Soe. A 366 635）.展开更多
基金National Key R&D Program of China (2022YFC3004200)National Natural Science Foundation of China (42305007,41730960,41875057)National Science Foundation (AGS-1834300)。
文摘This study investigates the effect of the initial tropical cyclone(TC)vortex structure on the intensity change during the eyewall replacement cycle(ERC)of TCs based on two idealized simulations using the Weather Research and Forecasting(WRF)model.Results show that an initially smaller TC with weaker outer winds experienced a much more drastic intensity change during the ERC than an initially larger TC with stronger outer winds.It is found that an initially larger TC vortex with stronger outer winds favored the development of more active spiral rainbands outside the outer eyewall,which slowed down the contraction and intensification of the outer eyewall and thus prolonged the duration of the concentric eyewall and slow intensity evolution.In contrast,the initially smaller TC with weaker outer winds corresponded to higher inertial stability in the inner core and weaker inertial stability but stronger filamentation outside the outer eyewall.These led to stronger boundary layer inflow,stronger updraft and convection in the outer eyewall,and suppressed convective activity outside the outer eyewall.These resulted in the rapid weakening during the formation of the outer eyewall,followed by a rapid re-intensification of the TC during the ERC.Our study demonstrates that accurate initialization of the TC structure in numerical models is crucial for predicting changes in TC intensity during the ERC.Additionally,monitoring the activity of spiral rainbands outside the outer eyewall can help to improve short-term intensity forecasts for TCs experiencing ERCs.
文摘目的总结经胃窦后胆肠吻合术的临床优势。方法回顾性分析2007年1月至2017年12月间第二军医大学东方肝胆外科医院胆道外科行胆肠吻合术患者392例临床资料,其中70例行胃窦后胆肠吻合手术(改良组),其余322例行传统的结肠后胆肠吻合术(对照组)。对比分析两组患者的临床病理特点和术后恢复情况。结果与传统结肠后胆肠吻合术相比,两组在住院时间、术中出血量、术后胆漏发生率和并发症发生率方面无统计学差异(P> 0.05)。经胃窦后胆肠吻合手术组胃排空障碍的发生率明显下降[2(2.9%) vs 32(9.9%),P=0.003],术后进食流质时间间隔明显缩短[(64.7±16.3)h vs (76.1±24.6)h,P=0.041]。结论经胃窦后胆肠吻合术有助于早期胃肠功能恢复,特别适合于肥胖和肠系膜较短的患者。
文摘针对采煤机在实际工作过程中的振动问题,运用多体动力学理论,综合考虑采煤机导向滑靴与销排的接触特性、平滑靴与刮板输送机的中部槽之间的摩擦及采煤机滚筒、摇臂、机身各部分之间的连接特性和机身的振动摆角,建立了采煤机侧向的6个自由度的动力学模型。并将采煤机滚筒轴向栽荷作为外部激励,采用数值分析方法,求解了不同煤岩硬度对采煤机侧向振动特性的影响。结果表明:当煤岩的截割阻抗均值在200〜400 kN/m之间变化时,对采煤机前后截割部的振动位移影响较大,前后滚筒的变化范围分别为3.241~7.062 m m和3.077~6.703 m m,前后摇臂的变化范围分别为1.298~2.829 mm,1.133~2.468 m m,最后通过试验对模型结果进行了验证。
基金Supported by the National Natural Science Foundation of China under Grant Nos 11002093 and 11172183the Science and Technology Plan Project of Hebei Science and Technology Department(No 11215643).
文摘The effects of constant excitation on the recently proposed smooth-and-discontinuous(SD)oscillator are investigated,which may lead to the variation of equilibrium and the property of phase portrait.By solving a quartic algebraic equation,the transition set and bifurcation for SD oscillator under constant excitation(CSD)are presented,while the number of equilibria depends on the values of the smoothness parameter and the constant excitation.Complicated structures of Kolmogorov–Arnold–Moser(KAM)structures on the Poincarésection are depicted for the driven system without dissipation.Chaotic behaviour is also demonstrated numerically for the system perturbed by both viscous-damping and external excitation.The results show that CSD is an unsymmetrical system that displays different dynamical behaviours from an SD oscillator and will enrich the range of the SD oscillator in research and application.
基金supported by the National Natural Science Foundation of China (Grant Nos.11002093,11072065,and 10872136)the Science Foundation of the Science and Technology Department of Hebei Province of China (Grant No.11215643)
文摘Nonlinear dynamical systems with an irrational restoring force often occur in both science and engineering, and always lead to a barrier for conventional nonlinear techniques. In this paper, we have investigated the global bifurcations and the chaos directly for a nonlinear system with irrational nonlinearity avoiding the conventional Taylor＇s expansion to retain the natural characteristics of the system. A series of transformations are proposed to convert the homoclinic orbits of the unperturbed system to the heteroclinic orbits in the new coordinate, which can be transformed back to the analytical expressions of the homoclinic orbits. Melnikov＇s method is employed to obtain the criteria for chaotic motion, which implies that the existence of homoclinic orbits to chaos arose from the breaking of homoclinic orbits under the perturbation of damping and external forcing. The efficiency of the criteria for chaotic motion obtained in this paper is verified via bifurcation diagrams, Lyapunov exponents, and numerical simulations. It is worthwhile noting that our study is an attempt to make a step toward the solution of the problem proposed by Cao Q J et al. （Cao Q J, Wiercigroch M, Pavlovskaia E E, Thompson J M T and Grebogi C 2008 Phil. Trans. R. Soe. A 366 635）.
