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The wake of falling disks at low Reynolds numbers

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Acta Mechanica Sinica 2012年第2期28卷 367-371页

作者： Hong-jie zhong Cun-Biao Lee Aero Science Key Lab of High ReynoldsAerodynamic Force at High Speed AVIC Aerodynamics Research InstituteNo.701 PO-Box110034 ShenyangChina State Key Laboratory of Turbulence and Complex Systems College of EngineeringPeking University100871 BeijingChina

We visualized the wake structure of circular disks falling vertically in quiescent water. The evolution of the wake was shown to be similar to the flow patterns behind a fixed disk. The Reynolds number, Re = Ud/v, is in the range of 40 - 200. With the ascension of Reynolds numbers, a regular bifurcation occurred at the first critical Reynolds number Reel, leading to a transition from an axisymmetric wake structure to a plane symmetric one; A Hopf bifurcation took place at the second critical Reynolds number Rec2, as the wake structure became unsteady. Plane symmetry of the wake structure was first lost as periodic vortex shedding ap- peared, but recovered at higher Reynolds number. The differ- ence between the two critical Reynolds numbers was found to be shape-dependent, as we compared our results for thin discs with those for other falling bodies, such as spheres and cones. This observation could be understood in terms of the instability mechanism of the vortical structure.

关键词： Flow visualization- Transition Wake

PARAMETRIC STUDY ON THE THRUST OF BUBBLY WATER RAMJET WITH A CONVERGING-DIVERGING NOZZLE

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Journal of Hydrodynamics 2009年第5期21卷 591-599页

作者： FU Ying-jie WEI Ying-jie ZHANG Jia-zhong School of Astronautics Harbin Institute of Technology Harbin 150001 China

To predict the thrust of bubbly water ramjet with a converging-diverging nozzle, the physical processes occurring in the diffuser, mixing chamber and nozzle were analyzed. The mathematical models were constructed separately under the restrictions of certain assumptions. The bubbly nozzle flow was examined using a two-fluid model and accomplished by specifying the water velocity distribution in the nozzle. The numerical analysis of flow field in the nozzle shows that the Mach number at the throat is 1.009, near unity, and supersonic bubble flow appears behind the throat. There is greater thrust produced by bubbly water ramjet, compared with single-phase air ramjets. Subsequently, the influences of vessel velocity, air mass flow rate, inlet area Ai, area ratio （i.e., mixing chamber to inlet area Am/Ai）, and initial bubble radius on the thrust were emphatically investigated. Results indicate that the thrust increases with the increase of air mass flow rate, inlet area and the area ratio, and the decrease of initial bubble radius. However, the thrust weakly depends on the vessel velocity. These analytical and numerical results are useful for further investigation of bubbly water ramjet engine.

关键词： bubbly water ramjet converging-diverging nozzle bubbly flow ramjet thrust numerical simulation

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夺冠之路:有机光伏电池的奇妙赛程

高分子通报 2024年第7期37卷 993-1000页

作者：王灵心李中杰何田占玲玲尹守春杭州师范大学材料与化学化工学院哈尔科夫学院杭州311121

有机光伏电池——绿色能源的代言人。本文以舞台表演的形式,生动展示了“光伏大赛”过程,包括激子产生、扩散、分离、电荷传输和收集等关键环节;以展示不同活性层形貌和电子受体材料在提高光伏效率方面的作用,并颁发最佳活性层形貌奖、... 详细信息

有机光伏电池——绿色能源的代言人。本文以舞台表演的形式,生动展示了“光伏大赛”过程,包括激子产生、扩散、分离、电荷传输和收集等关键环节;以展示不同活性层形貌和电子受体材料在提高光伏效率方面的作用,并颁发最佳活性层形貌奖、最佳电子受体材料奖和最佳策略奖,为读者提供有关有机光伏电池的重要信息和进展。

关键词：有机光伏电池电子受体材料活性层形貌多元策略

The Maximum Surplus Distribution before Ruin in an Erlang（n） Risk Process Perturbed by Diffusion

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Acta Mathematica Sinica,English Series 2011年第9期27卷 1869-1880页

作者： Zhen zhong ZHANG jie zhong ZOU Yuan Yuan LIU College of Science Donghua University Shanghai 201620 P. R. China andSchool of Mathematics Central South University Changsha 410075 P. R. China School of Mathematics Central South University Changsha 410075 P. R. China

In this paper, we consider the distribution of the maximum surplus before ruin in a generalized Erlang（n） risk process （i.e., convolution of n exponential distributions with possibly different parameters） perturbed by diffusion. It is shown that the maximum surplus distribution before ruin satisfies the integro-differential equation with certain boundary conditions. Explicit expressions are obtained when claims amounts are rationally distributed. Finally, the surplus distribution at the time of ruin and the surplus distribution immediately before ruin are presented.

关键词： Sparre Anderson risk model generalized Erlang(n) inter-claim times integro-differential equation diffusion process maximum surplus distribution

An Analytical Solution to the Model for Single Three-Level Trapped Ion Driven by External Fields

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Communications in Theoretical Physics 2007年第4期47卷 725-727页

作者： WANG zhong-jie CHEN Feng Department of Physics Anhui Normal University Wuhu 241000 China

The interaction of a single three-level trapped ion with two laser beams has been studied theoretically. With application of two successive unitary transformations, an analytical solution to this quantum system has be... 详细信息

关键词： three-level trapped ion unitary transformation Lamb-Dicke limit

Dynamical Suppression of Nonlocal Decoherence in Two-State Quantum Systems

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Communications in Theoretical Physics 2009年第11期52卷 832-834页

作者： WANG zhong-jie ZHANG Kan Department of Physics Anhui Normal University Wuhu 241000 China

Nonlocal decoherence of two qubits due to pure phase damping has been *** have proposeda scheme to keep the entanglement of two qubits from nonlocal *** applying a series of±π pulses,nonlocaldecoherence can be thoro... 详细信息

关键词： entanglement quantum bits dynamical suppression

On Hereditarily Indecomposable Banach Spaces

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Acta Mathematica Sinica,English Series 2006年第3期22卷 751-756页

作者： Li Xin CHENG Huai jie zhong Department of Mathematics Xiamen University The Institute of Mathematical Sciences The Chinese University of Hang Kong Department of Mathematics Fujian Normal University

This paper shows that every non-separable hereditarily indecomposable Banach space admits an equivalent strictly convex norm, but its bi-dual can never have such a one; consequently, every non-separable hereditarily i... 详细信息

关键词： decomposition of spaces hereditarily indecomposable Banach space renormings

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中国经济高质量发展水平测度与区域差异分析

陇东学院学报 2024年第2期35卷 32-39页

作者：张忠杰刘雪柯兰州财经大学统计与数据科学学院甘肃兰州730020

构建一个完整的指标体系,通过熵权TOPSIS法衡量全国30个省域的经济高质量发展水平,并利用Dagum基尼系数分析四大区域之间的差异,使用fsQCA方法分析指标体系中不同维度的组合效应以及如何推动这些指标的有机结合。研究发现:全国经济高质... 详细信息

构建一个完整的指标体系,通过熵权TOPSIS法衡量全国30个省域的经济高质量发展水平,并利用Dagum基尼系数分析四大区域之间的差异,使用fsQCA方法分析指标体系中不同维度的组合效应以及如何推动这些指标的有机结合。研究发现:全国经济高质量发展水平呈上升趋势;四个区域中东部表现最优,其次是中部、东北和西部;经济高质量发展差异主要来自区域间的差异,总体上呈下降趋势,其中东—西部以及东—中部的组间差异降幅较大。由此提出,加强省域间的合作与交流,缩小区域间差异;因地制宜,发挥各省域优势,推动城市群融合发展。

关键词：高质量发展熵权TOPSIS法 Dagum基尼系数 fsQCA

数字经济对区域经济高质量发展的影响机理研究

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石家庄学院学报 2024年第2期26卷 5-13页

作者：张忠杰吴艺丹兰州财经大学统计学院甘肃兰州730020

数字经济随着信息化发展已成为促进经济增长的新引擎。通过构建数字经济与经济高质量发展的综合指标评价体系,根据中国2011—2021年31个省份的数据,分析数字经济对区域经济高质量发展的作用程度以及在产业结构升级水平的作用下,数字经... 详细信息

数字经济随着信息化发展已成为促进经济增长的新引擎。通过构建数字经济与经济高质量发展的综合指标评价体系,根据中国2011—2021年31个省份的数据,分析数字经济对区域经济高质量发展的作用程度以及在产业结构升级水平的作用下,数字经济对区域经济高质量发展的影响程度。结果表明:数字经济对经济高质量发展存在双重影响作用,一是数字经济直接促进经济高质量发展,二是数字经济通过产业结构升级间接的促进经济高质量发展;基于区域异质性视角,我国数字经济促进经济高质量发展的程度按照东中西部地区的顺序依次减弱。

关键词：数字经济产业结构升级数字化转型经济高质量发展