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Dynamic coefficients and stability analysis of a water-lubricated hydrostatic bearing by solving the uncoupled Reynolds equation

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Chinese Journal of Aeronautics 2020年第8期33卷 2110-2122页

作者： Jialei du Guozhu LIANG School of Astronautics Beihang UniversityBeijing 100083China

This paper concerns the dynamic characteristics of incompressible laminar flow hydrostatic bearings. An improved method based on the mathematical perturbation technique for calculating the stiffness and damping coefficients of hydrostatic bearings is presented;it raises the calculation efficiency by uncoupling the recess flow continuity equations from the solving of the Reynolds equation. The dynamic coefficients of a water-lubricated four-recess hydrostatic bearing are calculated with both the improved method and the conventional method. The comparisons between these two methods validate the effectiveness and correctness of the improved method. Furthermore, the dynamic response and stability characteristics of a rotor supported by the hydrostatic bearing are calculated and compared with experimental results. First, the dynamic responses calculated with the linear and nonlinear bearing dynamic coefficients models show that the linear model is inaccurate if the rotor whirls in a large eccentricity ratio range, owing to the nonlinearity of stiffness and damping. Second, according to the numerical and experimental results, the nonlinearity of bearing stiffness and damping coefficients could induce double rotational frequency component in the unbalance response frequency spectrum. Finally, the numerical results indicate that the stability threshold speed of the bearing increases with eccentricity ratio. The improved method proposed can be used to evaluate the dynamic performance of hydrostatic bearings efficiently, and the bearing characteristics presented could contribute to a better understanding of the performance of waterlubricated hydrostatic bearings.

关键词： Damping Hydrostatic bearing Laminar flow Stability Stiffness Water lubrication

Relative Gromov-Witten invariants of projective completions of vector bundles

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Science China Mathematics 2019年第7期62卷 1429-1438页

作者： Chengyong du School of Mathematical Sciences Sichuan Normal University

It was proved by Fan and Lee(2016) and Fan(2017) that the absolute Gromov-Witten invariants of two projective bundles P(Vi)→ X are identified canonically when the total Chern classes c(V1) and c(V2) satisfy c(V1)= c(V2) for two bundles V1 and V2 over a smooth projective variety X. In this paper, we show that the relative Gromov-Witten invariants of(P(Vi ⊕ O), P(Vi)), i = 1, 2 are identified canonically when c(V1)= c(V2),where P(Vi ⊕ O) are the projective completions of the bundles Vi → X, and the projective bundles P(Vi) are the exceptional divisors in P(Vi ⊕ O).

关键词： projective completion relative Gromov-Witten invariant uniqueness blow-up along complete intersection

Time Optimal Trajectory Planning Algorithm for Robotic Manipulator Based on Locally Chaotic Particle Swarm Optimization

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Chinese Journal of Electronics 2022年第5期31卷 906-914页

作者： du Yuxiao CHEN Yihang School of Automation Guangdong University of Technology

Optimal trajectory planning is a fundamental problem in the area of robotic research. On the time-optimal trajectory planning problem during the motion of a robotic arm, the method based on segmented polynomial interpolation function with a locally chaotic particle swarm optimization(LCPSO) algorithm is proposed in this paper. While completing the convergence in the early or middle part of the search, the algorithm steps forward on the problem of local convergence of traditional particle swarm optimization(PSO) and improved learning factor PSO(IFPSO) algorithms. Finally, simulation experiments are executed in joint space to obtain the optimal time and smooth motion trajectory of each joint,which shows that the method can effectively shorten the running time of the robotic manipulator and ensure the stability of the motion as well.

关键词： particle swarm optimisation convergence robotic arm path planning smooth motion trajectory interpolation local convergence segmented polynomial interpolation function robotic manipulator factor PSO algorithms parameter estimation fundamental problem polynomials traditional particle swarm optimization chaos time-optimal trajectory planning problem robotic research running time locally chaotic particle swarm optimization algorithm time optimal trajectory planning algorithm manipulators

融合相似预报方法在陇东南短期强降水预报中的应用

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高原气象 2025年第1期44卷 214-223页

作者：黄晓远李旭杜梦莹叶培龙李艳兰州大学大气科学学院甘肃兰州730000 兰州中心气象台甘肃兰州730020

基于逐步过滤相似法和自组织映射(SOM)神经网络方法,提出了一种融合相似预报方法。利用ECMWF模式预报产品、ERA5再分析资料和地面气象台站观测数据,使用该方法对2021-2022年陇东南地区开展了时效为72 h的强降水预报试验,并对预报效果进... 详细信息

基于逐步过滤相似法和自组织映射(SOM)神经网络方法,提出了一种融合相似预报方法。利用ECMWF模式预报产品、ERA5再分析资料和地面气象台站观测数据,使用该方法对2021-2022年陇东南地区开展了时效为72 h的强降水预报试验,并对预报效果进行了检验。结果表明:(1)融合相似预报方法的TS评分处于4.5%~9.1%之间,与ECMWF模式预报结果相比表现出一定的优势。随着预报时效的增长,强降水预报的TS评分呈现减小的趋势,其在08:00(北京时,下同)起报的TS评分相对较高。(2)相比于单独使用逐步过滤相似预报,融合相似预报方法的准确性有所提升,并能在一定程度上降低空报率。其中08:00起报和20:00起报的TS评分提高了1.31%和0.63%,而FAR同时下降了2.39%和1.25%。

关键词：强降水短期预报相似预报逐步过滤相似自组织映射(SOM)

Energy consumption simulations of rural residential buildings considering differences in energy use behavior among family members

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Building Simulation 2024年第8期17卷 1335-1358页

作者： Xi Luo Lina du School of Building Services Science and Engineering Xi'an University of Architecture and Technology(XAUAT)Xi'an 710055China State Key Laboratory of Green Building Xi'an 710055China

The“average occupant”methodology is widely used in energy consumption simulations of residential buildings;however,it fails to consider the differences in energy use behavior among family *** on a field survey on the Central Shaanxi Plain,to identify the energy use behavior patterns of typical families,a stochastic energy use behavior model considering differences in energy use behavior among family members was proposed,to improve the accuracy of energy consumption simulations of residential *** results indicated that the surveyed rural families could be classified into the following four types depending on specific energy use behavior patterns:families of one elderly couple,families of one middle-aged couple,families of one elderly couple and one child,and families of one couple and one ***,on typical summer days,the results of daily building energy consumption simulation obtained by the“average occupant”methodology were 25.39%and 28%lower than the simulation results obtained by the model proposed in this study for families of one elderly couple and families of one middle-aged couple,and 13.05%and 23.05%higher for families of one elderly couple and one child,and families of one couple and one *** typical winter days,for the four types of families,the results of daily building energy consumption simulation obtained by the“average occupant”methodology were 21.69%,10.84%,1.21%,and 8.39%lower than the simulation results obtained by the model proposed in this study,respectively.

关键词： typical energy use behavior pattern differences in occupant behavior building energy consumption simulation stochastic energy use behavior simulation

THREE-DIMENSIONAL FINITE ELEMENT DELAUNAY MESH GENERATION BY A PERFECTED NODE CONNECTION METHOD

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Chinese Journal of Mechanical Engineering 2000年第2期13卷 153-158页

作者： du Qungui 华南理工大学广东兰州广东省五金矿产进出口集团公司广东

How to automatically generate three-dimensional finite element Delaunay mesh by a peifected node connection method is introduced, where nodes are generated based on existing elements, instead of independence of node creation and elements generation in traditional node connection method. Therefore, Ihe the difficulty about how to automatically create nodes in the traditional method is overcome.

关键词： Finite element Mesh generation Delaunay triangulation Node connection method

Development Mechanism of Urban System in Rapidly Changing Period in China

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Chinese Geographical Science 2007年第1期17卷 10-18页

作者： du Guoqing College of Tourism Rikkyo （St. Paul） University Japan

The purpose of this research is to investigate the socio-economic development mechanism of China’s urban system in terms of spatial structure and its change. Totally 246 cities from 340 designated cities in 1985, and 488 from 640 designated cities in 1995 are selected as sample cities. And 22 attributes concerning urban features are analyzed to clarify the socio-economic characteristics and their changes in the urban system. Finally, the primary development factors are verified with the relationship of spatial structure and socio-economic characteristics. In conclusion, the socio-economic changes occurred more extremely than spatial structure changes. Furthermore, foreign investment be- came a major power for the development of China’s urban system in the period of 1985–1995.

关键词： urban system socio-economic development foreign investment China

Post-infarct cardiac injury, protection and repair:roles of non-cardiomyocyte multicellular and acellular components

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Science China(Life Sciences) 2018年第3期61卷 266-276页

作者： Xiaojun du Experimental Cardiology Laboratory Baker Heart and Diabetes Institute

Following myocardial infarction(MI), cardiomyocytes and infarct size are the focus of our attention when evaluating the extent of cardiac injury, efficacy of therapies or success in repairing the damaged heart by stem cell therapy. Numerous interventions have been shown by pre-clinical studies to be effective in limiting infarct size, and yet clinical trials designed accordingly have yielded disappointing outcomes. The ultimate goal of cardiac protection is to limit the adverse cardiac remodeling. Accumulating studies have revealed that post-infarct remodeling can be attenuated without infarct size limitation. To reconcile this, one needs to appreciate the significance of various cellular and acellular myocardial components that, like cardiomyocytes, undergo significant damage and dysfunction, which impact the ultimate cardiac injury and remodelling. Microvascular injury following ischemia-reperfusion may influence infarct size and promote inflammation. Myocardial injury evokes innate immunity with massive inflammatory infiltration that, although essential for the healing process, exacerbates myocardial injury and damage to extracellular matrix leading to dilative remodeling. It is also important to consider the multiple non-cardiomyocyte components in evaluating therapeutic efficacy. Current research indicates the pivotal role of these components in achieving cardiac regeneration by cell therapy. This review summarizes findings in this field, highlights a broad consideration of therapeutic targets,and recommends cardiac remodeling as the ultimate target.

关键词： myocardial infarction ventricular remodelling infarct size inflammation extracellular matrix microvascular damage autonomic nerves

Microwave Assisted Hydrothermal Way Towards Highly Crystalized N-Doped Carbon Quantum Dots and Their Oxygen Reduction Performance

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Chemical Research in Chinese Universities 2019年第2期35卷 171-178页

作者： HUANG He LIANG Chen SHA Haoyan YU Ying LOU Yue CHEN cailing LI Chunguang CHEN Xiaobo SHI Zhan FENG Shouhua State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin UniversityChangchun 130012P.R.China School of Engineering EMIT UniversityCarltonVIC 3053Australia Department of Chemical Engineering University of CaliforniaDavisCA 95616USA

We proposed a green microwave-assisted hydrothermal way to synthesize highly crystalized N-doped carbon quantum dots(N-CQDs).The N-CQDs obtained by this microwave method have good crystalline degree(ID/IG=0.6)and a high molar ratio of N/C(11.1%)comparing with those obtained from traditional top-down *** experimental results show that glycerine plays a key role ill the fonnation of highly crystalized *** as-prepared N-CQDs have good luminescent property and may be utilized as fluorescent probe to detect ions or mark *** the majority of N atoms in the N-CQDs were pyridinic type(64.8%),the as-prepared N-CQDs were used as a catalyst for the oxygen reduction reaction(ORR)electrocatalysis in the anode of the fuel cell(the onset potential is-0.121V),which was a 4e-transfer procedure and the catalyst showed good stability after 100 cycles.

关键词： Carbon-dot Nitrogen-dopping Highly-crystalized Oxygen reduction reaction(ORR)