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Nonlinear Forced Vibration of Cantilevered Pipes Conveying Fluid

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Acta Mechanica Solida Sinica 2018年第1期31卷 32-50页

作者： Zhi-yuan Liu Lin Wang xi-Ping Sun Department of Mechanics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment Wuhan 430074 China Tianjin Research Institute Water Transport Engineering M.O.T. Test Detection Center of Water Transport Engineering Tianjin 300356 China

The nonlinear forced vibrations of a cantilevered pipe conveying fluid under base excitations are explored by means of the full nonlinear equation of motion, and the fourth- order Runge-Kutta integration algorithm is used as a numerical tool to solve the discretized equations. The self-excited vibration is briefly discussed first, focusing on the effect of flow velocity on the stability and post-flutter dynamical behavior of the pipe system with parameters close to those in previous experiments. Then, the nonlinear forced vibrations are examined using several concrete examples by means of frequency response diagrams and phase-plane plots. It shows that, at low flow velocity, the resonant amplitude near the first-mode natural frequency is larger than its counterpart near the second-mode natural frequency. The second-mode frequency response curve clearly displays a softening-type behavior with hysteresis phenomenon, while the first-mode frequency response curve almost maintains its neutrality. At moderate flow velocity, interestingly, the first-mode resonance response diminishes and the hysteresis phenomenon of the second-mode response disappears. At high flow velocity beyond the flutter threshold, the frequency response curve would exhibit a quenching-like behavior. When the excitation frequency is increased through the quenching point, the response of the pipe may shift from quasiperiodic to periodic. The results obtained in the present work highlight the dramatic influence of internal fluid flow on the nonlinear forced vibrations of slender Pipes.

关键词： Pipe conveying fluid Base excitation Nonlinear dynamics Primary resonance,Superharmonie resonance Forced vibration

Monte Carlo simulation of sequential structure control of AN-MA-IA aqueous copolymerization by different operation modes

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Chinese Journal of Chemical Engineering 2022年第6期35卷 231-242页

作者： Tong Qin Zhenhao xi Ling Zhao Weikang yuan State Key Laboratory of Chemical Engineering East China University of Science and TechnologyShanghai 200237China College of Chemistry and Chemical Engineering Xinjiang UniversityUrumqi 830046China

The regulation of polyacrylonitrile(PAN)copolymer composition and sequence structure is the precondition for producing high-quality carbon fiber high *** this work,the sequential structure control of acrylonitrile(AN),methyl acrylate(MA)and itaconic acid(IA)aqueous copolymerization was investigated by Monte Carlo(MC)*** parameters used in Monte Carlo were optimized via machine learning(ML)and genetic algorithms(GA)using the experimental data from batch *** results reveal that it is difficult to control the aqueous copolymerization to obtain PAN copolymer with uniform sequence structure by batch polymerization with one-time *** contrary,it is found that the PAN copolymer with uniform composition and sequence structure can be obtained by adjusting IA feeding quantity in each reactor of a train of five ***,the results obtained in this work can provide valuable information for the understanding and optimization of AN copolymerization process to obtain high-quality PAN copolymer precursor.

关键词： Polyacrylonitrile Monte Carlo simulation Machine learning Genetic algorithms Sequence structure Operation method

Aerobic granular sludge formation based on substrate availability:Effects of flow pattern and fermentation pretreatment

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Frontiers of Environmental Science & Engineering 2020年第3期14卷 155-164页

作者： Quan yuan Hui Gong Hao xi Kaijun Wang State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China

The influences of flow patterns(mixed-flow and plug-flow)and fermentation pretreatment on aerobic granular sludge(AGS)formation with various substrate availability levels were investigated by running four identical laboratory-scale sequencing batch reactors(R1-R4),comparing two anaerobic feeding strategies and three kinds of substrates.R1 achieved faster granulation with a fast influent fill step followed by a modified anaerobic mixed-flow phase,but the AGS showed poorer stability with a cracked structure and a high suspended solids concentration in the *** anaerobic plug-flow feeding mode(with influent fed slowly from the bottom)in R2 provided deeper penetration depth for the substance to reach the core of A G S and accordingly strengthen A G S *** acidogenic upflow sludge bed reactor was introduced as a pretreatment to improve the AGS performance by enhancing glucose pre-fermentation(R4).AGS fed with mixed volatile fatty acids(VFA)after glucose fermentation showed similar performance compared with the reactor fed with acetate in the aspects of stability,structure,size distribution and nitrogen removal efficiency,and 74%similarity in the microbial *** actual wastewater with low VFA concentrations,fermentation treatment was suggested as a promising pretreatment for stable AGS granulation and operation.

关键词： Anaerobic plug-flow feeding mode Anaerobic mixed-flow mode Fermentation pretreatment Substrate gradient Penetration depth

Oviposition preference, larval performance and adaptation of Trichoplusia ni on cabbage and cotton

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Insect Science 2015年第2期22卷 273-282页

作者： yuan-xi Li Tong-xian Liu Department of Entomology College of Plant Protection Nanjing Agricultural University Nanjing State Key Laboratory of Crop Stress Biology for Arid Areas and Key Laboratory of Crop IPM for the Loess Plateau Ministry of Agriculture of China at Northwest A&F University Yangling Shaanxi China

Most female herbivores ensure to lay eggs where their offspring can develop successfully. The oviposition preferences of females affect strategies in pest management. In this study, the performance of two cohorts of Trichoplusia ni larvae on cabbage and cotton （after they had been transferred from their original host plants） were investigated. The preferences of female moth ovipositing and larval feeding on these two host plants were observed. The results indicated that plants significantly affected oviposition preference of the female adults and development and survival of larvae of T. ni. All females preferred to lay eggs on cabbage than cotton regardless from which host they originated. The detrimental effects of cotton on the development and survival of T. ni larvae originated from cabbage （CaTn） increased with the increase of the larval age when they were transferred. In addition, the host plant change did not significantly affect the development and survival of larvae of T. ni originating from cotton （CoTn）. Larvae of CaTn preferred cabbage plants as compared to cotton plants, whereas larvae of CoTn did not show a significant choice. Although the adult females preferred laying eggs on cabbage, they did not show preferences between cotton and cabbage in a Y-tube olfactometer test. The hypothesis of oviposition preference and performance of larvae was supported by the results of CaTn, whereas they not supported by those from CoTn. Based on these results, the strategy to manage this serious pest was discussed.

关键词： cabbage looper development larval choice oviposition preference

Recent advances in molecular biology research of a rice pest, the brown planthopper

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Journal of Integrative Agriculture 2019年第4期18卷 716-728页

作者： BAO Yan-yuan ZHANG Chuan-xi State Key Laboratory of Rice Biology and Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insects Institute of Insect Sciences Zhejiang University

The brown planthopper, Nilaparvata lugens St?l, has become a major threat in tropical Asian and China since the rice green revolution of the 1960 s. Currently, insecticide application remains the primary choice for controlling this rice insect pest, but heavy use of insecticides poses dangerous risks to beneficial natural enemies and pollinators, and stimulates N. lugens reproductivity, and has caused a resurgence of the pest in the major rice-planting regions throughout Asia. Achieving the long-lasting goal of sustainable management of N. lugens requires understanding of the molecular basis of outbreaks of the pest and the development of environment-friendly pest-control strategies. Here, we review the recent molecular advances in N. lugens research on the aspects of its endosymbionts, virus transmission, insecticide resistance, and interaction between N. lugens and rice plants. We also put forward further research directions that may shed some lights on management of the rice pest.

关键词： Nilaparvata lugens endosymbionts virus transmission insecticide resistance interaction with rice biological management

Methodology to determine regional water demand for instream flow and its application in the Yellow River Basin

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Journal of Environmental Sciences 2006年第5期18卷 1031-1039页

作者： ZHANG yuan YANG Zhi-feng Wang xi-qin School of Environmental Sciences State Key Laboratory of Water Environment Simulation Beijing Normal University Beijing 100875 China Chinese Research Academy of Environmental Sciences Beijing 100012 China School of Natural Resources and Environment Renmin Universitiy of China Beijing 100872 China

In order to realistically reflect the difference between regional water demand for instream flow and river ecological water demand as well as to resolve the problem that water demand may be counted repeatedly, a concept of regional water demand for minimum instream flow have been developed. The concept was used in the process of determining river functions and calculating ecological water demand for a river. The Yellow River watershed was used to validate the calculation methodology for regional water demand. CaIculation results indicate that there are significant differences in water demands among the different regions. The regional water demand at the downstream of the Yellow River is the largest about 14.893 × 10^9 m^3/a. The regional water demand of upstream, Lanzhou-Hekou section is the smallest about -5.012 × 10^9 m^3/a. The total ecological water demand of the Yellow River Basin is 23.06 × 10^9 m^3/a, about the 39% of surface water resources of the water resources should not exceed 61% in the Yellow River Basin. Yellow River Basin. That means the maximum available surface The regional river ecological water demands at the Lower Section of the Yellow River and Longyangxia-Lanzhou Section exceed the surface water resources produced in its region and need to be supplemented from other regions through the water rational planning of watershed water resources. These results provides technical basis for rational plan of water resources of the Yellow River Basin.

关键词： regional water demand instream flow environmental flow methodology the Yellow River Basin

Anxiety: a concept analysis

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Frontiers of Nursing 2020年第1期7卷 9-12页

作者： yuan xi The Operating Theatre The First Affiliated Hospital of Suchow UniversitySuchowJiangsu 215000China

Anxiety is often mentioned in people's daily life,especially in the field of medicine and *** nursing,a clear understanding of anxiety is conducive to clinical nursing practice and *** the guidance of the Walker and Avant method,this article conducts a concept analysis of anxiety that provides a comprehensive and rounded analysis of anxiety and helps nurses gain a better understanding of anxiety.

关键词： anxiety concept analysis defining attributes antecedents consequences empirical referents

On the Products Arising from the Kummer Conjecture

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Acta Mathematica Sinica,English Series 2012年第8期28卷 1677-1688页

作者： Jun Huai ZHANG yuan YI Ping xi Research center for Basic Science Xi'an Jiaotong University

Let q be a sufficiently large integer and X be a Dirichlet character modulo q. In this paper, we extend the product x（-1）=-1 L（1, X） with prime q, arising from the Kummer conjecture, to the products of some genera... 详细信息

关键词： Kummer conjecture I)irichlet L-function Dirichlet character

Least-Squares Solution with the Minimum-Norm for the Matrix Equation A^TXB+B^TX^TA = D and Its Applications

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Acta Mathematicae Applicatae Sinica 2007年第2期23卷 269-280页

作者： An-ping Liao yuan Lei xi-yan Hu Coilege of Mathematics and Econometrics Hunan University Changsha 410082 China Department of Mathematics and Information Sciences Changsha University Changsha 410003 China

An efficient method based on the projection theorem, the generalized singular value decomposition and the canonical correlation decomposition is presented to find the least-squares solution with the minimum-norm for the matrix equation A^TXB＋B^TX^TA = D. Analytical solution to the matrix equation is also derived. Furthermore, we apply this result to determine the least-squares symmetric and sub-antisymmetric solution of the matrix equation C^TXC = D with minimum-norm. Finally, some numerical results are reported to support the theories established in this paper.

关键词： Matrix equation minimum-norm solution generalized singular value decomposition canonical correlation decomposition